Protective device for a DC electrical network, vehicle electrical system, vehicle and DC charging station

Description

[0001] The invention relates to a protective device for an electrical direct current network according to the features of the preamble of claim 1, an on-board network for a vehicle, a vehicle and a direct current charging station.

[0002] From the prior art, the generic document DE 10 2019 202 892 A1 describes an on-board power supply system for a motor vehicle, wherein the on-board power supply system has a high-voltage energy storage device for providing a first high-voltage potential and a second high-voltage potential. A total voltage can be tapped between the first and second high-voltage potentials, wherein a first insulation resistance exists between the first high-voltage potential and a predetermined electrical ground, and a second insulation resistance exists between the second high-voltage potential and the predetermined electrical ground.An insulation monitoring device monitors the first and second insulation resistance and has a compensation circuit which is designed to carry out an active balancing process so that a difference between the first insulation resistance and the second insulation resistance is at least reduced by the active balancing process.

[0003] DE 10 2018 211 625 A1 also discloses an on-board electrical system arrangement for a motor vehicle with a high-voltage energy storage device for providing a first and a second high-voltage potential between which a total voltage can be tapped. The on-board electrical system arrangement is designed symmetrically such that a first insulation resistance between the first high-voltage potential and a ground, and a second insulation resistance between the second high-voltage potential and ground, differ by a maximum predeterminable amount. For this purpose, the on-board electrical system arrangement has a symmetry monitoring device designed to monitor the on-board electrical system symmetry and triggers predetermined measures if the first insulation resistance differs from the second insulation resistance by more than the predeterminable amount.

[0004] A method for operating electrical on-board networks is also known from the prior art, as described in DE 10 2017 009 355 A1. In the method for operating a first on-board network supplied with a first electrical direct voltage and a second on-board network supplied with a second electrical direct voltage, the first and second on-board networks are electrically coupled by means of an energy coupler having a first clocked energy converter. The first and second electrical direct voltages are electrically insulated from an electrical reference potential by means of an electrical insulation device. The electrical insulation device is monitored. The first and second on-board networks are galvanically coupled by means of the energy coupler.In the event of a fault in the insulation device in one area of ​​one of the two on-board networks, the energy coupler controls electrical potentials of the other of the two on-board networks in such a way that the respective potential differences between these electrical potentials and the reference potential are smaller than a predetermined comparison value.

[0005] DE 10 2019 008 833 describes a protective device for an electrical direct current network, in particular for a high-voltage network, an on-board electrical system for a vehicle, a vehicle, and a direct current charging station. The protective device comprises either a first voltage measuring device between a positive potential line and a reference potential line for measuring a voltage between the positive potential line and the reference potential line, and a second voltage measuring device between a negative potential line and the reference potential line for measuring a voltage between the negative potential line and the reference potential line, or a residual current measuring device in the reference potential line.The protective device further comprises a protective circuit, either with an electrical series connection of a discharge resistor and a first protective switch between the positive potential line and the reference potential line and an electrical series connection of the discharge resistor and a second protective switch between the negative potential line and the reference potential line, or with two protective circuit parts, wherein the first protective circuit part comprises an electrical series connection of a first discharge resistor and a first protective switch between the positive potential line and the reference potential line and the second protective circuit part comprises an electrical series connection of a second discharge resistor and a second protective switch between the negative potential line and the reference potential line.The first circuit breaker can be triggered to close when the voltage falls below a predetermined value determined by the first and / or second voltage measuring device, and the second circuit breaker can be triggered to close when the voltage falls below the predetermined value determined by the second and / or first voltage measuring device. Alternatively, the first circuit breaker and / or the second circuit breaker can be triggered to close when the fault current is measured by the residual current measuring device.

[0006] The invention is based on the object of specifying a protective device for an electrical direct current network that is improved compared to the prior art, an on-board network for a vehicle that is improved compared to the prior art, a vehicle with such an on-board network that is improved compared to the prior art, and a direct current charging station that is improved compared to the prior art.

[0007] The object is achieved according to the invention by a protective device for an electrical direct current network having the features of claim 1, an on-board network for a vehicle having the features of claim 5, a vehicle having the features of claim 6 and a direct current charging station having the features of claim 7.

[0008] Advantageous embodiments of the invention are the subject of the subclaims.

[0009] A protective device according to the invention for an electrical direct current network, in particular for a high-voltage network, for example for an on-board electrical system of a vehicle, comprises a first voltage measuring device between a positive potential line and a reference potential line for measuring a voltage between the positive potential line and the reference potential line, and a second voltage measuring device between a negative potential line and the reference potential line for measuring a voltage between the negative potential line and the reference potential line. The reference potential is in particular an electrical ground potential, in particular a vehicle ground potential when the protective device is used in a vehicle, and for example an earth potential when the protective device is used in a direct current charging station.

[0010] Furthermore, the protective device comprises a protective circuit for reducing an electric shock caused by Y capacitors of the electrical direct current network, in particular to a person, i.e. a human body.

[0011] The protective circuit comprises a first circuit breaker between the positive potential line and the reference potential line and a second circuit breaker between the negative potential line and the reference potential line. Several triggering criteria are specified, whereby the first circuit breaker and / or the second circuit breaker can only be triggered to close if all of the predetermined triggering criteria determined by the first voltage measuring device and / or the second voltage measuring device are met. The triggering criteria relate in particular to fault causes / malfunctions that can occur and whose occurrence should prevent the circuit breaker from closing. Advantageously, for each of these fault causes / malfunctions, at least one triggering criterion is specified such that it triggers in the event of physical contact, i.e. contact between a person, i.e.a human body with one of the high-voltage potentials, and does not occur when the respective fault cause occurs. Tripping, i.e., the closing of the respective circuit breaker, only occurs when all specified tripping criteria are met. This ensures that the respective circuit breaker is only closed upon physical contact, i.e., when a person, i.e., a human body, comes into contact with one of the high-voltage potentials, and that faulty closing due to the occurrence of one or more of the fault causes / malfunctions is reliably avoided.

[0012] An electrical on-board network according to the invention, in particular a high-voltage on-board network, for a vehicle, in particular for an electric vehicle or hybrid vehicle, comprises such a protective device.

[0013] A vehicle according to the invention, in particular an electric vehicle or hybrid vehicle, comprises such a protective device, in particular such an electrical on-board network, in particular a high-voltage on-board network, with such a protective device.

[0014] A direct current charging station according to the invention, in particular external to the vehicle, in particular a high-voltage direct current charging station, in particular for electrically charging a vehicle, in particular an electric vehicle or hybrid vehicle, in particular a high-voltage battery of such a vehicle, comprises such a protective device.

[0015] The term "high-voltage" refers in particular to a direct electrical voltage that is greater than approximately 60 V. In particular, the term "high-voltage" is to be interpreted in accordance with the ECE R 100 standard.

[0016] The solution according to the invention advantageously ensures that the protective circuit triggers very quickly in order to keep the charge and energy converted into body resistance to a minimum, and that false triggering occurs as little as possible or is advantageously avoided. False triggering would lead to an insulation fault for a very short period of time. In addition, the protective circuit causes a massive shift in the high-voltage potentials, which represents a maximum deviation from the energetic minimum of the energy stored in the Y capacitors. Furthermore, repeated false triggering of the protective circuit can impair the function of an insulation monitor. For example, sources of interference in the vehicle and / or in the DC charging station can cause the protective circuit to trigger incorrectly. This is avoided or at least significantly reduced by the solution according to the invention.

[0017] The inventive solution makes the evaluation of the protective circuit more stable against false triggering by requiring multiple triggering criteria to occur simultaneously. The individual triggering criteria are evaluated, in particular, using an AND operation. The individual triggering criteria depend on the type of fault. The fault form is compared with the characteristic of a discharge of the Y capacitors through a body resistance. To distinguish any fault from such a CY body resistance discharge, at least one characteristic is advantageously found that can be detected by measurement or evaluation. At least this one characteristic per fault must differ from the characteristic of the CY body current discharge.Examples include the distinction between common-mode and differential-mode events, minimum charge reversal voltages, time constants of capacitor charge reversal (time constant of the e-function), frequencies / frequency spectra or repetition rates of a clocking disturbance, etc. The voltage measurement by means of the voltage measuring devices is used as the measurement input variable, ie between the positive potential line and the reference potential line and between the negative potential line and the reference potential line.

[0018] By linking the triggering of the protective circuit to various characteristic features of a CY body discharge, the number of false triggering events can be minimized or completely avoided. At the same time, a very fast triggering time is achieved, thus minimizing the energy / charge transferred to the human body.

[0019] The voltages measured by the voltage measuring devices are evaluated in particular as follows: Determination of deviations in the currently applied voltages dU from the positive potential line to the reference potential line and from the negative potential line to the reference potential line in relation to a voltage value determined previously, and / or determination of voltage changes dU / dt, i.e. over time, of the voltages from the positive potential line to the reference potential line and from the negative potential line to the reference potential line, and / or observation of the opposite sign, in particular in the above two determinations, with regard to the evaluation of the voltages from the positive potential line to the reference potential line and from the negative potential line to the reference potential line, and / or observation of a cyclical repetition of an occurring disturbance.

[0020] The trigger criteria therefore include: the voltage deviation of the voltage currently applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line from the voltage value determined previously, and / or the voltage changes over time of the voltage applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line, and / or the opposite sign of the voltage applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line, and / or the absence of a cyclic repetition of the other triggering criteria.

[0021] The first circuit breaker and / or the second circuit breaker can only be controlled if the voltage deviation of the voltage currently applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line from the voltage value determined previously exceeds a predetermined limit value, in one possible embodiment a limit value of 30 V, and the voltage changes over time of the voltage applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line exceeds a predetermined limit value, and the opposite sign of the voltage applied between the positive potential line and the reference potential line and the voltage applied between the negative potential line and the reference potential line is present.

[0022] The limit values ​​are particularly dependent on the time constant to be considered, t = R*C. Here, R is the human body resistance, which according to standard specifications is assumed to be the lowest value up to 500 ohms. For example, body resistances in the range of 300 ohms to 30k ohms are taken into account. C depends on the total capacitance of the Y capacitors in the high-voltage system, i.e. in the high-voltage direct current network. This depends, for example, on the vehicle situation, for example, whether only the vehicle is considered, for example during driving, or the vehicle in connection with a direct current charging station. For example, a range of 200 nF (in particular only the vehicle, in particular optimized for low capacitances of the Y capacitors) up to a value for megawatt charging, i.e. direct current charging with high power, of approximately 8 µF (DC charging station and vehicle) is assumed for C. All capacitance values ​​refer to each high-voltage potential, i.e.The total capacitance is assumed to be twice this value. The protective circuit must be active at voltages above 60 V. For example, excessively low frequencies of the insulation monitors (approx. 800 kOhm test resistance, cycle time approx. 10 s) are considered as a limitation, and for frequencies above the tripping time constant, an inverter with a cycle frequency of at least 2 kHz is considered.

[0023] According to the invention, the first circuit breaker and / or the second circuit breaker can only be controlled if, in addition, the non-existence of a cyclic repetition of the other triggering criteria is determined.

[0024] For example, an analog and / or digital evaluation of the voltage determined by means of the first voltage measuring device and / or by means of the second voltage measuring device is provided.

[0025] For example, in analog evaluation, two evaluations are connected to each high-voltage potential via operational amplifier circuits, one voltage measurement output (e.g., a high-impedance resistor divider). The operational amplifier circuits have two different time constants. The operational amplifier circuit with the first time constant (low frequency, below the time constant of a discharge across a human body resistance) determines the voltage deviation from the previously determined voltage value. The operational amplifier circuit with the second time constant (higher frequency, above the time constant of a discharge across a human body resistance) determines the voltage change over time.These two trigger criteria are linked in a logical AND operation, and a logical AND operation is simultaneously performed with the negated result of the evaluation of the respective other high-voltage potential to determine whether the two voltages have opposite signs. If the overall result is "true," the protection circuit is activated.

[0026] In digital evaluation, the measured voltages are recorded, for example, by a microcontroller, ASIC (application-specific integrated circuit), or FPGA (field-programmable gate array, i.e., a digital integrated circuit into which a logic circuit can be loaded). Software-based filtering and determination of the voltage deviation from the previously determined voltage value and the voltage change over time for each high-voltage potential are performed. Subsequently, the AND operations described for analog evaluation are applied. If the overall result is "true," the protection circuit is activated.

[0027] For example, analog and digital evaluation are implemented simultaneously, especially as redundancy.

[0028] The described solution ensures that contact with a high-voltage potential by a human body is detected as quickly as possible, and the protective circuit is activated. This rapid activation is due to the relatively rapid discharge / recharge process of the Y capacitors when the human body comes into contact with a high-voltage potential (on the order of approximately 10 ms). The majority of the energy converted in the body or the charge flowing through the body occurs at the beginning of the discharge / recharge process. It attenuates along an e-function. This also makes it necessary to trigger the protective circuit as quickly as possible.

[0029] However, it is also necessary that false triggering due to other influencing factors is ruled out or at least occurs only rarely. An incorrectly triggered protective circuit leads to a very unfavorable energy distribution from the respective high-voltage potential to the reference potential, whereby the amount of energy stored in the Y capacitors approaches its maximum value, for example, positive potential to reference potential approximately 0 V and reference potential to negative potential approximately close to a system voltage of the high-voltage system, for example 800 V. In addition, an incorrectly triggered protective circuit creates an insulation fault for the moment the protective circuit is activated. When switched on using a capacitor in the protective circuit, an additional capacitor is connected in parallel to the Y capacitors, which fundamentally offers the possibility of storing more energy in the now increased total Y capacitor.

[0030] Since the protective circuit must detect the discharge caused by the human body's resistance as quickly as possible, it must be designed to react quickly. This also makes it sensitive to other interference. The solution described avoids or at least significantly reduces false triggering, which could be caused by this increased sensitivity.Means for distinguishing between interference and contact with a human body resistance are provided, as already described above, for example by comparing the signs of the two measured voltages, which enables a distinction to be made between common-mode interference and differential-mode interference, filters for distinguishing interference frequencies, averaging or voltage change compared to an average value over a defined period of time, in particular for distinguishing between small energetic influences, a maximum voltage swing of the charging processes, and / or sampling processes according to predetermined repetition rates, for example for detecting regularly pulsating interferers, such as inverters.

[0031] Considering the recharging process of the Y capacitors when touched by a human body, this corresponds to common-mode interference or the induction of common-mode currents. This is advantageously distinguished from the following influences: Common-mode interference, also known as common-mode interference, of a pulsing high-voltage component would result in a common current contribution via the reference potential, just as with a body discharge. The frequency range can be widely spread due to the large number of pulsing high-voltage components in the vehicle, their different clock frequencies, and possibly even variable clock frequencies, for example, in an on-board charger with an isolating LLC DC / DC converter.

[0032] In addition to the common-mode interference described above, pulsed high-voltage loads also cause differential-mode interference. Their noise levels can also affect the evaluation circuit. An insulation monitor also causes a charge-reversal behavior identical to that caused by a body discharge of the Y capacitors. Of the two known insulation monitor principles, the insulation monitor, which uses the charge-reversal resistor, is particularly critical here.

[0033] The following table compares the CY body discharge with the interferences described above in terms of frequency spectrum, voltage swing, type of interference (CM or DM) and repetition rate. Type of error / disturbance Frequency range (interference) spectrum Voltage swing EVM fault (Common Mode (CM) or Differential Mode (DM)) Refresh rate CY body discharge T = CY*R_body, approx. 2 kHz Full transhipment CM One-off or slowly recurring Pulsing consumer: Inverter, pulse disturbance 0 Hz - 1 MHz <25 V CM and DM >10 kHz Pulsing consumer: Inverter, fundamental wave 0 Hz - 1 MHz <25 V CM and DM 0-2 kHz Clocking consumer: DC / DC converter 0 Hz - 100 MHz <25 V CM and DM >50 kHz Pulsing consumer: heater 0 Hz - 1 MHz <25 V CM and DM approx. 50 Hz Pulsing consumer: electric refrigerant compressor 0 Hz - 100 MHz <25 V CM and DM approx. 10 kHz Insulation monitor T=CY* 1 MOhm, approx. 1 Hz Full transhipment CM <1 Hz, recurring Current ripple (DC charging) Approx. 5 - 100 kHz 100 A*100 mOhm = 10 V CM and DM >100 kHz

[0034] The solution to avoid false triggering of the protective circuit lies in linking several features together.

[0035] For example, a bandpass filter can be provided for voltage measurement, which can be implemented using hardware or software. This allows for the separation of common-mode interference from the human body's resistance from interference from an insulation monitor, particularly from the lower frequency range, and from common-mode interference from clocked components, particularly from the higher frequency range. This reduces interaction between the protection circuit and the insulation monitor, high-voltage loads, and a charging station (EVSE).

[0036] For example, a logical connection of the voltage triggering for positive and negative potentials is provided. This enables a reliable distinction between common-mode and differential-mode faults, so that only common-mode faults need to be considered in the future. This reduces interaction between the protection circuit and pulsed loads.

[0037] For example, a minimum charge transfer range, such as 50 V, is taken into account, meaning the protection circuit is only triggered at that level. Thus, small disturbances are ignored. This reduces interaction between the protection circuit and pulsed loads.

[0038] For example, a moving average, i.e., an average voltage value over a specified period of time, is taken into account, and the protective circuit is only triggered when this value is reached. Very low-impedance and recurring disturbances are thus given less weight. This reduces the protective circuit's interaction with pulsed loads.

[0039] In one possible embodiment, a common voltage evaluation unit coupled to the voltage measuring devices and the circuit breakers is provided for evaluating the voltage determined by the first voltage measuring device and the voltage determined by the second voltage measuring device and for controlling the first circuit breaker and / or the second circuit breaker exclusively upon the occurrence of all predetermined triggering criteria determined by means of the first voltage measuring device and / or by means of the second voltage measuring device.

[0040] The respective circuit breaker is designed, for example, as a semiconductor switch, for example as a MOSFET, IGBT or thyristor.

[0041] In one possible embodiment, the protective circuit comprises, for example, an electrical series connection of a discharge resistor and the first protective switch between the positive potential line and the reference potential line, and an electrical series connection of the discharge resistor and the second protective switch between the negative potential line and the reference potential line. Alternatively, the protective circuit comprises, for example, two protective circuit parts, wherein the first protective circuit part comprises an electrical series connection of a first discharge resistor and the first protective switch between the positive potential line and the reference potential line, and the second protective circuit part comprises an electrical series connection of a second discharge resistor and the second protective switch between the negative potential line and the reference potential line.

[0042] The described solution solves the problems associated with Y capacitors in vehicles, particularly in electric vehicles and hybrid vehicles, and in DC charging stations, as explained below. Such Y capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, they pose an increased risk for high-voltage safety reasons. For example, the SAE J1772, IEC60479-1 and -2 standards list the amount of charge contained in the Y capacitors as a health hazard (C1 characteristic curve). As the vehicle's operating voltage increases, it becomes increasingly difficult to comply with the limit values ​​required by these standards. In some cases, alternative measures to comply with safety requirements, such as reinforced, especially double, electrical insulation, are not permitted.The additional standard LV123 and related standards, for example, stipulate a maximum energy content of 0.2 J for the charge quantity of all Y capacitors. If alternative measures are permitted, then the aforementioned reinforced, particularly double, electrical insulation can be used. However, this is only feasible if all high-voltage systems that are coupled to one another have correspondingly reinforced insulation. This means that, for example, with direct current charging, both the vehicle and the direct current charging station, especially the charging column, must have correspondingly reinforced insulation. However, since no mandatory standard exists for this, coupling systems with different insulation designs would also be possible, which would result in non-compliance with safety requirements.

[0043] This problem is solved by the circuit described. By measuring the voltage between each high-voltage potential and the reference potential, in particular the ground potential, a shift in the high-voltage potential relative to the reference potential is detected. This shift may be the result of a body current, i.e. the result of body contact, particularly in humans, with one of the high-voltage potentials and the reference potential. In order to reduce the voltage as quickly as possible at the affected high-voltage potential, at which the voltage relative to the reference potential is reduced, the discharge resistor and, advantageously, an uncharged protective capacitor are connected in parallel. The voltage between the affected high-voltage potential and the reference potential thereby suddenly jumps to a significantly lower level, whereby the body current is reduced proportionally to the voltage.The described solution thus enables a reduction in the risk of electric shock to the body, especially to humans, caused by the Y capacitors. Compliance with the requirements described above is thus made possible. It is also possible to limit the electrical energy dissipated by the Y capacitors through body resistance to a level below 0.2 J, even though the energy stored in the Y capacitors can be considerably higher.

[0044] As mentioned above, a protective capacitor is advantageously connected electrically in parallel with the discharge resistor. The discharge resistor alone would have to have a very low resistance to quickly reduce the body current. However, the disadvantage is that this creates a low-resistance insulation fault. Therefore, the combination of a discharge resistor and a protective capacitor connected electrically in parallel is much more advantageous. The discharge resistor ensures that the protective capacitor connected electrically in parallel was de-energized at the moment of activation. After activation, it ensures rapid discharge of the Y capacitors of the affected high-voltage potential.

[0045] The protective circuit thus comprises, for example, the electrical series connection of the discharge resistor and the first protective switch between the positive potential line and the reference potential line and the electrical series connection of the discharge resistor and the second protective switch between the negative potential line and the reference potential line, wherein the protective capacitor is electrically connected in parallel to the discharge resistor.Alternatively, the protective circuit comprises the two protective circuit parts, wherein the first protective circuit part comprises the electrical series connection of the first discharge resistor and the first protective switch between the positive potential line and the reference potential line, wherein a first protective capacitor is electrically connected in parallel to the first discharge resistor, and wherein the second protective circuit part comprises the electrical series connection of the second discharge resistor and the second protective switch between the negative potential line and the reference potential line, wherein a second protective capacitor is electrically connected in parallel to the second discharge resistor.

[0046] For example, not only is the protective capacitor electrically connected in parallel with the discharge resistor, but an electrical series circuit consisting of the protective capacitor and a protective resistor is also electrically connected in parallel. The protective resistor advantageously limits the current flowing through the protective capacitor.

[0047] The protective circuit thus comprises, for example, the electrical series connection of the discharge resistor and the first protective switch between the positive potential line and the reference potential line and the electrical series connection of the discharge resistor and the second protective switch between the negative potential line and the reference potential line, wherein the electrical series connection of the protective capacitor and the protective resistor is electrically connected in parallel to the discharge resistor.Alternatively, the protective circuit comprises the two protective circuit parts, wherein the first protective circuit part comprises the electrical series connection of the first discharge resistor and the first protective switch between the positive potential line and the reference potential line, wherein an electrical series connection of the first protective capacitor and a first protective resistor is electrically connected in parallel to the first discharge resistor, and wherein the second protective circuit part comprises the electrical series connection of the second discharge resistor and the second protective switch between the negative potential line and the reference potential line, wherein an electrical series connection of the second protective capacitor and a second protective resistor is electrically connected in parallel to the second discharge resistor.

[0048] In a further embodiment, the protective circuit comprises an electrical series circuit of an electrical resistor and a first protective switch between the positive potential line and the reference potential line, and an electrical series circuit of the electrical resistor and a second protective switch between the negative potential line and the reference potential line. The electrical resistor is, in particular, an electrical resistor with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than a human body resistance, i.e., than a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or smaller than 50 Ω, for example, smaller than 5 Ω. This significantly reduces the current flowing through the human body.Alternatively, the electrical resistor is, for example, a voltage-dependent electrical resistor which is designed such that a resistance value of the voltage-dependent electrical resistor reduces, in particular increasingly reduces, with an increasing electrical voltage across terminals of the voltage-dependent electrical resistor, wherein a maximum resistance value of the voltage-dependent electrical resistor is, for example, a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than a human body resistance, i.e. than a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or smaller than 50 Ω, for example smaller than 5 Ω. This therefore applies to all resistance values ​​which the voltage-dependent electrical resistor can have at the electrical voltages occurring across its terminals.This significantly reduces the current flowing through the human body. The voltage-dependent electrical resistance is designed so that its resistance value decreases as the voltage across its terminals increases.

[0049] This embodiment of the protective circuit is a component-optimized protective circuit. In the protective circuit, which serves to reduce a CY shock, i.e. an electric shock to a person using Y capacitors, it can be assumed that only one potential, i.e. a positive potential or a negative potential, is connected to a housing ground via a person's body resistance. If both potentials were connected to the housing ground, this would be equivalent to a short circuit in a vehicle battery when the protective device is used in the vehicle, or a short circuit in a DC charging station, e.g. a charging column, when the protective device is used in the DC charging station, which must be separated by a fuse or a current sensor with a shutdown device controlled by it. This makes it clear that the protective circuit for the positive potential and the negative potential are never used at the same time.Thus, the electrical resistance can be used in the manner described to protect both potentials.

[0050] Alternatively, the protective circuit comprises two protective circuit sections, wherein the first protective circuit section comprises an electrical series connection of a first electrical resistor and a first protective switch between the positive potential line and the reference potential line, and the second protective circuit section comprises an electrical series connection of a second electrical resistor and a second protective switch between the negative potential line and the reference potential line. The respective electrical resistor is an electrical resistor with the fixed resistance value specified above. This significantly reduces the current flowing through the human body.Alternatively, the respective electrical resistor is a voltage-dependent electrical resistor which is designed such that a resistance value of the voltage-dependent electrical resistor reduces, in particular increasingly reduces, with an increasing electrical voltage across terminals of the voltage-dependent electrical resistor, wherein a maximum resistance value of the voltage-dependent electrical resistor corresponds to the values ​​for the maximum resistance value specified above. This therefore applies to all resistance values ​​that the voltage-dependent electrical resistor can have at the electrical voltages occurring across its terminals. This significantly reduces the current flowing through the human body. The voltage-dependent electrical resistor is thus designed such that its resistance value assumes smaller resistance values ​​as the voltage across its terminals increases.

[0051] In the above-described embodiment of the protective circuit, which comprises only one electrical resistor, i.e. uses the same electrical resistor for the electrical series connection with the first protective switch between the positive potential line and the reference potential line and with the second protective switch between the negative potential line and the reference potential line, it is provided in particular that not both protective switches can be or are controlled to close, in particular not simultaneously, but only one of the two protective switches at a time.

[0052] The described solution solves the problems associated with Y capacitors in vehicles, particularly in electric vehicles and hybrid vehicles, and in DC charging stations, as explained below. Such Y capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, they pose an increased risk for high-voltage safety reasons. Various standards identify the charge contained or the stored energy of the Y capacitors as a health hazard. For example, the SAE J1772, IEC60479-1 and -2 standards identify the charge contained in the Y capacitors as a health hazard (C1 characteristic curve). As the vehicle's operating voltage increases, it becomes increasingly difficult to comply with the required limit values ​​of these standards.In some cases, alternative measures, so-called alternative measures, for compliance with safety requirements, such as reinforced, especially double, electrical insulation, are not permitted. The further standard LV123 and related standards, for example, stipulate a maximum energy content of 0.2 J for the charge quantity of all Y capacitors. If the alternative measures are permitted, then the aforementioned reinforced, especially double, electrical insulation can be used. However, this is only feasible if all high-voltage systems that are coupled to one another have correspondingly reinforced insulation. This means that, for example, with direct current charging, both the vehicle and the direct current charging station, especially the charging column, must have correspondingly reinforced insulation.However, since there is no mandatory standard for this, coupling of systems with different insulation designs would also be possible, which would mean that the safety requirements would not be met.

[0053] This problem is solved by the circuit described. By measuring the voltage at each high-voltage potential relative to the reference potential, in particular ground potential, a shift in the high-voltage potential relative to the reference potential is detected. This shift could be the result of a body current, i.e. the result of body contact, particularly in humans, with one of the high-voltage potentials and with the reference potential. In order to reduce the voltage as quickly as possible at the affected high-voltage potential, at which the voltage relative to the reference potential is reduced, the resistor is added. The voltage between the affected high-voltage potential and the reference potential suddenly jumps to a much lower level, whereby the body current is reduced proportionally to the voltage. The solution described thus makes it possible to reduce the risk of electric shock to the body, particularly to humans, caused by the Y capacitors.This makes it possible to comply with the requirements described above. It is also possible to limit the electrical energy dissipated by the Y capacitors through body resistance to below 0.2 J, even though the energy stored in the Y capacitors can be considerably higher.

[0054] The advantage of the protective circuit of the protective device with the electrical series connection of the resistor, or the first and second resistors, with the respective circuit breaker between the respective potential line and the reference potential line, compared to a parallel connection of a capacitor connected in series with a protective resistor and a discharge resistor, electrically connected in series with the respective circuit breaker, is that the protective circuit of the described solution does not require such a discharge resistor. This automatically returns to a state with higher insulation resistance when lower voltages are reached between the positive potential and the reference potential or between the negative potential and the reference potential, even though the first and / or second circuit breaker are still closed.In the protective circuit with the capacitor connected in series with the protective resistor and the discharge resistor, which are electrically connected in series with the respective circuit breaker, the protective resistor would reduce the overall insulation value of a high-voltage system, especially the DC network, such as the vehicle's electrical system, to a smaller value when the first or second circuit breaker is closed. This is avoided by the solution described.

[0055] The protective circuit of the described solution can also provide an equivalent discharge path for body current each time a high-voltage potential, i.e., the positive or negative potential, is touched in rapid succession. In contrast, with the protective circuit comprising the capacitor connected in series with the protective resistor and the discharge resistor, which are electrically connected in series with the respective circuit breaker, one must either wait until the protective capacitor has been discharged to a very low voltage via the discharge resistor, or this protective circuit provides a diminishing level of protection with rapidly successive body contacts with a high-voltage potential, because the protective capacitor still has a residual voltage and can no longer store as much energy.

[0056] It is therefore advantageously provided that the protective device described here, in particular its protective circuit, is designed in such a way that it is able to switch on independently, i.e., to close the first and / or second circuit breaker, and after a short period of time in this switched-on state, to open the respective closed circuit breaker again. Communication within the vehicle to a higher-level control unit, which carries out measures such as opening contactors, in particular charging contactors and / or main contactors, and discharging the Y capacitors, is advantageously dispensed with. The detection of a permanently present insulation fault, i.e.A fault in the insulation resistance, for example, rather than a defective protective sheath of a high-voltage cable, is advantageously detected by another device, such as an insulation monitor and / or a measurement of a high-voltage potential distribution, which is not part of the protective device and its protective circuit described here and is not connected to it. As mentioned, the protective device and its protective circuit described here are capable of repeatedly triggering at very short intervals, even in the event of rapid, recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC disturbance, does not lead to further measures in the vehicle, such as an incorrect shutdown of the high-voltage system.The autonomous function of the protective device, especially its protective circuit, allows for flexible and easy integration into an existing high-voltage system. This autonomous function also reduces the safety requirements for the protective device and its protective circuit, for example, eliminating the need for a secured function / communication with another control unit.

[0057] In contrast to the protective circuit with the parallel connection of the capacitor connected in series with the protective resistor and the discharge resistor, which is electrically connected in series with the respective protective switch, the solution described here does not lead to an increase in the total capacitance between positive potential and reference potential and between negative potential and reference potential.

[0058] A comparison of the solution described here with the protective circuit and the parallel connection of the capacitor connected in series with the protective resistor and the discharge resistor, electrically connected in series with the respective circuit breaker, shows that at the moment the protective circuit is switched on, the uncharged capacitor has a lower impedance, which allows a faster reduction of the body current. The transferred charge and the energy converted in the human body are therefore somewhat lower at first. As time progresses, however, the capacitor is charged and its impedance thus increases. The electrical resistance of the solution described here, which is designed as a voltage-dependent resistor in the form of a varistor, remains almost constant until its varistor voltage of, for example, 80 V is reached and can therefore reduce the body current more quickly thereafter.

[0059] In one possible embodiment, the voltage-dependent electrical resistance, and thus in the above-specified embodiment with the one electrical resistance, this one electrical resistance, and in the above-specified alternative embodiment with the two protective circuit parts and the first and second electrical resistances, the first electrical resistance and / or the second electrical resistance, is designed as a varistor or as a series circuit and / or parallel circuit of several varistors, for example with and / or without additional circuitry. The additional circuitry is, in particular, a series resistance to limit the varistor current.

[0060] In one possible embodiment, the electrical resistor and / or the first electrical resistor and / or the second electrical resistor are electrically connected in series with an electrical protective resistor. This means that in the above-mentioned embodiment with the one electrical resistor, this electrical resistor is electrically connected in series with an electrical protective resistor. The electrical series connection of the electrical resistor and the electrical protective resistor forms a common discharge network between the positive potential and the reference potential and between the negative potential and the reference potential.In the above-specified alternative embodiment with the two protective circuit components and the first and second electrical resistors, the first electrical resistor is electrically connected in series with an electrical protective resistor and / or the second electrical resistor is electrically connected in series with an electrical protective resistor. The electrical series connection of the respective electrical resistor and the respective electrical protective resistor forms a discharge network between the positive potential and the reference potential, or a discharge network between the negative potential and the reference potential. The electrical protective resistor or the respective electrical protective resistor serves to prevent the respective circuit breaker from being destroyed by excessive current.The electrical protective resistor or the respective electrical protective resistor can be omitted, for example, if the electrical resistor or the respective electrical resistor, in particular in its design as a voltage-dependent electrical resistor, always ensures that a maximum current flow is limited in such a way that it cannot lead to the destruction of the respective circuit breaker.

[0061] The above-mentioned human body resistance, i.e. the body resistance of a person, is assumed to be a resistance value of 500 Ω, in particular in accordance with the information in the standards to be observed.

[0062] In a further embodiment, the protective circuit comprises an electrical series circuit of an electrical protective capacitor, an electrical protective resistor and the first protective switch between the positive potential line and the reference potential line and an electrical series circuit of the electrical protective capacitor, the electrical protective resistor and the second protective switch between the negative potential line and the reference potential line, wherein an electrical discharge resistor is electrically connected in parallel to the protective capacitor and protective resistor and an electrical series circuit comprising an electrical rapid discharge resistor and a rapid discharge switch is electrically connected in parallel to the protective capacitor or to the protective capacitor and protective resistor.

[0063] This embodiment of the protective circuit is a component-optimized protective circuit. In the protective circuit, which serves to reduce a CY shock, i.e. an electric shock to a person using Y capacitors, it can be assumed that only one potential, i.e. a positive potential or a negative potential, is connected to a housing ground via a person's body resistance. If both potentials were connected to the housing ground, this would be equivalent to a short circuit in a vehicle's battery when the protective device is used in the vehicle, or a short circuit in a DC charging station, e.g. a charging column, when the protective device is used in the DC charging station, which must be separated by a fuse or a current sensor with a shutdown device controlled by it. This makes it clear that the protective circuit for the positive potential and the negative potential are never used at the same time.Thus, this embodiment of the protective circuit can be used in the manner described to protect both potentials.

[0064] In a method for operating this embodiment of the protective device, the first protective switch or the second protective switch is closed when the triggering criteria occur and opened again after the protective capacitor has been charged, and then the rapid discharge switch is closed and opened again after the protective capacitor has been discharged.

[0065] Advantageously, in this embodiment of the protective circuit, it is provided that not both protective switches are controllable or controlled to close, in particular not simultaneously, but only one of the two protective switches at a time, in particular depending thereon.

[0066] In an alternative embodiment, the protective circuit comprises two protective circuit parts. The first protective circuit part comprises an electrical series circuit of a first electrical protective capacitor, a first electrical protective resistor, and the first protective switch between the positive potential line and the reference potential line, wherein a first electrical discharge resistor is electrically connected in parallel to the first protective capacitor and the first protective resistor, and an electrical series circuit comprising a first electrical rapid discharge resistor and a first rapid discharge switch is electrically connected in parallel to the first protective capacitor or to the first protective capacitor and the first protective resistor.The second protective circuit part comprises an electrical series circuit of a second electrical protective capacitor, a second electrical protective resistor and the second protective switch between the negative potential line and the reference potential line, wherein a second electrical discharge resistor is electrically connected in parallel to the second protective capacitor and second protective resistor and an electrical series circuit of a second electrical rapid discharge resistor and a second rapid discharge switch is electrically connected in parallel to the second protective capacitor or to the second protective capacitor and second protective resistor.

[0067] In the method for operating the protective device, the first protective switch is then closed when the triggering criteria occur and opened again after the first protective capacitor has been charged, and then the first rapid discharge switch is closed and opened again after the first protective capacitor has been discharged, and / or the second protective switch is closed when the triggering criteria occur and opened again after the second protective capacitor has been charged, and then the second rapid discharge switch is closed and opened again after the second protective capacitor has been discharged.

[0068] The described solution solves the problems associated with Y capacitors in vehicles, particularly in electric vehicles and hybrid vehicles, and in DC charging stations, as explained below. Such Y capacitors are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). However, they pose an increased risk for high-voltage safety reasons. For example, the SAE J1772, IEC60479-1 and -2 standards list the amount of charge contained in the Y capacitors as a health hazard (C1 characteristic curve). As the vehicle's operating voltage increases, it becomes increasingly difficult to comply with the limit values ​​required by these standards. In some cases, alternative measures to comply with safety requirements, such as reinforced, especially double, electrical insulation, are not permitted.The additional standard LV123 and related standards, for example, stipulate a maximum energy content of 0.2 J for the charge quantity of all Y capacitors. If alternative measures are permitted, then the aforementioned reinforced, particularly double, electrical insulation can be used. However, this is only feasible if all high-voltage systems that are coupled to one another have correspondingly reinforced insulation. This means that, for example, with direct current charging, both the vehicle and the direct current charging station, especially the charging column, must have correspondingly reinforced insulation. However, since no mandatory standard exists for this, coupling systems with different insulation designs would also be possible, which would result in non-compliance with safety requirements.

[0069] This problem is solved by the circuit described. By measuring the voltage between each high-voltage potential and the reference potential, in particular the ground potential, a shift in the high-voltage potential relative to the reference potential is detected. This shift may be the result of a body current, i.e. the result of body contact, particularly in humans, with one of the high-voltage potentials and the reference potential. In order to reduce the voltage as quickly as possible at the affected high-voltage potential, at which the voltage relative to the reference potential is reduced, the discharge resistor and, advantageously, an uncharged protective capacitor are connected in parallel. The voltage between the affected high-voltage potential and the reference potential thereby suddenly jumps to a significantly lower level, whereby the body current is reduced proportionally to the voltage.The described solution thus enables a reduction in the risk of electric shock to the body, especially to humans, caused by the Y capacitors. Compliance with the requirements described above is thus made possible. It is also possible to limit the electrical energy dissipated by the Y capacitors through body resistance to a level below 0.2 J, even though the energy stored in the Y capacitors can be considerably higher.

[0070] The combination of a discharge resistor and a parallel-connected protective capacitor is particularly advantageous. The discharge resistor ensures that the parallel-connected protective capacitor is de-energized at the moment of connection. After connection, it ensures rapid discharge of the Y capacitors of the affected high-voltage potential.

[0071] Since not only the protective capacitor is electrically connected in parallel to the discharge resistor, but also the electrical series circuit consisting of the protective capacitor and the protective resistor, a current via the protective capacitor is advantageously limited by means of the protective resistor.

[0072] Thanks to the additional rapid discharge resistor, which is electrically connected in parallel to at least the protective capacitor or to the protective capacitor and protective resistor, the protective circuit of the described solution can also provide an equivalent discharge path for body current each time a high-voltage potential, i.e., the positive potential or the negative potential, is touched in rapid succession. Without this additional rapid discharge resistor, the protective capacitor would be charged after initial activation, depending on its capacitance to the capacitance of the Y capacitors of the high-voltage system, for example, to 80 V. If it were switched on again very briefly with this voltage, a slightly higher voltage would ultimately be present across the human body because the charge in the protective capacitor could not be completely dissipated. With each further short-term activation, the protective function would therefore be reduced.This would mean either waiting until the protective capacitor had been discharged to a very low voltage via the discharge resistor, or this protective circuit would have a diminishing protective effect with rapid, successive body contacts to a high-voltage potential, as the protective capacitor would still have residual voltage and could no longer store as much energy. This problem is solved by the described protective circuit, which is expanded to include a fast discharge circuit for quickly discharging the protective capacitor. As described, the respective protective switch is first activated. After the protective capacitor has been charged, this protective switch is opened again. The protective capacitor is then discharged via the parallel fast discharge resistor and the closing of the fast discharge switch.After the protective capacitor has been discharged, the quick discharge switch is opened again and the protective circuit is ready for use again.

[0073] Advantageously, the protective device described here, in particular its protective circuit, is designed in such a way that it is capable of autonomously switching on, i.e., closing the first and / or second circuit breaker, and, after a short time in this switched-on state, opening the respective closed circuit breaker again. Communication within the vehicle to a higher-level control unit, which carries out measures such as opening contactors, in particular charging contactors and / or main contactors, and discharging the Y capacitors, is advantageously dispensed with. The detection of a permanently present insulation fault, i.e.A fault in the insulation resistance, for example, rather than a defective protective sheath of a high-voltage cable, is advantageously detected by another device, such as an insulation monitor and / or a measurement of a high-voltage potential distribution, which is not part of the protective device and its protective circuit described here and is not connected to it. As mentioned, the protective device and its protective circuit described here are capable of repeatedly triggering at very short intervals, even in the event of rapid, recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC disturbance, does not lead to further measures in the vehicle, such as an incorrect shutdown of the high-voltage system.The autonomous function of the protective device, especially its protective circuit, allows for flexible and easy integration into an existing high-voltage system. This autonomous function also reduces the safety requirements for the protective device and its protective circuit, for example, eliminating the need for a secured function / communication with another control unit.

[0074] Embodiments of the invention are explained in more detail below with reference to drawings.

[0075] Showing: Fig. 1 schematically shows an embodiment of a direct current network with an embodiment of a protective device, Fig. 2 schematically shows an embodiment of a protective device, Fig. 3 schematically shows a further embodiment of a direct current network with an embodiment of a protective device, Fig. 4 schematically shows a further embodiment of a protective device, Fig. 5 schematically shows a further embodiment of a direct current network with an embodiment of a protective device, and Fig. 6 schematically shows a further embodiment of a protective device.

[0076] Corresponding parts are provided with the same reference numerals in all figures.

[0077] Based on the Figures 1 to 6A protective device 8 for an electrical direct current network 1, in particular for a high-voltage network, for example for an on-board electrical system 3 of a vehicle 2, is described below. It comprises a first voltage measuring device SV1 between a positive potential line HV+L and a reference potential line ML for measuring a voltage between the positive potential line HV+L and the reference potential line ML and a second voltage measuring device SV2 between a negative potential line HV-L and the reference potential line ML for measuring a voltage between the negative potential line HV-L and the reference potential line ML. The reference potential M is in particular an electrical ground potential, when the protective device 8 is used in a vehicle 2, in particular a vehicle ground potential, when the protective device 8 is used in a direct current charging station 5, for example an earth potential.

[0078] Furthermore, the protective device 8 comprises a protective circuit 9, in particular for reducing an electric shock caused by Y capacitors CyF+, CyF-, CyL+, CyL- of the electrical direct current network 1, in particular to a person, ie a human body.

[0079] The protective circuit 9 comprises a first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and a second protective switch SS2 between the negative potential line HV-L and the reference potential line ML. Several triggering criteria are specified, wherein the first protective switch SS1 and / or the second protective switch SS2 can be triggered to close only when all of the predetermined triggering criteria determined by the first voltage measuring device SV1 and / or the second voltage measuring device SV2 occur. The triggering criteria relate in particular to fault causes / malfunctions that can occur and whose occurrence should prevent the closing of the protective switches SS1, SS2. Advantageously, for each of these fault causes / malfunctions, at least one triggering criterion is specified such that it triggers in the event of physical contact, i.e. contact between a person, i.e.of a human body with one of the high-voltage potentials HV+, HV-, and does not occur when the respective cause of the fault occurs. Tripping, i.e. the closing of the respective circuit breaker SS1, SS2, only occurs when all specified tripping criteria are met. This ensures that the respective circuit breaker SS1, SS2 is only closed in the event of body contact, i.e. when a person, i.e. a human body, comes into contact with one of the high-voltage potentials HV+, HV-, and that faulty closing due to the occurrence of one or more of the fault causes / malfunctions is reliably avoided.

[0080] An electrical system 3, in particular a high-voltage electrical system 3, for a vehicle 2, in particular for an electric vehicle or hybrid vehicle, comprises such a protective device 8.

[0081] A vehicle 2, in particular an electric vehicle or hybrid vehicle, comprises such a protective device 8, in particular such an electrical system 3, in particular a high-voltage electrical system 3, with such a protective device 8.

[0082] A direct current charging station 5, in particular a high-voltage direct current charging station, in particular for electrically charging a

[0083] Vehicle 2, in particular an electric vehicle or hybrid vehicle, in particular a high-voltage battery 6 of such a vehicle 2, comprises such a protective device 8.

[0084] The voltages measured by the voltage measuring devices SV1, SV2 are evaluated in particular as follows: Determination of deviations in the currently applied voltages dU from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML in relation to a voltage value determined previously, and / or determination of voltage changes dU / dt, i.e. over time, of the voltages from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML, and / or observation of the opposite sign, in particular in the above two determinations, with regard to the evaluation of the voltages from the positive potential line HV+L to the reference potential line ML and from the negative potential line HV-L to the reference potential line ML, and / or observation of a cyclical repetition of an occurring fault.

[0085] The trigger criteria therefore include in particular: the voltage deviation of the voltage currently applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML from the previously determined voltage value, and / or the voltage changes over time of the voltage applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML, and / or the opposite sign of the voltage applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML, and / or the absence of a cyclic repetition of the other triggering criteria.

[0086] The first circuit breaker SS1 and / or the second circuit breaker SS2 can only be controlled if the voltage deviation of the voltage currently applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML from the voltage value determined previously exceeds a predetermined limit value, in one possible embodiment a limit value of 30 V, and the voltage changes over time of the voltage applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML exceeds a predetermined limit value, and the opposite sign of the voltage applied between the positive potential line HV+L and the reference potential line ML and the voltage applied between the negative potential line HV-L and the reference potential line ML is present.

[0087] For example, a common voltage evaluation unit 12 coupled to the voltage measuring devices SV1, SV2 and the circuit breakers SS1, SS2 is provided for evaluating the voltage determined by the first voltage measuring device SV1 and the voltage determined by the second voltage measuring device SV2 and for controlling the first circuit breaker SS1 and / or the second circuit breaker SS2 exclusively upon the occurrence of all predetermined triggering criteria determined by means of the first voltage measuring device SV1 and / or by means of the second voltage measuring device SV2.

[0088] The Figures 1 and 2 , 3 and 4 as well as 5 and 6 show various embodiments of the protection circuit 9, wherein the Figures 2 , 4 and 6 show a component-optimized version of the respective embodiment.

[0089] In the examples shown, the high-voltage network 3 is a high-voltage on-board electrical system 3 of a vehicle 2, in particular an electric vehicle or hybrid vehicle, in which the protective device 8 is advantageously used. However, the protective device 8 can alternatively or additionally also be used in a direct current charging station 5, to which the vehicle 2 and other vehicles, in particular electric vehicles and hybrid vehicles, can be connected for electrically charging a high-voltage battery 6 of the vehicle 2. When the vehicle 2 is connected, the direct current network 1 then comprises the on-board electrical system 3, in particular the high-voltage on-board electrical system 3, of the vehicle 2 and the direct current charging station 5. The high-voltage battery 6 of the vehicle 2, which is electrically charged at this direct current charging station 5, serves in particular to provide electrical energy for at least one electric drive unit of the vehicle 2 for driving the vehicle 2.

[0090] Both in vehicle 2 and in DC charging station 5, Y-capacitors CyF+, CyF-, CyL+, and CyL- are used as a measure to reduce the emission of EMC interference (EMC = electromagnetic compatibility). In particular, Y-capacitors CyF+, CyF-, CyL+, and CyL- are generally cheaper and more compact EMC filter measures than inductive interference filters, such as common- or differential-mode chokes. From an EMC perspective, it would therefore be advantageous to use Y-capacitors CyF+, CyF-, CyL+, and CyL- with large capacitance values.

[0091] However, a disadvantage of an electrified vehicle 2, i.e., for example, an electric vehicle or hybrid vehicle, is that the energy content of the Y capacitors CyF+, CyF-, CyL+, CyL- can be felt by a vehicle user if they can touch a high-voltage potential HV+, HV- and are simultaneously connected to ground potential. They then receive an electric shock. Depending on the severity of this electric shock, this can be hazardous to health. For example, it can lead to ventricular fibrillation or death. Such an electric shock represents a so-called "single fault" and must be avoided. Therefore, the energy content of the Y capacitors CyF+, CyF-, CyL+, CyL- is normatively limited to prevent any danger to the vehicle user.

[0092] From a high-voltage safety perspective, small capacitance values ​​for the Y capacitors CyF+, CyF-, CyL+, and CyL- are advantageous. Normative requirements, for example, regulated in regulation LV123, require that a maximum energy content, specifically 0.2 J, in the Y capacitors CyF+, CyF-, CyL+, and CyL- not be exceeded, or that so-called "alternative measures" be provided, such as reinforced insulation. However, this always means that when two high-voltage systems are coupled, for example, vehicle 2 and DC charging station 5, if reinforced insulation is selected as the "alternative measure," both devices must always have this reinforced insulation at the same time. However, this cannot currently be guaranteed.

[0093] In other standards, such as SAE J1772, IEC 60479-1, and IEC 60479-2, the energy content of the Y capacitors CyF+, CyF-, CyL+, and CyL- is not specified as a health-endangering quantity that must not be exceeded. Instead, a charge quantity is specified as the damaging mechanism, which must not exceed a specified value. For example, a graph showing the relationship between the duration of a body current and the value of the body current is provided. An alternative approach, such as reinforced insulation, is not accepted here.

[0094] The Figures 1 , 3 and 5show a circuit structure of the respective embodiment of the electrical direct current network 1 designed as a high-voltage network during a direct current charging process of the vehicle 2. The direct current network 1 therefore comprises the high-voltage on-board network 3 of the vehicle 2 and the direct current charging station 5 connected to it by means of a charging cable 4. In the example shown, the charging cable 4 is already connected to connection contacts AK+, AK- of a direct current charging connection of the vehicle 2 and charging contactors LS+, LS- of the vehicle 2 in high-voltage potential lines HV+L, HV-L are still open.

[0095] On the left side is the DC charging station 5 with a charging station voltage source 13, a charging station internal resistance R LS and the Y capacitors CyL+, CyL-.

[0096] Charging cable 4 is shown to the right.

[0097] To the right, the vehicle 2 is shown with its high-voltage electrical system 3, comprising the charging contactors LS+, LS-, the Y capacitors CyF+, CyF-, for example EMC filters, an X capacitor Cx, for example of a DC intermediate circuit, and the high-voltage battery 6 with its main contactors HS+, HS-. The high-voltage battery 6 is shown as an electrical battery energy source 7, comprising, for example, a plurality of individual cells electrically connected in series and / or parallel, with an internal battery resistance R Batt .

[0098] Additionally, this circuit diagram depicts the human body MK with a body resistance RK and a switch symbol for an insulation fault IF, for example, in the case of a defective charging cable 4, here an example of a fault at the positive potential HV+. The insulation fault IF can also occur at the negative potential HV-. This is not depicted here. If the insulation fault IF occurs, the switch symbol is closed. In the event of such an insulation fault IF and contact between the human body MK and one of the high-voltage potentials HV+, HV- and a reference potential M, a discharge occurs through the human body MK.

[0099] In order to prevent this discharge through the human body MK or at least to reduce it to a permissible level, particularly with regard to a health hazard, the protective device 8 with the protective circuit 9 is provided to reduce the electric shock through the Y capacitors CyF+, CyF-, CyL+, CyL-. In all examples shown, the protective device 8 comprises the two voltage measuring devices SV1, SV2 and the protective circuit 9 with the two circuit breakers SS1, SS2. This connects a discharge network between the positive potential HV+ and the reference potential M, in particular the bodyshell, or a discharge network between the negative potential HV- and the reference potential M, in particular the bodyshell. These discharge networks are configured in the example according to the Figures 1 , 3 and 5 the protective circuit parts 9.1, 9.2 of the protective circuit 9.

[0100] The respective discharge network, ie the respective protective circuit part 9.1, 9.2, consists in the embodiment according to the Figures 1 and 2 preferably consisting of an uncharged capacitor, hereinafter referred to as protective capacitor Cs, Cs1, Cs2, and a resistor connected electrically in parallel, hereinafter referred to as discharge resistor Re, Re1, Re2. In addition, a protective resistor Rs, Rs1, Rs2 is provided, which is electrically connected in series with the protective capacitor Cs, Cs1, Cs2. For example, only the discharge resistor Re, Re1, Re2 could be provided, but this must have a very low resistance in order to quickly reduce the body current. The disadvantage, however, is that this creates a low-resistance insulation fault. Therefore, only the combination with protective capacitor Cs, Cs1, Cs2 and discharge resistor Re, Re1, Re2 is considered below.

[0101] The respective discharge resistors Re, Re1, Re2 ensure that the parallel-connected protective capacitors Cs, Cs1, Cs2 are de-energized at the moment of connection. After connection, they ensure a rapid discharge of the Y capacitors CyF+, CyF-, CyL+, CyL- of the affected high-voltage potential HV+, HV-. In the example shown, Figure 1 The protective device 8 with the protective circuit 9 is shown arranged in the vehicle 2. However, it can also be arranged in the DC charging station 5 while performing the same function.

[0102] During the direct current charging process, the high-voltage potentials HV+ and HV- do not necessarily have to be distributed symmetrically with respect to the reference potential M, but a minimum insulation value of the high-voltage potentials HV+ and HV- relative to the reference potential M must be ensured, for example, greater than 100 ohms / volt. Touching a high-voltage potential HV+ and HV- by a person results in a reduction in insulation resistance and, as a result, a shift in the high-voltage potentials HV+ and HV- relative to the reference potential M.

[0103] Although an insulation monitor in vehicle 2 or in the DC charging station 5 cyclically checks the insulation resistances, the time until an insulation fault IF is detected is far too long, at a maximum of 30 seconds in vehicle 2 or a maximum of two minutes in the DC charging station 5, to be able to provide protection against a human shock in the event of an open insulation from the energy stored in the Y capacitors CyF+, CyF-, CyF+, CyF-.

[0104] The functionality of the protective device 8 with its protective circuit 9 for reducing a Cy shock is based, for example, on the limit values ​​regarding the hazard potential described in the SAE J1772, IEC 60479-1, and IEC 60479-2 standards. The damaging mechanism is defined as the amount of charge flowing through the human body MK, which is represented in a diagram. The goal is therefore to detect and reduce the body current as quickly as possible in order to minimize the flow of charge. Solely controlling the mechanical charging contactors LS+, LS- and / or main contactors HS+, HS- would be too slow for this.

[0105] In the protective circuit 9 described above, a drop in the insulation value is quickly detected by the voltage measurement and as a result, the discharged protective capacitor Cs, Cs1, Cs2 is immediately connected to the affected high-voltage potential HV+, HV- with body resistance RK or

[0106] Y-capacitors CyF+, CyF-, CyL+, and CyL- are connected in parallel. This abruptly reduces the voltage across this high-voltage potential HV+, HV-, and the reference potential M. The current flow through the human body MK decreases proportionally with the voltage reduction.

[0107] The discharge resistors Re, Re1, Re2 have two functions. Firstly, they ensure the complete discharge of the protective capacitor Cs, Cs1, Cs2 before it is switched on. Secondly, they accelerate the reduction of the already reduced voltage between this high-voltage potential HV+, HV- and the reference potential M after it is switched on, whereby the current through the human body MK is further reduced as the voltage continues to fall. The other high-voltage potential HV-, HV+ increases its voltage with respect to the reference potential M to the same extent, but is not touched by the human body MK and is therefore non-critical. In a further step, the main contactors HS+, HS- of the high-voltage battery 6 are advantageously opened, contactors in the DC charging station 5 and / or the charging contactors LS+, LS- are opened, and in a final step, the active discharge of the X-capacitor Cx and the Y-capacitors CyF+, CyF- of the vehicle 2 is carried out.

[0108] The protective device 8 with its protective circuit 9 enables compliance with specified standards, such as IEC 60479-1. The higher the DC charging voltage, the higher the voltage across the Y capacitors CyF+, CyF-, CyL+, CyL-. This results in a current at the beginning of the contact process, proportional to the voltage of the Y capacitors CyF+, CyF-, CyL+, CyL-, assuming a body resistance RK. The current through the body decreases as a capacitor discharges across a resistor, particularly in the form of an exponential function. The current at the beginning of contact is calculated from the quotient of voltage and resistance. Assuming a maximum charging voltage of 920 V and a high-voltage potential distribution also assumed to be symmetrical with respect to the reference potential M (460 V across each Y capacitor), this results in an initial value of the touch current of 460 V / 1200 Ohm = 383 mA.Starting from this initial current value, this current can be converted to a sinusoidal AC current by dividing by the square root of 6. This corresponds to the value on the x-axis in the so-called C1 characteristic curve in the SAE J 1772 standard. The duration of this current can be determined by calculating the time constant of the capacitor discharge t = R x C. The corresponding duration (y-axis) corresponds to 3 x t. For example, a dwell time in this state of approximately 100 ms is still permissible. The target was a residual body current of less than 5 mA, i.e. the residual voltage must be less than 6 V.

[0109] The higher the voltage across a Y capacitor CyF+, CyF-, CyL+, CyL-, for example, in the case of an asymmetrical high-voltage potential distribution relative to the reference potential M, the shorter the maximum dwell time. A current exceeding 500 mA is not permitted, as this would result in a maximum voltage of 600 V across a Y capacitor CyF+, CyF-, CyL+, CyL-. Above this value, the charging process must be aborted.

[0110] Using the protective device 8 with its protective circuit 9, it can therefore be calculated whether it is still capable of maintaining the required maximum current durations. If this condition is not met, the charging process must be aborted immediately, as a further error would endanger personnel. Input variables for this calculation are voltage measurements across the Y capacitors CyF+, CyF-, CyL+, CyL- of both high-voltage potentials HV+, HV-, knowledge of the circuit's own reaction speed, and the table of values ​​for the maximum permissible current dwell times.

[0111] A voltage evaluation unit 12 is provided here, in which the voltages detected by the voltage measuring devices SV1, SV2 are evaluated and the circuit breakers SS1, SS2 can be controlled accordingly. Furthermore, it can be provided that this voltage evaluation unit 12 can output further information, in particular to slower control units or to the DC charging station 5. Examples of information include the opening or closing of the charging contactors LS+, LS-, an interruption of the DC charging process, the opening or closing of the main contactors HS+, HS- of the high-voltage battery 6, the initiation of active discharge of the high-voltage intermediate circuit of the vehicle 2, and / or the information that everything is OK and the DC charging process can therefore be started.

[0112] In a direct current network 1 without the direct current charging station 5, particularly for driving the vehicle 2, for alternating current charging, and for assembly and service work, the only difference from the situation with direct current charging is that the direct current charging station 5 is missing. Possible failure mechanisms include, for example, a defective high-voltage cable or a defective housing of a high-voltage electronics unit as a result of an accident. Even if the high-voltage system is damaged during assembly or service, the protective device 8 with its protective circuit 9 can reduce the charge quantity.

[0113] The protective circuit 9 for reducing the Y-voltage surge caused by an insulation fault IF remains identical to that described above. For this purpose, the protective device 8 with its protective circuit 9 is naturally located in the vehicle 2. Its function is identical to that described above for the insulation fault during DC charging. Upon detection of a voltage reduction between one of the high-voltage potentials HV+, HV- and the reference potential M, the respective protective capacitor Cs, Cs1, Cs2 is switched on, and the total capacitance of the Y-capacitors CyF+, CyF-, CyL+, CyL- of the affected high-voltage potential HV+, HV- is discharged. Furthermore, the main contactors HS+, HS- of the high-voltage battery 6 are advantageously commanded to open, and an active discharge of the X-capacitor Cx and both Y-capacitors CyF+, CyF- of the vehicle 2 is initiated. The charging contactors LS+, LS- are already open and always remain open.

[0114] Figure 2shows the component-optimized protective circuit 9. In the protective circuit 9 for reducing a Cy shock, it can be assumed that only one high-voltage potential HV+, HV- is connected to the reference potential M, for example, the housing ground, via the body resistance RK. If both high-voltage potentials HV+, HV- were connected to the reference potential M, in particular the housing ground, this would amount to a short circuit in the high-voltage battery 6 or DC charging station 5, which must be interrupted by a fuse or a current sensor with a shutdown device controlled by it.

[0115] This clearly shows that the protective circuit 9 for reducing a Cy surge for the positive potential HV+ and the negative potential HV- is never used at the same time. Therefore, a single protective capacitor Cs, discharge resistor Re, and additional protective resistor Rs can be used to protect both high-voltage potentials HV+ and HV-, as shown in Figure 2shown. Therefore, two protective circuit sections 9.1, 9.2 are no longer required. The voltage measurements using the two voltage measuring devices SV1, SV2 and the two circuit breakers SS1, SS2 for connecting the protective circuit 9 must remain in place. Figure 2shows such a component optimization. This is useful if the discharge resistance Re must also assume larger component values ​​due to, for example, high operating voltages or large capacitances of the Y capacitors CyF+, CyF-, CyL+, CyL- in vehicle 2 and the DC charging station 5. The protective device 8, in particular its protective circuit 9, is reduced here to the necessary additional effort that must be integrated in vehicle 2 or at the DC charging station 5. Connections AHV+, AHV-, AM to the positive potential HV+, negative potential HV- and reference potential M can be kept very small, since a current in the millisecond range only flows in the event of a fault. Otherwise, the connections AHV+, AHV-, AM are current-free and serve only for voltage measurement. This means that rapid integration of the protective device 8 with its protective circuit 9 into an existing high-voltage system is possible with minor changes.If there is more planning time, this function can of course also be integrated into an existing device.

[0116] The protective circuit 9 thus comprises the electrical series connection of the discharge resistor Re and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the, i.e. the same, discharge resistor Re and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in Figure 2 shown.

[0117] Alternatively, the protective circuit 9 comprises two protective circuit parts 9.1, 9.2, wherein the first protective circuit part 9.1 comprises the electrical series connection of the first discharge resistor Re1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the second protective circuit part 9.2 comprises the electrical series connection of the second discharge resistor Re2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in Figure 1 shown.

[0118] As already mentioned above, the protective capacitor Cs, Cs1, Cs2 is advantageously connected electrically in parallel to the discharge resistor Re, Re1, Re2, ie the sole protective capacitor Cs is electrically connected in parallel to the sole discharge resistor Re, as in Figure 2shown, or to the discharge resistor Re1, Re2 of the respective protective circuit part 9.1, 9.2, the respective protective capacitor Cs1, Cs2 is electrically connected in parallel, as in Figure 1 shown.

[0119] The protective circuit 9 thus comprises the electrical series connection of the discharge resistor Re and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the discharge resistor Re and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the protective capacitor Cs is electrically connected in parallel to the discharge resistor Re, as in Figure 2shown. Alternatively, the protective circuit 9 comprises the two protective circuit parts 9.1, 9.2, wherein the first protective circuit part 9.1 comprises the electrical series connection of the first discharge resistor Re1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML, wherein the first protective capacitor Cs1 is electrically connected in parallel to the first discharge resistor Re1, and wherein the second protective circuit part 9.2 comprises the electrical series connection of the second discharge resistor Re2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the second protective capacitor Cs2 is electrically connected in parallel to the second discharge resistor Re2, as in Figure 1 shown.

[0120] In the examples shown here, not only the protective capacitor Cs, Cs1, Cs2 is electrically connected in parallel to the discharge resistor Re, Re1, Re2, but an electrical series circuit consisting of the protective capacitor Cs, Cs1, Cs2 and a protective resistor Rs, Rs1, Rs2 is electrically connected in parallel.

[0121] The protective circuit 9 thus comprises the electrical series connection of the discharge resistor Re and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the discharge resistor Re and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the electrical series connection of the protective capacitor Cs and the protective resistor Rs is electrically connected in parallel to the discharge resistor Re, as in Figure 2shown. Alternatively, the protective circuit 9 comprises the two protective circuit parts 9.1, 9.2, wherein the first protective circuit part 9.1 comprises the electrical series connection of the first discharge resistor Re1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML, wherein the electrical series connection of the first protective capacitor Cs1 and the first protective resistor Rs1 is electrically connected in parallel to the first discharge resistor Re1, and wherein the second protective circuit part 9.2 comprises the electrical series connection of the second discharge resistor Re2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the electrical series connection of the second protective capacitor Cs2 and the second protective resistor Rs2 is electrically connected in parallel to the second discharge resistor Re2, as in Figure 1 shown.

[0122] The Figures 3 and 4show a further embodiment of the protective device 8, in particular of its protective circuit 9, wherein Figure 4 shows the component-optimized version.

[0123] The respective unloading network in Figure 3 thus the respective protective circuit part 9.1, 9.2, preferably consists of an electrical series connection of a resistor R, R1, R2 and a protective resistor Rs, Rs1, Rs2.

[0124] In the example shown, the electrical resistance R, R1, R2 is a voltage-dependent electrical resistance which is designed such that a resistance value of the voltage-dependent electrical resistance reduces, in particular increasingly reduces, with an increasing electrical voltage across terminals of the voltage-dependent electrical resistance, wherein a maximum resistance value of the voltage-dependent electrical resistance is a maximum of 800 Ω, in particular a maximum of 600 Ω, in particular smaller, in particular significantly smaller, than the human body resistance RK, i.e. than a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or smaller than 50 Ω, for example smaller than 5 Ω. As a result, the current flowing through the human body is significantly reduced.The voltage-dependent resistor is designed, for example, as a varistor or as a series connection and / or parallel connection of several varistors, for example with and / or without additional circuitry.

[0125] Alternatively, the electrical resistance R, R1, R2 is an electrical resistance with a fixed resistance value of a maximum of 800 Ω, in particular a maximum of 600 Ω, which is in particular smaller, in particular significantly smaller, than the human body resistance RK, i.e., a body resistance of a person, in particular a maximum of 200 Ω, in particular a maximum of or smaller than 50 Ω, for example, less than 5 Ω. This also significantly reduces the current flowing through the human body.

[0126] For example, only the resistors R, R1, and R2 can be provided. The electrical protective resistors Rs, Rs1, and Rs2 serve to prevent the respective circuit breaker SS1 and SS2 from being destroyed by excessive current. The electrical protective resistors Rs, Rs1, and Rs2 can thus be omitted, for example, if the electrical resistors R, R1, and R2, particularly in their voltage-dependent configuration, always ensure that the maximum current flow is limited to such an extent that it cannot lead to the destruction of the respective circuit breaker SS1 and SS2.

[0127] In the example shown according to Figure 3 The protective device 8 with the protective circuit 9 is shown arranged in the vehicle 2. However, it can also be arranged in the DC charging station 5 while performing the same function.

[0128] In the protective device 8 shown here, in particular the protective circuit 9, in particular the respective protective circuit part 9.1, 9.2, fault detection takes place via the voltage measurement related to the reference potential M.

[0129] During a direct current charging process, in which the Figure 3 When the charging contactors LS+, LS- shown open are closed, the high-voltage potentials HV+, HV- do not necessarily have to be distributed symmetrically with respect to the reference potential M, but a minimum insulation value of the high-voltage potentials HV+, HV- with respect to the reference potential M must be ensured, for example, greater than 100 ohms / volt. Touching a high-voltage potential HV+, HV- by a person results in a reduction in insulation resistance and, as a result, a shift in the high-voltage potentials HV+, HV- with respect to the reference potential M.

[0130] Although an insulation monitor in vehicle 2 or in the DC charging station 5 cyclically checks the insulation resistances, the time until an insulation fault IF is detected is far too long, at a maximum of 30 seconds in vehicle 2 or a maximum of two minutes in the DC charging station 5, to be able to provide protection against a human shock in the event of an open insulation from the energy stored in the Y capacitors CyF+, CyF-, CyF+, CyF-.

[0131] The functionality of the protective device 8 with its protective circuit 9 for reducing a Cy shock is based, for example, on the limit values ​​regarding the hazard potential described in the SAE J1772, IEC 60479-1, and IEC 60479-2 standards. The damaging mechanism is defined as the amount of charge flowing through the human body MK, which is represented in a diagram. The goal is therefore to detect and reduce the body current as quickly as possible in order to minimize the flow of charge. Solely controlling the mechanical charging contactors LS+, LS- and / or main contactors HS+, HS- would be too slow for this.

[0132] In the protective circuit 9 described above, a drop in the insulation value is quickly detected by the voltage measurement and as a result, the electrical resistance R, R1, R2 to the affected high-voltage potential HV+, HV- with body resistance RK or

[0133] Y-capacitors CyF+, CyF-, CyL+, and CyL- are connected in parallel. This abruptly reduces the voltage across this high-voltage potential HV+, HV-, and the reference potential M. The current flow through the human body MK decreases proportionally with the voltage reduction.

[0134] The respective other high-voltage potential HV-, HV+ increases its voltage with respect to the reference potential M to the same extent, but is not touched by the human body MK and is therefore uncritical.

[0135] In a further step, the main contactors HS+, HS- of the high-voltage battery 6 are advantageously opened, contactors in the DC charging station 5 and / or the charging contactors LS+, LS- are opened and, in a final step, the active discharge of the X capacitor Cx and the Y capacitors CyF+, CyF- of the vehicle 2 is carried out.

[0136] The protective device 8 with its protective circuit 9 enables compliance with specified standards, such as IEC 60479-1. The higher the DC charging voltage, the higher the voltage across the Y capacitors CyF+, CyF-, CyL+, CyL-. This results in a current at the beginning of the contact process, proportional to the voltage of the Y capacitors CyF+, CyF-, CyL+, CyL-, assuming a body resistance RK. The current through the body decreases as a capacitor discharges across a resistor, particularly in the form of an exponential function. The current at the beginning of contact is calculated from the quotient of voltage and resistance. Assuming a maximum charging voltage of 920 V and a high-voltage potential distribution also assumed to be symmetrical with respect to the reference potential M (460 V across each Y capacitor), this results in an initial value of the touch current of 460 V / 1200 Ohm = 383 mA.Starting from this initial current value, this current can be converted to a sinusoidal alternating current by dividing by the square root of 6. This corresponds to the value on the x-axis in the so-called C1 characteristic curve in the SAE J 1772 standard. The duration of this current can be determined by calculating the time constant of the capacitor discharge t = R x C. The corresponding duration (y-axis) corresponds to 3 x t. For example, a dwell time in this state of approximately 100 ms is still permissible. The target was a residual body current of less than 5 mA, i.e. the residual voltage must be less than 6 V.

[0137] The higher the voltage across a Y capacitor CyF+, CyF-, CyL+, CyL-, for example, in the case of an asymmetrical high-voltage potential distribution relative to the reference potential M, the shorter the maximum dwell time. A current exceeding 500 mA is not permitted, as this would result in a maximum voltage of 600 V across a Y capacitor CyF+, CyF-, CyL+, CyL-. Above this value, the charging process must be aborted.

[0138] Using the protective device 8 with its protective circuit 9, it can therefore be calculated whether it is still capable of maintaining the required maximum current durations. If this condition is not met, the charging process must be aborted immediately, as a further error would endanger personnel. Input variables for this calculation are voltage measurements across the Y capacitors CyF+, CyF-, CyL+, CyL- of both high-voltage potentials HV+, HV-, knowledge of the circuit's own reaction speed, and the table of values ​​for the maximum permissible current dwell times.

[0139] Since the protective circuit 9 can represent an equivalent discharge path for body current each time a high-voltage potential HV+, HV- is touched very quickly one after the other, it is advantageously provided that the protective device 8 described here, in particular its protective circuit 9, is designed in such a way that it is able to switch on independently, i.e., to close the first and / or second circuit breaker SS1, SS2, and after a short time in this switched-on state, to open the respective closed circuit breaker SS1, SS2 again. Communication within the vehicle 2 to a higher-level control unit, which carries out measures such as opening the charging contactors LS+, LS- and / or main contactors HS+, HS- and discharging the Y capacitors CyF+, CyF-, CyL+, CyL-, is advantageously dispensed with. The detection of a permanently present insulation fault, i.e.a low insulation resistance and not, for example, a defective protective sheath of a high-voltage cable, is advantageously detected by another device, for example by an insulation monitor and / or by measuring a high-voltage potential distribution, which is not part of the protective device 8 described here and its protective circuit 9 and is also not connected to it. As mentioned, the protective device 8 described here and its protective circuit 9 are capable of repeatedly triggering at very short intervals and thus even in the event of rapidly recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC disturbance, does not lead to further measures in the vehicle 2, such as an incorrect shutdown of the high-voltage system.The autonomous function of the protective device 8, in particular its protective circuit 9, enables flexible and simple integration into an existing high-voltage system. This autonomous function also reduces the safety requirements for the protective device 8 and its protective circuit 9; for example, a secured function / communication with another control unit is no longer required.

[0140] The protective device 8 can also be used in a direct current network 1 without the direct current charging station 5, in particular for driving the vehicle 2, for alternating current charging, and for assembly and service work. The only difference compared to direct current charging is that the direct current charging station 5 is missing. Possible failure mechanisms include, for example, a defective high-voltage cable or a defective housing of a high-voltage electronics unit as a result of an accident. Even if the high-voltage system is damaged during assembly or service, the protective device 8, with its protective circuit 9, can reduce the charge quantity.

[0141] The protective circuit 9 for reducing the Y-voltage surge caused by an insulation fault IF remains identical to that described above. For this purpose, the protective device 8 with its protective circuit 9 is naturally located in the vehicle 2. Its function is identical to that described above for the insulation fault during DC charging. Upon detection of the reduction in voltage between one of the high-voltage potentials HV+, HV- and the reference potential M, the respective electrical resistor R, R1, R2 is switched on, and the total capacitance of the Y-capacitors CyF+, CyF-, CyL+, CyL- of the affected high-voltage potential HV+, HV- is discharged. Furthermore, the opening of the main contactors HS+, HS- of the high-voltage battery 6 is advantageously commanded, and an active discharge of the X-capacitor Cx and both Y-capacitors CyF+, CyF- of the vehicle 2 is initiated. The charging contactors LS+, LS- are already open and always remain open.

[0142] Figure 4shows the component-optimized protective circuit 9. In the protective circuit 9 for reducing a Cy shock, it can be assumed that only one high-voltage potential HV+, HV- is connected to the reference potential M, for example, the housing ground, via the body resistance RK. If both high-voltage potentials HV+, HV- were connected to the reference potential M, in particular the housing ground, this would amount to a short circuit in the high-voltage battery 6 or DC charging station 5, which must be interrupted by a fuse or a current sensor with a shutdown device controlled by it.

[0143] This clearly shows that the protective circuit 9 for reducing a Cy surge for the positive potential HV+ and the negative potential HV- is never used at the same time. Therefore, a single resistor R and optionally a single protective resistor Rs can be used to protect both high-voltage potentials HV+ and HV-, as shown in Figure 4shown. Therefore, two protective circuit sections 9.1, 9.2 are no longer required. The voltage measurements using the two voltage measuring devices SV1, SV2 and the two circuit breakers SS1, SS2 for connecting the protective circuit 9 must remain in place.

[0144] The protective device 8, in particular its protective circuit 9, is in Figure 4reduced to the necessary additional effort that must be integrated in the vehicle 2 or at the DC charging station 5. Connections AHV+, AHV-, AM to the positive potential HV+, negative potential HV-, and reference potential M can be kept very small, since a current in the millisecond range only flows in the event of a fault. Otherwise, the connections AHV+, AHV-, AM are de-energized and serve only for voltage measurement. This means that the protective device 8 with its protective circuit 9 can be quickly integrated into an existing high-voltage system with minimal changes. If more planning time is available, this function can of course also be integrated into an existing device.

[0145] The protective circuit 9 thus comprises, for example, as in Figure 4shown, the electrical series connection of the electrical resistor R and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the, i.e. the same, electrical resistor R and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML.

[0146] The electrical resistance R is, for example, an electrical resistance with the above-mentioned fixed resistance value, or, as in the Figures 4Shown is a voltage-dependent electrical resistor, which is designed such that the resistance value of the voltage-dependent electrical resistor decreases, in particular progressively decreases, with an increasing electrical voltage across the terminals of the voltage-dependent electrical resistor, with the maximum resistance value being provided as described above. This significantly reduces the current flowing through the human body.

[0147] The electrical resistance R designed as a voltage-dependent electrical resistance is designed, for example, as a varistor or as a series connection and / or parallel connection of several varistors with and / or without additional circuitry.

[0148] Alternatively, the protection circuit 9 comprises, as in Figure 3shown, two protective circuit parts 9.1, 9.2, wherein the first protective circuit part 9.1 comprises the electrical series connection of the first electrical resistor R1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the second protective circuit part 9.2 comprises the electrical series connection of the second electrical resistor R2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML.

[0149] The respective electrical resistance R1, R2 is, for example, an electrical resistance with the above-mentioned fixed resistance value or as in Figure 3Shown is a voltage-dependent electrical resistor, which is designed such that the resistance value of the voltage-dependent electrical resistor decreases, in particular progressively decreases, with increasing electrical voltage across the terminals of the voltage-dependent electrical resistor, with the maximum resistance value being provided as stated above. This significantly reduces the current flowing through the human body.

[0150] The respective electrical resistor R1, R2 designed as a voltage-dependent electrical resistor is designed, for example, as a varistor or as a series circuit and / or parallel circuit of several varistors with and / or without additional circuitry.

[0151] In one possible embodiment, as already mentioned above, the electrical resistor R, R1, R2 is electrically connected in series with an electrical protective resistor Rs, Rs1, Rs2. This means that the sole electrical resistor R is electrically connected in series with the sole electrical protective resistor Rs, as shown in Figure 4 shown, or the electrical resistance R1, R2 of the respective protective circuit part 9.1, 9.2 is electrically connected in series with the electrical protective resistance Rs1, Rs2 of the respective protective circuit part 9.1, 9.2, as in Figure 3 shown.

[0152] The electrical series connection of the respective electrical resistors R, R1, R2 and the respective electrical protective resistors Rs, Rs1, Rs2 forms a discharge network between the positive potential HV+ and the reference potential M or a discharge network between the negative potential HV- and the reference potential M. The electrical protective resistor Rs or the respective electrical protective resistors Rs1, Rs2 serve to prevent the respective circuit breaker SS1, SS2 from being destroyed by excessive current. The electrical protective resistor Rs or the respective electrical protective resistors Rs1, Rs2 can be omitted, for example, if the electrical resistor R or the respective electrical resistors R1, R2, particularly in their design as voltage-dependent electrical resistors, always ensures that the maximum current flow is limited in such a way that it cannot lead to the destruction of the respective circuit breaker SS1, SS2.

[0153] If the electrical protective resistor Rs or the respective protective resistor Rs1, Rs2 is present, the protective circuit 9 thus comprises the electrical series connection of the electrical resistor R, the electrical protective resistor Rs and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the electrical series connection of the resistor R, the electrical protective resistor Rs and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in Figure 4shown, or the protective circuit 9 comprises the two protective circuit parts 9.1, 9.2, wherein the first protective circuit part 9.1 comprises the electrical series connection of the first electrical resistor R1, the first electrical protective resistor Rs1 and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and the second protective circuit part 9.2 comprises the electrical series connection of the second electrical resistor R2, the second electrical protective resistor Rs2 and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, as in Figure 3 shown.

[0154] As the above-mentioned human body resistance RK , ie the body resistance of a person, ie of the human body MK, a resistance value of 500 Ω is assumed, in particular in accordance with the information in the standards to be observed.

[0155] The Figure 5 and 6show a further embodiment of the protective device 8, in particular of its protective circuit 9, wherein Figure 6 shows the component-optimized version.

[0156] The respective discharge network, ie in Figure 5 The respective protective circuit part 9.1, 9.2 preferably comprises an uncharged capacitor, hereinafter referred to as protective capacitor Cs, Cs1, Cs2, and a resistor electrically connected in parallel, hereinafter referred to as discharge resistor Re, Re1, Re2. Additionally, a protective resistor Rs, Rs1, Rs2 is provided, which is electrically connected in series with the protective capacitor Cs, Cs1, Cs2. Furthermore, a rapid discharge resistor Rse, Rse1, Rse2 is provided in parallel with the protective capacitor Cs, Cs1, Cs2 and, for example, also in parallel with the protective resistor Rs, Rs1, Rs2, and is electrically connected in series with a rapid discharge switch Se, Se1, Se2.

[0157] The respective discharge resistors Re, Re1, and Re2 ensure that the parallel-connected protective capacitors Cs, Cs1, and Cs2 are de-energized at the moment of connection. After connection, they ensure rapid discharge of the Y capacitors CyF+, CyF-, CyL+, and CyL- of the affected high-voltage potential HV+ and HV-.

[0158] Thanks to the additional rapid discharge resistors Rse, Rse1, Rse2, the protective circuit 9 can also provide an equivalent discharge path for body current each time a high-voltage potential HV+, HV- is contacted in rapid succession. Without this additional rapid discharge resistor Rse, Rse1, Rse2, the protective capacitor Cs, Cs1, Cs2 would be charged after initial activation, depending on its capacitance, to the capacitance of the Y capacitors CyF+, CyF-, CyL+, CyL- of the high-voltage system, for example, to 80 V. If the capacitors were switched on again very briefly with this voltage, a slightly higher voltage would ultimately be present across the human body MK because the charge in the protective capacitor Cs, Cs1, Cs2 could not be completely dissipated. Thus, with each subsequent short-term activation, the protective function would be reduced.It would therefore either be necessary to wait until the protective capacitor Cs, Cs1, Cs2 had been discharged to a very low voltage value via the discharge resistor Re, Re1, Re2, or this protective circuit would have a diminishing protective effect with rapid, successive body contacts to a high-voltage potential HV+, HV-, because the protective capacitor Cs, Cs1, Cs2 would still have a residual voltage and could no longer store as much energy. This problem is solved by the described protective circuit 9, which is expanded to include a fast discharge circuit for quickly discharging the protective capacitor Cs, Cs1, Cs2. In this case, the respective protective switch SS1, SS2 is activated first. After the protective capacitor Cs, Cs1, Cs2 has been charged, this protective switch SS1, SS2 is opened again.The protective capacitor Cs, Cs1, Cs2 is now discharged through the parallel rapid discharge resistor Rse, Rse1, Rse2, and the rapid discharge switch Se, Se1, Se2 is closed. After the protective capacitor Cs, Cs1, Cs2 is discharged, the rapid discharge switch Se, Se1, Se2 is opened again, and the protective circuit 9 is ready for use again.

[0159] Advantageously, the protective device 8 described here, in particular its protective circuit 9, is designed in such a way that it is capable of being switched on autonomously, i.e., closing the first and / or second circuit breaker SS1, SS2, and, after a short time in this switched-on state, opening the respective closed circuit breaker SS1, SS2 again. Communication within the vehicle 2 to a higher-level control unit, which carries out measures such as opening contactors, in particular charging contactors LS+, LS- and / or main contactors HS+, HS-, and discharging the Y capacitors CyF+, CyF-, CyL+, CyL-, is advantageously dispensed with. The detection of a permanently present insulation fault, i.e.a low insulation resistance and not, for example, a defective protective sheath of a high-voltage cable, is advantageously detected by another device, for example by an insulation monitor and / or by measuring a high-voltage potential distribution, which is not part of the protective device 8 described here and its protective circuit 9 and is also not connected to it. As mentioned, the protective device 8 described here and its protective circuit 9 are capable of repeatedly triggering at very short intervals and thus even in the event of rapidly recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC disturbance, does not lead to further measures in the vehicle 2, such as an incorrect shutdown of the high-voltage system.The autonomous function of the protective device 8, in particular its protective circuit 9, enables flexible and simple integration into an existing high-voltage system. This autonomous function also reduces the safety requirements for the protective device 8 and its protective circuit 9; for example, a secured function / communication with another control unit is no longer required.

[0160] In the example shown according to Figure 5 The protective device 8 with the protective circuit 9 is shown arranged in the vehicle 2. However, it can also be arranged in the DC charging station 5 while performing the same function.

[0161] In the protective device 8 shown here, in particular the protective circuit 9, in particular the respective protective circuit part 9.1, 9.2, fault detection takes place via the voltage measurement related to the reference potential M.

[0162] During a direct current charging process, in which the Figure 5 When the charging contactors LS+, LS- shown open are closed, the high-voltage potentials HV+, HV- do not necessarily have to be distributed symmetrically with respect to the reference potential M, but a minimum insulation value of the high-voltage potentials HV+, HV- with respect to the reference potential M must be ensured, for example, greater than 100 ohms / volt. Touching a high-voltage potential HV+, HV- by a person results in a reduction in insulation resistance and, as a result, a shift in the high-voltage potentials HV+, HV- with respect to the reference potential M.

[0163] Although an insulation monitor in vehicle 2 or in the DC charging station 5 cyclically checks the insulation resistances, the time until an insulation fault IF is detected is far too long, at a maximum of 30 seconds in vehicle 2 or a maximum of two minutes in the DC charging station 5, to be able to provide protection against a human shock in the event of an open insulation from the energy stored in the Y capacitors CyF+, CyF-, CyL+, CyL-.

[0164] The functionality of the protective device 8 with its protective circuit 9 for reducing a Cy shock is based, for example, on the limit values ​​regarding the hazard potential described in the SAE J1772, IEC 60479-1, and IEC 60479-2 standards. The damaging mechanism is defined as the amount of charge flowing through the human body MK, which is represented in a diagram. The goal is therefore to detect and reduce the body current as quickly as possible in order to minimize the flow of charge. Solely controlling the mechanical charging contactors LS+, LS- and / or main contactors HS+, HS- would be too slow for this.

[0165] In the protective circuit 9 described above, a drop in the insulation value is quickly detected by the voltage measurement and as a result, the discharged protective capacitor Cs, Cs1, Cs2 is immediately connected to the affected high-voltage potential HV+, HV- with body resistance RK or

[0166] Y-capacitors CyF+, CyF-, CyL+, and CyL- are connected in parallel. This abruptly reduces the voltage across this high-voltage potential HV+, HV-, and the reference potential M. The current flow through the human body MK decreases proportionally with the voltage reduction.

[0167] The discharge resistors Re, Re1, Re2 have two functions. Firstly, they ensure the complete discharge of the protective capacitor Cs, Cs1, Cs2 before it is switched on. Secondly, they accelerate the reduction of the already reduced voltage between this high-voltage potential HV+, HV- and the reference potential M after it is switched on. As the voltage continues to fall, the current through the human body MK is also further reduced. The other high-voltage potential HV-, HV+ increases its voltage with respect to the reference potential M by the same amount, but is not touched by the human body MK and is therefore not critical. In a further step, the main contactors HS+, HS- of the high-voltage battery 6, the contactors in the DC charging station 5 and / or the charging contactors LS+, LS- can be opened. In a final step, the active discharge of the X-capacitor Cx and the Y-capacitors CyF+, CyF- of vehicle 2 can be carried out.As described above, however, in the solution described here, this opening of the contactors does not occur, at least not by the protective device 8, but rather the rapid discharge of the protective capacitor Cs, Cs1, Cs2 by means of the rapid discharge resistor Rse, Rse1, Rse2 takes place in the manner described above, whereby the protective circuit 9 is quickly ready for use again.

[0168] The protective device 8 with its protective circuit 9 enables compliance with specified standards, such as IEC 60479-1. The higher the DC charging voltage, the higher the voltage across the Y capacitors CyF+, CyF-, CyL+, CyL-. This results in a current at the beginning of the contact process, proportional to the voltage of the Y capacitors CyF+, CyF-, CyL+, CyL-, assuming a body resistance RK. The current through the body decreases as a capacitor discharges across a resistor, particularly in the form of an exponential function. The current at the beginning of contact is calculated from the quotient of voltage and resistance. Assuming a maximum charging voltage of 920 V and a high-voltage potential distribution also assumed to be symmetrical with respect to the reference potential M (460 V across each Y capacitor), this results in an initial value of the touch current of 460 V / 1200 Ohm = 383 mA.Starting from this initial current value, this current can be converted to a sinusoidal alternating current by dividing by the square root of 6. This corresponds to the value on the x-axis in the so-called C1 characteristic curve in the SAE J 1772 standard. The duration of this current can be determined by calculating the time constant of the capacitor discharge t = R x C. The corresponding duration (y-axis) corresponds to 3 x t. For example, a dwell time in this state of approximately 100 ms is still permissible. The target was a residual body current of less than 5 mA, i.e. the residual voltage must be less than 6 V.

[0169] The higher the voltage across a Y capacitor CyF+, CyF-, CyL+, CyL-, for example, in the case of an asymmetrical high-voltage potential distribution relative to the reference potential M, the shorter the maximum dwell time. A current exceeding 500 mA is not permitted, as this would result in a maximum voltage of 600 V across a Y capacitor CyF+, CyF-, CyL+, CyL-. Above this value, the charging process must be aborted.

[0170] Using the protective device 8 with its protective circuit 9, it can therefore be calculated whether it is still capable of maintaining the required maximum current durations. If this condition is not met, the charging process must be aborted immediately, as a further error would endanger personnel. Input variables for this calculation are voltage measurements across the Y capacitors CyF+, CyF-, CyL+, CyL- of both high-voltage potentials HV+, HV-, knowledge of the circuit's own reaction speed, and the table of values ​​for the maximum permissible current dwell times.

[0171] Since the protective circuit 9 can represent an equivalent discharge path for body current each time a high-voltage potential HV+, HV- is touched very quickly one after the other, it is advantageously provided that the protective device 8 described here, in particular its protective circuit 9, is designed such that it is able to switch on independently, i.e., to close the first and / or second circuit breaker SS1, SS2, and after a short time in this switched-on state, to open the respective closed circuit breaker SS1, SS2 again. Communication within the vehicle 2 to a higher-level control unit, which carries out measures such as opening the charging contactors LS+, LS- and / or main contactors HS+, HS- and discharging the Y capacitors CyF+, CyF-, CyL+, CyL-, is advantageously dispensed with. The detection of a permanently present insulation fault, i.e.a low insulation resistance and not, for example, a defective protective sheath of a high-voltage cable, is advantageously detected by another device, for example by an insulation monitor and / or by measuring a high-voltage potential distribution, which is not part of the protective device 8 described here and its protective circuit 9 and is also not connected to it. As mentioned, the protective device 8 described here and its protective circuit 9 are capable of repeatedly triggering at very short intervals and thus even in the event of rapidly recurring contact by a person, thus ensuring protection for the person. Accidental triggering, for example due to an EMC disturbance, does not lead to further measures in the vehicle 2, such as an incorrect shutdown of the high-voltage system.Due to the autonomous function of the protective device 8, in particular of its protective circuit 9, a flexible and simple integration into an existing high-voltage system is possible.

[0172] The autonomous function also reduces the safety requirements for the protective device 8 and its protective circuit 9, for example, there is no longer any need for a secured function / communication to another control unit.

[0173] The protective device 8 can also be used in a direct current network 1 without the direct current charging station 5, in particular for driving the vehicle 2, for alternating current charging, and for assembly and service work. The only difference compared to direct current charging is that the direct current charging station 5 is missing. Possible failure mechanisms include, for example, a defective high-voltage cable or a defective housing of a high-voltage electronics unit as a result of an accident. Even if the high-voltage system is damaged during assembly or service, the protective device 8, with its protective circuit 9, can reduce the charge quantity.

[0174] The protective circuit 9 for reducing the Y-voltage surge caused by an insulation fault IF remains identical to that described above. For this purpose, the protective device 8 with its protective circuit 9 is naturally located in vehicle 2. Its function is identical to that described above for the insulation fault during DC charging. Upon detection of a voltage reduction between one of the high-voltage potentials HV+, HV- and the reference potential M, the respective protective capacitor Cs, Cs1, Cs2 is switched on, and the total capacitance of the Y-capacitors CyF+, CyF-, CyL+, CyL- of the affected high-voltage potential HV+, HV- is discharged. For example, it is also possible to command the opening of the main contactors HS+, HS- of the high-voltage battery 6, and initiate an active discharge of the X-capacitor Cx and both Y-capacitors CyF+, CyF- of vehicle 2. The charging contactors LS+, LS- are already open and always remain open.

[0175] Figure 6shows the component-optimized protective circuit 9. In the protective circuit 9 for reducing a Cy shock, it can be assumed that only one high-voltage potential HV+, HV- is connected to the reference potential M, for example, the housing ground, via the body resistance RK. If both high-voltage potentials HV+, HV- were connected to the reference potential M, in particular the housing ground, this would amount to a short circuit in the high-voltage battery 6 or DC charging station 5, which must be interrupted by a fuse or a current sensor with a shutdown device controlled by it.

[0176] This clearly shows that the protective circuit 9 for reducing a Cy surge for the positive potential HV+ and the negative potential HV- is never used at the same time. Therefore, a single protective capacitor Cs, discharge resistor Re, protective resistor Rs, rapid discharge resistor Rse, and rapid discharge switch Se can be used to protect both high-voltage potentials HV+ and HV-, as shown in Figure 6 shown. Therefore, two protective circuit sections 9.1, 9.2 are no longer required. The voltage measurements using the two voltage measuring devices SV1, SV2 and the two circuit breakers SS1, SS2 for connecting the protective circuit 9 must remain in place. Figure 6shows such a component optimization. This is useful if the discharge resistance Re also needs to assume larger component values ​​due, for example, to high operating voltages or large capacitances of the Y capacitors CyF+, CyF-, CyL+, CyL- in vehicle 2 and the DC charging station 5.

[0177] Figure 6 also shows an embodiment of the entire protective device 8 with this component-optimized protective circuit 9, i.e., without the two protective circuit parts 9.1, 9.2. The protective device 8, in particular its protective circuit 9, is reduced here to the necessary additional effort that must be integrated in the vehicle 2 or at the DC charging station 5.

[0178] Connections AHV+, AHV-, AM to the positive potential HV+, negative potential HV-, and reference potential M can be kept very small, since a current only flows in the millisecond range in the event of a fault. Otherwise, the connections AHV+, AHV-, AM are de-energized and serve only for voltage measurement. This means that the protective device 8 with its protective circuit 9 can be quickly integrated into an existing high-voltage system with minimal modifications. If more planning time is available, this function can of course also be integrated into an existing device.

[0179] The protective circuit 9 thus comprises, as in Figure 6shown, an electrical series connection of the electrical protective capacitor Cs, the electrical protective resistor Rs and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML and an electrical series connection of the electrical protective capacitor Cs, the electrical protective resistor Rs and the second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein the electrical discharge resistor Re is electrically connected in parallel to the protective capacitor Cs and protective resistor Rs and an electrical series connection of the electrical rapid discharge resistor Rse and the rapid discharge switch Se is electrically connected in parallel to the protective capacitor Cs or to the protective capacitor Cs and protective resistor Rs.

[0180] In a method for operating the protective device 8, the first protective switch SS1 or the second protective switch SS2 is closed when the triggering criteria occur and opened again after the protective capacitor Cs has been charged, and then the rapid discharge switch Se is closed and opened again after the protective capacitor Cs has been discharged.

[0181] In an alternative embodiment, the protection circuit 9 comprises, as in Figure 5shown, two protective circuit parts 9.1, 9.2. The first protective circuit part 9.1 comprises an electrical series connection of the first electrical protective capacitor Cs1, the first electrical protective resistor Rs1, and the first protective switch SS1 between the positive potential line HV+L and the reference potential line ML, wherein a first electrical discharge resistor Re1 is electrically connected in parallel to the first protective capacitor Cs1 and the first protective resistor Rs1, and an electrical series connection comprising a first electrical rapid discharge resistor Rse1 and a first rapid discharge switch Se1 is electrically connected in parallel to the first protective capacitor Cs1 or to the first protective capacitor Cs1 and the first protective resistor Rs1. The second protective circuit part 9.2 comprises an electrical series circuit of a second electrical protective capacitor Cs2, a second electrical protective resistor Rs2 and a second protective switch SS2 between the negative potential line HV-L and the reference potential line ML, wherein a second electrical discharge resistor Re2 is electrically connected in parallel to the second protective capacitor Cs2 and the second protective resistor Rs2 and an electrical series circuit of a second electrical rapid discharge resistor Rse2 and a second rapid discharge switch Se2 is electrically connected in parallel to the second protective capacitor Cs2 or to the second protective capacitor Cs2 and the second protective resistor Rs2.

[0182] In the method for operating the protective device 8, the first protective switch SS1 is then closed when the triggering criteria occur and opened again after the first protective capacitor Cs1 has been charged, and then the first rapid discharge switch Se1 is closed and opened again after the first protective capacitor Cs1 has been discharged, and / or the second protective switch SS2 is closed when the triggering criteria occur and opened again after the second protective capacitor Cs2 has been charged, and then the second rapid discharge switch Se2 is closed and opened again after the second protective capacitor Cs2 has been discharged.

[0183] Advantageous applications of the protective device 8 are described below. In vehicles 2 with a high-voltage system at the 800 V level, it becomes difficult to comply with the standardized discharge limits for Y capacitors CyF+, CyF-, CyL+, CyL-. This applies particularly to existing vehicles 2, which, due to the already occupied installation space in the vehicle 2, do not allow for adaptations to the high-voltage system for large additional components. The described solution is ideal here because it is simple, cost-effective, and requires minimal installation space in the vehicle 2.

[0184] Furthermore, the described solution complies with regulations, particularly those contained in standards, thereby facilitating or even enabling the approval of vehicle 2. This protective device 8 and its protective circuit 9 allow the limit values ​​to be met by adding a small electronic component, without requiring any modifications to the high-voltage system and its components.

[0185] The maximum energy content of 0.2 J required by LV123 is already exceeded at 632 V by DC charging station 5. "Alternative measures" are therefore absolutely necessary. Double insulation is currently being discussed as the only solution. All coupled systems, i.e., vehicle 2 and DC charging station 5, would then have to have reinforced insulation at the same time, which cannot currently be guaranteed. However, the protective device 8 and its protective circuit 9 can also keep the energy flowing through the human body MK to a value below 0.2 J. It thus represents another solution for "alternative measures."

[0186] The protective device 8 and its protective circuit 9 make it possible to reduce the dangerous discharge current of the Y capacitors CyF+, CyF-, CyL+, CyL- upon human contact in the event of damaged insulation during DC charging, for example, due to a damaged charging plug or charging cable 4. In all other vehicle states, the dangerous discharge current is also reduced upon human contact in the event of damaged insulation.

[0187] Improved EMC suppression is possible by enlarging the Y capacitors CyF+, CyF-, CyL+, and CyL-. This eliminates the requirement for double insulation of the entire high-voltage system. This applies to vehicle 2 and DC charging station 5.

[0188] The protective device 8 with its protective circuit 9 can be arranged in the vehicle 2 and / or in the DC charging station 5. List of reference symbols

[0189] 1 DC network 2 Vehicle 3 High-voltage electrical system 4 Charging cable 5 DC charging station 6 High-voltage battery 7 Battery energy source 8 Protection device 9 Protection circuit 9.1, 9.2 Protection circuit section 12 Voltage evaluation unit 13 Charging station voltage source AHV+, AHV-, AM connection AK+, AK connection contact Cs, Cs1, Cs2 Protection capacitor CxX capacitor CyF+, CyF-Y capacitor vehicle CyL+, CyL-Y capacitor DC charging station HS+, HS main contactor HV+, HV high-voltage potential HV+L, HV-L High-voltage potential line IFI Insulation fault LS+, LS charging contactor M Reference potential ML Reference potential line MK Human body R Batt Battery internal resistance R, R1, R2 Resistance Re, Re1, Re2 Discharge resistance RK Body resistance R LS Charging station internal resistance Rs, Rs1, Rs2 Protection resistance Rse, Rse1, Rse2 Rapid discharge resistance Se, Se1, Se2 Rapid discharge switch SS1, SS2 Circuit breaker SV1, SV2 Voltage measuring device

Claims

1. Safety device (8) for an electric DC grid (1), comprising - a first voltage measuring device (SV1) between a positive potential line (HV+L) and a reference potential line (ML) for measuring a voltage between the positive potential line (HV+L) and the reference potential line (ML), and - a second voltage measuring device (SV2) between a negative potential line (HV-L) and the reference potential line (ML) for measuring a voltage between the negative potential line (HV-L) and the reference potential line (ML), and - a protective circuit (9) for reducing an electric shock caused by Y capacitors of the electric DC grid (1), wherein the protective circuit (9) comprises a first circuit breaker (SS1) between the positive potential line (HV+L) and the reference potential line (ML), and a second circuit breaker (SS2) between the negative potential line (HV-L) and the reference potential line (ML), - wherein a plurality of triggering criteria are specified and the first circuit breaker (SS1) and / or the second circuit breaker (SS2) can be actuated so as to close exclusively in the event of all predefined triggering criteria being met, as determined by means of the first voltage measuring device (SV1) and / or by means of the second voltage measuring device (SV2), characterized in that the triggering criteria include: - a voltage deviation of a voltage currently applied between the positive potential line (HV+L) and the reference potential line (ML) and a voltage applied between the negative potential line (HV-L) and the reference potential line (ML) from a previously determined voltage value, - a voltage change in the voltage applied between the positive potential line (HV+L) and the reference potential line (ML) and the voltage applied between the negative potential line (HV-L) and the reference potential line (ML), - an opposite sign of the voltage applied between the positive potential line (HV+L) and the reference potential line (ML) and the voltage applied between the negative potential line (HV-L) and the reference potential line (ML), and - a lack of cyclical repetition of the other triggering criteria, the first circuit breaker (SS1) and / or the second circuit breaker (SS2) only being actuatable if - the voltage deviation of the voltage currently applied between the positive potential line (HV+L) and the reference potential line (ML) and the voltage applied between the negative potential line (HV-L) and the reference potential line (ML) from the previously determined voltage value exceeds a predefined limit value, and - the voltage change of the voltage applied between the positive potential line (HV+L) and the reference potential line (ML) and the voltage applied between the negative potential line (HV-L) and the reference potential line (ML) exceeds a predefined limit value, and - the opposite sign of the voltage applied between the positive potential line (HV+L) and the reference potential line (ML) and the voltage applied between the negative potential line (HV-L) and the reference potential line (ML) is present, and if, in addition, the lack of cyclical repetition of the other triggering criteria is determined.

2. Safety device (8) according to claim 1, characterized in that an analog and / or digital evaluation of the voltage determined by means of the first voltage measuring device (SV1) and / or by means of the second voltage measuring device (SV2) is provided.

3. Safety device (8) according to either claim 1 or claim 2, characterized in that a common voltage evaluation unit (12) coupled to the voltage measuring devices (SV1, SV2) and the circuit breakers (SS1, SS2) is provided for evaluating the voltage determined by the first voltage measuring device (SV1) and the voltage determined by the second voltage measuring device (SV2) and for actuating the first circuit breaker (SS1) and / or the second circuit breaker (SS2) exclusively in the event of all predefined triggering criteria being met, as determined by means of the first voltage measuring device (SV1) and / or by means of the second voltage measuring device (SV2).

4. Safety device (8) according to any of the preceding claims, characterized in that the relevant circuit breaker (SS1, SS2) is designed as a semiconductor switch.

5. On-board network (3), in particular a high-voltage on-board network (3), for a vehicle (2), comprising a safety device (8) according to any of the preceding claims.

6. Vehicle (2), in particular an electric vehicle or hybrid vehicle, comprising an on-board network (3) according to claim 5.

7. DC charging station (5), in particular a high-voltage DC charging station, comprising a safety device (8) according to any of claims 1 to 4.