Overvoltage protection for current collectors

Abstract

This invention relates to an overvoltage protection circuit (20) for a current collector (3) in an electrically driven vehicle (6). The overvoltage protection circuit (20) includes a first overvoltage protection device (1a) located between the positive contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3). The first overvoltage protection device (1a) is configured to monitor the voltage (U1) between the positive contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3), detect overvoltage, and limit the overvoltage by reducing the resistance of the first overvoltage protection device (1a) when an overvoltage occurs. The overvoltage protection circuit (20) also includes a second overvoltage protection device (1b) located between the negative contact (VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3). The second overvoltage protection device (1b) is configured to monitor the voltage (U2) between the negative contact (VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3), detect overvoltage, and limit the overvoltage by reducing the resistance of the second overvoltage protection device (1b) when an overvoltage occurs. A current collector (3) is also described. An electrically driven vehicle (6) is also described. In addition, a method for reducing overvoltage using an overvoltage protection circuit (20) is given.

Description

[0001] This invention relates to an overvoltage protection circuit for a current collector. It also relates to a current collector. Furthermore, this invention relates to an electrically driven vehicle. Additionally, this invention relates to a method for reducing overvoltage through an overvoltage protection circuit.

[0002] Current collectors used in vehicles, especially road vehicles that draw DC power from overhead lines, are typically double-insulated for electrical safety reasons. For double insulation, the current collector has three distinct sections, also called "layers," which are electrically insulated from each other. The first layer, also known as the traction voltage layer, can contact the overhead line and is at the overhead line's potential. The second layer, also known as the intermediate layer, lies between the traction voltage layer and the third layer. The third layer, also known as the chassis layer, is electrically connected to the vehicle chassis. The arrangement of the intermediate layer ensures that it is inaccessible to personnel during normal operation.

[0003] In conventional electrically driven vehicles, an overvoltage discharger is installed in the current collector between the positive and negative potentials of the traction voltage from the overhead line. This discharger protects the cables, current collector, and vehicle components from overvoltage. Previously, one of the two contact wires, typically the one with the "negative" potential, was grounded. However, there is currently a pursuit of designing the overhead line voltage to be "symmetrical," where the two contact wires of the overhead line should have positive and negative voltages relative to their common grounding point.

[0004] However, if an overvoltage occurs in the overhead line, for example, caused by lightning, the overvoltage may break down between the two contact wires of different polarities and the chassis layer of the vehicle, because the vehicle is not adequately insulated relative to the ground.

[0005] Therefore, components of vehicles using overhead lines must be protected from overvoltages originating from the overhead lines. Because of the impedance of the overhead lines, even with overvoltage limiting measures in the infrastructure, overvoltages that are not limited to the required level can still occur on the vehicle.

[0006] Therefore, the technical problem to be solved by the present invention is to provide overvoltage protection for the current collector of an electrically driven vehicle that is supplied with DC power by an overhead line, especially an overhead line with a symmetrically distributed potential contact wire, through a current collector.

[0007] The technical problem is solved by the overvoltage protection circuit for a current collector according to claim 1, the current collector according to claim 6, the electrically driven vehicle according to claim 8, and the method for reducing overvoltage by means of an overvoltage protection circuit according to claim 9.

[0008] The overvoltage protection circuit of the current collector for an electrically driven vehicle according to the present invention has a first overvoltage protection device, preferably a first overvoltage discharger, between the positive contact of the current collector and the intermediate layer of the current collector, and a second overvoltage protection device, preferably a second overvoltage discharger, between the negative contact of the current collector and the intermediate layer of the current collector.

[0009] The current collector has a traction voltage layer that is in electrical contact with the voltage of the overhead line. The traction voltage layer extends to power electronics connected downstream of the current collector, which adapts the voltage on the current collector, preferably low voltage (voltage class B), to a vehicle-specific traction voltage.

[0010] Overvoltage protection devices are used to protect electronic circuits or equipment from current surges and transient voltages. The overvoltage protection device is connected in parallel with the power supply circuit of the load to be protected. This overvoltage protection device changes its resistance according to the applied voltage. In particular, the resistance decreases when the applied voltage increases, or more precisely, approaches or exceeds a predetermined threshold corresponding to the overvoltage. The overvoltage protection device preferably includes a so-called overvoltage discharger, which is a semiconductor element, preferably a semiconductor switch, having a resistance that varies with the applied voltage. The semiconductor element may include a characteristic curve showing the continuous change of resistance with the applied voltage, or it may include a semiconductor switch exhibiting normal switching characteristics between two different resistance values ​​with the applied voltage. The overvoltage protection device may also include a spark gap that becomes conductive at a so-called breakdown voltage.

[0011] As previously mentioned, the intermediate layer is electrically insulated from the traction voltage layer, particularly including the contacts of the current collector. The intermediate layer is arranged so that it is inaccessible to personnel during normal operation. By installing two overvoltage protection devices between the two different potentials of the overhead line contacts and the intermediate layer, overvoltages that may occur between the contacts with positive potentials and the intermediate layer, as well as overvoltages that may occur between the contacts with negative potentials, can be discharged.

[0012] To this end, a first overvoltage protection device is configured to monitor the voltage between the positive contact of the current collector and the intermediate layer of the current collector, detect overvoltage, and reduce its resistance or preferably conduct when an overvoltage occurs, thereby limiting the overvoltage. Furthermore, a second overvoltage protection device is configured to monitor the voltage between the negative contact of the current collector and the intermediate layer of the current collector, detect overvoltage, and reduce its resistance or preferably conduct when an overvoltage occurs, thereby limiting the overvoltage.

[0013] The intermediate layer forms a ground wire between different potentials, which is insulated relative to the traction voltage layer and the chassis layer. The first and second overvoltage protection devices preferably include the aforementioned overvoltage dischargers (or surge arresters or lightning arresters). These overvoltage dischargers contain elements whose resistance varies with the applied voltage. Preferably, such overvoltage dischargers include switches, particularly preferably semiconductor switches, configured to block during normal operation and conduct when an overvoltage occurs, to eliminate the overvoltage toward the intermediate layer. The overvoltage protection devices preferably have dimensions such that the voltage applied thereto is limited to a predetermined value. During normal operation, the overvoltage protection devices are high-resistance, and in the conducting state, they are low-resistance. In the conducting state, the overvoltage protection devices form an electrical connection between the traction voltage layer and the intermediate layer. Advantageously, overvoltages can be limited or avoided not only between the contacts of the current collector but also between the contacts of the current collector and the intermediate layer. This is particularly necessary when using two ungrounded contact wires with positive or negative potentials relative to ground.

[0014] The current collector according to the invention comprises: a traction voltage layer at the potential of the overhead line for receiving electrical energy from the overhead line; a chassis layer at the potential of the chassis of an electrically driven vehicle containing the current collector; an intermediate layer located between the traction voltage layer and the chassis layer; and an overvoltage protection circuit according to the invention located at least between the traction voltage layer and the intermediate layer. The current collector according to the invention has the advantage of the overvoltage protection circuit according to the invention.

[0015] The electric vehicle according to the invention has a current collector according to the invention for receiving electrical energy from an overhead line. Furthermore, the electric vehicle according to the invention includes power electronics for converting the voltage applied to the current collector into the operating voltage or traction voltage of the vehicle's electric traction unit, which also has such an electric traction unit to drive the vehicle. The electric vehicle according to the invention has the advantages of the current collector according to the invention.

[0016] In the method for reducing overvoltage according to the invention using an overvoltage protection circuit, the voltage between the positive contact of the current collector and the intermediate layer of the current collector in an electrically driven vehicle equipped with the overvoltage protection circuit according to the invention is monitored. Furthermore, if the monitored voltage exceeds a first predetermined threshold, an overvoltage is detected based on the monitored voltage. Moreover, when such an overvoltage occurs, the overvoltage is limited by reducing the resistance of a first overvoltage protection device of the overvoltage protection circuit according to the invention between the positive contact of the current collector and the intermediate layer of the current collector. The reduction depends on the voltage between the positive contact of the current collector and the intermediate layer of the current collector, or, if the first overvoltage protection device has a switching function, it turns on when the first predetermined threshold is reached, thereby eliminating the overvoltage by allowing current to flow through the first overvoltage device.

[0017] In addition, the voltage between the negative contact of the current collector and the intermediate layer of the current collector is monitored. If the monitored voltage exceeds a second predetermined threshold, an overvoltage is detected between the negative contact of the current collector and the intermediate layer based on the monitored voltage. When such an overvoltage occurs, the overvoltage between the negative contact of the current collector and the intermediate layer of the current collector is limited by reducing the resistance of a second overvoltage protection device.

[0018] Therefore, the resistance of the second overvoltage protection device between the negative contact of the current collector and the intermediate layer of the current collector varies according to the voltage between the negative contact of the current collector and the intermediate layer of the current collector, or if the second overvoltage protection device has a switching function, the overvoltage protection device is turned on, thereby eliminating the overvoltage by allowing current to flow through the second overvoltage device.

[0019] Advantageously, the method according to the invention allows overvoltages that may occur between a contact with a positive potential and the intermediate layer, as well as overvoltages that may occur between a contact with a negative potential and the intermediate layer, to be discharged via the intermediate layer forming the intermediate ground wire through the resistance reduction of the first and second overvoltage protection devices. This is particularly necessary when using two ungrounded contact wires having a positive or negative potential relative to ground.

[0020] A portion of the previously mentioned components of the overvoltage protection circuit according to the invention can be implemented, wholly or partially, as software modules in the processor of a corresponding computing system, such as by the control unit of an electrically driven vehicle or an existing computing system. The advantage of largely implementing it in software is that computing systems currently in use can also be easily retrofitted via software upgrades to operate in accordance with the invention.

[0021] In this regard, the aforementioned technical problem is also solved by a corresponding computer program product having a computer program that can be directly loaded into the computing system of an electrically driven vehicle and having program segments to execute the steps of the method according to the invention when the program runs in the computing system. Advantageously, the threshold values ​​of the components of the overvoltage protection circuit, especially the threshold values ​​of the overvoltage protection device or the insulation monitoring device described below, can be adapted to variable boundary conditions, for example, through targeted control. For example, the permissible voltage value may depend on and vary depending on the voltage applied to the overhead line. Therefore, in this case, it may be meaningful to adjust the switching characteristics or characteristic curve of the overvoltage protection device by changing the control voltage of an additional external control. For overvoltage devices with alarm contacts or insulation monitoring devices, the status of the overvoltage device can be read and analyzed by the control system. Furthermore, with such a computer program, information regarding the type of fault, especially of the overvoltage device, and the identity of the faulty component can be determined and automatically transmitted to other technical components or technicians when necessary. Based on this information, protective measures can be advantageously taken automatically or manually, such as removing the current collector or shutting down the electrically driven vehicle or performing maintenance, to avoid or eliminate the danger caused by the overvoltage protection circuit failure. Such computer program products may include, in addition to the computer program, additional components, such as documentation, and / or additional components, as well as hardware components, such as hardware keys (dongles, etc.) for using the software.

[0022] For transmission to and / or storage on or within a computing system, a computer-readable medium, such as a memory stick, hard disk, or other portable or fixed-mount data carrier, may be used, on which program segments of a computer program readable and executable by the computing system are stored. The computing system may, for example, have one or more cooperating microprocessors.

[0023] The dependent claims and the following description each contain particularly advantageous embodiments and improvements. A claim of one claim class can also be further improved in a manner similar to a dependent claim of another claim class and its description. Furthermore, within the scope of this invention, different embodiments and different features of the claims can be combined to form new embodiments.

[0024] Preferably, the overvoltage protection circuit according to the invention includes a third overvoltage protection device between the intermediate layer and the chassis layer of the vehicle. This third overvoltage protection device is configured to monitor the voltage between the intermediate layer and the chassis layer of the current collector, detect overvoltage, and reduce its resistance or even conduct when an overvoltage occurs, thereby limiting the overvoltage. The third overvoltage protection device preferably has dimensions such that the voltage between the intermediate layer and the chassis layer is limited to a predetermined value. Advantageously, overvoltage protection is established between the intermediate layer and the chassis layer, and in combination with the first and second overvoltage protection devices, overvoltage protection is established between the traction voltage layer and the chassis layer.

[0025] Particularly preferably, the overvoltage protection circuit according to the invention includes a first insulation monitoring device configured to monitor the insulation resistance between the contacts of the current collector and the intermediate layer. Monitoring the insulation resistance enables the identification of a single fault in the overvoltage device that leads to low resistance. This single fault may occur due to manufacturing defects or lightning strikes. The first insulation monitoring device is particularly designed to monitor the functionality of both the first and second overvoltage protection devices during normal operation.

[0026] Particularly preferably, the overvoltage protection circuit according to the invention includes a second insulation monitoring device configured to monitor the insulation resistance between the intermediate layer and the chassis layer. The second insulation monitoring device is particularly designed to monitor the functionality of a third overvoltage protection device during normal operation. Advantageously, by monitoring the insulation resistance, dangerous voltages at the vehicle chassis can be prevented during normal operation.

[0027] If the overvoltage protection device becomes low-resistance due to a fault in the absence of overvoltage, the special arrangement of the overvoltage protection device and the insulation monitoring device ensure that there is no dangerous contact voltage at the vehicle chassis, and the fault can be detected by the insulation monitoring device. The current collector and the relevant vehicle can then immediately enter a safe state through control.

[0028] In a variation of the overvoltage protection circuit according to the invention, the first and / or second insulation monitoring devices are configured to output a fault report if the insulation resistance is determined to be below a predetermined minimum value when monitoring the corresponding insulation resistance. Advantageously, the operator receives a warning about a single fault. On the one hand, the operator can avoid contact with potentially live parts, and on the other hand, the faulty overvoltage protection device can be identified and replaced with the corresponding intact component. Furthermore, upon receiving such a fault report, the entire system can enter a safe state. In particular, the current collector can be disconnected from the overhead line to avoid dangerous contact voltages during overvoltage protection device failures.

[0029] In a variation of the method according to the invention for reducing overvoltage via an overvoltage protection circuit, the voltage between the intermediate layer and the chassis layer of the current collector is monitored. Furthermore, if the monitored voltage exceeds a third predetermined threshold, an overvoltage is detected based on the monitored voltage. Finally, in the event of an overvoltage, the overvoltage is limited between the intermediate layer and the chassis layer of the current collector by reducing the resistance or even turning on a third overvoltage protection device. Advantageously, overvoltage protection is established between the intermediate layer and the chassis layer, and overvoltage protection is established between the traction voltage layer and the chassis layer in combination with the first and second overvoltage devices.

[0030] To identify overvoltage protection device malfunctions or monitor their functionality, it is preferable to monitor the insulation resistance between the current collector contacts and the intermediate layer using a first insulation monitoring device. Similarly, it is preferable to monitor the insulation resistance between the intermediate layer and the chassis layer using a second insulation monitoring device. Advantageously, this allows for timely identification of overvoltage protection device malfunctions that could lead to dangerous voltages on the chassis, and enables the implementation of countermeasures such as decommissioning or maintenance.

[0031] When overvoltage occurs and the device responds correctly, the resistance-time characteristic of the overvoltage protection device differs from the resistance-time characteristic of the insulation resistance during a fault. Therefore, based on this difference in characteristics, insulation monitoring devices can distinguish between the correct functioning of the overvoltage protection device and the insulation resistance during a fault.

[0032] To inform operators or maintenance personnel of faults in the overvoltage protection device and to identify the faulty overvoltage discharger, it is preferable to output a fault report when the insulation resistance of the overvoltage protection device remains below a predetermined minimum value. The fault report preferably includes information for identifying the faulty component, and particularly preferably includes an automatic control command to disconnect the vehicle's current collector from the overhead line to prevent dangerous voltage at the chassis. Furthermore, it is preferable to prevent the current collector from re-establishing contact with the overhead line to avoid harm to the vehicle's operators or maintenance personnel.

[0033] The invention will now be described in detail again with reference to the accompanying drawings and embodiments. In the drawings:

[0034] Figure 1 A schematic diagram of a conventional overvoltage protection circuit for a current collector is shown.

[0035] Figure 2 A schematic diagram of an overvoltage protection circuit for a current collector according to an embodiment of the present invention is shown.

[0036] Figure 3 A flowchart illustrating a method for reducing overvoltage according to an embodiment of the present invention is shown.

[0037] Figure 4A schematic diagram of a current collector having an overvoltage protection circuit according to an embodiment of the present invention is shown.

[0038] Figure 5 An electrically driven vehicle having a current collector according to an embodiment of the present invention is shown.

[0039] Figure 1 A conventional overvoltage protection circuit 10 for a current collector in an electrically driven vehicle is shown. This overvoltage protection circuit 10 is designed for use on a grounded overhead line that provides a DC voltage. The overvoltage protection circuit 10 is connected between the positive terminal VCL+ and the negative terminal VCL- of the current collector. It is possible that... Figure 1 The upper part, represented by horizontal lines, shows the traction voltage layer TL and the ground layer, i.e., the intermediate layer IL (not shown), and... Figure 1 The overvoltage between the chassis layers CL, represented by the horizontal line in the lower part, is not limited in the current collector and must therefore be taken into account in the vehicle design. Figure 1 The overvoltage protection circuit 10 shown includes two fuses 1 connected in series between the current collector terminals VCL+ and VCL-, with an overvoltage discharger 2 connected between the fuses. The overvoltage discharger 2 can discharge any overvoltage occurring between the current collector terminals VCL+ and VCL- to the grounded negative terminal VCL-. The overvoltage discharger 2 has high resistance during normal operation and switches to a low-resistance state when an overvoltage occurs.

[0040] Figure 2 An overvoltage protection circuit 20 for a current collector of an electrically driven vehicle according to an embodiment of the present invention is shown. Figure 2 The overvoltage protection circuit 20 shown in the figure is... Figure 1 The conventional arrangement shown in the figure also includes two fuses 1 connected between the two poles VCL+ and VCL- of the current collector. Figure 2 The overvoltage protection circuit 20 shown in the figure is... Figure 1 The difference between the conventional overvoltage protection circuit 10 shown is that the positive terminal VCL+ and the negative terminal VCL- of the current collector are connected to the... Figure 2 The middle layer IL of the current collector, indicated by a horizontal line, is provided with first and second overvoltage dischargers 1a and 1b. A third overvoltage discharger 2 is connected between the middle layer IL of the current collector and the... Figure 2The current collectors are located between the chassis layers CL, indicated by horizontal lines at the bottom. Therefore, the voltages between the traction voltage layer TL and the intermediate layer IL, and between the intermediate layer IL and the chassis layer CL, are limited by overvoltage dischargers 1a, 1b, and 2, respectively. Overvoltage protection between the positive terminal VCL+ and the negative terminal VCL- of the current collector is achieved through the series connection of the first and second overvoltage dischargers 1a and 1b. Overvoltage protection between the intermediate layer IL and the chassis layer CL is achieved through the series connection of the first and third overvoltage dischargers 1a and 2, and the series connection of the second and third overvoltage dischargers 1b and 2.

[0041] Overvoltage dischargers 1a, 1b, and 2 are sized such that the voltage between the three layers TL, IL, and CL is limited to a fixed value. This provides a certain degree of overvoltage protection for the electrical components in the vehicle. During normal operation, all overvoltage dischargers 1a, 1b, and 2 are high-resistance. However, if an overvoltage occurs, the overvoltage dischargers 1a, 1b, and 2 become low-resistance, thereby limiting the overvoltage.

[0042] Figure 2 The arrangement of overvoltage dischargers 1a, 1b, and 2 shown is monitored by insulation monitoring devices IMD1 and IMD2. The first insulation monitoring device IMD1 monitors the insulation resistance between the traction voltage layer TL and the intermediate layer IL, while the second insulation monitoring device IMD2 monitors the insulation resistance between the intermediate layer IL and the chassis layer CL. If, during normal operation, the resistance value of one of the insulation devices falls below a predetermined value, this resistance value is measured by one of the insulation monitoring devices IMD1 or IMD2, and the fault condition is reported.

[0043] Figure 3 A flowchart 300 is shown, illustrating a method for reducing overvoltage using an overvoltage protection circuit 20 according to an embodiment of the present invention.

[0044] In step 3.I, the voltage U1 between the positive contact VCL+ and the intermediate layer IL of the current collector is monitored by the first overvoltage discharger 1a of the overvoltage protection circuit 20, which is located between the positive contact VCL+ of the current collector and the intermediate layer IL of the current collector.

[0045] In step 3.II, it is checked whether there is an overvoltage exceeding a first predetermined threshold SW1 on the first overvoltage discharger 1a. If the first predetermined threshold SW1 is exceeded, this... Figure 3If "y" is used to represent this, then proceed to step 3.III. In step 3.III, the resistance of the first overvoltage protection device 1a decreases with the height of the overvoltage, and the first overvoltage discharger 1a thereby discharges the overvoltage appearing between the traction voltage layer TL and the intermediate layer IL. If the first predetermined threshold SW1 is not exceeded, this... Figure 3 If "n" is used to represent the value, then return to step 3.I and continue monitoring.

[0046] In step 3.IV, the voltage U2 between the negative contact VCL- and the intermediate layer IL of the current collector is monitored by the second overvoltage discharger 1b of the overvoltage protection circuit 20, which is located between the negative contact VCL- of the current collector and the intermediate layer IL of the current collector.

[0047] In step 3.V, it is checked whether there is an overvoltage exceeding the second predetermined threshold SW2 at the second overvoltage discharger 1b. If the second predetermined threshold SW2 is exceeded, this... Figure 3 If "y" is used to represent this, then proceed to step 3.VI. In step 3.VI, the resistance of the second overvoltage discharger 1b decreases with the height of the overvoltage, and the second overvoltage discharger 1b thereby discharges the overvoltage appearing between the traction voltage layer TL and the intermediate layer IL. If the second predetermined threshold SW2 is not exceeded, this... Figure 3 If "n" is used to represent the value, then return to step 3.IV and continue monitoring.

[0048] In step 3.VII, the voltage U3 between the intermediate layer IL and the chassis layer CL is monitored by the third overvoltage discharger 2 of the overvoltage protection circuit 20, which is located between the intermediate layer IL and the chassis layer CL of the vehicle.

[0049] In step 3.VIII, it is checked whether there is an overvoltage exceeding the third predetermined threshold SW3 at the third overvoltage discharger 2. If the third predetermined threshold SW3 is exceeded, this... Figure 3 If "y" is used to represent this, then proceed to step 3.IX. In step 3.IX, the resistance of the third overvoltage discharger 2 decreases with the height of the overvoltage, and the third overvoltage discharger 2 thereby discharges the overvoltage occurring between the intermediate layer IL and the chassis layer CL. If the third predetermined threshold SW3 is not exceeded, this... Figure 3 If "n" is used to represent the value, then return to step 3.VII and continue monitoring.

[0050] After the overvoltage protection circuit 20 returns to normal operation where there is no overvoltage at the current collector, in step 3.X, the first insulation monitoring device IMD1 checks whether the insulation resistance R-TL-IL between the traction voltage layer TL and the intermediate layer IL is lower than a first predetermined resistance threshold SWR1. If the measured insulation resistance R-TL-IL is lower than the first predetermined resistance threshold SWR1, this... Figure 3 If "y" is used to represent this, then proceed to step 3.XI and output the first fault report FM1. This fault report notifies that the insulation resistance R-TL-IL between the traction voltage layer TL and the intermediate layer IL is too low. If the measured insulation resistance R-TL-IL exceeds the first predetermined resistance threshold SWR1, this... Figure 3 If “n” is used to represent a fault, it is considered that there is no fault, and the process proceeds to steps 3.I and 3.IV, and continues to monitor the system through the first and second overvoltage dischargers 1 and 2.

[0051] In step 3.XII, also during normal operation, the second insulation monitoring device IMD2 checks whether the insulation resistance R-IL-CL between the intermediate layer IL and the chassis layer CL is lower than a second predetermined resistance threshold SWR2. If the measured insulation resistance R-IL-CL is lower than the second predetermined resistance threshold SWR2, this... Figure 3 If "y" is used to indicate this, then proceed to step 3.XIII and output the second fault report FM2. This fault report notifies that the insulation resistance R-IL-CL between the intermediate layer IL and the chassis layer CL is too low. The corresponding fault reports FM1 and FM2 may also include requirements for replacing the relevant overvoltage dischargers 1a, 1b, and 2, and instructions to prevent the current collector from operating, such as a re-touch instruction, to prevent electrical hazards. If the measured insulation resistance R-IL-CL exceeds the second predetermined resistance threshold SWR2, this... Figure 3 If “n” is used to represent a fault, it is considered that there is no fault, and the process proceeds to step 3.VII, and monitoring continues through the third overvoltage discharger 2.

[0052] Figure 4 A schematic diagram of a current collector 3 having an overvoltage protection circuit 20 according to an embodiment of the present invention is shown. The current collector 3 contacts (or makes contact with) an overhead line 5, which is in... Figure 4 The upper part is shown. The current collector 3 has a traction voltage layer TL, which is in voltage electrical contact with the overhead line 5. The traction voltage layer TL extends to a power electronics 4, which is connected downstream of the current collector 3 and adapts the low voltage (voltage level B) applied to the current collector 3 to a vehicle-specific traction voltage. An intermediate layer IL, insulated from the traction voltage layer TL, surrounds the traction voltage layer TL and is separated from the chassis layer CL by an insulating layer. Figure 4The location of an overvoltage protection circuit 20 according to an embodiment of the present invention is also shown, which limits the voltage between the individual layers TL, IL, CL.

[0053] Figure 5 An electrically driven vehicle 6 is shown, having a current collector 3 according to an embodiment of the present invention. The electrically driven vehicle 6 contacts an overhead line 5 via the current collector 3 and obtains the electrical energy required for its traction from the overhead line 5. Figure 5 The current collector 3 shown has an overvoltage protection circuit 20 according to an embodiment of the present invention. If the insulation monitoring devices IMD1, IMD2 (see...) of the overvoltage protection circuit 20... Figure 2 If an insulation fault is reported in the overvoltage protection circuit 20 or a fault in the overvoltage dischargers 1a, 1b, or 2, the current collector 3 will automatically disconnect from the overhead line 5 and prevent re-contact with the overhead line to avoid harm to the operators or maintenance personnel of the vehicle 6.

[0054] Finally, it should be reiterated that the above-described methods and apparatus are merely preferred embodiments of the present invention, and those skilled in the art can make modifications to the invention without departing from the scope of the invention as defined by the claims. For completeness, it should also be noted that the use of the indefinite articles "an" or "a kind" does not preclude the possibility that the involved features may exist multiple times. Similarly, the term "unit" does not preclude that it is composed of multiple components, which may also be spatially distributed. Nouns and pronouns relating to persons in this patent application generally do not specify a particular gender.

Claims

1. An overvoltage protection circuit (20) for a current collector (3) of an electrically driven vehicle (6), the overvoltage protection circuit comprising: - A first overvoltage protection device (1a) is located between the positive contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3). The first overvoltage protection device is configured to monitor the voltage (U1) between the positive contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3), detect possible overvoltages, and limit the overvoltage by reducing the resistance of the first overvoltage protection device (1a) when an overvoltage occurs. - A second overvoltage protection device (1b) is located between the negative contact (VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3). The second overvoltage protection device is configured to monitor the voltage (U2) between the negative contact (VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3), detect possible overvoltages, and limit the overvoltages by reducing the resistance of the second overvoltage protection device (1b) when an overvoltage occurs.

2. The overvoltage protection circuit according to claim 1, wherein the overvoltage protection circuit has a third overvoltage protection device (2) located between the intermediate layer (IL) of the current collector (3) and the chassis layer (CL) of the current collector (3), the third overvoltage protection device being configured to monitor the voltage (U3) between the intermediate layer (IL) of the current collector (3) and the chassis layer (CL) of the current collector (3), detect possible overvoltage, and limit the overvoltage by reducing the resistance of the third overvoltage protection device (2) when an overvoltage occurs.

3. The overvoltage protection circuit according to claim 1 or 2, wherein the overvoltage protection circuit has a first insulation monitoring device (IMD1), the first insulation monitoring device being configured to monitor the insulation resistance between the contacts (VCL+, VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3).

4. The overvoltage protection circuit according to claim 2 or 3, wherein the overvoltage protection circuit has a second insulation monitoring device (IMD2), the second insulation monitoring device being configured to monitor the insulation resistance between the intermediate layer (IL) of the current collector (3) and the chassis layer (CL) of the current collector (3).

5. The overvoltage protection circuit according to claim 3 or 4, wherein, The first and / or second insulation monitoring devices (IMD1, IMD2) are configured to output a fault report (FM1, FM2) if the insulation resistance is determined to be lower than a predetermined minimum value (SWR1, SWR2) when monitoring the corresponding insulation resistance.

6. A current collector (3) for an electrically driven vehicle (6), the current collector comprising: - A traction voltage layer (TL) for receiving electrical energy from the overhead line (5), the traction voltage layer being at the potential of the overhead line (5), - Chassis layer (CL), the chassis layer being at the potential of the chassis of the electrically driven vehicle (6), - Intermediate layer (IL), which is located between the traction voltage layer (TL) and the chassis layer (CL). - The overvoltage protection circuit (20) according to any one of the preceding claims is located at least between the traction voltage layer (TL) and the intermediate layer (IL).

7. The current collector according to claim 6, wherein, The overvoltage protection circuit (20) is arranged between the traction voltage layer (TL) and the intermediate layer (IL) and between the intermediate layer (IL) and the chassis layer (CL).

8. An electrically driven vehicle (6) comprising: - According to claim 6 or 7, the current collector (3) is used to receive electrical energy from the overhead line (5). - Power electronics (4), which are used to convert the voltage applied to the current collector (3) into the operating voltage of the electric traction unit of the vehicle (6). - An electric traction unit for driving the vehicle (6).

9. A method for reducing overvoltage using an overvoltage protection circuit (20) according to any one of claims 1 to 5, the method comprising the following steps: - Monitor the voltage (U1) between the positive contact (VCL+) and the intermediate layer (IL) of the current collector (3). - If the monitored voltage (U1) exceeds a first predetermined threshold (SW1), an overvoltage is detected based on the monitored voltage (U1). - In the event of an overvoltage, the overvoltage is limited by reducing the resistance of the first overvoltage protection device (1a) between the positive contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3). - Monitor the voltage (U2) between the negative contact (VCL+) of the current collector (3) and the intermediate layer (IL) of the current collector (3). - If the monitored voltage (U2) exceeds the second predetermined threshold (SW2), an overvoltage is detected based on the monitored voltage (U2). - In the event of an overvoltage, the overvoltage is limited by reducing the resistance of the second overvoltage protection device (1b) between the negative contact (VCL-) of the current collector (3) and the intermediate layer (IL) of the current collector (3).

10. The method according to claim 9, wherein the method comprises the following steps: - Monitor the voltage (U3) between the intermediate layer (IL) and the chassis layer (CL) of the current collector (3). - If the monitored voltage (U3) exceeds the third predetermined threshold (SW3), an overvoltage is detected based on the monitored voltage (U3). - In the event of an overvoltage, the overvoltage is limited by reducing the resistance of the third overvoltage protection device (2) between the intermediate layer (IL) of the current collector (3) and the chassis layer (CL) of the current collector (3).

11. The method according to claim 9 or 10, wherein, The insulation resistance between the contacts (VCL+, VCL-) of the current collector (3) and the intermediate layer (IL) is monitored by the first insulation monitoring device (IMD1).

12. The method according to any one of claims 9 to 11, wherein, The insulation resistance between the intermediate layer (IL) and the chassis layer (CL) is monitored by the second insulation monitoring device (IMD2).

13. The method according to claim 11 or 12, wherein, If the insulation resistance is found to be lower than the predetermined minimum value (SWR1, SWR2) when monitoring the corresponding insulation resistance, a fault report (FM1, FM2) is output.

14. A computer program product comprising a computer program capable of being directly loaded into a storage unit of a computing system of an electrically driven vehicle according to claim 8, and having program segments for executing the method according to any one of claims 9 to 13 when the computer program is run in the computing system.

15. A computer-readable medium having stored thereon a program segment executable by a computer system so as to perform the method according to any one of claims 9 to 13 when the program segment is executed by the computer system.

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