pipeline network

Abstract

A wiring network, in particular a vehicle electrical system, comprising a DC voltage source and an electrical load connected to the DC voltage source via a supply line, wherein the supply line has multi-layer insulation with an inner insulating layer and an outer insulating layer, wherein the inner insulating layer has a lower electrical resistance than the outer insulating layer, wherein the wiring network further comprises a device for monitoring the wiring network with regard to a possible parallel arc, and the device for this purpose comprises a voltage measuring element for measuring a voltage between the supply line and a reference point, wherein a switchable resistor is arranged for voltage measurement, which is connected in series with the conductive layer.

Description

[0001] The invention relates to a wiring network, in particular an on-board network of a motor vehicle.

[0002] In conventional vehicle electrical systems, the on-board voltage is typically 14V. Due to this low voltage, arcing usually does not pose a problem. However, with the use of higher voltages in the electrical system, for example, by increasing the battery voltage to 48V or through the development of hybrid or electric vehicles with, for instance, a second voltage level within the electrical system of several hundred volts, the issue of arcing formation must be considered.

[0003] With an electrical system voltage of, for example, 48 volts, an interruption of the circuit under load can cause a (series) arc flash if the current is sufficiently high and the ambient conditions are conducive to an arc flash. This arc flash poses a fire hazard to the wiring harness and thus to the vehicle, and must therefore be prevented under all circumstances or extinguished quickly enough.

[0004] A series arc generally refers to the bridging of the conductor ends of a defective and / or interrupted line. If an arc occurs, there is also the risk that a stable operating point of the arc will be established, causing it to burn continuously. Therefore, the overall risk of fire is very high when an arc occurs.

[0005] There is the option of electronic detection or mechanical prevention.

[0006] Electronic arc flash detection devices are comparatively expensive and complex to implement, as they require modifications to the vehicle's electrical system architecture.

[0007] Mechanical preventative measures, such as a temperature-resistant protective conduit, cannot prevent an arc flash under all circumstances, but only reduce its probability of occurrence. A vehicle fire is therefore not completely ruled out. Furthermore, such protective conduits require valuable installation space and are relatively complex to manufacture, as the cables must be threaded through them. Likewise, such protective conduits are comparatively expensive.

[0008] In DE 101 49 458 C1 a method for protecting a power grid against serial arcs is described.

[0009] US 2012 / 0 234 577 A1 specifies a multilayer conductor structure to avoid the skin effect in high-frequency applications, in which individual conductor layers are separated from each other by an intermediate layer.

[0010] From DE 21 49 938 C3 a current limiter can be seen in which individual wires consist of a PTC material and are surrounded by an insulating layer.

[0011] Based on this, the invention aims to avoid arcing, and in particular the associated fire hazard, in a simple and cost-effective manner in a (direct current) power supply network, especially in a motor vehicle electrical system.

[0012] The problem is solved by claim 1 and according to the invention described below as the third aspect. Advantageous further developments of the invention result from the features of the dependent claims and, in particular, from the features listed below for the first and second aspects.

[0013] The invention provides a conductor for preventing arcing caused by series faults in the conductor, particularly at voltages above 12 volts. The conductor comprises at least one, preferably a plurality, of individual wires, preferably bundled together or stranded together, which are preferably enclosed by a common insulating sheath. The common insulating sheath is typically extruded and protects the individual wires from mechanical stresses, especially abrasion. Furthermore, the insulating sheath is responsible for dielectric strength.

[0014] The cable serves primarily to carry a supply current between, for example, the vehicle's electrical system and an electrical component. The electrical component can be any part of the vehicle that uses electrical energy to function. Generally, a component can be an actuator or a sensor, representing an electrical consumer or load.

[0015] According to the first aspect, the individual wires consist of a temperature-dependent alloy, whereby the resistance of the individual wire increases with an increasing wire temperature.

[0016] Each individual wire preferably serves as a single temperature-dependent resistor, with the individual wires being made of a special alloy possessing current-limiting properties. Such an alloy can, for example, be a combination of different materials. This material combination could, for instance, consist of semiconducting polycrystalline ceramics that, within a specific temperature range, form a barrier layer of lattice defects, thus impeding current flow. Lattice defects could, for example, be grain boundaries of a crystal lattice. This combination results in higher temperature coefficients compared to conventional metal wires.

[0017] Common metal wires can be, for example, copper or aluminum wires, which have a relatively lower temperature coefficient.

[0018] The invention has the advantage that, when the temperature rises at a conductor break, the resistances of the individual wires increase with the temperature, and this increase in turn leads to current limiting. This prevents a series arc, which can be caused by the conductor break. A break can occur, for example, due to a successive conductor failure, which can be caused, for instance, by vibrations of the conductor or other external influences. The temperature increase at the break is a measure of the proportion of undamaged individual wires. The resistance of the remaining individual wires increases more sharply the greater the number of broken individual wires.

[0019] In a training course, the individual wires are configured as PTC resistors or positive temperature coefficient (PTC) thermistors. A PTC resistor is a temperature-dependent resistor that exhibits a positive temperature coefficient. A PTC thermistor, for example, consists of a doped polycrystalline titanate ceramic. These so-called PTC thermistors have low resistance when cold and therefore exhibit good electrical conductivity. As the temperature increases, the conductivity decreases and the resistance increases.

[0020] Preferably, the supply line has a plurality of individual wires which are twisted together or otherwise connected, in particular to form a stranded conductor or other wire bundle.

[0021] According to the second aspect, which can be combined with the first but also implemented independently, each individual wire is insulated, specifically with an insulating layer. This insulating layer prevents electrical current from flowing between the individual wires. Instead, the insulation acts as a non-conductor with a very high specific electrical resistance. Due to the insulation, each wire has a defined resistance, current-carrying capacity, and / or power dissipation. Furthermore, the individual wire insulation distributes the power dissipation along the entire length of the conductor, rather than concentrating it at a single point of failure.

[0022] In a further development of the invention, the insulating layer is a coating applied to a wire surface. This insulating layer can be, for example, a synthetic resin lacquer and / or coating applied to the wire surface. Alternatively, the insulating layer can be, for example, a polymer solution that is sprayed onto the wire surface and then baked on. The insulating layer is thermally, chemically, and / or mechanically resistant. Furthermore, the insulating layer remains undamaged despite high wire temperatures and high bending rates, thus maintaining its insulating function over its entire service life, at least until a wire breakage occurs. A surface coating can be applied using a wide variety of methods.Such a coating can be applied, for example, through a painting process, an electroplating process, a hot-dip coating process, a sintering process, a chemical vapor deposition (CVD) process, a physical vapor deposition process, and / or a thermal spraying process. Other coating options are not excluded.

[0023] Preferably, the individual wires are connected in parallel. This creates the necessary conditions to prevent a series arc. The parallel connection means that if one wire fails, the total current is distributed among the remaining wires according to Kirchhoff's current law, causing a temperature increase in the individual wires and the entire cable. Due to the temperature dependence of the individual wires, the resistance of each wire increases with rising temperature. According to Ohm's law, this reduces the total current and the currents in the individual wires. As the failure rate of individual wires increases, excessive temperatures occur in the individual wires or in the individual wire itself, so that the maximum possible resistance is reached in the individual wires or in the individual wire, and consequently, the total current is reduced to a minimum.

[0024] The specific design of the supply line provides inherent protection against series arcs. Further measures for detecting or preventing (series) arcs are neither necessary nor, in particular, planned. Specifically, an evaluation circuit for detecting (series) arcs is omitted.

[0025] Preferably, the individual wires are connected between a voltage source and an electrical load. A connection between a voltage source or an electrical load and ground is also possible.

[0026] In particular, it is designed so that a complete line break under load, i.e., at the moment the circuit is disconnected under an electronic load, especially a component or assembly used as a replacement for conventional load resistors, does not result in a series arc. A complete line break is defined as the breaking of the last individual wire in the line. The current required to ignite an arc is reduced by the current-limiting properties of the individual wires to such an extent that a low current cannot produce an arc.

[0027] The line is preferably designed for a supply voltage greater than 12 volts, typically 48 volts. It can typically be assumed that an arc will only occur at a voltage of approximately 12V (between 12V and 13V for copper, and from about 10V for aluminum), depending on the material of the current-carrying conductor.

[0028] According to the third aspect of the invention, it is provided that a current-carrying supply line in operation is provided with a multi-layer insulation comprising an inner and an outer insulating layer, wherein the inner insulating layer has a certain electrical conductivity or a lower electrical resistance than the outer insulating layer.

[0029] In particular, sufficient conductivity is present so that a measuring current can flow through the inner insulation layer. For example, the inner insulation layer has a resistance that is at least 10 or at least 100 times lower than that of the outer insulation layer.

[0030] Furthermore, the inner insulation layer has an electrical resistance that is at least 10 times higher, preferably at least 100 times higher or at least 1000 times higher, than that of a conductor in the supply line.

[0031] The invention is based on the premise that a potential (parallel) arc can be detected if a fault current occurs at a defective point due to insulation damage and this current can be determined by measuring current or voltage. Such a determination can then be made, for example, by existing electronics, such as in the battery, which are used for the current or voltage measurement.

[0032] The fault current can be determined by detecting a high-resistance short circuit that occurs when the outer insulation layer is damaged and the inner insulation layer comes into contact with another potential. Damage to the outer insulation layer, for example due to mechanical or thermal influences, creates a current flow between the potential, which could be a section of the vehicle body, and the inner insulation layer. The inner insulation layer has a predefined resistance or conductivity. The damage alters the electrical conditions in the vehicle's electrical system, particularly current, voltage, and resistance, which can be detected using a suitable measurement method.

[0033] Damage to the insulating layer and the resulting short circuit are preferably diagnosed by taking a voltage measurement in a de-energized state along a damaged load path. Preferably, the voltage measurement is taken between a conductor and a ground point.

[0034] Voltage measurement is achieved by connecting an additional resistor. In the event of damage to the inner insulation layer and contact with ground potential, an additional insulation resistance is present across the inner conductive layer, which is preferably connected in series with the switchable resistor. Preferably, a resistor also known as a pull-up resistor is used. A pull-up resistor is a high-resistance resistor that, for example, connects the damaged conductor to a higher voltage potential. The series connection of the pull-up resistor briefly provides a voltage divider, enabling voltage measurement across the inner insulation layer.

[0035] Preferably, the measurement takes place before a load is connected. More precisely, the diagnosis is performed when the affected load path is de-energized, meaning both the power source (e.g., a battery) and any electrical load in the vehicle are switched off. For example, a measurement can be taken after the vehicle is unlocked, as no electrical load is yet activated at this point. Preferably, the pull-up resistor is briefly connected to the circuit under measurement by unlocking the vehicle, acting as a voltage divider and enabling a measurement of the internal insulation resistance. This brief period is preferably the time during which the measurement takes place, with the measurement duration being less than a few milliseconds.

[0036] Insulation damage can be detected, for example, by a difference in a predefined operating voltage. If the operating voltage matches the voltage identified by the voltage measurement, then a fault or insulation damage can be ruled out. However, if the measured voltage is significantly lower than the actual operating voltage, then insulation damage must be assumed.

[0037] The corresponding voltage change is advantageously used to trigger a protective measure. This protective measure includes at least a warning in the form of a signal or a reduction in current in the supply line. However, it is expedient to interrupt the connection between the supply line and the power source, and thus the current flowing through it, by a switch preferably located in the supply line itself. This switch is controlled directly by the detection current or indirectly by the voltage preferably measured at the detection line. For this purpose, a pyrotechnic disconnect switch triggered by the detection current, an electromechanical switch (e.g., a relay), or a semiconductor switch can be used, for example.

[0038] In a preferred embodiment, the pull-up resistor and the associated voltage measurement are integrated into the battery. For example, existing battery electronics used for voltage measurement can be used for this purpose. The voltage measurement can also be performed, for example, via a battery management system.

[0039] The layered structure designed to detect a potential arc flash features an outer insulating layer, which can be made of PVC or other plastics such as polyurethane or polyethylene. Other insulating materials are also conceivable, protecting the conductor from external influences, specifically from electric and / or magnetic fields. External influences can include mechanical, thermal, and / or chemical factors such as abrasion, temperature fluctuations, or high movement rates. The outer insulating layer prevents the flow of electric current. Instead, the insulation acts as a non-conductor with a very high specific electrical resistance.

[0040] The layered structure is complemented by an inner insulating layer, which has a defined resistance and electrical conductivity. The specific electrical resistance of the inner insulating layer is lower than that of the outer insulating layer, with the electrical resistance of a current-carrying conductor being lowest, preferably approaching zero. The current-carrying conductor is preferably a conductive core strand of the cable, which is encased by the inner and outer insulating layers. The inner insulating layer is preferably a conductive polymer, where a conductive polymer is a plastic with electrical conductivity. Conductive polymers can be, for example, intrinsically conductive polymers or polymers with electrically conductive fillers such as aluminum flakes, carbon black, or other conductive materials.

[0041] The conductive core strand, or wire, is preferably made of copper due to its very good electrical conductivity, or alternatively, aluminum. Furthermore, the core strand can consist of a temperature-dependent metal or alloy. For example, a temperature-dependent metal or alloy can act as a PTC thermistor.

[0042] The two insulating layers are preferably designed as an inner and an outer sheathing layer surrounding a conductor core of the supply line. The two sheathing layers are preferably applied by extrusion.

[0043] Exemplary embodiments of the invention are explained below with reference to the figures, each of which shows a highly simplified representation of a wiring network, in particular a vehicle electrical system: Fig. 1A - 1D a sequence of images on serial faults (line breakage) and the avoidance of serial arcs Fig.2A - 2D: Image sequence for parallel faults (cable insulation damage) - prevention of parallel arcs Explanation of the image sequence according to Fig. 1A-1D A (serial error) Regarding the first aspect:

[0044] Each individual wire in the cable is made of a special alloy with current-limiting properties. This means that the resistance of the individual wire increases with increasing temperature – similar to the property of a PTC element.

[0045] When conductors break down gradually (e.g., due to vibration of the cable), the temperature at the break point increases. The temperature is a measure of the proportion of individual wires that are still intact. Therefore, the resistance of the remaining individual wires increases the greater the number of broken wires.

[0046] If a complete line break ultimately occurs, no series arc can be generated when the last individual wire of the line breaks – i.e., at the moment the circuit is interrupted under load – because the current through the last individual wire is insufficient for arc ignition.

[0047] This measure prevents the occurrence of a serial arc. Regarding the second aspect:

[0048] Each individual wire within the braided conductor is insulated (e.g., lacquer-coated). Therefore, each individual wire has a defined resistance, or a defined current-carrying capacity and a defined power dissipation.

[0049] The single-wire insulation distributes the power loss over the entire length of the cable and prevents it from being concentrated at the break point. Explanation of the image sequence according to Fig. 2A-2D (parallel error): Regarding the third aspect of the invention:

[0050] The cable insulation consists of a two-layer structure. The outer insulation ensures mechanical and thermal robustness (abrasion resistance, temperature class), while the inner insulation has a defined resistance (RI) with electrical conductivity (e.g., through the addition of conductive carbon black).

[0051] If the outer insulation layer is damaged (e.g., by rubbing against a sharp edge of the vehicle body), causing the inner layer to come into contact with the body, this damage can be diagnosed by measuring the voltage UI between the conductor and ground when the affected load path is de-energized and both the power source and the load are switched off (e.g., when unlocking or locking the doors). For this purpose, a voltage divider is activated, for example, by connecting a pull-up resistor RP for the duration of the measurement. This voltage measurement can be performed centrally, for example, via the battery management system. Preferably, the pull-up resistor and the associated voltage measurement should be integrated into the battery. The reason for this is the existing electronics in the battery (e.g., a 48-volt battery) that can be used for voltage measurement.

[0052] If the measured voltage UI is equal to the battery voltage (e.g., 48 volts), there is no fault. If the measured voltage UI is significantly lower than the battery voltage (e.g., 10 volts), the cable insulation is damaged. In this case, a warning will be triggered, and the 48-volt system may be shut down.

[0053] This measure prevents the occurrence of a parallel arc.

[0054] Overall, the measures described here will achieve the following advantages: • # Suppression of a serial arc in the event of a line break is possible and provided for without any electronics. • # Prevention of a parallel arc on the supply line through diagnosable line insulation in combination with voltage measurement. • # Integration of voltage measurement for diagnosing the condition of the wiring into the battery. • # The special cable is preferably assembled with existing / standard crimp contacts. The wall thickness of the inner insulation layer preferably corresponds to that of a FLRY cable; thus, a terminal with an iso-crimp (designed for a FLY / FLRY cable) can be attached by means of stepped stripping. • Existing welding and crimping methods can be used to connect the new cable. For example, crimp contacts designed for aluminum cables (breaking the individual wire insulation) can be used.

[0055] The supply cable described here is a special type of cable used in all electrical systems (onboard power supplies) with arc-relevant voltages (e.g., 48 volts, high voltage) as a supply and / or ground cable. Voltage measurement is not required in the ground path, as a parallel arc cannot occur.

Claims

[1] A wiring network, in particular a vehicle electrical system, comprising a DC voltage source and an electrical load connected to the DC voltage source via a supply line, wherein the supply line has multi-layer insulation with an inner insulating layer and an outer insulating layer, wherein the inner insulating layer has a lower electrical resistance than the outer insulating layer, wherein the wiring network further comprises a device for monitoring the wiring network with regard to a possible parallel arc, and the device for this purpose comprises a voltage measuring element for measuring a voltage between the supply line and a reference point, wherein for voltage measurement a switchable resistor is arranged which is connected in series with the conductive layer. [2] Transmission network according to the preceding claim, wherein the reference point is a basic or mass potential. [3] A transmission network according to one of the preceding claims, in which a so-called pull-up resistor is arranged as a switchable resistor. [4] Line network according to one of the preceding claims, wherein the DC voltage source is designed as an intelligent source unit and at least some components of the device, in particular the switchable resistor and / or an evaluation unit, are integrated into the source unit. [5] Conducting network according to one of the preceding claims, wherein the inner insulating layer is designed as a conductive polymer. [6] Conduit network according to one of the preceding claims, wherein the supply line has at least one single wire made of a temperature-dependent alloy. [7] Conductor network according to the preceding claim, in which a temperature-dependent resistance, in particular a PTC resistor or a PTC thermistor, is formed by the temperature-dependent alloy and the resistance value of the individual wire increases with an increasing wire temperature. [8] Line network according to one of the preceding claims, wherein the supply line has a plurality of individual wires, each provided with insulation, in particular with a coating, and the voltage source is designed in particular for a mains voltage greater than 12 volts. [9] Wiring network according to one of the preceding claims, wherein the individual wires are connected in parallel. [10] A transmission network according to one of the preceding claims, wherein the supply line is connected between the voltage source or a zero potential and the electrical load.

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