System for detecting faults in electrical wiring

Abstract

A system for detecting faults in electrical wiring is disclosed. A main electrical wiring is subject to variations in ambient temperature over its length. A detection system for detecting faults in a main electrical wiring that can lead to series arcing or junction heating includes a monitoring electrical wiring placed alongside the main electrical wiring, and a controllable current generator that injects a current at the input end of the monitoring electrical cable that is proportional to the current flowing through the main electrical wiring. The main electrical wiring and monitoring electrical wiring set join at an output end, electronic circuitry measures the difference between the potential at the input end of the main electrical wiring and the potential at the input end of the monitoring electrical wiring, and detects a fault in the main electrical wiring when the difference in the potentials exceeds a predefined threshold. Thus, faults in the main electrical wiring can be detected despite temperature variations.

Description

Technical Field

[0001] This invention relates to a system for detecting faults in electrical wiring. This invention is particularly applicable to the aerospace field. Background Technology

[0002] Electrical installations include power supply cabling that can reach tens of meters in length. Cabling should be understood as power cables and any electrical connections between them. Environmental conditions along these power cables can vary. For example, in an aircraft, electrical cabling connects the generator at the turbojet engine outlet (typically on one of the aircraft's wings) to the power supply system (e.g., the power distribution center in the cockpit area). This electrical cabling is subjected to variations in environmental conditions, more specifically, temperature, along its length. These variations can be significant depending on the cabling area considered (on the wing and, depending on its proximity to the turbojet engine, in a pressurized compartment, etc.), the phase of the aircraft's operation (on the ground, in flight), and weather conditions (time of day, season, region of the world, etc.). It can also be noted that the temperature rise of the electrical cabling is related to resistive heating caused by the current flowing through it.

[0003] In electrical wiring, cable wear or electrical connection failures can lead to series arcing or significant localized temperature increases at the connection points. Arcing is typically detected using circuit breakers, which are particularly effective for parallel arcing, but these circuit breakers cannot detect series arcing (because the current does not increase). Temperature variations along electrical wiring render the potential voltage drop from the generator to the distribution center negligible, as temperature affects cable resistance. For example, the resistance of copper changes by 100% over a temperature range from -40°C to +150°C, which could result in a voltage difference of 10 or even 20 volts in the aircraft's power cables at the same current intensity. Since the voltage drop associated with the formation of series arcing or increased connection resistance is of the same order of magnitude, electrical wiring faults cannot be detected simply by measuring the voltage drop due to the aforementioned temperature variations. Although series arcing is less dangerous than parallel arcing, it is desirable to be able to proactively detect electrical wiring faults (especially in aircraft electrical systems) that could lead to the formation of series arcing or increased connection resistance through anticipated maintenance operations. Summary of the Invention

[0004] To this end, a detection system is provided for detecting faults in electrical wiring in a DC electrical facility, the electrical wiring having a cross-section S1 and referred to as main electrical wiring, the main electrical wiring being installed such that it is subjected to changes in ambient temperature along its length.

[0005] According to a first embodiment, the detection system includes: another electrical wiring, referred to as a monitoring electrical wiring, designed to be placed alongside the main electrical wiring, having the same length and composition as the main electrical wiring, and having a cross-section S2 smaller than the cross-section S1; a controllable current generator that injects a current I2 at the input end of the monitoring cable, the current being substantially equal to the current I1 flowing through the main electrical wiring multiplied by an attenuation gain equal to the ratio S2 / S1, the main electrical wiring and the monitoring electrical wiring being joined at their output ends; and an electronic circuit system arranged to compare the potential at the input end of the main electrical wiring with the potential at the input end of the monitoring electrical wiring, and to detect a fault in the main electrical wiring when the difference in potential exceeds a predefined threshold. Therefore, faults in the main electrical wiring causing series arcing or temperature rise at the connection point can be detected despite temperature variations.

[0006] According to a particular embodiment, the detection system includes a current probe that measures the intensity of the current I1, and wherein the electronic circuitry includes: an attenuator that controls the controllable current generator based on the intensity of the current I1 measured by the current probe; a differential amplifier for obtaining the difference between the potential at the input of the main electrical wiring and the potential at the input of the monitoring electrical wiring; and a comparator that compares the output of the differential amplifier with a predefined potential Vref corresponding to the predefined threshold.

[0007] According to one particular embodiment, a low-pass filter is present at the output of the comparator.

[0008] An electrical facility is also provided, comprising electrical wiring, referred to as main electrical wiring, designed to be installed in an environment where the main electrical wiring is subjected to variations in ambient temperature along its length, and the electrical facility further comprising the detection system described above.

[0009] According to one particular embodiment, the monitoring electrical wiring is placed against the main electrical wiring along its length.

[0010] According to one particular embodiment, the electrical facility further includes a circuit breaker, wherein the electronic circuitry is configured to trigger the circuit breaker when the potential at the input of the main electrical wiring and the potential at the input of the monitoring electrical wiring exceed the predefined threshold.

[0011] An aircraft is also provided, which includes the electrical facilities described above, with the main electrical wiring installed in areas of the aircraft subjected to different ambient temperatures.

[0012] According to one particular embodiment, the main electrical wiring is installed between a generator mounted on the wing of the aircraft at the outlet of the turbojet engine and a power distribution center installed in the pressurized cabin of the aircraft.

[0013] According to the second embodiment, the detection system includes: another electrical wiring, referred to as the monitoring electrical wiring, having a cross-section S2 smaller than the cross-section S1, and designed to be placed side by side with the main electrical wiring as a return loop; a monitoring device; and a return cable that brings the potential at the output end of the main electrical wiring back to the monitoring device. Furthermore, the monitoring device includes: a controllable current generator that injects a current I2 at the input of the monitoring cable, the current being equal to a current I1 attenuated by an attenuation factor G1, the current I1 flowing through the main electrical wiring, the controllable current generator being connected between the input and output of the monitoring electrical wiring, the attenuation factor G1 causing currents I1 and I2 to result in the same temperature rise in the main electrical wiring and the monitoring electrical wiring, respectively; and an electronic circuit system including a first differential amplifier implemented by means of an operational amplifier, the operational amplifier being connected to a first input at the input of the main electrical wiring and to a second input at the output of the main electrical wiring via a return cable, the electronic circuit system being arranged to determine the voltage difference between the output of the first differential amplifier and the voltage between the input and output of the monitoring electrical wiring, obtained by means of a gain G2, where G2 = S2 / (2.G1.S1), and detecting a fault in the main electrical wiring when the voltage difference exceeds a predefined margin. Therefore, faults in the main electrical wiring that cause series arcing or increased temperature at connections can still be detected despite temperature variations.

[0014] According to a particular embodiment, the detection system includes a current probe that measures the intensity of the current I1, and wherein the electronic circuitry includes: an attenuator that controls the controllable current generator based on the intensity of the current I1 measured by the current probe; a second differential amplifier arranged at its output to indicate, after adaptation of the voltage between the input and output of the monitored electrical wiring by means of the gain G2; a third differential amplifier arranged at its output to indicate, at its output, the difference between the voltage at the output of the second differential amplifier and the voltage at the output of the first differential amplifier; and a comparator that compares the output of the third differential amplifier with a predefined potential Vref corresponding to the predefined margin.

[0015] According to one particular embodiment, a low-pass filter is present at the output of the comparator.

[0016] An electrical facility is also provided, comprising electrical wiring, referred to as main electrical wiring, designed to be installed in an environment where the main electrical wiring is subjected to variations in ambient temperature along its length, and the electrical facility further comprising a detection system as described above.

[0017] According to one particular embodiment, the monitoring electrical wiring is placed against the main electrical wiring along its return loop length.

[0018] According to a particular embodiment, the electrical facility further includes a circuit breaker, and wherein the electronic circuitry is arranged to trigger the circuit breaker when the voltage difference between the output of the first differential amplifier and the voltage between the input and output of the monitoring electrical wiring, obtained by means of a gain G2, exceeds the predefined margin.

[0019] An aircraft is also provided, which includes the electrical facilities described above, with the main electrical wiring installed in areas of the aircraft subjected to different ambient temperatures.

[0020] According to one particular embodiment, the main electrical wiring is installed between a generator mounted on the wing of the aircraft at the outlet of the turbojet engine and a power distribution center installed in the pressurized cabin of the aircraft. Attached Figure Description

[0021] The above and other features of the invention will become more apparent from the following description of an exemplary embodiment presented with reference to the accompanying drawings:

[0022] Figure 1A top-view schematic diagram illustrates an aircraft equipped with electrical facilities according to a first embodiment of the present invention, the electrical facilities including a system for detecting faults in electrical wiring;

[0023] Figure 2 A simplified cross-section of a particular arrangement of electrical wiring in an electrical installation according to a first embodiment of the present invention is schematically shown.

[0024] Figure 3 The arrangement of a system for detecting faults in electrical wiring in an electrical installation according to a first embodiment of the present invention is illustrated schematically.

[0025] Figure 4 The change of electric potential over time in an electrical facility according to a first embodiment of the present invention is illustrated.

[0026] Figure 5 A top-view schematic diagram illustrates an aircraft equipped with electrical facilities according to a second embodiment of the present invention, the electrical facilities including a system for detecting faults in electrical wiring;

[0027] Figure 6 A simplified cross-section of a particular arrangement of electrical wiring in an electrical installation according to a second embodiment of the present invention is schematically shown.

[0028] Figure 7 The diagram schematically illustrates the arrangement of a system for detecting faults in electrical wiring within an electrical installation according to a second embodiment of the present invention; and

[0029] Figure 8 The change of electric potential over time in an electrical facility according to a second embodiment of the present invention is illustrated. Detailed Implementation

[0030] Figure 1 An aircraft 100 is schematically shown in a top view, equipped with an electrical facility 110 according to a first embodiment of the present invention, the electrical facility including a system for detecting faults in the electrical wiring in the electrical facility 110.

[0031] The electrical installation includes a power source 120 and an electrical system 160 (generally referred to as a load) powered by the power source 120. The power source 120 and the electrical system 160 are connected by means of electrical wiring 130. The electrical wiring 130 includes at least one power supply cable and potentially also includes one or more electrical connections.

[0032] Electrical installation 110 is subjected to temperature variations along electrical wiring 130. For example, power source 120 is considered to be a generator at the output (mechanical sampling) of the turbojet engine of aircraft 100, and electrical system 160 is the power distribution center of aircraft 100. In this example, electrical wiring 130 is also considered to extend within one of the wings of aircraft 100 and then into the pressurized compartment of aircraft 100. Electrical wiring 130 thus traverses three regions Z1, Z2, and Z3 that have different environmental conditions, more specifically, different in terms of ambient temperature. Region Z1 corresponds to the wing region covering a distance D around the turbojet engine, region Z2 corresponds to the wing region beyond distance D, and region Z3 corresponds to the pressurized compartment of aircraft 100.

[0033] A system for detecting faults in electrical wiring includes an electrical cable 140 extending along and of the same length as electrical cable 130. Electrical cable 140 serves as a reference electrical cable and is installed to withstand the same environmental variations, particularly temperature variations, as those of electrical cable 130. In this specification, electrical cable 130 is referred to as the main cable, and electrical cable 140 is referred to as the monitoring electrical cable.

[0034] The monitoring electrical wiring 140 has the same composition as the main electrical wiring 130. Specifically, these cables have conductive cores made of the same alloy. However, the cross-sectional area S2 of the monitoring electrical wiring 140 is smaller than the cross-sectional area S1 of the main electrical wiring 130, thereby allowing for a limitation on the weight generated by the monitoring electrical wiring 140. Therefore, the resistance R2 of the monitoring electrical wiring 140 is higher than the resistance R1 of the main electrical wiring 130.

[0035] Figure 2 A specific installation of monitoring electrical wiring 140 relative to main electrical wiring 130 is shown. The figure shows a simplified cross-section, with conductive core 201 (typically made of copper) surrounded by an insulating sheath 202 of the main electrical wiring 130, and conductive core 203 (typically made of copper) surrounded by an insulating sheath 204 of the monitoring electrical wiring 140. Figure 2 In this configuration, the monitoring electrical wiring 140 is positioned along its length against the main electrical wiring 130 to closely match the temperature rise associated with resistive heating. For this purpose, the monitoring electrical wiring 140 may be attached to or bonded to the main electrical wiring 130.

[0036] Monitoring electrical wiring 140 is connected to main electrical wiring 130 at the output of main electrical wiring 130 (in other words, at load 160). Monitoring electrical wiring 140 and main electrical wiring 130 therefore have the same potential at their junction.

[0037] The system for detecting faults in electrical wiring also includes a monitoring device 150, which is arranged to inject a current I2 proportional to the current I1 injected by power supply 120 at the input of main electrical wiring 130 into monitoring electrical wiring 140. Current I2 is substantially equal to the current I1 flowing in main electrical wiring 130 multiplied by an attenuation gain equal to the ratio S2 / S1. Monitoring device 150 is also arranged to measure the difference between the potential at the input of main electrical wiring 130 (in other words, at power supply 120) and the potential at the input of monitoring electrical wiring 140, and to detect a fault in main electrical wiring 130 when the difference in potentials exceeds a predefined threshold.

[0038] Figure 3 The diagram schematically illustrates a system for detecting faults in electrical wiring, and more specifically, a particular embodiment of monitoring device 150. Figure 3 A load L 160 is shown connected to a power supply SRC 120 via a main electrical wiring 130. Current I1 flows in the main electrical wiring 130. Figure 3 Monitoring electrical wiring 140 is also shown, which is installed alongside main electrical wiring 130 and connects to main electrical wiring 130 at point c, just upstream of load L 160. Therefore, the heat dissipation due to resistive heating is similar in both sets of electrical wiring, and consequently, the resistance change and the resulting voltage drop are also similar. Thus, as long as main electrical wiring 130 is not faulty, the difference in voltage drops across these two sets of electrical wiring remains close to 0 volts (within a predefined margin).

[0039] Monitoring device 150 includes a current probe 310 mounted just upstream of the input terminal of main electrical wiring 130 to measure the strength of current I1. Monitoring device 150 also includes an attenuator ATT 330, which controls a controllable current generator 320 at the input terminal of monitoring electrical wiring 140 based on the strength of current I1 measured by current probe 310. Attenuator ATT 330 has a gain G1 = R1 / R2 = S2 / S1. Therefore, the current I2 in monitoring electrical wiring 140 is equal to G1 * I1. Thus, in the absence of a fault in main electrical wiring 130, the voltage Uac between input terminal a of main electrical wiring 130 and the aforementioned junction c and the voltage Ubc between input terminal b of monitoring electrical wiring 140 and the aforementioned junction c are equal to a predefined potential error margin (predefined threshold).

[0040] The monitoring device 150 also includes a differential amplifier DIFF 340, which is connected at a first input to input b of the monitoring electrical wiring 140 and at a second input to input a of the main electrical wiring 130. The differential amplifier DIFF 340 is configured to measure the difference between the potential at the input of the main electrical wiring 130 and the potential at the input of the monitoring electrical wiring 140. This difference is provided at the output d of the differential amplifier DIFF 340. For example, the differential amplifier DIFF 340 is an operational amplifier with a gain G2 = 1—configured as a subtractor, where the first input is a "-" input and the second input is a "+" input. Reversed connections of these two inputs are also possible, provided the polarities of the voltage Vref are also reversed, or the inputs of the comparator COMP350 (described in detail below) are reversed.

[0041] The monitoring device 150 also includes a comparator COMP 350, whose first input terminal "-" is applied with a predefined potential Vref corresponding to the aforementioned predefined potential error margin, and whose second input terminal "+" is connected to the output terminal d of the differential amplifier DIFF 340. A low state at the output terminal e of the comparator COMP 350 indicates normal operation of the main electrical wiring 130, while a high state at the output terminal e of the comparator COMP 350 indicates abnormal operation of the main electrical wiring 130, i.e., a fault in the main electrical wiring 130 leading to the formation of a series arc or an abnormal increase in connection resistance.

[0042] The monitoring device 150 also includes a control unit CU 370, which is arranged to monitor whether the state at the output terminal e of the comparator COMP 350 is high or low, and to actuate mechanisms that respond to fault detection in the main electrical wiring 130. Preferably, the control unit CU 370 is a trigger for a circuit breaker positioned upstream of the main electrical wiring 130 to interrupt power supply via the main electrical wiring 130. Then, as needed, a backup power supply is routed to the load L 160. As a variant or supplement, the control unit CU 370 includes a communication interface designed to send warnings of detected faults in the main electrical wiring 130 to, for example, instrument panel instruments in the cockpit or an onboard maintenance server.

[0043] The monitoring device 150 may also include a low-pass filter F 360 at the output e of the comparator COMP 350 (upstream of the control unit CU 370) to filter out any potential electromagnetic interference and provide time for the temperature of the electrical wiring to stabilize as the current changes, thereby avoiding false detections.

[0044] Other arrangements of the monitoring device 150 using an electronic circuit system are also possible, provided that an appropriate current I2 is injected into the monitoring electrical wiring 140 and the comparison and difference measurement functions detailed above are implemented. For example, the functions performed by the attenuator ATT 330 and / or the differential amplifier DIFF 340 and / or the comparator COMP 350 and / or the control unit CU 370 can be implemented by means of an FPGA (Field Programmable Gate Array), or an ASIC (Application-Specific Integrated Circuit), DSP (Digital Signal Processor), or a component consisting of a microcontroller and a memory storing a computer program including instructions to cause the microcontroller to perform the functions in question.

[0045] Figure 4 The change in potential of electrical installation 110 over time is illustrated. It is explained that the electrical wiring core is made of copper, is 100 meters long, and has a cross-section S1 of 50 mm². 2 This indicates that the resistance at +60℃ is 40mΩ, and the voltage Uac is 10V when the current I1 is 250A. Furthermore, the cross-section S2 is assumed to be 0.75mm². 2 This indicates that the resistance at +60°C is 2.67Ω and the current I2 is 3.75A, with a voltage Ubc of 10V. Considering the normal difference between Uac and Ubc is ±3V (in other words, the potential Vb at input b of monitoring electrical wiring 140 differs from the potential Va at input a of main electrical wiring 130 by 3V within the range of minimum Vb min to maximum Vb max), the value of +Vref is fixed at 5V. Finally, it is assumed that a fault in main electrical wiring 130 will cause a voltage drop of 15V in the 270VDC power supply framework.

[0046] At time t1, a fault occurs in the main electrical wiring 130, causing the formation of a series arc or a sudden increase in temperature in the connection. The potential Vc at junction c decreases along with the potential Vb. The formation of the series arc maintains the potential Va. As a result, the potential Vd at the output d of the differential amplifier DIFF 340 (ranging from a minimum value Vd min to a maximum value Vd max, with a difference of 6V between the minimum and maximum values) increases. By exceeding the threshold defined by Vref, the state Se of the output e of the comparator COMP 350 changes from a low state (“0”) to a high state (“1”), indicating that a fault in the main electrical wiring 130 has been detected.

[0047] If the voltage Uac changes due to temperature variations along the main electrical wiring, then considering that the monitoring electrical wiring 140 is installed side-by-side with the main electrical wiring 130 and that the current I2 is regulated according to the current I1, the voltage Ubc will change in the same manner. Despite these temperature variations, a fault in the main electrical wiring 130 that could lead to the formation of a series arc or an increase in connection resistance, thus causing a rise in temperature at the connection point, will still be detected.

[0048] The above description details embodiments based on a generator supplying a positive DC voltage. For those skilled in the art, adapting these embodiments to a generator supplying a negative DC voltage is readily available (current direction, connections at the inputs of the differential amplifier DIFF340 and comparator COMP 350, etc.).

[0049] In the case of an AC voltage generator, these two voltages are converted to RMS (root mean square) values ​​upstream by, for example, using a thresholdless converter or full-wave rectifier and a low-pass filter before inputting the voltage "a" at the output of the power supply SRC 120 and the voltage "b" at the output of the controllable current generator 320 to the differential amplifier DIFF 340.

[0050] Figure 5 An aircraft 100 is schematically shown in a top view, equipped with an electrical facility 110 according to a second embodiment of the present invention, the electrical facility including a system for detecting faults in the electrical wiring in the electrical facility 110.

[0051] The electrical installation includes a power source 120 and an electrical system 160 (generally referred to as a load) powered by the power source 120. The power source 120 and the electrical system 160 are connected by electrical wiring 130. The electrical wiring 130 includes at least one power supply cable and potentially also includes one or more electrical connections.

[0052] Electrical installation 110 is subjected to temperature variations along electrical wiring 130. For example, power source 120 is considered to be a generator at the output (mechanical sampling) of the turbojet engine of aircraft 100, and electrical system 160 is the power distribution center of aircraft 100. In this example, electrical wiring 130 is also considered to extend within one of the wings of aircraft 100 and then into the pressurized compartment of aircraft 100. Electrical wiring 130 thus traverses three regions Z1, Z2, and Z3 that have different environmental conditions, more specifically, different in terms of ambient temperature. Region Z1 corresponds to the wing region surrounding the turbojet engine at a distance D, region Z2 corresponds to the wing region beyond distance D, and region Z3 corresponds to the pressurized compartment of aircraft 100.

[0053] A system for detecting faults in electrical wiring includes electrical wiring 140, which extends forward and backward along electrical wiring 130 between its input and output ends (in other words, along a portion of the cable to be monitored). Electrical wiring 140 is therefore arranged in a long loop configuration. Thus, the electrical wiring 140 is installed such that the length of the portion of electrical wiring 140 that connects the forward and return segments along electrical wiring 130 is negligible relative to the length of electrical wiring 130.

[0054] Electrical wiring 140 serves as reference electrical wiring and is installed (both forward and return sections) to withstand the same environmental variations, particularly temperature variations, as electrical wiring 130. In this specification, electrical wiring 130 is referred to as the main cable, and electrical wiring 140 is referred to as monitoring electrical wiring.

[0055] However, the cross-section S2 of the monitoring electrical wiring 140 is smaller than the cross-section S1 of the main electrical wiring 130, thus allowing for a limitation on the weight generated by the monitoring electrical wiring 140. Therefore, the resistance R2 of the monitoring electrical wiring 140 is higher than the resistance R1 of the main electrical wiring 130. This allows the current flowing in the monitoring electrical wiring 140 to be significantly lower than the current flowing in the main electrical wiring 130.

[0056] Figure 6 A specific installation of monitoring electrical wiring 140 relative to main electrical wiring 130 is shown. The figure shows a simplified cross-section, with conductive core 201 (typically made of copper) surrounded by an insulating sheath 202 of the main electrical wiring 130, and conductive core 203 (typically made of copper) surrounded by an insulating sheath 204 of the monitoring electrical wiring 140. Figure 6 In this configuration, the monitoring electrical wiring 140 is positioned against the main electrical wiring 130 on its forward and return sections to closely match the temperature rise associated with resistive heating. For this purpose, the monitoring electrical wiring 140 may be attached to or bonded to the main electrical wiring 130.

[0057] The system for detecting faults in electrical wiring also includes a monitoring device 150, which includes a controllable current generator arranged to inject a current I2 at the input of the monitored electrical wiring 140, the current being equal to a current I1 attenuated by an attenuation factor G1, the current I1 being injected by a power supply 120 at the input of the main electrical wiring 130, the controllable current generator being connected between the input and output of the monitored electrical wiring 140.

[0058] The system for detecting faults in electrical wiring also includes a return cable 145. The return cable 145 carries the potential at the output of the main electrical wiring 130 back to the monitoring device 150; in other words, it carries it back to the location of the input and output of the monitored electrical wiring 140. As described below, the return cable 145 is connected to the input of a differential amplifier formed by operational amplifiers. A weak current, such as a few microamps, flows in the return cable 145. Therefore, even if temperature conditions cause changes in the resistance of the return cable, the potential difference across the return cable 145 is negligible. For example, if the current in the return cable 145 is 1 μA and the resistance of the return cable 145 is approximately 10 Ω, the measurement error is 10 μV, which is practically negligible.

[0059] The monitoring device 150 is also arranged to determine the voltage difference between the voltage between the input and output terminals of the main electrical wiring 130 on the one hand and the voltage between the input and output terminals of the monitoring electrical wiring 140 on the other hand, by means of a gain G2 to obtain an adapted value, wherein G2 = S2 / (2.G1.S1), and to detect a fault in the main electrical wiring 130 when the voltage difference exceeds a predefined margin.

[0060] The attenuation factor G1 ensures that currents I1 and I2 result in the same temperature rise in the main electrical wiring 130 and the monitoring electrical wiring 140, respectively. Therefore, assuming no fault in the main electrical wiring 130, the aforementioned voltage difference is included within a predefined margin.

[0061] Therefore, the ratio of cross section S1 to cross section S2 can be defined as a function of the target current I2 in the monitored electrical wiring 140 with respect to the expected current I1 in the main electrical wiring 130. If the insulating sheaths 202 and 204 are different, the ratio of cross section S1 to cross section S2 preferably also takes into account the thermal resistance of these insulating sheaths. Other parameters may also be relevant, such as the alloy used for the conductive cores 201 and 203, the construction of the conductive cores (braided or otherwise), the voltage range used, etc.

[0062] In one embodiment, the monitoring electrical wiring 140 has the same composition as the main electrical wiring 130. Specifically, these cables have conductive cores made of the same alloy. Thus, for example, a 50mm² cable can be selected when the nominal current I1 is 200A. 2 The cross section S1 is selected, and a 0.75mm diameter is chosen when the nominal value of current I2 is 15A. 2 The cross section S2.

[0063] Figure 7 The diagram schematically illustrates a system for detecting faults in electrical wiring, and more specifically, a particular embodiment of monitoring device 150. Figure 7A load L 160 is shown connected to a power supply SRC 120 via a main electrical wiring 130. Current I1 flows in the main electrical wiring 130. Figure 7 Monitoring electrical wiring 140, installed alongside main electrical wiring 130 as a return loop, is also shown. Therefore, heat dissipation due to resistive heating is similar in both sets of electrical wiring, as are the resistance changes and the resulting voltage drops, provided there is no fault in main electrical wiring 130.

[0064] Monitoring device 150 includes a current probe 310 mounted just upstream of input terminal a of main electrical wiring 130 to measure the intensity of current I1. Monitoring device 150 also includes an attenuator ATT 330, which controls a controllable current generator 320 that injects current I2 into the monitored electrical wiring 140. Figure 7 As shown, the controllable current generator 320 is connected between the input terminal b and the output terminal d of the monitoring electrical wiring 140.

[0065] The intensity of current I2 is defined as a function of the intensity of current I1 measured by current probe 310. Attenuator ATT330 has a gain G1 as defined above. Therefore, monitoring current I2 in electrical wiring 140 is performed such that I2 = G1 * I1.

[0066] The monitoring device 150 also includes a first differential amplifier DIFF 341, which is connected at a first input terminal to input terminal a of the main electrical wiring 130 and at a second input terminal to output terminal c of the main electrical wiring 130 via a return cable 145. The differential amplifier DIFF 341 is configured to indicate at its output terminal f the value of the voltage Uac existing between input terminal a and output terminal c of the main electrical wiring 130. In other words, the first amplifier DIFF 341 is configured at its output terminal to indicate a voltage value equal to the voltage drop across the terminals of the main electrical wiring 130. The first differential amplifier DIFF 341 is formed by an operational amplifier with a gain G3 = 1, wherein the first input terminal is a positive input terminal and the second input terminal is a negative input terminal. Reversed input connections are also possible.

[0067] The monitoring device 150 also includes a second differential amplifier DIFF 342, which is connected at a first input terminal to input terminal b of the monitoring electrical wiring 140 and at a second input terminal to output terminal d of the monitoring electrical wiring 140. Therefore, the second differential amplifier DIFF 342 is arranged at its output terminal e to indicate the voltage Ubd between input terminal b and output terminal d of the monitoring electrical wiring 140, a value obtained by means of gain G2. For example, the second differential amplifier DIFF 342 is formed by an operational amplifier with gain G2 = S2 / (2.G1.S1), where the first input terminal is a "-" input terminal and the second input terminal is a "+" input terminal. Reversed connections of the input terminals are also possible.

[0068] The monitoring device 150 also includes a third differential amplifier DIFF 343, which is connected at a first input to the output e of the second differential amplifier DIFF 342 and at a second input to the output f of the first differential amplifier DIFF 341. The third differential amplifier DIFF 343 is configured to indicate the difference between the voltage Uac and the voltage Ubd, adapted by gain G2, at its output g. For example, the third differential amplifier DIFF 343 is formed by an operational amplifier with gain G4 = 1, where the first input is a "-" input and the second input is a "+" input. Reversed input connections are also possible.

[0069] The monitoring device 150 also includes a comparator COMP 350, whose first input "+" is applied with a predefined potential +Vref corresponding to the aforementioned predefined margin, and the output g of the third differential amplifier DIFF 343 is connected to its second input "-". A low state at the output h of the comparator COMP 350 indicates normal operation of the main electrical wiring 130, while a high state at the output h of the comparator COMP 350 indicates abnormal operation of the main electrical wiring 130, i.e., a fault in the main electrical wiring 130 leading to the formation of a series arc or an increase in temperature at the connection.

[0070] The monitoring device 150 also includes a control unit CU 370, which is arranged to monitor whether the state at the output g of the comparator COMP 350 is high or low, and to actuate mechanisms that respond to fault detection in the main electrical wiring 130. Preferably, the control unit CU 370 is a trigger for a circuit breaker positioned upstream of the main electrical wiring 130 to interrupt power supply via the main electrical wiring 130. Then, as needed, a backup power supply is routed to the load L 160. As a variant or supplement, the control unit CU 370 includes a communication interface designed to send warnings of detected faults in the main electrical wiring 130 to, for example, instrument panel instruments in the cockpit or an onboard maintenance server.

[0071] The monitoring device 150 may also include a low-pass filter F 360 at the output g of the comparator COMP 350 (upstream of the control unit CU 370) to filter out any potential electromagnetic interference and provide time for the temperature of the electrical wiring to stabilize as the current changes, thereby avoiding false detections.

[0072] Other arrangements of the monitoring device 150 using electronic circuitry are possible. For example, the functions performed by the attenuator ATT 330 and / or the first differential amplifier DIFF 341 and / or the second differential amplifier DIFF 342 and / or the third differential amplifier DIFF 343 and / or the comparator COMP 350 and / or the control unit CU 370 can be implemented using an FPGA (Field Programmable Gate Array), or an ASIC (Application-Specific Integrated Circuit), DSP (Digital Signal Processor), or a component consisting of a microcontroller and a memory storing a computer program, which includes instructions to cause the microcontroller to perform the functions in question.

[0073] Figure 8 The change of potential in electrical installation 110 over time is shown. It is illustrated that the core of the electrical wiring assembly is made of copper. Furthermore, it is assumed that the main electrical wiring 130 is 100 meters long and has a cross-section S1 of 50 mm². 2 This indicates a resistance of 40mΩ at +60℃. Considering a nominal current I1 of 200A, this results in a nominal voltage Uac of 8V. Furthermore, it is assumed that the length of the monitoring electrical wiring 140 is 200 meters, and the cross-section S2 is 0.75mm². 2This indicates a resistance of 5.33Ω at +60℃. Therefore, the nominal voltage Ubd is 80V, G1 = 0.075, and G2 = 0.1. Considering the normal difference between Uac and G2.Ubd (in other words, the value at the output terminal e of the second differential amplifier DIFF 342) is ±2V, the value of Vref is fixed at 3V. Finally, it is assumed that a fault in the main electrical wiring 130 will cause a voltage drop of 15V in the 270VDC power supply framework.

[0074] At time t1, a fault occurs in the main electrical wiring 130, causing the formation of a series arc or a sudden increase in temperature during the connection. The potential Vc at the output terminal c of the main electrical wiring 130 decreases together with the potential Vb at the input terminal b of the monitoring electrical wiring 140. The formation of the series arc maintains the potential Va at the input terminal of the main electrical wiring 130. As a result, the voltage Uac increases, which increases the voltage at the output terminal g of the third differential amplifier DIFF 343. When the voltage at the output terminal g of the third differential amplifier DIFF 343 exceeds Vref, the state Sh of the output terminal h of the comparator COMP 350 changes from a low state (“0”) to a high state (“1”), indicating that a fault in the main electrical wiring 130 and the formation of a series arc have been detected.

[0075] If the voltage Uac changes due to temperature variations along the main electrical wiring, then considering that the monitoring electrical wiring 140 is installed alongside the main electrical wiring 130 and that the current I2 is regulated according to the current I1, the voltage Ubd will change in the same manner. This change will be negligible in terms of the potential variation along the return cable 145. Despite these temperature variations, faults in the main electrical wiring 130 that could lead to the formation of a series arc or an increase in connection resistance will still be detected.

[0076] The above description details embodiments based on a generator supplying a positive DC voltage. For those skilled in the art, adapting these embodiments to a generator supplying a negative DC voltage is readily available (current direction, connections of the differential amplifier DIFF and the inputs of the comparator COMP 350, etc.).

[0077] In the case of an AC voltage generator, the two voltages are converted to RMS (root mean square) values ​​upstream by, for example, using a thresholdless converter or full-wave rectifier followed by a low-pass filter before feeding the voltage “e” at the output of differential amplifier DIFF 342 and the voltage “f” at the output of differential amplifier DIFF 341 to differential amplifier DIFF 343.

Claims

1. A detection system for detecting faults in a main electrical wiring (130) in a DC electrical facility, the main electrical wiring having a cross-sectional area S1, the main electrical wiring (130) being installed such that the main electrical wiring is subjected to variations in ambient temperature along its length, characterized in that, The detection system includes: - Monitoring electrical wiring (140), the monitoring electrical wiring is designed to be placed side by side with the main electrical wiring (130), has the same length as the main electrical wiring (130), has the same composition, and has a cross-sectional area S2 that is smaller than the cross-sectional area S1; - A controllable current generator (320) injects a current I2 at the input of the monitoring electrical wiring (140), the current being substantially equal to the current I1 flowing through the main electrical wiring (130) multiplied by an attenuation gain equal to the ratio S2 / S1, the main electrical wiring (130) and the monitoring electrical wiring (140) being connected at their outputs; and - An electronic circuit system arranged to measure the difference between the potential at the input of the main electrical wiring (130) and the potential at the input of the monitoring electrical wiring (140), and to detect a fault in the main electrical wiring (130) when the difference in potential exceeds a predefined threshold.

2. The detection system according to claim 1, comprising a current probe (310) that measures the intensity of the current I1, wherein, The electronic circuit system includes: - Attenuator (330), which controls the controllable current generator (320) based on the intensity of the current I1 measured by the current probe (310). - A differential amplifier (340) for obtaining the difference between the potential at the input of the main electrical wiring (130) and the potential at the input of the monitoring electrical wiring (140); and - Comparator (350) compares the output of the differential amplifier (340) with a predefined potential Vref corresponding to the predefined threshold.

3. The detection system according to claim 2, wherein, A low-pass filter (360) is present at the output of the comparator (350).

4. An electrical facility (110) comprising a main electrical wiring (130) designed to be installed in an environment in which the main electrical wiring (130) is subjected to changes in ambient temperature along its length, and the electrical facility further comprising a detection system according to any one of claims 1 to 3.

5. The electrical facility according to claim 4, wherein, The monitoring electrical wiring (140) is placed against the main electrical wiring (130) along its length.

6. The electrical installation according to any one of claims 4 and 5, further comprising a circuit breaker, wherein, The electronic circuit system is configured to trigger the circuit breaker when the potential at the input of the main electrical wiring and the potential at the input of the monitoring electrical wiring exceed the predefined threshold.

7. An aircraft (100) comprising electrical facilities (110) according to any one of claims 4 to 6, wherein the main electrical wiring (130) is installed in areas of the aircraft (100) subjected to various ambient temperatures.

8. The aircraft (100) according to claim 7, wherein, The main electrical wiring (130) is installed between the generator (120) mounted on the wing of the aircraft (100) at the outlet of the turbojet engine and the power distribution center (160) installed in the pressurized cabin of the aircraft (100).

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