Patent Publication Number: US-11650239-B2

Title: System for detecting faults in electrical cabling

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to French patent application number 20 09873 filed on Sep. 29, 2020, the entire disclosure of which is incorporated by reference herein. 
     TECHNICAL FIELD 
     The disclosure herein relates to a system for detecting faults in electrical cabling. The disclosure herein is notably applicable in the field of aeronautics. 
     BACKGROUND 
     An electrical installation comprises power supply cabling which may reach several tens of meters. Cabling is understood to mean the power supply cables together with any electrical connections between these power supply cables. Along these power supply cables, the environmental conditions may be different. For example, in an aircraft, electrical cabling connects an electrical generator at the outlet of a turbojet, typically on one of the wings of the aircraft, and an electrical power supply system, for example an electrical power distribution center in the area of the cockpit of the aircraft. This electrical cabling is subject to variations in environmental conditions, more particularly in temperature, over its length. These variations may be significant in view of the cabling area being considered (on the wings and depending on whether this area is close or not to the turbojet, in the pressurized cabin, etc,), in view of the phase of operation of the aircraft (on the ground, in flight) and in view of the meteorological conditions (time of day, season, region of the world, etc.). An increase in temperature of the electrical cabling may also be noted that is linked to the resistive heating induced by the passage of current within the electrical cabling. 
     In the case of wear of an electrical cable or of an electrical connection fault in the electrical cabling, a serial arc or significant local increase in temperature at a connection may occur. The formation of an electrical arc is typically detected by virtue of circuit breakers, which is particularly effective with respect to parallel arcs, but these circuit breakers cannot detect the formation of a serial arc (because the current does not increase). The variations in temperature along the electrical cabling render a potential measurement of the voltage drop, between the start at the electrical generator and the arrival at the electrical power distribution center, insignificant because the temperature affects the resistance of the electrical cables. For example, the resistance of copper varies by 100% over the temperature range from −40° C. to +150° C., which may, for the same intensity of current, lead to a voltage difference of 10 Volts, or even 20 Volts, in an electrical supply cable in an aircraft. Since a voltage drop associated with the formation of a serial arc or an increase in resistance of a connection is of the same order of magnitude, the detection of the fault in the electrical cabling is not therefore possible by a simple measurement of the voltage drop owing to the aforementioned variations in temperature. Although the danger from serial arcs is less than that from parallel arcs, it is desirable to be able to detect in a pre-emptive manner faults in electrical cabling leading to the formation of serial arcs or increase in connection resistance, notably in an aircraft electrical installation, in such a manner as to anticipate maintenance operations. 
     SUMMARY 
     For this purpose, a detection system is provided for detecting, in a Direct Current (DC) electrical installation, a fault in an electrical cabling, referred to as main electrical cabling, of cross-section S1, the main electrical cabling being installed such that it is subject to variations in ambient temperature over its length. 
     According to a first embodiment, the detection system comprises: another electrical cabling, referred to as monitor electrical cabling, designed to be placed alongside the main electrical cabling, of same length as the main electrical cabling, of same composition and of cross-section S2 less than the cross-section S1; a controllable current generator injecting, at the input of the monitor electrical cable, a current I 2  substantially equal to a current I 1  flowing through the main electrical cabling multiplied by an attenuation gain equal to the ratio S2/S1, the main electrical cabling and the monitor electrical cabling being joined at the output; and an electronic circuitry arranged for comparing the electrical potential at the input of the main electrical cabling and the electrical potential at the input of the monitor electrical cabling, and for detecting a fault in the main electrical cabling when the difference of the electrical potentials exceeds a predefined threshold, Thus, a fault in the main electrical cabling leading to a serial arc or an increase in temperature of a connection is detected despite the variations in temperature. 
     According to one particular embodiment, the detection system comprises a current probe measuring the intensity of the current I 1 , and in which the electronic circuitry comprises: an attenuator controlling the controllable current generator as a function of the intensity of the current I 1  measured by the current probe; a differential amplifier for the difference between the electrical potential at the input of the main electrical cabling and the electrical potential at the input of the monitor electrical cabling; and a comparator comparing the output of the differential amplifier with a predefined potential Vref corresponding to the predefined threshold. 
     According to one embodiment, a low-pass filter is present at the output of the comparator. 
     An electrical installation is also provided comprising an electrical cabling, referred to as main electrical cabling, the main electrical cabling being designed to be installed in an environment where the main electrical cabling is subject to variations in ambient temperature over its length, and furthermore comprising a detection system such as previously described. 
     According to one embodiment, the monitor electrical cabling is placed, over its length, against the main electrical cabling. 
     According to one embodiment, the electrical installation furthermore comprises a circuit breaker and in which the electronic circuitry is arranged for triggering the circuit breaker when the electrical potential at the input of the main electrical cabling and the electrical potential at the input of the monitor electrical cabling exceeds the predefined threshold. 
     An aircraft is also provided comprising an electrical installation such as described hereinabove, the main electrical cabling being installed in areas of the aircraft subject to different ambient temperatures. 
     According to one embodiment, the main electrical cabling is installed between an electrical generator installed on a wing of the aircraft at the outlet of a turbojet and an electrical distribution center installed in the pressurized cabin of the aircraft. 
     According to a second embodiment, the detection system comprises: another electrical cabling, referred to as monitor electrical cabling, of cross-section S2 less than the cross-section S1, designed to be placed as a return loop alongside the main electrical cabling; a monitoring device; a return cable bringing back the electrical potential at the output of the main electrical cabling to the monitoring device. In addition, the monitoring device comprises: a controllable current generator injecting, at the input of the monitor electrical cable, a current I 2  equal to a current I 1  attenuated by an attenuation factor G1, the current I 1  flowing through the main electrical cabling, the controllable current generator being connected between the input and the output of the monitor electrical cabling, the attenuation factor G1 being such that the currents I 1  and I 2  respectively lead to the same increase in temperature in the main electrical cabling and in the monitor electrical cabling; and an electronic circuitry comprising a first differential amplifier implemented by virtue of an operational amplifier connected to a first input at the input of the main electrical cabling and to a second input at the output of the main electrical cabling, via the return cable, the electronic circuitry being arranged for determining a difference in voltages between the outputs of the first differential amplifier and an adaptation by virtue of a gain G2 of the voltage between the input and the output of the monitor electrical cabling, with G2=S2/(2.G1.S1),y and for detecting a fault in the main electrical cabling when the difference in voltages exceeds a predefined margin. Thus, a fault in the main electrical cabling leading to a serial arc or an increase in temperature of a connection is detected despite the variations in temperature. 
     According to one embodiment, the detection system comprises a current probe measuring the intensity of the current I 1 , and in which the electronic circuitry comprises: an attenuator controlling the controllable current generator as a function of the intensity of the current I 1  measured by the current probe; a second differential amplifier arranged for indicating at the output a value, adapted by virtue of the gain G2, of voltage between the input and the output of the monitor electrical cabling; a third differential amplifier arranged for indicating at the output which difference exists 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 comparing the output of the third differential amplifier with a predefined potential Vref corresponding to the predefined margin. 
     According to one embodiment, a low-pass filter is present at the output of the comparator. 
     An electrical installation is also provided comprising an electrical cabling, referred to as main electrical cabling, the main electrical cabling being designed to be installed in an environment where the main electrical cabling is subject to variations of ambient temperature over its length, and furthermore comprising a detection system such as described hereinabove. 
     According to one embodiment, the monitor electrical cabling is placed, over its return loop length, against the main electrical cabling. 
     According to one embodiment, the electrical installation furthermore comprises a circuit breaker and in which the electronic circuitry is arranged for triggering the circuit breaker when the difference in voltages between the output of the first differential amplifier and the adaptation by virtue of a gain G2 of the voltage between the input and the output of the monitor electrical cabling exceeds the predefined margin. 
     An aircraft is also provided comprising an electrical installation such as described hereinabove, the main electrical cabling being installed in areas of the aircraft subject to different ambient temperatures. 
     According to one embodiment, the main electrical cabling is installed between an electrical generator installed on a wing of the aircraft at the outlet of a turbojet and an electrical distribution center installed in the pressurized cabin of the aircraft. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the disclosure herein mentioned hereinabove, together with others, will become more clearly apparent upon reading the following description of one example embodiment, the description being presented in relation with the appended drawings, of which: 
         FIG.  1    illustrates schematically, as a top view, an aircraft equipped with an electrical installation comprising a system for detecting faults in electrical cabling according to a first embodiment of the disclosure herein; 
         FIG.  2    illustrates schematically a simplified cross-section of one particular arrangement of the electrical cabling in the electrical installation according to a first embodiment of the disclosure herein; 
         FIG.  3    illustrates schematically an arrangement of the system for detecting faults in electrical cabling in the electrical installation according to a first embodiment of the disclosure herein; 
         FIG.  4    illustrates variations of electrical potentials over time in the electrical installation according to a first embodiment of the disclosure herein; 
         FIG.  5    illustrates schematically, as a top view, an aircraft equipped with an electrical installation comprising a system for detecting faults in electrical cabling according to a second embodiment of the disclosure herein; 
         FIG.  6    illustrates schematically a simplified cross-section of one particular arrangement of the electrical cabling in the electrical installation according to a second embodiment of the disclosure herein; 
         FIG.  7    illustrates schematically an arrangement of the system for detecting faults in electrical cabling in the electrical installation according to a second embodiment of the disclosure herein; and 
         FIG.  8    illustrates variations of electrical potentials over time in the electrical installation according to a second embodiment of the disclosure herein. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    illustrates schematically, as a top view, an aircraft  100  equipped with an electrical installation  110  comprising a system for detecting faults in electrical cabling in the electrical installation  110  according to a first embodiment of the disclosure herein. 
     The electrical installation comprises an electrical source  120  and an electrical system  160  (typically referred to as load) to be electrically powered by the electrical source  120 . The electrical source  120  and the electrical system  160  are connected by virtue of an electrical cabling  130 . The electrical cabling  130  comprises at least one electrical supply cable, and potentially furthermore one or more electrical connections. 
     The electrical installation  110  is subject to variations in temperature along the electrical cabling  130 . It is for example considered that the electrical source  120  is an electrical generator at the output (mechanical sampling) of a turbojet of the aircraft  100  and that the electrical system  160  is an electrical distribution center of the aircraft  100 . It is furthermore considered in this example that the electrical cabling  130  runs in one of the wings of the aircraft  100 , then into the pressurized cabin of the aircraft  100 . The electrical cabling  130  thus passes through three areas Z 1 , Z 2 , Z 3  having different environmental conditions, more particularly in terms of ambient temperature. The area Z 1  corresponds to an area of the wing which covers a distance D around the turbojet, the area Z 2  corresponds to an area of the wing beyond the distance D, and the area Z 3  corresponds to the pressurized cabin of the aircraft  100 . 
     The system for detecting faults in electrical cabling comprises an electrical cabling  140  which runs along the electrical cabling  130 , of same length as the latter. The electrical cabling  140  serves as a reference electrical cabling and is installed so as to be subject to the same environmental variations, notably in terms of temperature, as the electrical cabling  130 . In the present description, the electrical cabling  130  is called main electrical cable and the electrical cabling  140  is called monitor electrical cabling. 
     The monitor electrical cabling  140  is of same composition as the main electrical cabling  130 . Notably, the electrical cables have conducting cores made of the same alloy. However, the monitor electrical cabling  140  has a cross-section S2 that is smaller than the cross-section of the main electrical cabling  130  thus allowing the weight due to the monitor electrical cabling  140  to be limited. The resistance R 2  of the monitor electrical cabling  140  is therefore higher than the resistance R 1  of the main electrical cabling  130 . 
     One particular installation of the monitor electrical cabling  140  with respect to the main electrical cabling  130  is shown in  FIG.  2   . This shows as a simplified cross-section a conducting core  201  (typically made of copper) surrounded by an insulating sheath  202  of the main electrical cabling  130 , and a conducting core  203  (typically made of copper) surrounded by an insulating sheath  204  of the monitor electrical cabling  140 . In  FIG.  2   , the monitor electrical cabling  140  is placed, over its length, against the main electrical cabling  130 , so as to closely match their increase in temperature associated with resistive heating. For this purpose, the monitor electrical cabling  140  may be attached or bonded to the main electrical cabling  130 . 
     The monitor electrical cabling  140  is connected to the main electrical cabling  130  at the output of the main electrical cabling  130 , in other words at the load  160 . The monitor electrical cabling  140  and the main electrical cabling  130  therefore have the same electrical potential at their junction point. 
     The system for detecting faults in electrical cabling furthermore comprises a monitoring device  150  arranged for injecting into the monitor electrical cabling  140  a current I 2  proportional to the current I 1  injected by the electrical source  120  at the input of the main electrical cabling  130 . The current I 2  is substantially equal to the current I 1  flowing in the main electrical cabling  130  multiplied by an attenuation gain equal to the ratio S 2 IS 1 . The monitoring device  150  is furthermore arranged for measuring the difference between the electrical potential at the input of the main electrical cabling  130  (in other words at the electrical source  120 ) and the electrical potential at the input of the monitor electrical cabling  140 , and for detecting a fault in the main electrical cabling  130  when the difference of the electrical potentials exceeds a predefined threshold. 
       FIG.  3    illustrates schematically one particular embodiment of the system for detecting faults in electrical cabling, and more particularly of the monitoring device  150 .  FIG.  3    shows the load L  160  connected to the electrical source SRC  120  by virtue of the main electrical cabling  130 . A current I 1  flows in the main electrical cabling  130 .  FIG.  3    also shows the monitor electrical cabling  140  installed alongside the main electrical cabling  130 , and joined to the main electrical cabling  130  at a point c just upstream of the load L  160 . Thus, the heat dissipation due to resistive heating is similar in the two sets of electrical cabling, and hence as are also the variation in resistance and the induced voltage drops. The difference between the voltage drops appearing on the two sets of electrical cabling therefore remains close to 0 Volts (to within a predefined margin) as long as there is no fault in the main electrical cabling  130 . 
     The monitoring device  150  comprises a current probe  310  installed just upstream of the input of the main electrical cabling  130  in order to measure the intensity of the current I 1 . The monitoring device  150  furthermore comprises an attenuator ATT  330  responsible for controlling a controllable current generator  320  at the input of the monitor electrical cabling  140  as a function of the intensity of the current I 1  measured by the current probe  310 . The attenuator ATT  330  has a gain G1=R 1 /R 2 =S2/S1. Thus a current I 2 =G1.I 1  in the monitor electrical cabling  140 , Thus, in the absence of a fault on the rain electrical cabling  130 , the voltage Uac between the input a of the main electrical cabling  130  and the aforementioned junction point c and the voltage Ubc between the input b of the monitor electrical cabling  140  and the aforementioned junction point c are equal, to within a predefined potential margin of error (predefined threshold). 
     The monitoring device  150  furthermore comprises a differential amplifier DIFF  340 , connected at a first input to the input b of the monitor electrical cabling  140  and at a second input to the input a of the main electrical cabling  130 . The differential amplifier DIFF  340  is arranged for measuring the difference between the electrical potential at the input of the main electrical cabling  130  and the electrical potential at the input of the monitor electrical cabling  140 . The difference between these two electrical potentials is supplied 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 the input “−” and the second input is the input “+”. The inverse connection of the inputs is also possible as long as the polarity of the voltage Vref is also inverted, or the inputs of the comparator COMP  350  (detailed hereinafter) are inverted. 
     The monitoring device  150  furthermore comprises a comparator COMP  350 , to a first input “−” of which a predefined potential Vref is applied corresponding to the aforementioned predefined potential margin of error, and to a second input “+” of which the output d of the differential amplifier DIFF  340  is connected. A low state at the output e of the comparator COMP  350  indicates a normal operation of the main electrical cabling  130  and a high state at the output e of the comparator COMP  350  indicates an abnormal operation of the main electrical cabling  130 , namely a fault in the main electrical cabling  130  having resulted in the formation of a serial arc or an abnormal increase in the connection resistance. 
     The monitoring device  150  furthermore comprises a control unit CU  370  arranged for monitoring the state, high or low, at the output e of the comparator COMP  350 , and for actuating a mechanism for reacting to the detection of fault in the main electrical cabling  130 . Preferably, the control unit CU  370  is a trigger for a circuit breaker which is placed upstream of the main electrical cabling  130  in such a manner as to interrupt the electrical power supply via the main electrical cabling  130 . A backup electrical power supply then takes over for supplying electrical power to the load L  160 , as needed. As a variant or as a complement, the control unit CU  370  includes a communications interface designed to send a warning of the detection of a fault in the main electrical cabling  130 , for example, to a dashboard instrument in the cockpit or to an on-board maintenance server. 
     The monitoring device  150  may furthermore comprise a low-pass filter F  360  at the output e of the comparator COMP  350  (upstream of the control unit CU  370 ) so as to perform a filtering of any potential electromagnetic interference and to allow the time for the temperature of the electrical cabling to stabilize when the current varies, thus avoiding spurious detections. 
     Other arrangements of the monitoring device  150  are possible using an electronic circuitry, as long as the appropriate current I 2  is injected into the monitor electrical cabling  140  and as long as the comparison and difference measurement functions detailed hereinabove are implemented. For example, the functions carried out 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  may be implemented by virtue of an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit), a DSP (Digital Signal Processor) or an assembly formed of a microcontroller and a memory storing a computer program comprising instructions causing the implementation by the microcontroller of the functions in question. 
       FIG.  4    illustrates variations over time of electrical potentials in the electrical installation  110 . By way of illustration, it is considered that the cores of the electrical cabling are made of copper, of length 100 meters, that the cross-section S1 is 50 mm 2  and that this represents a resistance at +60° C. of 40 mΩ and a voltage Uac of 10 V for a current I 1  of 250 A, In addition, it is considered that the cross-section S2 is 0.75 mm 2  and that this represents a resistance at + 60 ° C. of 2.67 Ω and a voltage Ubc of 10 V for a current I 2  of 3.75 A. Considering that the normal difference between Usc and Ubc is ±3 V (in other words that the electrical potential Vb of the input b of the monitor electrical cabling  140  is in the range between a minimum value Vb min and a maximum value Vb max with a difference of 3 V with respect to the electrical potential Va of the input a of the main electrical cabling  130 ), the value of +Vref is fixed at 5 V. Lastly, it is considered that the occurrence of a fault in the main electrical cabling  130  leads to a voltage drop of 15 V in the framework of an electrical power supply of 270 VDC. 
     At the time t 1 , a fault in the main electrical cabling  130  appears, resulting in the formation of a serial arc or an abrupt increase of temperature in a connection. The electrical potential Vc at the junction point c decreases, together with the electrical potential Vb. The formation of a serial arc maintains the potential Va. As a consequence, the potential Vd (in the range between a minimum value Vd mfrs and a maximum value Vd max with a difference between them of 6 V) at the output d of the differential amplifier DIFF  340  increases. By exceeding the threshold defined by Vref, the state Se of the output e of the comparator COMP  350  goes from the low state (“0”) to the high state (“1”), which represents the detection of the fault in the main electrical cabling  130 . 
     If the electrical voltage Uac were to vary because of variations in temperature along the main electrical cabling, the voltage Ubc would vary in the same way given that the monitor electrical cabling  140  is installed alongside the main electrical cabling  130  and that the current I 2  is adjusted on the current I 1 . A fault in the main electrical cabling  130  leading to the formation of a serial arc or of an increase in connection resistance, and hence in temperature of this connection, would be detected despite these temperature variations. 
     The description hereinabove details embodiments based on an electrical generator supplying a positive DC voltage. Adapting them to a generator supplying a negative DC voltage is then trivial for those skilled in the art (direction of the current, connection of the inputs of the differential amplifier DIFF  340  and of the comparator COMP  350 , etc.). 
     In the case of an Alternating Current (AC) voltage generator, the voltages “a” at the output of the electrical source SRC  120  and “b” at the output of the controllable current generator  320  are transformed upstream into RMS (Root Mean Square) values, by for example using a converter or a full-wave rectifier without threshold followed by a low-pass filter, prior to being input into the differential amplifier DIFF  340 . 
       FIG.  5    illustrates schematically, as a top view, an aircraft  100  equipped with an electrical installation  110  comprising a system for detecting faults in electrical cabling in the electrical installation  110  according to a second embodiment of the disclosure herein. 
     The electrical installation comprises an electrical source  120  and an electrical system  160  (typically referred to as load) to be electrically powered by virtue of the electrical source  120 . The electrical source  120  and the electrical system  160  are connected by virtue of an electrical cabling  130 . The electrical cabling  130  comprises at least one electrical supply cable, and potentially furthermore one or more electrical connections. 
     The electrical installation  110  is subject to variations in temperature along the electrical cabling  130 . It is for example considered that the electrical source  120  is an electrical generator at the output (mechanical sampling) of a turbojet of the aircraft  100  and that the electrical system  160  is an electrical distribution center of the aircraft  100 . It is furthermore considered, in this example, that the electrical cabling  130  runs in one of the wings of the aircraft  100 , then into the pressurized cabin of the aircraft  100 . The electrical cabling  130  thus passes through three regions Z 1  Z 2 , Z 3  having different environmental conditions, more particularly in terms of ambient temperature. The region Z 1  corresponds to an area of the wing which covers a distance D around the turbojet, the region Z 2  corresponds to an area of the wing beyond the distance D, and the region Z 3  corresponds to the pressurized cabin of the aircraft  100 . 
     The system for detecting faults in electrical cabling comprises an electrical cabling  140 , which runs forward and backward along the electrical cabling  130 , between the input of the electrical cabling  130  and the output of the electrical cabling  130 , in other words over the portion of electrical cable to be monitored. The electrical cabling  140  thus takes the form of a longilineal loop. The installation of the electrical cabling  140  is then such that the portion of the electrical cabling  140  which connects the forward and the return sections along the electrical cabling  130  is of negligible length with respect to the length of the electrical cabling  130 . 
     The electrical cabling  140  serves as a reference electrical cabling and is thus installed (both the forward and return sections) so as to be subject to the same environmental variations, notably in terms of temperature, as the electrical cabling  130 . In the present description, the electrical cabling  130  is called main electrical cable and the electrical cabling  140  is called monitor electrical cabling. 
     However, the monitor electrical cabling  140  has a cross-section S2 that is smaller than the cross-section S1 of the main electrical cabling  130 , thus allowing the weight due to the monitor electrical cabling  140  to be limited. The resistance R 2  of the monitor electrical cabling  140  is therefore higher than the resistance R 1  of the main electrical cabling  130 . This allows the current flowing in the monitor electrical cabling  140  to be much lower than the current flowing in the main electrical cabling  130 . 
     One particular installation of the monitor electrical cabling  140  with respect to the main electrical cabling  130  is shown in  FIG.  6   . This shows as a simplified cross-section a conducting core  201  (typically made of copper) surrounded by an insulating sheath  202  of the main electrical cabling  130 , and a conducting core  203  (typically made of copper) surrounded by an insulating sheath  204  of the monitor electrical cabling  140 . In  FIG.  6   , the monitor electrical cabling  140  is placed, over its forward and return sections, against the main electrical cabling  130 , so as to closely match their increase in temperature associated with resistive heating, For this purpose, the monitor electrical cabling  140  may be attached or bonded to the main electrical cabling  130 . 
     The system for detecting faults in electrical cabling furthermore comprises a monitoring device  150  comprising a controllable current generator arranged for injecting at the input of the monitor electrical cabling  140  a current I 2  equal to the current I 1  attenuated by an attenuation factor G1, the current I 1  being injected by the electrical source  120  at the input of the main electrical cabling  130 , the controllable current generator being connected between the input and the output of the monitor electrical cabling  140 . 
     The system for detecting faults in electrical cabling furthermore comprises a return cable  145 . The return cable  145  brings the electrical potential at the output of the main electrical cabling  130  back to the monitoring device  150 , in other words the place where the input and the output of the monitor electrical cabling  140  are located. As explained hereinafter, the return cable  145  is connected to the input of a differential amplifier formed by virtue of an operational amplifier. A weak current, for example of the order of a few microamps, flows in the return cable  145 . Therefore, even if the temperature conditions cause the resistance of the return cable to vary, the potential difference between the two ends of the return cable  145  is negligible. For example, if the current in the return cable  145  is 1 μA and if the resistance of the return cable  145  is around 10 Ω, the measurement inaccuracy is 10 μV, which is effectively negligible. 
     The monitoring device  150  is furthermore arranged for determining a difference in voltages between, on the one hand, the voltage between the input and the output of the main electrical cabling  130  and, on the other hand, an adaptation by virtue of a gain G2 of the voltage between the input and the output of the monitor electrical cabling  140 , with G2=S2/(2,G1.S1), and for detecting a fault in the main electrical cabling  130  when this difference in voltages goes beyond a predefined margin. 
     The attenuation factor G1 is such that the currents I 1  and I 2  respectively result in the same increase in temperature in the main electrical cabling  130  and in the monitor electrical cabling  140 . Thus, in the absence of a fault on the main electrical cabling  130 , the aforementioned difference in voltages is contained within the predefined margin. 
     The ratio between the cross-section S1 and the cross-section S2 may thus be defined as a function of a target current I 2  in the monitor electrical cabling  140  with regard to an expected current I 1  in the main electrical cabling  130 . The ratio between the cross-section S1 and the cross-section S2 also preferably takes into account thermal resistance of the insulating sheaths  202  and  204 , if they differ. Other parameters may be relevant, such as the alloy used for the conducting cores  201 ,  203 , the  configuration of the conducting cores (braiding or otherwise), the range of voltages in use, etc. 
     In one embodiment, the monitor electrical cabling  140  is of same composition as the main electrical cabling  130 . Notably, the electrical cables have conducting cores made of the same alloy. It is then for example possible to choose a cross-section S1 of 50 mm 2  for a nominal value of the current I 1  of 2000 Å, and a cross-section S2 of 075 mm 2  for a nominal value of the current I 2  of 15 ÅA. 
       FIG.  7    illustrates schematically one particular embodiment of the system for detecting faults in electrical cabling, and more particularly of the monitoring device  150 .  FIG.  7    shows the load L  160  connected to the electrical source SRC  120  by virtue of the main electrical cabling  130 . A current I 1  flows in the main electrical cabling  130 .  FIG.  7    also shows the monitor electrical cabling  140  installed, as a return loop, alongside the main electrical cabling  130 . Thus, the heat dissipation due to resistive heating is similar in both sets of electrical cabling, and hence as are also the variation of resistance and the resulting voltage drops, as long as there is no fault in the main electrical cabling  130 . 
     The monitoring device  150  comprises a current probe  310  installed just upstream of the input a of the main electrical cabling  130  in order to measure the intensity of the current I 1 , The monitoring device  150  furthermore comprises an attenuator ATT  330  responsible for controlling a controllable current generator  320  injecting a current I 2  into the monitor electrical cabling  140 . As shown in  FIG.  7   , the controllable current generator  320  is connected between the input b and the output d of the monitor electrical cabling  140 . 
     The intensity of the current I 2  is defined as a function of the intensity of the current I 1  measured by the current probe  310 . The attenuator ATT  330  has a gain G1 as defined hereinabove. Thus, the current I 2  is such that I 2 =G1.I 1  in the monitor electrical cabling  140 . 
     The monitoring device  150  furthermore comprises a first differential amplifier DIFF  341 , connected at a first input to the input a of the main electrical cabling  130  and at a second input to the output c of the main electrical cabling  130 , via the return cable  145 . The differential amplifier DIFF  341  is arranged for indicating at the output f which value of voltage Uac exists between the input a of the main electrical cabling  130  and the output c of the main electrical cabling  130 . In other words, the first amplifier DIFF  341  is arranged for indicating at the output a value of voltage equal to the voltage drop across the terminals of the main electrical cabling  130 , The first differential amplifier DIFF  341  is formed by virtue of an operational amplifier with a gain G 3 =1, where the first input is the input “+” and the second input is the input “−”. The inverse connection of the inputs is also possible. 
     The monitoring device  150  furthermore comprises a second differential amplifier DIFF  342 , connected at a first input to the input b of the monitor electrical cabling  140  and at a second input to the output d of the monitor electrical cabling  140 . Thus, the second differential amplifier DIFF  342  is arranged for indicating at the output e a value, adapted by virtue of the gain G2, of voltage Ubd between the input b of the monitor electrical cabling  140  and the output d of the monitor electrical cabling  140 . For example, the second differential amplifier DIFF  342  is formed by virtue of an operational amplifier with a gain G2=S2/(2.G1.S1), where the first input is the input “−” and the second input is the input “+”, The inverse connection of the inputs is also possible. 
     The monitoring device  150  furthermore comprises a third differential amplifier DIFF  343 , 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 arranged for indicating at the output g which difference exists between the voltage Uac and the voltage Ubd adapted by the gain G2. The third differential amplifier DIFF  343  is for example formed by virtue of an operational amplifier with a gain G 4 =1, where the first input is the input “−” and the second input is the input “+”. The inverse connection of the inputs is also possible. 
     The monitoring device  150  furthermore comprises a comparator COMP  350 , to a first input “+” of which a predefined potential +Vref is applied corresponding to the aforementioned predefined margin, and to a second input “−” of which the output g of the third differential amplifier DIFF  343  is connected. A low state at the output h of the comparator COMP  350  indicates a normal operation of the main electrical cabling  130  and a high state at the output h of the comparator COMP  350  indicates an abnormal operation of the main electrical cabling  130 , namely a fault in the main electrical cabling  130  having caused the formation of a serial arc or an increase in the temperature of a connection. 
     The monitoring device  150  furthermore comprises a control unit CU  370  arranged for monitoring the state, high or low, at the output g of the comparator COMP  350 , and for actuating a mechanism for reaction to the detection of a fault in the main electrical cabling  130 . Preferably, the control unit CU  370  is a trigger for a circuit breaker which is placed upstream of the main electrical cabling  130  in such a manner as to interrupt the electrical power supply via the main electrical cabling  130 . A backup electrical power supply then takes over for supplying electrical power to the load L  160 , as needed. As a variant or as a complement, the control unit CU  370  includes a communications interface designed to send a warning of the detection of a fault in the main electrical cabling  130 , for example, to a dashboard instrument in the cockpit or to an on-board maintenance server. 
     The monitoring device  150  may furthermore comprise a low-pass filter F  360  at the output g of the comparator COMP  350  (upstream of the control unit CU  370 ) in order to carry out a filtering of any potential electromagnetic interference and to allow the time for the temperature of the electrical cabling to stabilize when the current varies, thus avoiding spurious detections. 
     Other arrangements of the monitoring device  150  are possible using an electronic circuitry. 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  may be carried out by virtue of an FPGA (Field-Programmable Gate Array) or an ASIC (Application-Specific Integrated Circuit), a DSP (Digital Signal Processor) or an assembly consisting of a microcontroller and of a memory storing a computer program comprising instructions causing the implementation by the microcontroller of the functions in question. 
       FIG.  8    illustrates variations over time of electrical potentials in the electrical installation  110 . By way of illustration, it is considered that the cores of the sets of electrical cabling are made of copper. It is furthermore considered that the length of the main electrical cabling  130  is 100 meters, with a cross-section S1 of 50 mm 2 , and that this represents a resistance at +60° C. of 40 mΩ. By considering a nominal current I 1  of 200 A, this results in a nominal voltage Uac of 8 V. In addition, it is considered that the length of the monitor electrical cabling  140  is 200 meters, with a cross-section S2 of 0.75 mm 2 , and that this represents a resistance at + 60 ° C. of 5.33 Ω. The nominal voltage Ubd is then 80 V, G1=0.075 and G2=0.1. Considering that the normal difference between Uac and G2. Ubd (in other words the value at the output e of the second differential amplifier DIFF  342 ) is ±2 V, the value of Vref is fixed at 3 V. It is lastly considered that the occurrence of a fault in the main electrical cabling  130  results in a voltage drop of 15 V in the framework of an electrical power supply of 270 VDC. 
     At the time t 1 , a fault in the main electrical cabling  130  appears, leading to the formation of a serial arc or an abrupt increase of temperature in a connection. The electrical potential Vc at the output c of the main electrical cabling  130  decreases, together with the electrical potential Vb at the input b of the monitor electrical cabling  140 . The formation of a serial arc maintains the electrical potential Va at the input of the main electrical cabling  130 . As a consequence, the voltage Uac increases, which increases the voltage at the output g of the third differential amplifier DIFF  343 . When the voltage at the output g of the third differential amplifier DIFF  343  exceeds Vref, the state Sh of the output h of the comparator COMP  350  goes from the low state (“0”) to the high state (“1”), which represents the detection of the fault in the main electrical cabling  130  and of the formation of a serial arc. 
     If the electrical voltage Uac were to vary because of variations in temperature along the main electrical cabling, the voltage Ubd would vary in the same way given that the monitor electrical cabling  140  is installed alongside the main electrical cabling  130  and that the current I 2  is adjusted on the current I 9 . As far as the variation of electrical potential along the return cable  145  is concerned, this would be negligible. A fault in the main electrical cabling  130  resulting in the formation of a serial arc or an increase in connection resistance would be detected despite these variations in temperature. 
     The description hereinabove details embodiments based on an electrical generator supplying a positive DC voltage. Adapting them to a generator supplying a negative DC voltage is then trivial for those skilled in the art (direction of the current, connection of the inputs of the differential amplifiers DIFF and of the comparator COMP  350 , etc.). 
     In the case of an AC voltage generator, the voltages “e” at the output of the differential amplifier DIFF  342  and “f” at the output of the differential amplifier DIFF  341  are transformed upstream into RMS (Root Mean Square) values by, for example, using a converter or a full-wave rectifier without threshold followed by a low-pass filter, prior to being fed into the differential amplifier DIFF  343 . 
     The subject matter disclosed herein can be implemented in or with software in combination with hardware and/or firmware. For example, the subject matter described herein can be implemented in software executed by a processor or processing unit. In one exemplary implementation, the subject matter described herein can be implemented using a computer readable medium having stored thereon computer executable instructions that when executed by a processor of a computer control the computer to perform steps. Exemplary computer readable mediums suitable for implementing the subject matter described herein include non-transitory devices, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein can be located on a single device or computing platform or can be distributed across multiple devices or computing platforms. 
     While at least one example embodiment of the invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the example embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “an” or “one” do not exclude a plural number, and the term “or” by either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.