Insulation fault detection device

Abstract

Electrical circuit (10, 40) comprising: a DC power supply (12); an electrical load (14); and an insulation fault detection device (15, 41), arranged in parallel with the load (14), comprising: a voltage divider; a diode bridge (23); and a comparator (34) comparing a voltage at the output of the diode bridge and a setpoint voltage (Vcons). Figure 1

Description

Title of the invention: Insulation fault detection device technical field

[0001] This disclosure relates to the field of electrical installations and, in particular, to a device for detecting a ground fault in an electrical installation. The intended application, without limitation, is related to onboard installations, and in particular to aircraft propulsion systems. Prior art

[0002] Climate change is a major concern for many legislative and regulatory bodies worldwide. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various states. In particular, an ambitious standard applies to both new types of aircraft and those already in service, requiring the implementation of technological solutions to bring them into compliance with current regulations. Civil aviation has been actively working for several years now to contribute to the fight against climate change.

[0003] Technological research efforts have already led to very significant improvements in the environmental performance of aircraft. The Applicant takes into account the factors impacting all phases of design and development in order to obtain aeronautical components and products that are less energy-intensive, more environmentally friendly, and whose integration and use in civil aviation result in moderate environmental consequences, with the aim of improving the energy efficiency of aircraft.

[0004] Consequently, the Applicant is constantly working to reduce its negative climate impact by using methods and operating virtuous development and manufacturing processes that minimize greenhouse gas emissions to the minimum possible in order to reduce the environmental footprint of its activity.

[0005] This sustained research and development work focuses on new generations of aircraft engines, the lightening of aircraft, in particular through the materials used and lighter on-board equipment, the development of the use of electrical technologies to provide propulsion, and, as essential complements to technological progress, aviation biofuels.

[0006] In this context, electric or hybrid electric-thermal propulsion consists of producing at least part of the energy required for an aircraft to fly by means of an electric machine. These electric propulsion systems use Network architectures isolated from the chassis. The objective of these architectures is to allow continuity of electrical distribution even in the event of a first insulation fault.

[0007] Electric propulsion systems therefore require insulation detection devices to identify current leakage to earth. These devices, using various components to monitor and measure voltage and current variations, must be capable of measuring leakage currents and providing alerts in the event of detected anomalies.

[0008] Thus, detecting insulation faults in an embedded power supply chain often requires additional hardware and software components, notably using algorithms to estimate leakage impedance. However, these solutions may require complex components and significant computing resources, without always providing an accurate measurement.

[0009] There is therefore a need for a device capable of overcoming these limitations, by providing a reliable measurement of leakage impedance, without requiring complex hardware components or algorithmic processing. Summary

[0010] This disclosure improves the situation.

[0011] To this end, an electrical circuit is proposed comprising: a direct current supply; an electrical load; an insulation fault detection device, arranged in parallel with the load, comprising: a voltage divider bridge comprising a first resistor between a first node and a second node, and a second resistor between the second node and a third node; a diode bridge, connected to the second node via a fourth node, said diode bridge comprising: a first diode arranged between the fourth node and a fifth node, capable of allowing a current to flow from the fifth node to the fourth node; a second diode arranged between the fourth node and a sixth node, capable of allowing a current to flow from the fourth node to the sixth node; a third diode arranged between the fifth node and a seventh node connected to electrical ground, capable of allowing a current to flow from the fifth node to the seventh node;and a fourth diode arranged between the seventh and sixth nodes, capable of allowing current to flow from the seventh node to the sixth node; a third resistor arranged in parallel with the diode bridge, between the fifth and sixth nodes; an isolation amplifier with one output and two inputs connected, one to the fifth node and the other to the sixth node; and a comparator comparing a voltage at the output of the isolation amplifier and a setpoint voltage.

[0012] An insulation fault refers to a situation in which the electrical insulation between a conductor and earth is compromised, thereby inducing an unwanted leakage current. Detecting these faults is important because this phenomenon can affect the proper functioning of isolated electrical systems, for example in an aircraft during flight.

[0013] An isolation amplifier is an electronic device used to transmit an electrical signal from one part of a circuit to another while preventing the direct flow of electric current between high-voltage and low-voltage parts of the circuit, thus ensuring the safety and integrity of the system. The isolation amplifier makes it possible to measure signals without interference, even in environments where significant potential differences exist.

[0014] The use of a voltage divider in the detection device makes it possible to measure voltage variations due to an insulation fault. Indeed, a voltage Vs across the third resistor, and consequently the output voltage of the isolation amplifier as well, represents a value indicative of the current leakage to earth. This voltage can, for example, be expressed as _ ye* ——JQ—— , where Ve is the voltage supplied by the DC power supply, / C is the resistance value of the third resistor, R is the resistance value of the first and second resistors, and Rf is the leakage resistance value.

[0015] The comparator allows the output voltage of the isolation amplifier, i.e., a voltage representing the current leakage, to be compared to a setpoint voltage. The setpoint voltage can be a predefined reference value based on a chosen maximum leakage current tolerance, i.e., minimum leakage resistance. For example, the tolerated leakage current could be on the order of a few tens of milliamperes. Thus, the setpoint voltage can serve as a threshold for triggering actions, such as alerts, for example, when the output voltage of the isolation amplifier exceeds this value. Alternatively, actions can be triggered when the difference between the output voltage of the isolation amplifier and the setpoint voltage is greater than a predetermined threshold.

[0016] Thus, the use of such a device makes it possible to simplify the detection of insulation faults without requiring hardware components or complex algorithmic calculations, unlike existing solutions.

[0017] Furthermore, the use of a diode bridge, connected to the voltage divider bridge, makes it possible to rectify the measured voltage, in other words, to ensure that the voltages across the third resistor and at the output of the isolation amplifier are always positive. This allows, with few hardware components, a comparison of the leakage voltage to a single, positive setpoint, regardless of the positioning of the insulation fault in the electrical circuit, on the side of the positive or negative terminal of the current source.

[0018] The direct current power supply may include at least one of a battery or a fuel cell.

[0019] The insulation fault detection device may further include an indicator light, located at the output of the comparator, which lights up when the voltage at the output of the isolation amplifier is greater than the setpoint voltage.

[0020] Adding an indicator light to the comparator output provides a visual indication when an insulation fault is detected. This simplifies the monitoring process by providing an easily identifiable, reliable, and robust alert, thus facilitating the maintenance of on-board electrical systems and enabling a rapid response to detected faults.

[0021] This configuration reduces the need for manual intervention or frequent checks, as the indicator light illuminates automatically when the isolation amplifier's output voltage exceeds the setpoint voltage. This improves operational efficiency by enabling targeted maintenance operations when a fault is detected.

[0022] The diode bridge can be a Graetz bridge.

[0023] The insulation fault detection device may further include: a variable resistor arranged in parallel with the first and second resistors, connected to the first and third nodes; and a second isolation amplifier whose inputs are connected to the first node and to a slider of the variable resistor, and whose output constitutes the setpoint voltage.

[0024] Integrating a variable resistor in parallel with the first and second resistors ensures a fixed setpoint voltage regardless of variations in the voltage across the current source. The wiper of the variable resistor is a moving element controlled according to the voltage Ve.

[0025] This configuration is particularly advantageous when using a battery or fuel cell for DC power supply. Indeed, the voltage can vary depending on its state of charge, and this configuration allows the variable resistor to be controlled according to the state of charge so that the setpoint voltage always corresponds to a fixed, acceptable leakage resistance. In other words, this configuration compensates for variations in the battery or fuel cell voltage and ensures a constant setpoint voltage. This therefore ensures reliable detection of insulation faults, regardless of fluctuations in the battery or fuel cell's state of charge.

[0026] The invention also relates to an aircraft propulsion system comprising an electrical circuit as described above.

[0027] The invention also relates to an aircraft comprising an electrical circuit as described above.

[0028] The invention also relates to a method for checking insulation faults in an isolated electrical system, comprising the steps of: providing the electrical system with an electrical circuit as described above; and detecting an insulation fault by means of the electrical circuit's insulation fault detection device.

[0029] Thus, when an insulation fault is detected during the process, for example when the voltage at the output of the isolation amplifier is greater than a setpoint voltage, it is possible to take preventive measures to ensure the safety of the electrical system.

[0030] The invention also relates to a method for checking an aircraft's insulation fault comprising the steps of: supplying an aircraft equipment with an electrical circuit as described above; if the indicator light at the output of the comparator of the insulation fault detection device lights up, checking the insulation of the equipment.

[0031] By integrating an electrical circuit as described above into aircraft equipment, for example a propulsion system, reliable detection of insulation faults is ensured, which is important to guarantee the safety of on-board electrical systems.

[0032] When, for example during flight, the warning light illuminates, the aircraft crew can perform an insulation check of the equipment at the next stop. The use in this method of the electrical circuit described above allows for the early detection of insulation faults and enables verification, or even maintenance, before the equipment or other aircraft systems are damaged. Brief description of the drawings

[0033] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0034] [Fig. 1] shows an electrical circuit comprising an insulation fault detection device according to a first embodiment.

[0035] [Fig.2] shows an electrical circuit comprising an insulation fault detection device according to a second embodiment. Description of the implementation methods

[0036] Figure 1 shows an electrical circuit 10 according to this document. The electrical circuit 10 comprises a DC power supply 12 having positive terminals 12a and negative terminals 12b. A load 14 is connected to terminal 12a of the power supply 12 via a high-voltage (HV+) branch and to terminal 12b of the power supply 12 via a low-voltage (HV-) branch. An insulation fault detection device 15 is arranged in parallel with the load 14, being connected at a node 20 of the HV+ branch and a node 16 of the HV- branch. The insulation fault detection device 15 comprises a voltage divider bridge including a resistor Ri arranged between node 16 and a node 18 and a resistor R2 arranged between node 20 and node 18. The resistors Ri and R2 may have the same value.

[0037] A branch 21 connects node 18 of the voltage divider bridge to a node 22 of a diode bridge 23. The diode bridge 23 includes a first diode D1, disposed between node 22 and a node 24, capable of allowing current to flow from node 24 to node 22. The diode bridge 23 also includes a second diode D2, disposed between node 22 and a node 26, capable of allowing current to flow from node 22 to node 26. The diode bridge 23 also includes a third diode D3, disposed between node 24 and a node 28 connected to ground 30, capable of allowing current to flow from node 24 to node 28. The diode bridge 23 also includes a fourth diode D4, disposed between node 28 and node 26, capable of allowing current to flow from node 28 to node 26. The diode bridge 23 can to be a Graetz bridge.

[0038] A third resistor R is arranged in parallel with the diode bridge 23, between node 24 and node 26.

[0039] The insulation fault detection device 15 also includes an insulation amplifier 32 having an output 32c and two inputs 32a, 32b. Input 32a is connected to node 26 and input 32b is connected to node 24. The insulation amplifier 32 allows an electrical signal to be transmitted from one part of a circuit to another while preventing the direct passage of electrical current between high-voltage and low-voltage parts of the circuit, thus ensuring the safety and integrity of the system.

[0040] The insulation fault detection device 15 also includes a comparator 34 having a first input 34a connected to the output 32c of the insulation amplifier and a second input 34b which receives a setpoint voltage Vcons. The comparator 34 allows the output voltage of the insulation amplifier 32, representing a current leakage, to be compared with a setpoint voltage Vcons.

[0041] The use of a diode bridge 23, connected to the voltage divider bridge, ensures that the voltages across resistor R and at the output 32c of the isolation amplifier 32 are positive, regardless of the location of an insulation fault. Thus, the voltage compared to the setpoint voltage Vcons by the comparator 34 is always positive, regardless of the position of the current leakage, which can, for example, be located just as easily at the HV+ branch as at the HV- branch of circuit 10. Indeed, for example, if we choose Ri=R2=Rpont, a voltage Vs across the resistor R can be expressed as yÿ — y^ — where Ve is the voltage delivered by the DC power supply 12, R is the resistance value of resistor R, Rpond is the combined resistance value of resistors Ri and R2, and Rf is the leakage resistance value (formed by the conductors responsible for the leakage, connecting the nominally insulated circuit to ground). This facilitates the analysis and interpretation of leakage data.

[0042] The comparator output 34c is connected to an indicator light 36. The indicator light 36 can, for example, light up when the output voltage of the isolation amplifier 32 is greater than the setpoint voltage Vcons.

[0043] Figure 2 shows an electrical circuit 40 constituting an alternative to the circuit electrical 10 of [Fig.1]. In the case of circuit 40, the insulation fault detection device 41 further includes a variable resistor P arranged in parallel with the resistors Ri and R2, and thus connected to nodes 16 and 20. The variable resistor P also includes a slider C allowing the resistance of the variable resistor P to be adjusted by changing the point of contact on the resistive material.

[0044] The insulation fault detection device 41 also includes a second insulation amplifier 38 having two inputs 38a, 38b and an output 38c. Input 38a is connected to the wiper C of the variable resistor P and input 38b is connected to one terminal of the variable resistor P, for example at node 16 of the HV- branch. The voltage delivered at output 38c constitutes the setpoint voltage Vcons. Output 38c is therefore connected to input 34b of comparator 34.

[0045] Integrating the variable resistor P in parallel with resistors Ri and R2 allows the setpoint voltage Vcons to be dynamically adjusted according to variations in the DC supply voltage 12. This configuration is particularly advantageous when using a battery for the DC supply 12. Indeed, the voltage of a battery can vary depending on its state of charge, and this configuration compensates for these variations, ensuring a constant setpoint voltage Vcons. This therefore ensures reliable detection of insulation faults, independent of fluctuations in the voltage delivered by the DC supply 12.

Claims

Demands

1. Electrical circuit (10, 40) comprising: a DC power supply (12); an electrical load (14); an insulation fault detection device (15, 41), arranged in parallel with the load (14), comprising: a voltage divider bridge comprising a first resistance (Ri) between a first node (16) and a second node (18), and a second resistance (R2) between the second node (18) and a third node (20); a diode bridge (23), connected to the second node (18) via a fourth node (22), said diode bridge (23) comprising: a first diode (Dl) arranged between the fourth node (22) and a fifth node (24), capable of allowing current to flow from the fifth node (24) to the fourth node (22); a second diode (D2) arranged between the fourth node (22) and a sixth node (26), capable of allowing a current to pass from the fourth node (22) to the sixth node (26);a third diode (D3) disposed between the fifth node (24) and a seventh node (28) connected to the electrical ground (30), capable of allowing a current to flow from the fifth node (24) to the seventh node (28); and a fourth diode (D4) disposed between the seventh node (28) and the sixth node (26), capable of allowing a current to flow from the seventh node (28) to the sixth node (26); a third resistor (R) disposed in parallel with the diode bridge (23), between the fifth node (24) and the sixth node (26); an isolation amplifier (32) having an output (32c) and two inputs (32a, 32b) connected, for one to the fifth node (24) and for the other to the sixth node (26); and a comparator (34) comparing a voltage at the output of the isolation amplifier (32) and a setpoint voltage (Vcons).

2. Electrical circuit (10, 40) according to claim 1, wherein the DC power supply (12) comprises at least one of a battery or a fuel cell.

3. Electrical circuit (10, 40) according to claim 1 or 2, wherein said insulation fault detection device (15, 41) comprises in addition an indicator light (36), located at the output of the comparator (34), which lights up when the voltage at the output of the isolation amplifier (32) is greater than the setpoint voltage (Vcons).

4. Electrical circuit (10, 40) according to any one of the preceding claims, wherein the diode bridge (23) is a Graetz bridge.

5. Electrical circuit (40) according to any one of the preceding claims, wherein said insulation fault detection device (41) further comprises: a variable resistor (P) arranged in parallel with the first (Ri) and second (R2) resistors, connected to the first (16) and third nodes (20); and a second insulation amplifier (38) whose inputs (38a, 38b) are connected to the first node (16) and to a slider (C) of the variable resistor (P), and whose output (38c) constitutes the setpoint voltage (Vcons).

6. Aircraft propulsion system comprising an electrical circuit (10, 40) according to any one of the preceding claims.

7. Aircraft comprising an electrical circuit (10, 40) according to any one of claims 1 to 5.

8. Method for checking insulation fault in an isolated electrical system, comprising the steps of: providing the electrical system with an electrical circuit (10, 40) according to any one of claims 1 to 5; and detecting an insulation fault by means of the insulation fault detection device (15, 41) of the electrical circuit (10, 40).

9. Method for checking an aircraft's insulation fault comprising the steps of: supplying an aircraft equipment with an electrical circuit (10, 40) according to claim 3, optionally in combination with one of claims 4 or 5; if the indicator light (36) at the output of the comparator (34) of the insulation fault detection device (15, 41) lights up, check the insulation of the equipment.

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