Method and device for protection against electric arcs

Abstract

The invention relates to a method for detecting an electric arc in a piece of equipment, the method comprising the steps of: electrically connecting the intermediate node of a supply voltage divider to the frame of the equipment.

Description

Description Title: METHOD AND DEVICE FOR PROTECTION AGAINST ELECTRIC ARCS technical field

[0001] This disclosure relates to the field of electrical installations and, in particular, a method and device for protecting an electrical installation in the event of an electric arc. The intended application, without limitation, is related to onboard installations, and specifically to aircraft propulsion systems. Previous technique

[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 different countries. 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 less energy-intensive and more environmentally friendly aeronautical components and products 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 weight reduction of aircraft, particularly 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 involves producing at least part of the energy required for an aircraft's flight using an electric machine. The use of this type of machine significantly increases the level of onboard electrical power.

[0007] The risk of electrical arcing is increasing. It is therefore essential to protect installations in the event of an electrical arc.

[0008] EP 3 442 087 A1 describes a means for detecting an electric arc. This system, implemented for an alternating current circuit, uses complex algorithms and requires significant computing power to ensure that the system's reaction time upon arc formation is sufficiently short to protect the installations. Reaction times sometimes exceed 100 ms, and the necessary hardware includes high-precision current sensors, resulting in increased costs and weight.

[0009] Therefore, there is a need for a method of detecting electric arcs that is suitable for direct current and does not require high-capacity computing resources. Summary

[0010] This disclosure improves the situation.

[0011] A method for detecting an electric arc in equipment is proposed, the method comprising the steps of: providing an electrical circuit comprising: a direct current supply providing at least 100 V, an electrical load and a voltage divider comprising a first resistance between a first node and a second node, and a second resistance between the second node and a third node; electrically connecting the second node to the chassis of the equipment; supplying the electrical load with current; measuring a first electrical voltage between the first and second nodes, a second electrical voltage between the second and third nodes, and a third electrical voltage between the first and third nodes;calculate a first detection voltage and / or a second detection voltage, the first detection voltage being obtained by subtracting twice the first voltage from the third voltage, and the second detection voltage being obtained by subtracting twice the second voltage from the third voltage; interrupt the current distribution in the equipment when the first and / or the second detection voltage exceeds a predetermined threshold.

[0012] It is therefore possible, by comparing voltages, to detect an electrical current passing through the chassis and a sign of an electric arc, without resorting to complex equipment with a large computing capacity, and with a faster reaction time.

[0013] According to another aspect, an electrical system is proposed comprising: equipment with a chassis; a DC power supply providing at least 100 V; an electrical load; a voltage divider comprising a first resistance between a first node and a second node, and a second resistance between the second node and a third node, the second node being connected to the chassis of the equipment; and a safety means configured to: measure a first electrical voltage between the first and second nodes, a second electrical voltage between the second and third nodes, and a third electrical voltage between the first and third nodes;calculate a first detection voltage and / or a second detection voltage, the first detection voltage being obtained by subtracting twice the first voltage from the third voltage, and the second detection voltage being obtained by subtracting twice the second voltage from the third voltage; and interrupt the distribution of; current in the equipment when the first and / or second detection voltage exceeds a predetermined threshold.

[0014] The equipment could be an aircraft propulsion system.

[0015] In one variant, the equipment may be a connector, such as a harness or a shielded cable.

[0016] The power supply can provide a DC voltage of at least 100 V.

[0017] The invention also relates to an aircraft comprising an electrical system according to one of the embodiments described above. Brief description of the drawings

[0018] Other features, details, and advantages will become apparent upon reading the detailed description below and analyzing the attached drawings, on which:

[0019] [Fig. 1] shows an electrical circuit according to the present disclosure.

[0020] [Fig. 2] illustrates an enlarged part of the circuit in Figure 1.

[0021] [Fig. 3] represents a chronograph of different voltages of the circuit of figure 1.

[0022] [Fig. 4] shows a process according to this disclosure. Description of the implementation methods

[0023] Figure 1 shows an electrical circuit 1 comprising a DC voltage power supply 2. The voltage can be at least 100 V, e.g., 600 V, 800 V, 1000 V or more.

[0024] The circuit aims to supply an electrical load 4 with electrical current. This can be all or part of an aircraft propulsion system, and in particular a DC motor, mechanically connected to a blade (blade, fan, vane, etc.) designed to generate thrust.

[0025] A voltage divider 6 is provided in circuit 1. The divider 6 comprises two resistors R of the same value, arranged between a first three nodes A, B, C of the circuit.

[0026] According to this disclosure, the chassis of equipment 8, which may be the chassis of the electrical load 4, is directly connected to point B, the midpoint of the voltage divider 6.

[0027] Two points in the circuit, marked 10 and 12, are a priori indeterminate points, between which an electric arc can form.

[0028] Under normal operating conditions, no current flows between chassis 8 and voltage divider 6 (i=0). The voltage Umonitoring+ across the first resistor is equal to the voltage Umonitoring- across the second resistor. These voltages are equal to half the supply voltage Ualim.

[0029] According to the illustration in Figure 2, when an arc forms which extends until it touches the chassis 8, there is therefore a voltage Uarc / 2 between point A and point 10, and a voltage Uarc / 2 between point B and point 12. In other words, the current i is non-zero.

[0030] We can define a voltage Udetect+ and Udetect- which are such that: Udetect+=Ualim- 2*Umonitoring+ and Udetect-=Ualim-2*Umonitoring-.

[0031] When i is non-zero, the values ​​of the voltage Udetect+ and / or Udetect- are non-zero.

[0032] Therefore, connecting chassis 8 to point B allows the presence of an arc to be detected by a simple calculation based on two measured voltage values. The change in these values ​​is immediate, and detection can be achieved in less than 50 ms.

[0033] Figure 3 illustrates a chronograph of events. In a phase labeled I, no electric arc is formed, or an arc has formed but is not large enough to pose a threat to equipment. This is the case, for example, during the switching of a contactor.

[0034] We observe that in phase 1, Umonitoring+=Umonitoring-=Ualim / 2. In this case, Udétect+ and Udétect- are harmful.

[0035] In phase 2, the electric arc grows and touches the chassis. A current (i>0 in Figure 2) is created. Udetect+ and Udetect- are directly harmless.

[0036] A predetermined threshold can trigger an alert indicating the presence of a threatening electrical arc. This threshold can be a few volts or several tens of volts. Therefore, as soon as Udétect+ and / or Udétect- exceeds this threshold, it is certain that an electrical arc is present.

[0037] In phase 3, it is possible to adjust the power supply to stop the expansion of the electric arc. The various voltages then return to zero.

[0038] This disclosure also relates to a method 100 for detecting an electric arc in equipment as illustrated in Figure 4. The method 100 includes providing 110 an electrical circuit as described in Figure 3, connecting the chassis 8 of the equipment to be monitored to point B, the midpoint of the voltage divider 6, supplying 130 current to the electrical load 4, and measuring 140 the various voltages Ualim, Umonitoring+, and Umonitoring-. Finally, the method consists of calculating 150 the voltages Udétect+ and Udétect- as described above and interrupting the current supply when one or both of these calculated voltages exceed a threshold, which may be a few volts (for example, 5V).

[0039] This disclosure also covers a system comprising the circuit described above, the equipment to be protected, and a safety device. The safety device is designed to react upon detection of an electric arc. The safety device may be an electronic control unit, a solenoid valve, a circuit breaker, etc., whose function is to extinguish the electric arc, specifically by interrupting the current flow in the area affected by the arc. The safety device may be configured to perform the process described above, namely, to measure the voltages Usup>Lim, Umonitoring+, and Umonitoring-, and to perform the calculations of Udetect+ and Udetect-.

[0040] This system and the process described above thus make it possible to quickly control the formation of an electric arc without having to have significant computing resources. List of reference signs

[0041] 1: Circuit 2: Food 4: charge 6: Voltage divider 8: Chassis 10, 12: points of contact of the arc A, B, C: nodes; i: intensity R: resistances

Claims

Demands

1. A method (100) for detecting an electric arc in equipment, the method comprising the steps of: providing (110) an electrical circuit (1) comprising: a direct current supply (2), an electrical load (4), and a voltage divider (6) comprising a first resistance between a first node (A) and a second node (B), and a second resistance between the second node (B) and a third node (C); electrically connect (120) the second node (B) to the chassis (8) of the equipment; supply (130) the electrical load (4) with current; measure (140) a first electrical voltage (Umonitoring+) between the first (A) and the second node (B), a second electrical voltage (Umonitoring-) between the second (B) and the third node (C), and a third electrical voltage (Ualim) between the first (A) and the third node (C); calculate (150) a first detection voltage (Udetect+) and / or a second detection voltage (Udetect-), the first detection voltage (Udetect+) being obtained by subtracting twice the first voltage (Umonitoring+) from the third voltage (Ualim), and the second detection voltage (Udetect-) being obtained by subtracting twice the second voltage (Umonitoring-) from the third voltage (Ualim); interrupt (160) the current distribution in the equipment when the first and / or second detection voltage (Udetect+, Udetect-) exceeds a predetermined threshold.

2. Method (100) according to claim 1, wherein the equipment is an aircraft propulsion system.

3. Method (100) according to claim 1, wherein the equipment is a connector, in particular a harness or a shielded cable.

4. An electrical system comprising: equipment with a chassis (8); a DC power supply (2); an electrical load (4); a voltage divider (6) comprising a first resistor between a first node (A) and a second node (B), and a second resistor between the second node (B) and a third node (C), the second node (B) being connected to the chassis (8) of the equipment; and a safety means configured to: measure (140) a first electrical voltage (Umonitoring+) between the first (A) and the second node (B), a second electrical voltage (Umonitoring-) between the second (B) and the third node (C), and a third electrical voltage (Ualim) between the first (A) and the third node (C); calculate (150) a first detection voltage (Udétect+) and / or a second detection voltage (Udétect-), the first detection voltage (Udétect+) being obtained by subtracting twice the first voltage (Umonitoring+) to the third voltage (Ualim), and the second detection voltage (Udétect-) being obtained by subtracting twice the second voltage (Umonitoring-) from the third voltage (Ualim); and interrupt (160) the current distribution in the equipment when the first and / or second detection voltage (Udétect+, Udétect-) exceeds a predetermined threshold.

5. System according to claim 4, wherein the equipment is an aircraft propulsion system.

6. A system according to claim 4, wherein the equipment is a connector, in particular a harness or a shielded cable.

7. An aircraft comprising an electrical system according to any one of claims 4 to 6.

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