Device and method for protecting an electrical installation

Abstract

The invention relates to a method for protecting an electrical installation, said electrical installation comprising:- a contactor- at least two sensors for measuring the electric current,- a pyrotechnic electrical cut-off device, the method comprising:- measuring the intensity of the current,- comparing said intensity of said current with two thresholds, and- if said intensity is between a first threshold and a second threshold, - transmitting a command to open said power contactor,- if said intensity is greater than said second threshold, - transmitting a command to trigger the opening of the pyrotechnic electrical cut-off device, - if the pyrotechnic electrical cut-off device does not open, - comparing said intensity of the current with a third threshold value, - if said intensity of the current is less than said third threshold value, transmitting a command to open said contactor.Figure for abstract: Fig. 1.

Description

Title of the invention: Device and method for protecting an electrical installation Technical field

[0001] The present invention relates to the general field of the protection of an electrical installation, and more particularly to the protection of a high voltage direct current power supply system. Prior art

[0002] Climate change is a major concern for many legislative and regulatory bodies around the world. Indeed, various restrictions on carbon emissions have been, are being, or will be adopted by various States. In particular, an ambitious standard applies both to new types of aircraft and those currently in circulation, requiring the implementation of technological solutions to make them compliant with current regulations. Civil aviation has been mobilizing for several years now to make a contribution to the fight against climate change.

[0003] Technological research efforts have already made it possible to significantly improve the environmental performance of aircraft. The Applicant takes into consideration the factors impacting all phases of design and development to obtain less energy-intensive, more environmentally friendly aeronautical components and products whose integration and use in civil aviation have moderate environmental impacts with the aim of improving the energy efficiency of aircraft. Consequently, the Applicant is constantly working to reduce its climate impact by using methods and operating virtuous development and manufacturing processes and minimizing greenhouse gas emissions to the minimum possible to reduce the environmental footprint of its activity.

[0004] This ongoing research and development work focuses in particular on the use of electrical technologies to provide propulsion.

[0005] In this context, electric vertical take-off and landing (eVTOL), electric conventional take-off and landing (eCTOL) and small aircraft for short flights (Air Taxi) platforms use new electric propulsion powered by high-voltage batteries. These high-voltage batteries, which contain significant amounts of energy, generally incorporate electrical protections based on fuses to be able to interrupt the line in the event of a direct short circuit, that is, when the two short-circuited points touch each other directly. These fuses thus protect the electrical source.

[0006] However, in the event of an overload or current flowing in an impedant short circuit, i.e. when the two short-circuited points are connected by an impedant medium, there is a first gray area between the protection provided by the fuses and that provided by a power contactor, in which the aircraft wiring is not protected. There is also a second gray area during very high short-circuit currents which can cause the contactor to levitate and damage it, and also limit the current flowing in the fuse, which delays its tripping.

[0007] Thus, the fuses and contactors usually present in high-voltage electrical networks, for example powered by high-voltage batteries, do not completely protect the electrical installation present between the electrical source and the load.

[0008] It is therefore desirable to have a means of electrical protection making it possible to protect the electrical installation of systems powered by a high voltage DC battery. Statement of the invention

[0009] The invention relates to a method for protecting an electrical installation placed between an electrical power supply and an electrical load, said electrical installation comprising: - a power contactor - at least two sensors configured to measure the electrical current flowing between the power supply and the load, - a pyrotechnic electrical cut-off device placed in series with the power contactor the method comprising: - measurement of the intensity of the current flowing in the electrical installation, - the comparison between said intensity of said current and a first threshold and a second threshold, said second threshold being greater than said first threshold, and - if said intensity is between said first threshold and said second threshold, - the transmission of a first command to open said power contactor, - if said intensity is greater than said second threshold, - the transmission of a first command to trigger the opening of the pyrotechnic electrical cut-off device, - if the pyrotechnic electrical cut-off device does not open, following said first command to trigger said pyrotechnic electrical cut-off device, - the comparison between said current intensity and a third threshold value representative of a breaking value of said power contactor, - if said current intensity is lower than said third threshold value, the transmission of a second command to open said power contactor.

[0010] The pyrotechnic electrical cut-off device, more commonly called a pyrofuse, is capable of opening the power circuit by a fuse effect when the currents are high (for example for currents up to 5 kA) or by a mechanical breaking effect thanks to the pyrotechnic actuator (present in the pyrofuse) for lower currents.

[0011] Thus, thanks to the device of the invention, the association of the pyrofuse and the power contactor makes it possible to open the power distribution line as soon as a short circuit or an overload appears.

[0012] Indeed, in the event of an overload, for example when the current measured by the sensors is between the nominal current and 1 kA), the fault current is seen by the current measurements made by the sensors and the controller can command the opening of the contactor. Whereas in the event of a short circuit, for example when the current measured by the sensors is between 1 kA and 5 kA, it is the pyrofuse which will be opened to protect the electrical installation.

[0013] According to certain embodiments, if said current intensity is greater than said third threshold value, the method comprises opening a fuse of said electrical installation.

[0014] According to certain embodiments, the method comprises: - if said contactor does not open, following said transmission of the first command to open said power contactor, - the transmission of a second command to trigger the opening of said pyrotechnic electrical cut-off device.

[0015] According to certain embodiments, the method comprises, - if said pyrotechnic electrical cut-off device (130) does not open, following the transmission of a second command to trigger the opening of said pyrotechnic electrical cut-off device (130), the opening of said fuse of said electrical installation.

[0016] This fuse provides additional protection for the electrical installation in the event of a major short circuit.

[0017] According to certain embodiments, the method comprises: - if said pyrofuse does not open, following the transmission of a second command to trigger the opening of said pyrotechnic electrical cut-off device, the opening of said fuse of said electrical installation.

[0018] According to certain embodiments, said opening of said cutting device pyrotechnic electric is operational after an initial delay.

[0019] According to certain embodiments, said opening of said power contactor is operational after a second time delay.

[0020] The invention also relates to an electrical device for protecting an electrical installation intended to be placed between an electrical power supply and an electrical load, the electrical power supply comprising positive and negative terminals, the device comprising: - a power contactor comprising a first contact intended to be connected to the positive terminal of the power supply and a second contact intended to be connected to the negative terminal of the power supply; - at least two sensors configured to measure the electric current flowing between the power supply and the electric load; - a pyrotechnic electrical cut-off device placed in series with the power contactor, and a controller configured to receive the electric current measured by the sensors and to - measure the intensity of the current flowing in the electrical installation, - comparing said intensity of said current and a first threshold and a second threshold, said second threshold being greater than said first threshold, and - if said intensity is between said first threshold and said second threshold, - transmit a first command to open said power contactor, - if said intensity is greater than said second threshold, - transmit a first command to trigger the opening of said pyrotechnic electrical cut-off device - if the pyrotechnic electrical cut-off device does not open, following said first command to trigger said pyrotechnic electrical cut-off device, - the comparison between said current intensity and a third threshold value representative of a breaking value of said power contactor (120), - if said current intensity is lower than said third threshold value, the transmission of a second command to open said power contactor.

[0021] The invention also relates to a high-voltage DC electrical power distribution board comprising the protection device according to at least one of the embodiments of the present invention and an electrical circuit for energizing an electrical load.

[0022] The invention also relates to an aircraft comprising an electrical protection device according to at least one of the embodiments of the present invention or a distribution board according to at least one of the embodiments of the present invention. invention.

[0023] Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an exemplary embodiment thereof without any limiting character. Brief description of the drawings

[0024] [Fig-1] [Fig.l] represents, in a schematic and partial manner, the device electrical protection according to one embodiment of the invention,

[0025] [Fig.2] [Fig.2] schematically represents a method of controlling the protection device of [Fig.l] according to an embodiment of the invention,

[0026] [Fig.3] [Fig.3] represents charts of the temporal evolution of the intensity in the different elements affected by an electrical fault. Description of the embodiments

[0027] In the description, the term “pyrofuse” designates the pyrotechnic electrical cut-off device.

[0028] [Fig.l] schematically and partially represents an electrical protection device 100 according to one embodiment of the invention.

[0029] The device 100 makes it possible to electrically protect an electrical installation which would be placed between the positive 1011 and negative 1012 terminals of an electrical power supply 101 and an electrical load 102. The electrical installation which is protected is formed of the device 100 and the power harnesses connecting the electrical load 102 and the electrical power supply 101 to the device 100.

[0030] The device 100 comprises a power contactor 120, a pyrotechnic electrical cut-off device 130, more commonly called a pyrofuse, two sensors at 161 and 162, a pre-charge circuit 150, a relay 140 and a controller 110.

[0031] The power contactor 120 and the pyrofuse 130 are connected in series.

[0032] The power contactor 120 comprises a first contact 121 which is connected to the positive terminal 1011 of the power supply 101 and a second contact 122 which is connected to the negative terminal 1012 of the power supply 101. It makes it possible to cut off the flow of current between the power supply 101 and the electrical load 102.

[0033] For example, the power contactor 120 has the particular characteristic of being able to open in a maximum of 20 ms for a current lower than its breaking capacity. This time is mainly due to mechanical constraints of the component.

[0034] The sensors 161 and 162 are configured to measure the electrical currents flowing between the power supply 101 and the power contactor 120.

[0035] The sensors 161 and 162 may be sensors of different types such as example, but not limited to, Hall effect sensors, or LEM sensors, or Néel effect sensors.

[0036] The pre-charging electrical circuit 150 comprises input terminals 151 and 152 which are placed between the electrical power supply 101 and the power contactor 120 and output terminals 153 and 154 which are connected to the electrical load 102. It makes it possible to limit the electrical current flowing to the electrical load 102 before the power contactor 120 closes.

[0037] The relay 140 is connected to the input terminals 151 and 152 of the precharging electrical circuit 150 in order to be able to connect or disconnect it from the main electrical network.

[0038] The pyrofuse 130 is connected to the negative terminal 1012 of the power supply 101 and to the second contact 122 of the power contactor 120.

[0039] For example, the pyrofuse 130 has the particular characteristic of being able to open in 3 ms maximum and for a current of several kilo-amperes. This time is mainly due to the detection of the fault, and the ignition of the pyrotechnic device.

[0040] The controller 110 is configured to receive the current measurements from the sensors 161 and 162 and to implement the method described with reference to [Fig.2].

[0041] The device 100 may also comprise a fuse connected to the positive terminal 1011 of the power supply 101 and to the first contact 121 of the power contactor 120. This fuse makes it possible to protect the power supply 101 in the event of a high current, for example between 5 kA and 50 kA, and also to have a dissimilarity of the electrical protection compared to the other devices mentioned (power contactor 120 and pyrofuse 130)

[0042] The device 100 may also comprise a magnetic probe, integrated at the level of the pyrofuse 130. This magnetic probe makes it possible to detect a short circuit and to trigger the opening of the pyrofuse 130 to protect the electrical installation. This makes it possible to detect an abnormal current in a manner different from the current sensors 161 and 162 and thus to improve the safety of the device 100.

[0043] [Fig.2] schematically represents a logic diagram of the control method implemented by the protection device 110 of [Fig.1] according to one embodiment of the invention.

[0044] Prior to the steps of this method, it is considered that the power contactor 120, the pyrofuse 130 are closed to the electrical load 102.

[0045] The method comprises, step E1, the measurement of the electric current flowing in the protection device 100 using the sensors 161, 162 and the comparison of the measured current I with a first current threshold Si. When the intensity of the measured current is greater than Si then it is monitored that this intensity remains between the threshold Si and a second threshold S2, step E2. When the measured intensity I passes above the threshold S2, the opening of the pyrofuse is triggered, step E4. This opening is triggered, for example, only after 5 ms, step E3. This time delay can be linked - to the fault detection time, - to the opening time of the pyrofuse, for example 3 ms as indicated previously.

[0046] The pyrofuse can be triggered in at least two ways. According to a first embodiment, the pyrofuse can comprise a magnetic sensor and it triggers its opening autonomously. According to a second embodiment, it can be controlled by a command from the controller 110 or from an external system. If the pyrofuse opens, step E5, then the process ends. It can be noted that the pyrofuse, following its opening, must be changed, for example during a maintenance operation.

[0047] If the pyrofuse does not open (for example because it has a fault), step E5, the change in the intensity I is detected during a step E6 and if this intensity is lower than the intensity which leads to a break in the contactor 120 (for example 4000A), then the opening of the contactor 120 is commanded, step E7.

[0048] In practice, the current cannot be measured up to 4000A. It can be ensured during the system design phase that the fuse will open the circuit before the contactor for current values ​​exceeding the contactor's capability threshold.

[0049] By rupture, we can mean that the protection of the contactor is no longer operational because beyond 4000A for example, the contactor can stick under the effect of the high intensity of the current and no longer open. Otherwise, if the intensity is greater than the intensity which leads to a rupture of the contactor 120, we move on to step E9 in which the fuse opens.

[0050] If, following the command to open the contactor 120, the contactor 120 opens, step E8, the method ends. Otherwise, if the contactor 120 does not open, we proceed to step E9 in which the is triggered. The method ends following step E9.

[0051] If, during step E2 the measured intensity is greater than Si but remains less than S2, then we move on to step Eli after a time delay of 200 ms for example, step E10. This time delay is preferably adjustable and can be adjusted according to the characteristics of the installation. During step Eli, an instruction to open the contactor 120 is transmitted, as during the previous step E7. If, following the command to open the contactor 120, the contactor 120 opens, step E12, the method ends. Otherwise, if the contactor 120 does not open, we move on to step E13 in which a command to open the pyrofuse 130 is transmitted. If the pyrofuse 130 opens, step El4, the method ends. Otherwise, if the pyrofuse 130 does not open, we move on to step E9 in which the fuse is triggered.

[0052] The first current threshold Si is for example between the nominal current and 1 kA, and the second current threshold S2 is for example between 1 kA and 5 kA. According to another example, the first current threshold Si is equal to the nominal current and the second current threshold S2 is equal to 1 kA. The IkA threshold is adjustable, for example according to the characteristics of the installation and the capacities of the contactor linked to the conditions of use and in particular the altitude.

[0053] The 5kA threshold may depend on the capabilities of the pyrotechnic device.

[0054] Another object of the invention is a high-voltage DC electrical power distribution board comprising the protection device of the invention and an electrical circuit for energizing an electrical load. The electrical energizing circuit is an electronic pre-charging system which makes it possible to charge the capacitors of the electrical loads by limiting the current, to avoid significant current draws (current of a few kiloamperes) linked to the connection of the capacitors of the high-voltage loads. This makes it possible to protect the electrical network during switching by being optimized in mass and volume compared to a conventional resistance system.

[0055] In the case of an electrically powered aircraft, the board can thus be connected at its output terminals to the various electrical loads of the aircraft and at its input terminals to the electrical power sources of the aircraft. The electrical power source can for example be a high voltage battery and the electrical load an electric motor.

[0056] It can also be connected to the overall aircraft control system and to the aircraft emergency system. The pyrofuse can thus, for example, be controlled by the overall aircraft system and / or by the emergency system.

[0057] In addition, the distribution board as described makes it possible to optimize the distribution of the electrical components of the protection device and the power-up circuit as well as the various electrical protections of the components present on the board.

[0058] The measurement or detection of excessive current intensity can also be carried out by a magnetic current probe integrated into the pyrofuse.

[0059] [Fig. 3] represents an evolution of the electrical protection curves and the main constraints of the different components according to certain embodiments. In [Fig. 3], time is represented on the abscissa and intensity is represented on the ordinate. The time and intensity scales are logarithmic scales. It is understood that the values ​​illustrated on these curves are given as examples.

[0060] The curves represent the intensity acceptable by different components of an aircraft, for a corresponding duration, represented by the time on the abscissa. We therefore see that the different components are capable of supporting high intensities for shorter durations than lower intensities.

[0061] The “fuse” curve represents an approximation of the melting curve of the power fuse integrated into the battery.

[0062] The “wiring 2” curve represents the energy limit acceptable by a type 2 cable, without there being any damaging effect (so-called “no-damage” curve) expressed in Amperes over time. For example, type 2 wiring can withstand an intensity slightly greater than 10000A for 300ms and withstand an intensity greater than the S2 threshold, approximately 380A for a continuous duration.

[0063] The “engine” curve represents the acceptable energy limit in the engine beyond which it can no longer contain this energy (piercing of the casing for example) and the fault can propagate to its environment.

[0064] The “engine envelope” points represent the operating points of the engine in its functional regimes.

[0065] This graph also shows the thresholds S1 and S2 implemented in the present invention. The thresholds S1 and S2 are determined so as to ensure that none of the components is exposed for a duration t to an intensity greater than that which it cannot withstand for this duration t. According to the example in [Fig. 3], S2 is set at 350 Amperes and S1 at 250 Amperes.

[0066] The threshold S2 is set so as to be lower than the smoke curve of cable 2, curve “wiring 2”.

[0067] The threshold Si is set so as to be higher than the operational current levels of the motors and corresponds to the so-called “overload” threshold.

[0068] The maximum height in intensity of the pyrofuse and contactor curves correspond to the maximum capacity of the components. According to the example given in [Fig.3], we can see that these values ​​correspond to 5000A for the pyrofuse and to 4000A for the contactor

[0069] Wiring 2 is protected by the pyrofuse and by the contactor, the threshold S2 can be determined so that it can protect wiring 2 from a possible fire. It can be seen that for a duration of 1000s and beyond, wiring 2 can withstand an intensity slightly higher than the value of threshold S2. Thus, wiring 2 is effectively protected both by the contactor and by the pyrofuse.

Claims

Claims

1. Method for protecting an electrical installation placed between a power supply (101) and an electrical load (102), said electrical installation comprising: - a power contactor (120) - at least two sensors (161, 162) configured to measure the electric current flowing between the power supply and the load (102), - a pyrotechnic electrical cut-off device (130) placed in series with the power contactor (120), the method comprising: - measuring the intensity of the current flowing in the electrical installation, - comparing said intensity of said current with a first threshold (SJ and a second threshold (S2), said second threshold (Si) being greater than said first threshold (S2), and - if said intensity is between said first threshold (Si) and said second threshold (S2), - transmitting a first command to open said power contactor (120),- if said intensity is greater than said second threshold (S2), - the transmission of a first command to trigger the opening of the pyrotechnic electrical cut-off device (130), - if the pyrotechnic electrical cut-off device (130) does not open, following said first command to trigger said pyrotechnic electrical cut-off device (130), - the comparison between said current intensity and a third threshold value representative of a breaking value of said power contactor (120), - if said current intensity is less than said third threshold value, the transmission of a second command to open said power contactor (120).,

2. Method according to claim 1 comprising: - if said current intensity is greater than said third threshold value, opening a fuse of said electrical installation.

3. Method according to one of the preceding claims comprising - if said contactor does not open, following said transmission of the first command to open said power contactor (120), - the transmission of a second command to trigger the opening of said pyrotechnic electrical cut-off device (130).

4. Method according to claim 3 comprising - if said pyrotechnic electrical cut-off device (130) does not open, following the transmission of a second command to trigger the opening of said pyrotechnic electrical cut-off device (130), the opening of said fuse of said electrical installation.

5. Method according to one of the preceding claims in which said opening of said pyrotechnic electrical cut-off device (130) is operational after a first time delay.

6. Method according to one of the preceding claims in which said opening of said power contactor (120) is operational after a second time delay.

7. An electrical device (100) for protecting an electrical installation intended to be placed between a power supply (101) and an electrical load (102), the power supply (101) comprising positive (1011) and negative (1012) terminals, the device comprising: - a power contactor (120) comprising a first contact (121) intended to be connected to the positive terminal (1011) of the power supply and a second contact (122) intended to be connected to the negative terminal (1012) of the power supply; - at least two sensors (161, 162) configured to measure the electric current flowing between the power supply (101) and the electrical load (102);- a pyrotechnic electrical cut-off device (130) placed in series with the power contactor (120), and a controller (110) configured to receive the electrical current measured by the sensors and to - measure the intensity of the current flowing in the electrical installation, - compare said intensity of said current and a first threshold (SJ and a second threshold (S2), said second threshold (S2) being greater than said first threshold (SJ, and - if said intensity is between said first threshold (Si) and said second threshold (S2), - transmit a first command to open said power contactor (120),;

8.

9. - if said intensity is greater than said second threshold (S2), - transmit a first command to trigger the opening of said pyrotechnic electrical cut-off device (130) - if the pyrotechnic electrical cut-off device (130) does not open, following said first command to trigger said pyrotechnic electrical cut-off device (130), - the comparison between said current intensity and a third threshold value representative of a breaking value of said power contactor (120), - if said current intensity is lower than said third threshold value, the transmission of a second command to open said power contactor (120). High voltage DC electrical power distribution board comprising the protection device according to claim 7 and an electrical circuit for energizing an electrical load. Aircraft comprising an electrical protection device according to claim 7 or a distribution board according to claim 8.

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