ELECTRICAL LINK COMPRISING AN ELECTRICAL PROTECTION DEVICE WITH INTEGRITY TEST

An electrical link between a DC source and a user apparatus (250) including an electrical conductor (240) having an insulating cover and an electrical protection device (200) which includes: a conductive sleeve (280) around the insulating cover, a circuit breaker (210) on the electrical conductor (240), a biasing module (245) configured to voltage-bias the conductive sleeve (280) with a DC voltage; a device (250a) for limiting the bias voltage of the conductive sleeve having a limit voltage lower than the test voltage; and a detection module (220) connected to the conductive sleeve (280) and configured to detect a limiting of the bias voltage of the conductive sleeve by the limiting device (250a), and to command the circuit breaker (210) on the basis of the detection.

RELATED APPLICATION

This application claims priority to French patent application 1755085 filed Jun. 8, 2017, the entirety of which is incorporated by reference.

TECHNICAL FIELD

The present invention relates to an electrical link for transmission of a DC high voltage to a user apparatus. The electrical link comprises an electrical protection device for supplying electric power in a secure manner.

BACKGROUND

An electrical power supply installation on an aircraft conventionally comprises an electric power source connected to an electrically powered user apparatus via an electrical link formed of an electrical conductor covered with an insulating cover. The conventional electrical link includes a circuit breaker that interrupts current in the conductor in response to an overload current or a short-circuit current in the conductor.

The demand for electric power on commercial aircraft has in recent years increased due to increasing demands of user devices in an aircraft. This increasing demand leads to a need power for increases in voltage levels of electric power supply systems on aircraft. For example, electrical power supply systems have in the past provided 115 volts AC (alternating current) and 28 volts DC (direct current). Current electrical power systems provide +/−270 volts DC or higher, such as 540 volts DC. The higher voltage levels in current aircraft electrical power supplies requires safety devices to, for example, ensure that aircraft maintenance staff may safely work on electrical systems in the event of disconnection or of breakage of an electrical link in the electrical supply installation. Conventional circuit breakers are not optimal, such as due to slow response times, for detecting a breakage of the electrical continuity of an electrical link.

SUMMARY

There is a need to find a device that provides electrical protection of an electrical link so that high-voltage electric power may be supplied user apparatus(es) in a vehicle.

The invention relates to an electrical link designed to link a DC high-voltage power source to a user apparatus. The electrical link comprises an electrical conductor surrounded by an insulating cover and an electrical protection device including: a conductive sleeve arranged around the insulating cover, and a circuit breaker arranged on the electrical conductor and configured to cut off a current transiting through the conductor. The electrical protection device may further comprise: (i) a biasing module configured to voltage-bias the conductive sleeve with a DC test voltage; (ii) a device for limiting the bias voltage of the conductive sleeve having a limit voltage lower than the test voltage; and (iii) a detection module connected to the conductive sleeve and configured to detect a limiting, or lack thereof, of the bias voltage of the conductive sleeve by the limiting device, and to command the circuit breaker to interrupt current in the conductor if there is no limits of the biases voltage on the conductive sleeve.

The biasing module may comprise a DC voltage source supplying the test voltage, connected to the conductive sleeve.

The detection module may comprise: (i) a comparator with a first input connected to the conductive sleeve and whose second input is connected to a DC voltage generator supplying a reference voltage; and (ii) a microcontroller connected between an output of the comparator and the circuit breaker, the microcontroller being configured to send a command signal to the circuit breaker on the basis of an output signal received from the comparator. An insulating cover may surround the conductive sleeve.

The invention may be embodied to ensure that a high-voltage electric power supply is safely connected to a user apparatus in a vehicle, such as an aircraft. The invention may interrupt current in response to certain unsafe electrical conditions and thereby provide safety to maintenance staff working on the electrical link and user apparatus.

DETAILED DISCLOSURE OF EMBODIMENTS

With reference toFIG. 1, an aircraft10includes an electrical installation having a high-voltage electric power source270connected to a user apparatus250via an electrical link290(FIG. 2) including a conductor240, a current return line260and an electrical protection device200.

The high-voltage electric power source270supplies a DC high voltage (HV) such as on the order of +/−270 volts DC, +/−540 volts DC or some other DC high voltage.

The aircraft10furthermore comprises a conductive structure (not shown) that is formed by any metal/conductive element of the aircraft that is at the reference potential and forms a ground for purposes of electricity in the aircraft.

With reference toFIGS. 2 to 4, the electrical link290comprises an electrical conductor240surrounded by an insulating cover320(for example a plastic sleeve). A conductive sleeve280is a sleeve on the insulating cover320. An insulating cover310is a sleeve on the conductive sleeve280.

The electrical link290also includes the electrical protection device200, configured to test electrical continuity of the conductive sleeve280. The electrical protection device includes a conductive sleeve280on the insulating cover320of the conductor240, and electrical devices including a circuit breaker210, a biasing module245and a detection module220.

The electronic devices, including the circuit breaker210, biasing module245, and detection module220, are arranged in a secure housing12that may be situated upstream (that is to say on the side of the electric power source270) of the electrical link290. Voltage or signal limiting electronic devices250aare arranged in a secure housing12asituated downstream (that is to say on the side of the user apparatus250) of the electrical link290.

The voltage or signal limiting electronic device250alimits (lowers) the voltage in the conductive sleeve280. A break, crack or other physical interruption in the conductive sleeve prevents the limiting electronic device250afrom lowing the voltage Vslev on the conductive sleeve at the opposite end of the sleeve280near the electrical protective device200. Thus, an increase in the voltage Vslev at the opposite end of the conductive sleeve indicates a break or other failure of the sleeve.

The electrical protection device200aims to test the mechanical/physical integrity of the electrical link290at the user apparatus250via a test of the electrical continuity of the conductive sleeve280over a defined test distance between the electronic devices210,245,220arranged in the secure housing12and the limiting electronic device250aarranged in the secure housing12a. The term ‘mechanical/physical integrity test’ is understood to mean the detection of a physical breakage of the electrical link290or a disconnection of the electrical link290from the secure housing12a, in particular when the electrical link290is formed from a plurality of parts connected to one another via connectors (not shown), the detection of the opening of the electrical link290at a connector.

The secure housing12amay be integrated into the user apparatus250, thus making it possible to detect a disconnection of the electrical link290from the user apparatus250.

The electronic devices210,220and245arranged in the housing12(seeFIG. 2) may comprise:

(i) a circuit breaker210connected to the electric power source270and, upon command, interrupts current from the electrical power source270to the user apparatus250via the electrical conductor240. The circuit breaker210operates as a switch that, when commanded, opens and thus interrupts current through the electrical conductor240;

(ii) a biasing module245for voltage-biasing the conductive sleeve280; and

(iii) a detection module220for testing the mechanical integrity of the electrical link290via a test of the electrical continuity of the conductive sleeve280.

With reference toFIG. 4, the biasing module245comprises a DC voltage source245asupplying a voltage V_test_PSS to apply a voltage bias the conductive sleeve280. The test voltage V_test_PSS delivered by the voltage source245ais a relatively low voltage, such as less than 50 volts in terms of absolute value.

The biasing module245furthermore comprises a protective circuit245b, such as for example a resistor in series or a current limiter (the limiter is shown inFIG. 4), that causes voltage fluctuations in the test voltage as it is applied to the conductive sleeve. The protective circuit245bis in series between the DC voltage supply245band the conductive sleeve280.

The test voltage may be applied to the conductive sleeve at a region of the sleeve nearest the end of the conductor connected to the high voltage DC power source270. The voltage Vslev is the voltage on the conductive sleeve and is related to the test voltage applied to the conductive sleeve.

The voltage source245ais connected in series between the current return line260and a first terminal of the protective circuit245b. A second terminal of the protective circuit245bis connected to the conductive sleeve280.

The detection module220comprises a comparator220aand a microcontroller220breceiving as an input the output signal VComp of the comparator220a. An output of the microcontroller220bis applied to control the circuit breaker210.

The microcontroller220breceives an output signal VComp of the comparator220a. The microcontroller220bis configured to supply a command signal to the circuit breaker210to cause the circuit breaker to open and thereby interrupt current in the electrical link.

The conductive sleeve280is biased, such as continually, by the test voltage. The detection module220may continuously monitor the continuity of the conductive sleeve280and is ready to command the circuit breaker in the event of an anomaly in the conductivity of the conductive sleeve. The conductivity of the conductive sleeve is monitored based on the voltage Vslev on the conductive sleeve.

The comparator220ais connected, at a first input, to the conductive sleeve280, and, at a second input, to a DC voltage generator (not shown) supplying what is termed a reference voltage Vref.

The comparator220acompares the voltage Vslev in the conductive sleeve280with the reference voltage Vref so as to test the mechanical/physical integrity of the electrical link290. The output signal VComp of the comparator is in either: a first state (for example 0 in Boolean logic) indicative of an absence of a physical/mechanical integrity fault with the electrical link290, or a second state (for example 1) indicative of a physical/mechanical integrity fault with the electrical link290(disconnection or breakage of the electrical link).

The reference voltage Vref is chosen depending on the value of the voltage Vlim of the limiting electronic device250a, and depending on the value of the test voltage V_test_PSS. The negative input of the comparator220ais linked to the DC voltage generator that supplies the reference voltage Vref. The reference voltage is lower than the voltage V_test_PSS.

The role of the limiting electronic device250aarranged is to assist in detecting a break or failure of the conductive sleeve280. The limiting electronic device250ais at an end of the conductive sleeve opposite to the end connected to the biasing module245and the comparator220. The limiting electronic device250alimits the voltage on the conductive sleeve280to a level below the test voltage V_test_PSS provided by the DC voltage source245b.

The limiting electronic device250amay be a voltage-limiting diode, such as a Zener diode, with a limit voltage Vlim chosen such that the voltage limiter limits the voltage Vslev on the conductive sleeve to a level less than the test voltage V_test_PSS supplied by the voltage source245d. Thus, Vlim is lower than the test voltage V_test_PSS. One terminal of the voltage-limiting diode250ais connected to a first termination at an end of the conductive sleeve280at or near a user apparatus. The other terminal of the limiting electronic device250ais connected to the current return line260.

According to this example, the voltage Vref is equal to 40 volts for V_test_PSS at 45 volts and a limit voltage Vlim at 35 volts. The output signal VComp of the comparator220ais in a first state (for example 0 in Boolean logic) as long as Vslev is lower than Vref (when there is no integrity fault with the sleeve280), and changes to the second state (for example 1) when Vslev is greater than Vref (thereby indicating a breakage of the continuity of the conductive sleeve280, and therefore potentially a disconnection of the electrical link290).

With reference toFIG. 5, what is shown is an example of the evolution of the signals Vref, Vslev, HV and VComp over time when, starting from a time T1, the electrical link290is disconnected from the user apparatus250, the latter comprising the secure housing12a.

In this example, the high-voltage power source270produces a positive voltage HV:

Before the time T1, there is no integrity fault with the conductive sleeve280. Before the time T1, the signal Vslev on the conductive sleeve280is equal to Vlim. The output signal VComp of the comparator220ais therefore in its first state, for example at 0 in Boolean logic.

Starting from the time T1, the continuity of the conductive sleeve280is broken. The break of the continuity of the conductive sleeve280interrupts current through the conductive sleeve. Thus, the limiting electronic device250aat the far end of the conductive sleeve is no longer able to limit the voltage Vslev at the opposite end of the conductive sleeve near the electrical protection device. Because there is no limiting by the limiting electronic device250a, the voltage on the conductive sleeve280is at the test voltage level V_test_PSS.

After T1, the voltage Vslev on the conductive sleeve280is equal to the test voltage V_test_PSS of 45 volts and is greater than the reference voltage Vref. Immediately after (or during a short period T5bsuch as a few milliseconds) the voltage Vslev becoming greater than the test voltage V_test_PSS, the comparator220aissues an output signal VComp indicative of the second state of the comparator. Upon receiving the output signal VComp indicative of the second state, the microcontroller220bimmediately (or within a short period (T5b) commands the circuit breaker210to interrupt and thereby shut off current to the conductor240and to the user apparatus250.

By virtue of the present invention, as soon as a breakage of the electrical continuity of the conductive sleeve280is detected, the circuit breaker is activated and current is interrupted in the electrical conductor240. The response time between breakage of the electrical continuity and interruption of the circuit may be a brief reaction time (T5b) of the electronic circuits.

The voltage-biased conductive sleeve280thus forms a detector that is capable of detecting the disconnection or breakage of the conductive sleeve280which is indicative of a break in the electrical link290. The fast cutting off (a few milliseconds) of the electric power secures possible interventions by maintenance staff by preventing the occurrence of electric arcing upon a disconnection of the electrical link from the user apparatus250.

In the above description, current return line260is understood to mean either a return conductor or a current return network. If the current return line266is a conductor set to a voltage different from that of the conductive structure of the aircraft, then an electrical protection device such as described above will have to be associated with the current return line260in order to secure the current return.

The invention may be embodied to protect transmission of electric power via an electrical link of an electrical installation on an aircraft10. The invention is applicable to any other type of vehicle, for example a boat or an automobile.