ELECTRICAL SWITCHING DEVICE WITH CURRENT MEASUREMENT

Description

[0001] The present invention relates to the field of electrical switching devices with current measurement.

[0002] In the field of electrical switching and protection equipment such as circuit breakers requiring tripping electronics, it is common to find current sensors of the current transformer or Rogowski toroid type arranged around the phase current line to measure the current flowing in the phase current line.

[0003] This type of sensor offers two main advantages: low impedance from the perspective of the phase current line and galvanic isolation. However, they also have the disadvantages of being bulky, difficult to implement in electrical protection equipment, and complex to manufacture with good repeatability, resulting in high production costs. Furthermore, these sensors are well-suited for AC switching and protection equipment but not for DC systems.

[0004] It is known to replace this type of sensor with a shunt to enable current measurement. However, using a shunt in a circuit breaker is not without its difficulties. Indeed, a shunt has the disadvantage of introducing an additional resistive element on the phase current line, which necessarily increases dissipation. Furthermore, another drawback of using a shunt is that it complicates the arrangement of the phase current line. All these disadvantages discourage those skilled in the art from using this solution for measuring current on the phase current line. EP3 644 077 A1 discloses a relay fault diagnosis system.

[0005] The present invention aims to overcome at least one of these drawbacks and to propose in particular a current measurement solution that is compact and easy to implement in said electrical switching equipment.

[0006] To this end, the invention relates to an electrical switching device comprising at least: a phase current line comprising at least one phase metallic conductor, a switching unit comprising at least one switching element on the phase current line, a measuring unit comprising at least one current sensor and a current measuring circuit, electrical switching equipment characterized in that: The current sensor incorporates a segment of said phase metallic conductor situated between a first connection point and a second connection point separated by a predefined distance, and in that the measuring unit comprises a first conductor connected by a first end to the first connection point and by a second end to the current measuring circuit and a second conductor connected by a first end to the second connection point and by a second end to the current measuring circuit, and the measuring unit further comprises a temperature sensor and a temperature measuring circuit and at least one thermocouple cable comprising a third conductor and a fourth conductor connected to each other at a so-called cold junction and a so-called hot junction, the third conductor comprising a first end and a second end,and the fourth conductor comprising a first end and a second end, which are connected respectively by their first end to a third connection point coinciding with or near the second connection point and being in the vicinity of the hot junction, and by their second end, being near the so-called cold junction, to the temperature measuring circuit, said measuring unit is configured at least to measure the value of the voltage difference between the first conductor and the second conductor, the value of the voltage difference of the thermocouple cable and the value of the absolute temperature near the so-called cold junction by means of the temperature sensor, so as to determine the value of the current flowing in the phase metallic conductor.

[0007] The invention will be better understood from the following description, which relates to several preferred embodiments, given by way of non-limiting examples, and explained with reference to the accompanying schematic drawings, in which: [ Fig. 1 ] there figure 1 represents a partial side view of an electrical switching device according to a first embodiment of the invention, [ Fig. 2 ] there figure 2 represents a partial side and perspective view of an electrical switching device according to a second embodiment of the invention, and [ Fig. 3 ] there figure 3 represents a schematic and partial view of a unit of measurement according to one possibility of the invention.

[0008] An electrical switching device includes at least: a phase L current line comprising at least one phase metallic conductor 1, a breaking unit 2 comprising at least one switching element 3a,3b on the phase L current line, a measuring unit 6 comprising at least one current sensor 7 and a current measuring circuit 8.

[0009] According to the invention, the electrical switching device is characterized in that: The current sensor 7 incorporates a segment 9 of said phase 1 metallic conductor situated between a first connection point P1 and a second connection point P2 separated by a predefined distance D, and in that the measuring unit 6 comprises a first conductor 10 connected by a first end 11 to the first connection point P1 and by a second end 12 to the current measuring circuit 8 and a second conductor 13 connected by a first end 14 to the second connection point P2 and by a second end 15 to the current measuring circuit 8, and the measuring unit 6 further comprises a temperature sensor 16 and a temperature measuring circuit 17 and at least one thermocouple cable 18 comprising a third conductor 19 and a fourth conductor 20 connected to each other at a so-called cold junction and a so-called hot junction, the third conductor 19 comprising a first end 21 and a second end 22,and the fourth conductor 20 comprising a first end 23 and a second end 24, which are connected respectively by their first end 21, 23 to a third connection point P3 coinciding with or near the second connection point P2 and being in the vicinity of the hot junction and by their second end 22, 24, being near the so-called cold junction, to the temperature measuring circuit 17, said measuring unit 6 is configured at least to measure the value of the voltage difference Vshunt between the first conductor 10 and the second conductor 13, the value of the voltage difference of the thermocouple cable 18 VthC and the value of the absolute temperature VΘRef near the so-called cold junction using the temperature sensor 16, so as to determine the value of the current flowing in the phase 1 metallic conductor. ,

[0010] Advantageously, the configuration according to the invention allows a portion of the phase 1 metallic conductor of the existing phase L current line in the electrical switching equipment to be used as a shunt, that is, by using the low resistance of a metallic component to measure the voltage drop due to the primary current. This avoids the need to add a resistive component. More precisely, it is sufficient to measure the voltage between two connection points P1 and P2 on the phase 1 metallic conductor, which are sufficiently spaced by a distance D on the phase 1 metallic conductor to obtain a measurable shunt voltage drop Vshunt. This approach is, however, complicated by various effects, the most significant being the heating of the phase 1 metallic conductor.Therefore, the configuration according to the invention includes, in addition to measuring the voltage drop Vshunt, measuring the voltage drop of the thermocouple cable 18 VthC at the third connection point P3 and measuring the absolute temperature VΘRef near the so-called cold junction. Thanks to the invention, a very precise temperature measurement of the phase 1 metallic conductor can be obtained, enabling appropriate compensation of the voltage drop Vshunt in order to deduce a measurement of the current flowing in the phase 1 metallic conductor with optimal accuracy. This solution also has the advantage of being inexpensive, compact, and offering improved linearity and therefore better performance, particularly compared to existing current measurement methods for AC-operated switching and protection devices such as Rogowski coils.Furthermore, this solution is suitable for measuring current for electrical switching equipment operating on alternating current but also on direct current.

[0011] Preferably, the phase L current line includes an upstream connection terminal 25 and a downstream connection terminal 26, said breaking unit 2 being located between the upstream connection terminal 25 and the downstream connection terminal 26.

[0012] According to the first variant of the embodiment illustrated in the figure 1 , the phase 1 metallic conductor is located between the upstream connection terminal 25 and the downstream connection terminal 26.

[0013] Advantageously, in this configuration, which is illustrated by the figure 1 A conductive metal component of the phase current line L, located between the upstream connection terminal 25 and the downstream connection terminal 26, is selected to measure the voltage drop due to the primary current. This eliminates the need for a resistive component. This solution has the advantage of being compact.

[0014] In this case, said at least one metallic phase 1 conductor may consist of a metallic bar, preferably made of copper.

[0015] Choosing a metal bar makes it easier to assemble, avoids mechanical aging because it is a fixed part, and provides sufficient length to produce a measurable signal.

[0016] According to the second embodiment, the phase 1 metallic conductor corresponds to the upstream connection terminal 25 or to the downstream connection terminal 26.

[0017] Advantageously, in this configuration, which is illustrated by the figure 2 The upstream connection terminal 25 or the downstream connection terminal 26 is selected to measure the voltage drop due to the primary current. This avoids the need for a resistive component. This solution has the advantage of being compact. Furthermore, the upstream connection terminal 25 or the downstream connection terminal 26, like the metal bar described previously, is a fixed component with the added advantages of being easily accessible, thus facilitating assembly, and providing sufficient clearance around it to accommodate the measuring unit 6.

[0018] Preferably, the measuring unit 6 comprises at least one electronic measuring module 27 and one electronic control module 28, the electronic measuring module 27 being configured to measure the value of the voltage difference Vshunt, the value of the voltage difference of the thermocouple cable 18 VthC and the value of the absolute temperature VΘRef, and the electronic control module 28 being configured at least to control said electronic measuring module 27 and to process said values ​​measured by the electronic measuring module 27.

[0019] Advantageously, thanks to this configuration, which is illustrated by the figure 3 The various functions performed by the measuring unit 6 are assigned at least partly to the measuring electronic module 27 and partly to the control electronic module 28. The measuring electronic module 27 is responsible for measuring at least three values: the voltage difference Vshunt, the voltage difference across the thermocouple cable 18 VthC, and the absolute temperature VΘRef, which may consist of analog data. The control electronic module 28 is responsible at least for controlling the measuring electronic module 27 and processing the measurement data from the measuring electronic module 27.In addition, the electronic control module 28 implements the combination of these three measurements to determine the value of the current flowing in the phase 1 metallic conductor consisting of a compensated measurement of the primary current, and this can then be used for protection and / or measurement purposes.

[0020] The measuring unit 6 may include an analog-to-digital digitizing module 29 electrically connected to the electronic measuring module 27 and the electronic control module 28 to digitize an analog value of the voltage difference Vshunt, an analog value of the voltage difference of the thermocouple cable 18 VthC and an analog value of the absolute temperature VΘRef from the electronic measuring module 27.

[0021] Advantageously, thanks to this configuration, which is illustrated by the figure 3 In the measuring unit 6, the analog-to-digital converter module 29 transforms an analog value of the voltage difference Vshunt, an analog value of the voltage difference of the thermocouple cable 18 VthC, and an analog value of the absolute temperature VΘRef from the electronic measuring module 27 into a digital value of the voltage difference Vshunt, a digital value of the voltage difference of the thermocouple cable 18 VthC, and a digital value of the absolute temperature VΘRef, respectively. This conversion facilitates the processing of the data received digitally by the electronic control module 28.

[0022] Preferably, said electronic measuring module 27, electronic control module 28 and analog-to-digital digitizing module 29 and temperature sensor 16 are integrated on at least one electronic board.

[0023] This design allows for the miniaturization of the unit of measurement 6.

[0024] Preferably, and as shown in the figures, the second conductor 13 and the fourth conductor 20 are combined into a single electrical conductor, preferably a metallic wire, and the second connection point P2 and the third connection point P3 are combined into a single connection point.

[0025] Advantageously, this configuration simplifies manufacturing by limiting the number of conductors and connection points on the phase 1 metallic conductor and therefore, where applicable, the welding.

[0026] Preferably, the first conductor 10, the second conductor 13, the fourth conductor 20 each consist of a metallic wire, preferably copper.

[0027] Preferably, the fourth conductor 20 and the third conductor 19 are respectively a first metal wire and a second metal wire made of different materials, the first metal wire preferably being copper and the second metal wire preferably being a copper nickel alloy wire called constantan.

[0028] Advantageously, we obtain a thermocouple cable 18 known as type T.

[0029] Preferably, said at least one metallic phase 1 conductor is made of a rigid metallic material.

[0030] Advantageously, this configuration makes it easier to manufacture and in particular to connect conductors 10, 13, 19, 20 to connection points P1, P2, P3 by means of durable electrical and thermal connection for example by crimping, riveting, brazing, welding or similar.

[0031] Preferably, the electrical switching equipment further includes a fault detection unit 4,5 and tripping unit on the phase L current line configured to, in the event of detection of at least one fault, cause the opening of said switching element 3a, 3b.

[0032] Advantageously, the electrical switching equipment allows for a function of switching and protection against at least one fault.

[0033] The phase 1 metallic conductor is an electrically conductive element located on the phase L current line and forming part of the current path of the switching equipment. It is not a shunt connected to the current path. The phase 1 metallic conductor comprises at least one metallic portion or is made of metallic material.

[0034] The breaking unit 2 has the function of opening and closing the phase current line L using the switching element 3a, 3b. The breaking unit 2 can be electromechanical or electronic.

[0035] The switching element 3a, 3b preferably consists of at least one set of fixed contacts 3a and moving contacts 3b that are separable and can thus assume a closed position in which they are in contact and an open position in which they are separated. The switching element could also consist of a semiconductor switch of the FET type.

[0036] The optional fault detection unit 4.5 has the function of detecting the presence of at least one fault and of causing the opening of said switching element 3a, 3b in the event of the occurrence of said at least one fault.

[0037] For example, the detection unit 4, 5 may be electromechanical and include a bimetallic thermal actuator 4 and / or a magnetic coil actuator 5, which respectively enable the detection of an overload and / or short-circuit fault. Alternatively or complementaryly, the detection unit 4, 5 may be electronic and enable the detection of an overload and / or short-circuit fault by measuring the current flowing in the phase 1 metallic conductor using the measuring unit 6. In this case, the detection unit 4, 5 and the measuring unit 6 are electrically connected for this purpose.

[0038] The measuring unit 6 has the function of providing a value of the current flowing in the phase L current line at least using the current sensor 7 associated with the current measuring circuit 8 and the temperature sensor 16 and the thermocouple cable 18 associated with the temperature measuring circuit 17. The value of the current flowing in the phase L current line thus measured can be used for measurement, communication and / or protection purposes.

[0039] Segment 9 is at least a portion of the phase 1 metallic conductor located between the first connection point P1 and the second connection point P2, which are separated by a distance D. The third connection point P3 is also located on the phase 1 metallic conductor and is either coincident with the second connection point P2 or in its immediate vicinity. The temperature at this third connection point P3 simply needs to be representative of the temperature of the phase 1 metallic conductor between the Vshunt measurement points, namely the first connection point P1 and the second connection point P2. Furthermore, if the thermocouple cable 18 is disconnected, it is preferable to connect it approximately in the middle of segment 9 between the voltage tapping points, that is, between the first connection point P1 and the second connection point P2.

[0040] The distance D depends on the linear resistance of the phase 1 metallic conductor, the expected current and the associated measuring means.

[0041] The first conductor 10 allows the first connection point P1 on the phase 1 metallic conductor to be connected to the current measurement circuit 8.

[0042] The first end 11 of the first conductor 10 is preferably connected by crimping and / or riveting and / or brazing, welding or similar to the first connection point P1.

[0043] The second end 12 of the first conductor 10 is preferably electrically connected to the current measurement circuit 8.

[0044] The second conductor 13 allows the second connection point P2 on the phase 1 metallic conductor to be connected to the current measurement circuit 8.

[0045] The first end 14 of the second conductor 13 is preferably connected by crimping and / or riveting and / or brazing, welding or similar to the second connection point P2.

[0046] The second end 15 of the second conductor 13 is preferably electrically connected to the current measurement circuit 8.

[0047] When current flows on the phase current line, a potential difference exists between the first connection point P1 and the second connection point P2, and thus the value of the voltage difference Vshunt can be determined by the unit of measurement 6.

[0048] The temperature sensor 16 associated with the temperature measurement circuit 17 allows the absolute temperature value VΘRef to be measured in the vicinity of the so-called cold weld.

[0049] The temperature sensor 16 is preferably positioned near the cold junction. This is because the cold junction exhibits little temperature variation and can therefore serve as a reference point. This is due to the relatively homogeneous temperature environment of the cold junction, as there is no localized heating. The required proximity of the temperature sensor 16 to the cold junction depends on the local temperature gradient; however, it is preferable to place it as close as possible to the cold junction.

[0050] The thermocouple cable 18 comprises the third conductor 19 and the fourth conductor 20 or the third conductor 19 and the second conductor 13. The third conductor 19 and the fourth conductor 20 / second conductor 13 are connected on one side by the so-called cold junction and on the other side by the so-called hot junction.

[0051] The hot weld corresponds to the point where the two metals of the third conductor 19 and the fourth conductor 20 / second conductor 13 are in direct contact under the influence of the temperature to be measured, i.e. near the second connection point P2 / third connection point P3.

[0052] The cold junction corresponds to the point where the two metals of the third conductor 19 and the fourth conductor 20 / second conductor 13 are brought into contact through a certain impedance in order to measure the voltage drop.

[0053] The thermocouple cable 18 associated with the temperature measurement circuit 17 allows the value of the voltage difference of the thermocouple cable 18 VthC to be measured.

[0054] From the absolute temperature VΘRef and the voltage difference across the thermocouple cable 18 VthC, it is possible to deduce the temperature value in the phase 1 metallic conductor. The voltage difference measured across the thermocouple terminals reflects the temperature difference between the hot and cold junctions. Therefore, the absolute temperature measured at the cold junction must be added to obtain the temperature at the hot junction.

[0055] The third conductor 19 allows the second connection point P2 / third connection point P3 on the phase 1 metallic conductor to be connected to the temperature measurement circuit 17.

[0056] The first end 21 of the third conductor 19 is preferably connected by crimping and / or riveting and / or brazing, welding or similar to the second connection point P2 / third connection point P3.

[0057] The second end 22 of the third conductor 19 is preferably electrically connected to the temperature measurement circuit 17.

[0058] The fourth conductor 20 allows the second connection point P2 / third connection point P3 on the phase 1 metallic conductor to be connected to the temperature measurement circuit 17.

[0059] The first end 23 of the fourth conductor 20 is preferably connected by crimping and / or riveting and / or brazing, welding or similar to the second connection point P2 / third connection point P3.

[0060] The second end 24 of the fourth conductor 20 is preferably electrically connected to the temperature measurement circuit 17.

[0061] The upstream connection terminal 25 and downstream connection terminal 26 can be a screw cage terminal ( figure 1 ) or self-tightening or a range for screw-in terminals ( figure 2 ).

[0062] The electronic measuring module 27 is part of the measuring unit 6 and allows the measurement of the voltage difference value Vshunt, the voltage difference value of the thermocouple cable 18 VthC, and the absolute temperature value VΘRef. It corresponds to the current measuring circuit 8 and the temperature measuring circuit 17.

[0063] The electronic control module 28 is part of the measuring unit 6 and allows control of said electronic measuring module 27 and processing of said values ​​measured by the electronic measuring module 27 in particular to deduce the value of the current flowing in the metallic phase conductor 1.

[0064] The analog-to-digital digitizing module 29 is part of the measuring unit 6 for digitizing an analog value of the voltage difference Vshunt, an analog value of the voltage difference of the thermocouple cable 18 VthC and an analog value of the absolute temperature VΘRef from the electronic measuring module 27.

[0065] The electronic control module 28 allows the analog-to-digital digitization module 29 to be controlled and the said values ​​measured and converted into digital data by the analog-to-digital digitization module 29 to be processed, in particular to deduce the value of the current flowing in the phase 1 metallic conductor.

[0066] The measuring unit 6 is preferably surrounded by a housing containing the temperature sensor 16, the electronic measuring module 27, the electronic control module 28 and the analog-to-digital digitization module 29.

[0067] Electrical switching equipment can be a contactor, a switch, or a controlled switch.

[0068] Electrical switching equipment can also perform a protective function and in this case may be a circuit breaker, a residual current switch, a residual current circuit breaker or similar.

[0069] There figure 1 This partially illustrates the electrical switching and protection equipment according to the first embodiment of the invention, which is of the circuit breaker type. In this example, the phase 1 metallic conductor is located between the upstream connection terminal 25 and the downstream connection terminal 26. The phase 1 metallic conductor is in the form of the rigid copper metal bar of the phase L current line. Segment 9 is a portion of the metal bar.

[0070] The phase L current line includes, upstream, the upstream connection terminal 25, electrically connected to the electromagnetic actuator of the magnetic coil type for short-circuit fault detection via the phase 1 metallic conductor, which is preferably a rigid copper metal bar. Segment 9 is part of the metal bar. The first connection point P1 is near the upstream connection terminal 25, while the second connection point P2 is near the electromagnetic actuator 5. In this example, the second conductor 13 and the fourth conductor 20 are combined into a single electrical conductor in the form of a metal wire, and the second connection point P2 and the third connection point P3 are combined into a single connection point. The breaking unit 2 includes a fixed contact 3a and a moving contact 3b.The electromagnetic actuator 5 is electrically connected to the fixed contact 3a. The moving contact 3b is connected to the bimetallic thermal actuator 4 for overload fault detection via a first braided flexible conductor 30. The thermal actuator 4 is electrically connected to the downstream connection terminal 26 by a second braided flexible conductor 31.

[0071] There figure 2 This partially illustrates an electrical switching device according to the second embodiment of the invention. In this example, the phase metallic conductor 1 corresponds to the downstream connection terminal 26. Therefore, segment 9 is part of the downstream connection terminal 26. The first connection point P1, the second connection point P2 / third connection point P3 are all on the downstream connection terminal 26. The second conductor 13 and the fourth conductor 20 are combined into a single electrical conductor in the form of a metallic wire, and the second connection point P2 and the third connection point P3 are combined into a single connection point.

[0072] There figure 3illustrates the measuring unit 6 according to one possibility of the invention which includes the temperature sensor 16, the electronic measuring module 27, the electronic control module 28 and the analog-to-digital digitizing module 29. The electronic measuring module 27 is connected to the first conductor 10 and to the thermocouple cable 18.

[0073] Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, particularly with regard to the composition of the various elements, without departing from the scope of protection of the invention.

Claims

1. Electrical switchgear comprising at least: - a phase current line (L) comprising at least one metal phase conductor (1), - a switching unit (2) comprising at least one switching element (3a, 3b) on the phase current line (L), - a measuring unit (6) comprising at least one current sensor (7) and a current measuring circuit (8), said electrical switchgear being characterized in that: - the current sensor (7) integrates a segment (9) of said metal phase conductor (1) located between a first connection point (P1) and a second connection point (P2) which are spaced apart from one another by a predetermined distance (D), and in that the measuring unit (6) comprises a first conductor (10) connected by a first end (11) to the first connection point (P1) and by a second end (12) to the current measuring circuit (8) and a second conductor (13) connected by a first end (14) to the second connection point (P2) and by a second end (15) to the current measuring circuit (8) and - the measuring unit (6) further comprises a temperature sensor (16) and a temperature measuring circuit (17) and at least one thermocouple cable (18) comprising a third conductor (19) and a fourth conductor (20) which are connected to one another at a so-called cold junction and a so-called hot junction, the third conductor (19) comprising a first end (21) and a second end (22), and the fourth conductor (20) comprising a first end (23) and a second end (24), which conductors are respectively connected by their first end (21, 23) to a third connection point (P3) combined with or near the second connection point (P2) and being in the vicinity of the hot junction and at their second end (22, 24), being close to the so-called cold junction, to the temperature measuring circuit (17), - said measuring unit (6) is configured at least to measure the value of the voltage difference (Vshunt) between the first conductor (10) and the second conductor (13), the value of the voltage difference of the thermocouple cable (18) (VthC) and the value of the absolute temperature (VΘRef) near the so-called cold junction by means of the temperature sensor (16), so as to determine the value of the current flowing through the metal phase conductor (1).

2. Electrical switchgear according to Claim 1, characterized in that the phase current line (L) comprises an upstream connection terminal (25) and a downstream connection terminal (26), the switching unit (2) being located between the upstream connection terminal (25) and the downstream connection terminal (26).

3. Electrical switchgear according to Claim 2, characterized in that the metal phase conductor (1) is located between the upstream connection terminal (25) and the downstream connection terminal (26).

4. Electrical switchgear according to Claims 2 and 3, characterized in that said at least one metal phase conductor (1) consists of a metal bar, preferably made of copper.

5. Electrical switchgear according to Claim 2, characterized in that the metal phase conductor (1) corresponds to the upstream connection terminal (25) or to the downstream connection terminal (26).

6. Electrical switchgear according to any one of Claims 1 to 5, characterized in that the measuring unit (6) comprises at least one electronic measuring module (27) and an electronic control module (28), the electronic measuring module (27) being configured to measure the value of the voltage difference (Vshunt), the value of the voltage difference of the thermocouple cable (18) (VthC) and the value of the absolute temperature (VΘRef), and the electronic control module (28) being configured at least to control said electronic measuring module (27) and to process said values measured by the electronic measuring module (27).

7. Electrical switchgear according to Claim 6, characterized in that the measuring unit (6) comprises an analogue-to-digital digitization module (29) electrically connected to the electronic measuring module (27) and to the electronic control module (28) in order to digitize an analogue value of the voltage difference (Vshunt), an analogue value of the voltage difference of the thermocouple cable (18) (VthC) and an analogue value of the absolute temperature (VΘRef) from the electronic measuring module (27).

8. Electrical switchgear according to Claims 6 and 7, characterized in that said electronic measuring module (27), the electronic control module (28) and the analogue-to-digital digitization module (29) and the temperature sensor (16) are integrated on at least one circuit board.

9. Electrical switchgear according to any one of Claims 1 to 8, characterized in that the second conductor (13) and the fourth conductor (20) are combined into a single electrical conductor, preferably a metal wire, and in that the second connection point (P2) and the third connection point (P3) are combined into a single connection point.

10. Electrical switchgear according to any one of Claims 1 to 9, characterized in that the first conductor (11), the second conductor (13) and the fourth conductor (20) each consist of a metal wire, preferably made of copper.

11. Electrical switchgear according to any one of Claims 1 to 10, characterized in that the fourth conductor (20) and the third conductor (19) are a first metal wire and a second metal wire, respectively, made of different materials, the first metal wire preferably being made of copper and the second metal wire preferably being a wire of copper-nickel alloy called constantan.

12. Electrical switchgear according to any one of Claims 1 to 11, characterized in that said at least one metal phase conductor (1) is made of a rigid metal material.

13. Electrical switchgear according to any one of Claims 1 to 12, characterized in that it further comprises a fault detection and tripping unit (4, 5) on the phase current line (L), configured to cause said switching element (3a, 3b) to open in the event of at least one fault being detected.