AU2017251485B2

AU2017251485B2 - System for detecting an overload and electrical differential protection device for an electrical line

Info

Publication number: AU2017251485B2
Application number: AU2017251485A
Authority: AU
Inventors: Gérard Blaess; Alexandre CHAMAGNE; Benjamin Charles; Pascal FRITSCH; Emmanuel Koenig; Georges MARINHO; Dominique Werner
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2016-04-14
Filing date: 2017-04-06
Publication date: 2022-04-14
Anticipated expiration: 2037-04-06
Also published as: FR3050335A1; CN109075554B; EP3300539B1; AU2017251485A1; FR3050335B1; WO2017178735A1; CN109075554A; EP3300539A1

Abstract

The present invention relates to an overload detection system (10) on an electrical line (N, P) comprising at least one conductor, said system (10) comprising: a measurement torus (2), a current shunt branch (4) through which a shunt current can flow and which can be connected in parallel on the electrical line, an actuator (3) controlled in response to an increase in current passing through said electrical line (N, P) in order to connect, directly or indirectly, in the event of overload, the shunt branch (4) to the electrical line, characterised in that the shunt branch (4) and the electrical line form a shunt loop when the actuator is activated in the case of overload, and in that the measurement torus (2) is intended to directly or indirectly detect the shunt current of the shunt loop. The invention also relates to a electrical differential device (8) placed on an electrical line (N, P) and characterised in that it comprises such a detection system (10).

Description

System for detecting an overload and electrical differential protection device for an electrical line

The present invention relates to a system for detecting an overload on an electrical line comprising at least one conductor, said system comprising a measurement toroid, a current bypass branch able to be traversed by a bypass current and to be connected in parallel on the electric line, an actuator controlled in response to an increase in current flowing through said electric line to connect, directly or indirectly, in case of overload, the bypass branch to the electric line.

It also relates to a differential electrical device such as a differential switch, a differential circuit breaker or a differential block, said device being placed on an electric line.

BACKGROUND

Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field.

Such devices must be able to open an electric line in the event of a fault such as a short circuit, a differential fault or an overload. To do this, they comprise a fixed contact and a movable contact that can be separated under the action of a mechanical trigger lock at the onset of the failure. These two contacts are arranged in series between two connection terminals which allow to insert the device in series into the electric line concerned.

Traditionally, these types of failures are respectively detected or supported by a magnetic protection element, a differential protection element and a thermal protection element of the device, the reaction times of which are very different and corresponding in practice to the fault which appears on the electric line.

Thus, on the one hand, a sudden and significant rise in current, which generally occurs during a short-circuit on the electrical line to be protected, must lead to a rapid opening of the contacts to avoid damaging the devices connected to the circuit. This is possible due to the magnetic protection element of the protective device.

On the other hand, in case of differential fault, it is the differential protection element of the device which is activated and detects the fault by means of a differential toroid which encloses the conductors and realizes the sum of currents to highlight a leakage current. Finally, an overload, reflecting a current demand on the electric line corresponding to a load that is too high, is taken over by the thermal protection element. The latter often takes the form of a bimetallic strip or a bimetallic strip which deforms under the action of excessive heating resulting from the current overload, and triggers mechanically a contact that actuates a mechanical lock causing the contacts to open.

This part of thermal protection is however sensitive, on the one hand, to wet aging because the envelopes which undergo creep and, on the other hand, to the external environment and in particular to the presence of dust, which causes seizure of the lock. As a result, the stroke and the mechanical force required to trigger the lock can change, and more particularly increase during the life of the lock until the metal band fails to ensure the is release of the lock and thus to render inoperative the thermal protection function of the device in which the bimetallic strip is mounted.

SUMMARY OF THE INVENTION

Embodiments of the present invention propose to overcome this drawback and to offer a solution capable of detecting an overload and of providing thermal protection for an electrical line in a reliable manner over time.

For this purpose, the subject of an embodiment of the present invention is an overload detection system as mentioned in the preamble, characterised in that the bypass branch and the electrical line form a bypass loop when the actuator is activated in case of overload, and in that the measuring toroid is provided for detecting / measuring directly or indirectly the bypass current of the bypass loop.

According to an embodiment of the invention, the measuring toroid and the bypass loop can be engaged one inside the other. They can be connected in the manner of links in a chain, one around the other and vice versa.

According to an embodiment of the invention, the electric line may comprise a single conductor and the measuring toroid may be traversed by the bypass branch.

As a variant, the electric line may comprise several conductors, the measuring toroid may be a differential toroid and be traversed by said conductors.

s In this latter configuration, the electric line may comprise at least one phase conductor and at least one neutral conductor and the bypass branch can be connected to at least one of said conductors.

According to a variant, the electrical line may comprise a neutral conductor and three phase conductors and the bypass branch may be connected to at least one of said conductors.

In the two aforementioned configurations, each conductor may comprise an actuator which connects a bypass branch in parallel to said conductor during an overload.

1s According to an embodiment of the invention, the actuator can undergo direct heating of said electrical line, can be disposed in said electrical line and be traversed by a current flowing in said electric line.

In addition, the system according to an embodiment of the invention may further comprise a switch disposed in the bypass branch and the actuator can actuate the switch.

The actuator can be selected from: a bimetallic strip, a thermo-variable rate spring, a permanent magnet, a thermal disc switch.

According to an embodiment of the invention, the actuator may comprise a bimetallic strip and the bypass branch may comprise a fixed contact on which, in the event of overload, the blade of the bimetallic strip is positioned to connect said bypass branch to the electric line. The bypass loop is preferably open on the fixed contact and the bimetallic strip is configured to touch said fixed contact when it has reached its trigger threshold.

The actuator may include a bimetallic strip indirectly heated by said electric line.

For this purpose, it can be heated by a resistant winding itself traversed by the current of said electric line.

Embodiments of the present invention also relate to a differential electrical device such as a differential switch, a differential circuit breaker or a differential block. This differential electric device is placed on an electric line and is characterised in that it comprises a detection system according to an embodiment of the invention.

This differential electric device, intended to protect said conductors of said electric line, comprises a protection lock, a toroid intended for the differential protection and at least one pair of fixed and movable contacts mounted on at least one of the said conductors and actuates by the protection lock and the toroid intended for the differential protection. In such a differential electrical device according to an embodiment of the invention, the toroid intended for the differential protection may correspond to the measuring toroid of the detection system and be connected to a device for actuating said protection lock. Such an actuating device can be a high sensitivity relay, for example.

1s According to a first aspect of the present invention, there is provided a system for detecting an overload on an electric line comprising at least one conductor, said system comprising: a measuring toroid, a current bypass branch able to be traversed by a bypass current and to be connected in parallel to the electric line, an actuator controlled in response to an increase in current passing through said electric line to connect, directly or indirectly, in case of overload, the current bypass branch to the electric line, the current bypass branch and the electric line forming a bypass loop when the actuator is activated in case of overload, and the measuring toroid being provided for directly or indirectly detecting the bypass current ofthe bypass loop, wherein the actuator comprises bimetallic strip mounted in series in the electric line which is to be protected.

According to a second aspect of the present invention, there is provided a differential electrical device such as a differential switch, a differential circuit breaker or a differential block, said differential electrical device being placed on an electric line, the device comprising a detection system according to the first aspect.

It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the invention will become apparent on reading the following description which refers to the appended sketches representing preferred embodiments of the invention, given solely by way of non-limiting examples, and in which:

1s Figure 1 is a schematic view of a system for detecting an overload according to the invention, without the presence of an overload,

Figure 2 is a view showing the system of Figure 1, in the presence of an overload,

Figure 3 is a schematic view of a differential electrical device comprising a system for detecting an overload, without the presence of an overload, according to another variant embodiment of the detection system of the invention,

Figure 4 is a view showing the differential electrical device of Figure 3, in the presence of an overload,

Figure 5 is a schematic view of a differential electrical device comprising a system for detecting an overload, without the presence of an overload, according to another variant embodiment of the invention, and

Figure 6 is a view showing the differential electrical device of Figure 5, in the presence of an overload.

DETAILED DESCRIPTION

The system 1, 10, 100 for detecting an overload according to the present invention comprises a measuring toroid 2, a bypass branch 4 and an actuator 3. The detection system s 1, 10, 100 makes it possible to detect an overload via the actuator 3 responsive to a current increase whose function is to transmit the information of the overload to a measuring toroid 2. This information is advantageously identified due to the presence of the bypass branch 4 which is connected in parallel to the electric line N and/or P in question during an overload to form a bypass loop D. The bypass loop D and the measuring toroid 2 are engaged one into the other, in other words, the bypass loop D is surrounded by the measuring toroid 2 and vice versa. The bypass branch 4 is able to be closed or connected to the monitored electrical line N and/or P by the actuator 3 in response to an increase in current flowing through said electrical line N and/or P. The actuator 3 is in thermal contact with the line N and/or P and 1s thus reacts to a heating of the latter. This reaction is used to close the bypass loop D. The closing of the bypass loop D makes it possible to divert a part 'it' of the current 'i' of overload of the electric line N and/or P, and to detect this diversion, which corresponds to an overload fault, by the measuring toroid 2. The measuring toroid 2, which surrounds the bypass loop D detects indeed a current difference.

In an alternative embodiment, shown in Figures 1 and 2, the measuring toroid 2 surrounds the bypass branch 4. In other words, the measuring toroid 2 is traversed by the bypass branch so that when the bypass branch 4 is not connected to the electrical line N and/or P, the toroid does not measure or detect current and, when the bypass branch is closed on the electric line N and/or P because of overload, the measuring toroid 2 directly identifies a bypass current 'it'.

In another variant embodiment, shown in Figures 3 to 6, two conductors, for example at least one neutral conductor N and at least one phase conductor P, pass through the measuring toroid 2 and the latter is a differential toroid. The bypass branch 4 is outside the measuring toroid 2 and is connected to the neutral conductor N, for example, in case of overload. Here, when the bypass loop D is open (Figures 3 and 5), the toroid does not measure or detect current because the sum of the currents of the neutral N and phase P conductors cancels each other out. When the bypass loop D is closed (Figures 4 and 6) because of an overload, the measuring toroid 2 indirectly detects a bypass current because there appears a difference between the currents of the N and P phase conductors. In other words, it indirectly measures the bypass current due to the appearance of an overload on the electric line.

According to the invention, the closing of the bypass loop D makes it possible to divert a part 'it' of the overload current 'i' of the electric line N and/or P and to make detect this diversion by a measuring toroid 2.

The actuator 3 sensitive to an increase in current may comprise a bimetallic strip, a thermo variable spring, a permanent magnet, a thermal disc switch or any other device able to react to a temperature increase due to overloading. The actuator 3 can be directly mounted on the electrical line, as illustrated in Figures 1 to 4. It can also be thermally connected to the electric line N and/or P without being traversed by the current flowing in said line N and/or P. For this purpose, Figures 5 and 6 show an alternative embodiment in which actuator 3 1s comprises a resistive winding 7 which thermally connects to the electric line. It is also conceivable to have the actuator 3 in the immediate vicinity of said electrical line N and/or P, to thermally connect to the latter by convection and conduction.

The thermo-sensitive actuator 3 is designed to maintain an open position in which the bypass loop D is kept open to a closed position in which the actuator 3 closes the bypass branch 4, either directly or indirectly.

In a switching device, the detection information can thus be exploited and transferred to a device that actuates a trigger protection lock 13 for the opening of its contacts. This transfer can be achieved in various ways, for example by means of an electronic interface 15 connected to the protection lock 13 by an intermediate device such as an electromagnetic relay 14 for example, suitable to control the opening of the contacts in case of overload detection. In a differential switch or circuit breaker, the toroid intended to the differential protection can thus correspond to the measuring toroid 2. Such a device is described below.

Figures 1 and 2 represent the system 1 for detecting an electrical line respectively without the presence of an overload and in the presence of an overload. In this embodiment, the electric line comprises a single conductor, namely a phase conductor P. It is of course possible that the electric line has several conductors, and all or only some of these conductors are connected to an actuator. A measuring toroid 2 is traversed by a bypass branch 4.

The actuator 3 shown in Figures 1 and 2 comprises a bimetallic strip disposed in series in the monitored phase conductor P. The measuring toroid 2 is traversed by the bypass branch 4 which is open on a fixed contact 6 and the deflection of the bimetallic strip during an overload in the phase conductor P drives a contact between said bimetallic strip 3 and the fixed contact 6 and thus the closing of the bypass loop D. As a result, the measuring toroid 2 identifies the appearance of the bypass current 'it'. This information can then be passed through an electronic interface 15, for example to a contact opening control system, such as an electromagnetic relay (not shown).

Figures 3 and 4 show a system 10 for detecting an electrical line N and/or P in which the electrical line comprises a neutral conductor N and a phase conductor P. These conductors is together traverse a measuring toroid 2 which is in fact a differential toroid. Figure 3 represents the system 10 without the presence of an overload and Figure 4 represents the system 10 during an overload in the neutral conductor N. The system 10 here also comprises an actuator constituted by a bimetallic strip 3 connected in series in the line to be protected, here in series in the neutral conductor N. In the embodiment presented here, the bypass branch 4 is connected to the neutral conductor N in case of overload on both sides and outside the measuring toroid 2. The bypass branch 4 is open on a fixed contact 6 of the bypass branch 4 and the deflection of the bimetallic strip during an overload in the neutral conductor N drives a contact between said bimetallic strip 3 and the fixed contact 6 of the bypass branch 4 and thus the closure of the bypass loop D. It follows from said closure that the sum of the currents in the differential toroid 20 is no longer nil value.

This system 10 is integrated into a differential electrical device 8. The differential electrical device 8 shown in Figures 3 to 6 comprises a pair of fixed 11 and 11' and movable 12, 12' contacts mounted on each of said conductors and actuated by a protection lock 13. Advantageously, the measuring toroid 2 also provides the differential function of the differential electrical device 8. Thus, upon the appearance of an overload, the closing of the bypass loop D by the bimetallic strip 3 causes the diversion of a part 'it' of the current 'i' of the neutral conductor N. As indicated above, a current imbalance is thus created which generates a voltage on the detection winding of the measuring toroid 2 which is connected to an actuating device 14 of said protection lock 13. In other words, the detection of the overload is performed by the actuator 3, that is to say the bimetallic strip 3, which closes the bypass loop D so that the measuring toroid or differential toroid 2 identifies the fault.

The security and reliability are improved because the bimetallic strip 3 does not actuate the release of the protection lock 13. Indeed, the bimetallic band of the actuator 3 serves only to close the bypass loop D by making contact with the fixed contact 6. This closure requires less force and mechanical energy than the unlocking of the protection lock 13 and thus minimizes the impact of aging and contamination of the protection lock 13 on the thermal protection function that it provides. In other words, its use has been diverted but its protection function is maintained. The actuator 3 carries out the function of detecting and transmitting the information of an overload to a device capable of triggering the protection lock 13. In the case of a differential electric device, the device which triggers the protection lock 13 is an electromagnetic relay 14 connected to the measuring toroid 2 by an electronic interface 15. The energy required for triggering the protection lock 13 is thus not delivered 1s by the actuator 3.

Figures 5 and 6 show a differential electrical device 9 comprising a system 100 for detecting an overload made according to a variant of the invention. The system 100 differs from that shown in Figures 3 and 4 in that the bimetallic strip 3 is heated by a resistive winding 7 itself traversed by the current of the neutral conductor N and that it operates in case of overloads a switch 5 arranged in series in the bypass loop D and maintained in the open position in the absence of overload. This resistive winding 7 may be constituted by a narrow wire or ribbon helically wound on an insulating sheath which surrounds the bimetallic strip 3.

The advantages mentioned with regard to the differential electric device 8 shown in Figures 3 and 4 apply to this differential electrical device 9 of Figures 5 and 6.

Although the differential devices 8 and 9 shown each comprise two pairs of contacts 11, 11', 12, 12', the invention is not limited to this number of contacts, and encompasses all variants comprising only a pair of contacts, but also, more than two pairs of contacts.

It is also possible to provide an overload detection system in which the actuator or the bimetallic strip 3 is, on the one hand, heated directly by the electric line and, on the other hand, actuates a switch 5 disposed in the bypass loop D. In the same manner, it is conceivable to provide an overload detection system in which the actuator 3 comprises a bimetallic strip 3 which is, on the one hand, heated by a resistive winding 7 itself traversed by the current of said electric line N and/or P and secondly, which itself directly closes the bypass loop D. Such detection systems can then be integrated into a differential electrical apparatus to achieve the cut-off when detecting an overload.

In the differential electric devices 8, 9 described, the opening of the differential electric device 8, 9 in the event of overload is therefore not ensured directly by means of the energy (force, travel) of the actuator or the bimetallic strip 3, but due to a device which in turn has enough energy to trigger the protection lock 13 of the differential electrical device 8 even in case of extreme dust pollution or wet aging. This advantage applies regardless of the actuator 3 or bimetallic strip used.

In other words, in the present invention, the overload detection function has been dissociated from the trigger function of the protection lock 13 and the actuator 3 which, in is the state of the art, performs these two functions, performs only the detection function in the present invention, to increase the durability and safety of the trigger function.

The actuator 3, unlike the state of the art, does not intervene directly in the mechanism triggering the opening of the contacts, which makes the latter much less dependent on dust and wet aging.

The configurations shown in the figures cited are only possible examples, in no way limiting, of the invention which, on the contrary, encompasses variants of shapes and designs within the reach of those skilled in the art.

Claims

1. A system for detecting an overload on an electric line comprising at least one conductor, said system comprising: a measuring toroid, a current bypass branch able to be traversed by a bypass current and to be connected in parallel to the electric line, an actuator controlled in response to an increase in current passing through said electric line to connect, directly or indirectly, in case of overload, the current bypass branch to the electric line, the current bypass branch and the electric line forming a bypass loop when the actuator is activated in case of overload, and the measuring toroid being provided for directly or indirectly detecting the bypass current ofthe bypass loop, wherein the actuator comprises bimetallic strip mounted in series in the electric line which is to be protected.

2. The system according to claim 1, wherein the measuring toroid and the bypass loop are engaged one in the other.

3. The system according to claim 1 or 2, wherein the electric line comprises a single conductor and the measuring toroid is traversed by the current bypass branch.

4. The system according to claim 1 or 2, wherein the electric line comprises several conductors and the measuring toroid is a differential toroid and is traversed by said conductors.

5. The system according to claim 4, wherein the electric line comprises at least one phase conductor and at least one neutral conductor and the current bypass branch is connected to at least one of said conductors.

6. The system according to claim 5, wherein the electric line comprises a neutral conductor and three phase conductors and the current bypass branch is connected to at least one of said conductors.

7. The system according to any one of the preceding claims, wherein the actuator undergoes direct heating of said electric line, is disposed in said electric line and is traveled by a current flowing in said electric line.

8. The system according to any one of the preceding claims, it further comprising a switch disposed in the current bypass branch and the actuator actuates the switch.

9. The system according to claim 8, wherein the actuator comprises a bimetallic strip and the current bypass branch comprises a fixed contact on which is positioned in case of overload a blade of the bimetallic strip for connecting said current bypass branch to the electric line.

10. A differential electrical device such as a differential switch, a differential circuit breaker or a differential block, said differential electrical device being placed on an electric line, the device comprising a detection system according to one of the preceding claims.

11. The differential electrical device according to claim 10, intended for protecting said conductors of said electric line, comprising a protection lock, a toroid intended for the differential protection and at least one pair of fixed and mobile contacts mounted on at least one of said conductors and actuated by the protection lock and the toroid intended for the differential protection, wherein the toroid intended for the differential protection corresponds to the measuring toroid of the detection system and is connected to an actuating device of said protection lock.