AU2016345559B2

AU2016345559B2 - Differential protection device with fire break function

Info

Publication number: AU2016345559B2
Application number: AU2016345559A
Authority: AU
Inventors: Hichem Chetouani
Original assignee: Hager Electro SAS
Current assignee: Hager Electro SAS
Priority date: 2015-10-29
Filing date: 2016-10-25
Publication date: 2021-01-21
Anticipated expiration: 2036-10-25
Also published as: FR3043270A1; EP3300541A2; WO2017072442A3; FR3043270B1; CN108352702A; WO2017072442A2; AU2016345559A1; EP3300541B1

Abstract

The present invention relates to a differential protection device allowing the detection of a leakage current or default current in an electrical installation supplied by at least one phase conductor forming the primary winding of a toroidal core (T), the signal induced at the secondary winding (S) of said toroidal core (T) when a differential default appears at the primary winding being used in at least one suitable signal processing stage (ETS) of said device, in order to control a relay (MC) of the device if a predefined threshold value is exceeded, said stage(s) (ETS) being directly or indirectly connected to the terminals of the secondary winding (S) under consideration.The device is characterized in that it comprises at least one circuit RC made up of a first resistance (R) having a defined value and a first capacitance (C) having a defined value, which are arranged in series, said circuit RC being connected to the terminals of the secondary winding (S) and mounted in parallel and upstream of the signal processing stage(s) (ETS).

Description

Differential protection device with a fire break function

The present invention relates to equipment and systems for the safety of goods and persons in the electrical field, more particularly the devices for protecting people with residual current (or RCD), and relates to a differential protection device incorporating a fire-break function.

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

This type of protection device is commonly integrated in domestic or tertiary electrical installations, upstream or at the entrance of the various hierarchy of the power supply circuits in place, or closer to the receivers to which they are respectively affected.

Typically, these electrical installations are powered by an alternating electric network, and protection devices of the aforementioned type are intended primarily to ensure the safety of people by detecting as soon as possible any possible leak to the earth in one of the circuits or receivers to be protected. Such leaks are caused for example by direct contacts of subjects with a non-insulated conductor or indirect contacts due to earth faults. These electrical incidents are likely to generate accidents, sometimes fatal, damage to equipment(s), fire starts, localized or generalised malfunctions or the like.

Differential protection, in the aforementioned context, is done in most cases in a fairly standardised manner: the conductors of the circuit to be protected, or the conductors of the supply line of this circuit, pass through a toroid of ferromagnetic material of a transformer whose aforementioned conductors form the primary and which comprises one or more winding (s) or secondary winding(s). The toroid plays the role of a magnetic flux concentrator. Thus, in the event of a leak, resulting in an imbalance of the input and output currents in the conductors of the lines to be protected, the flux created in the toroid by this imbalance at the primary level, induces a voltage in the secondary winding, used to control directly, or through dedicated electronics (signal processing stages), an actuator (for example relay type). The latter in turn actuates an associated trigger, breaking or opening mechanism, or those of other protective devices of the installation.

These apparatuses or electrical devices for differential protection may have variable characteristics. Thus, they are differentiable and characterised by their own sensitivity, which depends in particular on the type of electrical installation in which they are used and that they are intended to protect. In addition, some of these devices are only capable of detecting leaks for alternative currents (type AC) while others, which are more complete, offer solutions that are also applicable to pulsed direct current (types A and F) and smoothed (type B).

A device of the type B is for example described in the French patent application No. 2 993 058 in the name of the applicant.

In addition, for devices with the ability to detect alternative fault currents, the upper frequency limit of detection is another criterion for distinguishing between the different types: frequencies up to 1 kHz: type F; frequencies up to 2kHz: type B; frequencies up to 20kHz: type B +.

In particular, the type B + is, relative to the other types, specifically sensitive to fault or leakage current frequencies conducive for starting fires.

Currently, the existing solutions to reach the frequency gauge required for a type B + classification are mainly of two types:

- implementation of an active electronic assembly generating corrections adapted to the bandwidth of the sensitivity curve to the frequency of the fault current. A power failure of the electronic assembly transforms this type B + device into an A / AC type device only (the type F or type B functionalities are no longer fulfilled).

- implementation of an electronic relay to inhibit type A / AC protection and its replacement by an active means performing the function AC, A, F and B.

In the two aforementioned solutions, of the type B +, it leads to a complex, expensive and cumbersome construction based on the implementation of two independent circuits in parallel or in opposition, the fire-break function being inoperative in case of absence of power supply.

Embodiments of the present invention aim to overcome the disadvantages of the solutions mentioned above.

For this purpose, it relates to a differential protection device enabling the detection of leakage or fault current in an electrical installation powered by at least one phase conductor of a network and, where appropriate, by a neutral conductor of said network, at least one of said conductors constituting the primary of a toroid made of ferromagnetic material provided with one or more secondary winding(s) at the terminals of which is established a signal induced during the occurrence of a differential fault at said primary, said induced signal being operated by at least one signal processing stage adapted to said device for, in case of exceeding a predefined threshold value, controlling an electromagnetic actuator, a relay or similar breaking or opening means of the device, the said stage(s) being connected directly or not to the terminals of the secondary considered, the device characterised in that it comprises at least one RC circuit, formed of a first resistor with a determined value and a first capacitor with a determined value connected together in series, said RC circuit being connected at the terminal of said secondary and connected in parallel and upstream with respect to the signal processing stage or stages.

According to a first aspect of the present invention, there is provided a differential protection device enabling the detection of leakage or fault current in an electrical installation powered by at least one phase conductor of a network and, where appropriate, by a neutral conductor of said network, at least one of said conductors constituting the primary of a toroid (T) made of ferromagnetic material provided with one or more secondary windings(s) (S) at a set of terminals of which is established a signal induced by occurrence of a differential fault at said primary, said induced signal being operated by at least one signal processing stage (ETS) adapted from said device for, in case of exceeding a predefined threshold value, controlling an electromagnetic actuator, a relay or a similar breaking or opening means (MC) of the device, the said stage(s) (ETS) being connected directly or not to the terminals of the secondary (S), wherein the device comprises at least one RC circuit formed of a first resistor (R) with a determined value and a first capacitor (C) with a determined value connected together in series, said RC circuit being connected at the terminals of said secondary (S) and connected in parallel and upstream with respect to the signal processing stage or stages (ETS), the device further comprising at least a second resistor (R') connecting the terminals of the secondary (S) and connected in parallel with the RC series circuit, first resistor (R), first capacitor (C) and second resistor (R') thus forming mutually interlaced series and parallel RC circuits, wherein the first resistor (R) has a value such that its impedance is dominant, in the series RC circuit, for induced signal frequencies greater than about 300 Hz and the first resistor (R) has a value such that a trigger threshold value for high values of the frequency of the induced signal, typically between 1kHz and 20 kHz,is at most equal to 420 mA.

According to a second aspect of the present invention, there is provided a differential switch, incorporating at least one differential protection device according to the first aspect.

According to a third aspect of the present invention, there is provided a differential circuit breaker, incorporating at least one differential protection device according to the first aspect.

According to a fourth aspect of the present invention, there is provided an insulation tester, integrating at least one differential protection device according to the first aspect.

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".

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.

The invention will be better understood, with the aid of the following description, which refers to preferred embodiments, given by way of non-limiting examples, and explained with reference to the appended diagrammatic drawings, in which:

- Figures 1 to 3 are symbolic representations of three different embodiments of the differential protection device according to the invention;

-Figure 4 shows sensitivity curves in terms of the leakage current of the differential protection device according to the invention as a function of frequency, for different values of the resistor R of the series RC circuit forming part of the device represented on one of figures 1 to 3;

-Figure 5 represents a curve of the same nature as those represented in figure 4 for determined values of the capacitor C and the resistor R of the series RC circuit, and,

-Figure 6 is a curve of the variations of the total impedance Z of the series RC circuit, the impedance Zc of the capacitor C and the impedance ZRof the resistor R as a function of the frequency, illustrating the relative contributions of each of the components Zc andZR tothe impedance Z.

Figures 1 to 3 illustrate diagrammatically and partially according to three variant embodiments, a differential protection device enabling the detection of leakage or fault current in an electrical installation powered by at least one phase conductor of a network and, where appropriate, by a neutral conductor of said network, at least one, preferably at least two, of said conductors constituting the primary of a toroid T made of ferromagnetic material provided with one or more secondary winding(s) S at the terminals of which is established a signal induced at the occurrence of a differential fault at said primary. This induced signal is exploited by at least one ETS signal processing stage adapted from said device for, in case of exceeding a predefined threshold value, controlling an electromagnetic actuator, a relay or a similar switching or opening means MC of the device, the said ETS stage (s) being connected directly or not to the terminals of the secondary S in question.

According to the invention, the device further comprises at least one RC circuit, formed of a first resistor R with a determined value and a first capacitor C with a determined value connected together in series, said RC circuit being connected to terminals of said secondary S and connected in parallel and upstream with respect to the stage or stages of ETS signal processing.

Thus, the basic idea of the invention consists, by adding a series RC circuit, or even a simple resistor R when a capacitor C is already present, to provide a type A, AC, F or B differential protection device, with an additional fire-break function not dependent on the power supply of said device.

The inventive solution residing in the addition of a calibrated passive circuit for adapting the bandwidth of the device on which it is grafted to the frequency gauge to achieve the fire-break function has many advantages over the active solutions of the state of the art:

- not dependent on any power supply; - no significant additional consumption

- negligible additional cost; - no dysfunction related to aging; - limited footprint; - no substantial complexity of the structure of the existing device on which is grafted the fire-break function.

As is apparent from figures 4 and 6, it is advantageously provided that the first resistor R has a value such that its impedance is dominant, in the series RC circuit, for induced signal frequencies greater than approximately 300 Hz, preferably greater than approximately 150 Hz.

In accordance with a preferred embodiment of the invention, allowing the device in particular to comply with the regulations currently in force, and as shown graphically in figure 4, the first resistor R advantageously has a value such that the threshold value triggering for the high values of the frequency of the induced signal, typically between 1 kHz and 20 kHz, is at most equal to 420 mA.

Figures 4 and 5 show graphically on the curves (variation of the trigger threshold as a function of the frequency of the induced signal), that for frequencies greater than 100 Hz, the slope of the curve considered, before its inflection to tend towards a plateau for frequencies above 104Hz, is given by the value of the first capacitor C, while the new of said plateau is given by the value of the first resistor R (see lines PE and PL in figure 5).

The curves of figure 4 illustrate, for their part, the influence of the value of the first resistor R on the general shape (absence of a plateau for R = 0 / presence of a plateau for R * 0) or on the precise conformation of parties (different values of the plateau after about 1000 Hz, depending on the value of the first resistor R) of the threshold/frequency curve.

Figure 6, finally, illustrates for R = 8.2 x1039 and C = 68 x 10- 9 F, the evolution curve of the impedance Z of the RC series circuit. We can note the asymptotic shape of the curve which tends towards the value of the resistor R for the high frequencies, the resistance R becoming dominant with respect to the impedance of the capacitor C from about 300 Hz.

Those skilled in the art understand that, in addition to the aforementioned RC circuit, other components, in particular passive protection components,

for adjustment, for transformation or the like, may be mounted between the terminals of the secondary S and the stage(s) ETS.

Various non-limiting embodiments of a differential protection device according to the invention emerge from figures 1 to 3.

The simplest embodiment, without any additional component, is illustrated in figure 1.

With respect to this elementary construction, it may be provided that the device further comprises, as possible adjustment components, in particular the frequency of the device:

-at least one second resistor R connecting the terminals of the secondary S and connected in parallel with the RC series circuit, said components R, C, R' thus constituting mutually interleaved series and parallel RC circuits and / or,

-at least a second capacitor C connecting the terminals of the secondary S and connected in parallel with the RC series circuit.

Typical values for these components are, for example, R = 6.8 kOhm, R'= 200 kOhm, C = 27nF and C' = 1pF. These components R'and C'have the function of setting the threshold of the device at about 50 Hz with a significant impact in frequency for C'when used.

According to another characteristic of the invention and as shown in figure 3, the device may comprise, eventually in addition to at least one of the aforementioned components R'and C', at least one other resistor R", forming where appropriate a third resistor connected in series between one of the terminals of the secondary S, on the one hand, and the input of the ETS signal processing stage(s), on the other hand. This optional resistor R",whose value may for example be of the order of 1 kOhm, has the function of limiting the current to the secondary.

In relation with the embodiment shown in figure 3, and in agreement with another characteristic, the device according to the invention may further comprise at least one of the following additional components, in particular as a surge protection, mounted upstream of the ETS signal processing stage(s):

-a diode DT of the Transil diode type, mounted between the terminals of the secondary S upstream of any other component connected to said secondary,

- a voltage rectifier RC circuit, for example with diodes, connected in parallel, preferably immediately upstream of the stage(s) ETS signal processing.

Figure 3 details, in addition, the possible constituent functional components of the stage or ETS stages, this last one (s) realising a differential protection function of the type chosen from the group formed by the types A, AC, F and B.

The present invention also relates to a differential switch, a differential circuit breaker and an insulation tester, each of which is characterised in that it incorporates at least one differential protection device according to the invention.

Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications are possible, especially from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

1. Differential protection device enabling the detection of leakage or fault current in an electrical installation powered by at least one phase conductor of a network and, where appropriate, by a neutral conductor of said network, at least one of said conductors constituting the primary of a toroid (T) made of ferromagnetic material provided with one or more secondary windings(s) (S) at a set of terminals of which is established a signal induced by occurrence of a differential fault at said primary, said induced signal being operated by at least one signal processing stage (ETS) adapted from said device for, in case of exceeding a predefined threshold value, controlling an electromagnetic actuator, a relay or a similar breaking or opening means (MC) of the device, the said stage(s) (ETS) being connected directly or not to the terminals of the secondary (S), wherein the device comprises at least one RC circuit formed of a first resistor (R) with a determined value and a first capacitor (C) with a determined value connected together in series, said RC circuit being connected at the terminals of said secondary (S) and connected in parallel and upstream with respect to the signal processing stage or stages (ETS), the device further comprising at least a second resistor (R') connecting the terminals of the secondary (S) and connected in parallel with the RC series circuit, first resistor (R), first capacitor (C) and second resistor (R') thus forming mutually interlaced series and parallel RC circuits, wherein the first resistor (R) has a value such that its impedance is dominant, in the series RC circuit, for induced signal frequencies greater than about 300 Hz and the first resistor (R) has a value such that a trigger threshold value for high values of the frequency of the induced signal, typically between 1kHz and 20 kHz, is at most equal to 420 mA.

2. Differential protection device according to the claim 1, wherein the first resistor (R) has a value such that its impedance is dominant, in the series RC circuit, for induced signal frequencies greater than about 150 Hz.

3. Differential protection device according to claim 1 or claim 2, further comprising at least a second capacitor (C') connecting the terminals of the secondary (S) and connected in parallel with the RC series circuit.

4. Differential protection device according to any one of the preceding claims 1 to 3, further comprising at least one other resistor (R"), possibly forming a third resistor, connected in series between one of the secondary terminals (S), on the one hand, and an input of the signal processing stage(s) (ETS), on the other hand.

5. Differential protection device according to any one of the preceding claims 1 to 4, further comprising at least one of the following additional components, mounted upstream of the stage(s) of signal processing (ETS): a diode (DT) of the Transil diode type, mounted between the terminals of the secondary (S) upstream of any other component connected to said secondary, a voltage rectifier circuit (RC) connected in parallel.

6. Differential protection device according to claim 5, wherein the voltage rectifier circuit (RC) including diodes.

7. Differential protection device according to claim 5 or claim 6, wherein the voltage rectifier circuit (RC) is connected in parallel immediately upstream of the signal processing stage(s) (ETS).

8. Differential protection device according to any one of claims 1 to 7, wherein that the stage or stages of signal processing (ETS) perform(s) a differential protection function of the type chosen in the group formed by types A, AC, F and B.

9. Differential switch, incorporating at least one differential protection device according to any one of the preceding claims 1 to 8.

10. Differential circuit breaker, incorporating at least one differential protection device according to any one of the preceding claims 1 to 8.

11. Insulation tester, integrating at least one differential protection device according to any one of the preceding claims 1 to 8.

Control stage of Voltage the multiplier breaking or opening means

Curve Curve Curve