FR2666181A1 - Device for identifying a point of opening of an electrical circuit - Google Patents

Abstract

Device for identifying the position of open contacts constituting an opening of an electrical circuit (1), the said circuit including at least one coil (2), characterised in that at least one oscillator electrical circuit is connected in parallel with the coil (2) interacting with the said electrical circuit (1) to form an oscillator, an output signal of which oscillates with a frequency which is characteristic of the position of the point of opening on the electrical circuit (1), and in that it further includes means for detecting certain oscillation frequencies of the said output signal, the said frequencies characterising the opening of certain contacts. The said detection means can be connected to a central system for programmed supervision so as to display messages indicating at least the location of open contacts in the electrical circuit (1) when the said detection means detect an oscillation frequency characterising the opening of the said contacts.

Description

 The present invention relates to a device for locating an opening point of an electrical circuit.

 An industrial electrical installation generally comprises a main circuit or power circuit, which supplies and protects electrical devices such as for example electric motors, and an auxiliary circuit or control circuit which triggers the starting or stopping of electrical devices in function usually reopening or closing contacts.

 The control circuit generally comprises coils of contactor or auxiliary relay electromagnets. Each of said coils is connected to an electrical circuit included in the control circuit, comprising a certain number of contacts connected in series and / or in parallel. When all the contacts of the component's electrical circuit are closed, an electrical voltage is present across the coil. When at least some of the contacts of said electrical circuit are open, the electrical voltage across the coil disappears, which triggers an action which may be the extinction or the lighting of an indicator light, an audible alarm, stopping of a electrical device of the power circuit, an alarm message displayed on a supervision computer system, etc.

 In the case where the opening of the circuit means a fault requiring the intervention of an agent to repair the fault or reset a protection relay, it is necessary to locate the open contact (s). If the electrical installation is simple and not extensive, the search for open contacts can be simple and quick for a person skilled in the art.

 But for a complex and relatively extensive electrical installation, it is preferable to have a central supervision system which indicates the open contacts to locate the place where the agent must intervene and allow him to identify the possible breakdown.

 This can be achieved by connecting the terminals of each contact to the central supervision system, which may require significant, therefore expensive, and complex wiring. Or the contact terminals can be connected to remote transmission systems themselves linked to the central supervision system, which is also an expensive solution. In addition, in the case of an existing electrical installation which it is desired to modify in order to be able to detect the open contacts with stiffness of a central supervision system, these solutions require numerous modifications to the existing installation, and are complex and costly to implement.

 The present invention aims to avoid these drawbacks.

 The present invention relates to a device for locating an opening point on an electrical circuit comprising at least one coil, characterized in that at least one oscillator electrical circuit is connected in parallel with the coil by collaborating with said circuit electric to form an oscillator whose output signal oscillates with a frequency characteristic of the position of the opening point on the electric circuit. This device can be used to identify the position of open contacts constituting an opening of the electrical circuit advantageously, the device then comprises means for detecting certain frequencies of oscillation of said output signal, said frequencies characterizing the opening of certain contacts.

 Said detection means may comprise bandpass filters receiving the output signal from the oscillator, each filter having an output connected to an adjustable gain operational amplifier producing a continuous signal taking a first value when certain contacts are open, and taking a second value when said contacts are closed. The device can include as many oscillator circuits as there is a bandpass filter, said oscillator circuits being connected in parallel with the coil of the electrical circuit.

 Advantageously, said detection means are connected to a central supervision system programmed to display messages indicating at least the location of open contacts in the electrical circuit when said detection means detect an oscillation frequency characterizing the opening of said contacts.

Other characteristics and advantages of the present invention will become apparent during the detailed description which follows, given by way of nonlimiting example, with reference to the accompanying drawings, in which:
- Figure 1 is a diagram of the electrical circuit to which electronic cards are connected according to one embodiment of the invention;
- Figure 2 is an overall diagram of an embodiment of the device of the invention;
FIG. 3 is a diagram of an electronic card for locating an open contact according to one embodiment of the invention;
- Figure 4 is a diagram of an electronic interface card between the card of Figure 3 and a local computer network, according to one embodiment of the invention;
- Figure 5 is a diagram of an electronic interface card between the local computer network and a central supervision system, according to one embodiment of the invention;
- Figure 6 is a diagram of the oscillator circuit connected in parallel with the coil of the electrical circuit, according to one embodiment of the invention; and
FIG. 7 is a diagram of the signal processing chain at the output of the oscillator circuit of FIG. 6.

 In Figure 1 is shown a circuit 1 included in a control circuit of an electrical installation. Circuit 1 includes a solenoid coil 2 of a contactor or an auxiliary relay, connected in series to contacts C1, C2 ...

Cp connected in series, the assembly being connected between two supply terminals, positive and negative respectively in this particular example. A contact C11 is connected in parallel with the contact C1. Several contacts could be mounted in parallel on C1, or on any other contact C2, ... Cp. The circuit 1 also comprises an electric voltage source, so that, when at least some of the contacts are closed by closing the circuit, the coil 2 is traversed by an electric current.

 The coil 2 has two terminals 3 and 4 which connect it to circuit 1.

When certain contacts are open so as to open the circuit 1, the voltage between the terminals 3 and 4 of the coil disappears, and the current is no longer traversed by the current. This triggers either the opening or the closing of the relay or of the contactor corresponding to the coil, which causes an action such as for example the stopping of an electrical installation and / or an alarm intended to warn a user.

Generally, the user must then locate the open contact (s), for example to diagnose and repair a fault.

 In a particular embodiment, the device includes electronic contact location TPC cards, each comprising two connection terminals 5, 6 respectively connected to terminals 3 and 4 of a coil 2, as shown in FIG. 1.

 Each TPC card can be connected to a CPS interface card with a local network, said CPS card itself being connected to a cable 7 via a DB9 connector.

As shown in Figure 2, several sets of two TPC1 cards
CPS1, TPC2-CPS2, TPC3-CPS3, ..., TPCn-CPSn, each corresponding to a different coil 2, can be connected to a central supervision system via an interface card 8. The system central supervision can be a programmable controller or a microcomputer.

In the example presented in FIG. 2, each interface CPS card has two connectors on which two DB9 cable connectors 7 can be connected respectively. This constitutes a bus connection connecting the interface card 8 of the supervision system to a first CPS 1 card by a first cable, then the first CPS2 card by a second cable, up to the last card
CPSn comprising a first connector to which a cable is connected, and a second connector covered with a plug 9. The bus connection thus formed may for example be an RS422 type connection, and the interface card 8 of the supervision system can for example convert the signals received from the link
RS422 in RS232 format, standard on programmable logic controllers and microcomputers. Each CPS card has a coded address, making it possible to identify the signals received from said card or to send signals which are specifically intended for it.

As shown in FIG. 3, each TPC electronic card for locating an open contact may include a power supply 10, and detectors 11 connected to a component 12 for dialogue with the CPS card connected to the card.
TPC, to send information via a parallel link to the CPS card.

In this example, the detectors can be a maximum of thirty two, distributed in four columns of 8, and the TPC card comprises a block 14 of four switches making it possible to indicate which columns are fitted with detectors.

 The TPC card finally has a socket 13 and the CPS card has a complementary socket 20 in order to connect the two cards by a parallel link.

 The CPS card of FIG. 4 comprises a power supply 21, an input buffer memory 22 for receiving the information transmitted by the TPC card, a processor 23 sequenced by a clock 24 for processing said information received by the buffer memory 22, a memory output buffer 25 for storing the information processed by the processor 23 and an output signal generator 26 for transmitting a signal to the local network by at least one output socket 27.

 The interface card 8 with a central supervision system shown in FIG. 5, may include a power supply 30, a socket 31 for receiving information from the cards CPS1, CPS2, ..., CPSn, a first memory and input buffer 32 to receive said information byte by byte, a second input buffer 33 for storing said information before processing by a processor 34 sequenced by a clock 35, a first output buffer 36 for storing information processed by the processor 34, a second output buffer 37 for receiving said information byte by byte after storage in the first output buffer 36, and an output signal generator 39 for transmitting a signal to a central supervision system by a socket 38.

Each detector 11 of a TPC card comprises an oscillator circuit 40 which is provided with two input connection terminals 5 and 6 and an output So. The terminals 5 and 6 are respectively connected to the terminals 3 and 4 of the coil 2 included in the circuit 1. The circuit 40 comprises two resistors R1 and R2 connected in series; resistor R1 is connected between a positive terminal of the card supply
TPC and a point 41, and the resistor R2 is connected to a negative supply terminal and to point 41. An inductor L1 is connected between point 41 and a negative supply terminal. A transistor T, of NPN type, has its base connected to point 41, while its collector is connected to the output So. A resistor R3 is also connected between the emitter of transistor T and a positive supply terminal. A capacitor CA2 is connected in series with an inductance L2 between the emitter of transistor T and terminal 5, a capacitor CA1 is connected between the emitter of transistor T and a negative supply terminal at a point 42, a capacitor CA3 in series with an inductor L3 being also connected between point 42 and terminal 6.

Circuit I collaborates with circuit 40 to constitute a type oscillator
Collpits whose oscillation frequency depends in particular on the capacity of circuit 1, which itself depends on the length of circuit 1 not cut from the coil 1. Thus, if circuit 1 is cut in C1 and C'1 , the oscillation frequency will not be the same as if circuit 1 is cut at C2. If circuit 1 is cut at the same time in C1, C'î and C2, the oscillation frequency will be the same as if the circuit had not been cut in C2.

 The output So of the oscillator circuit 40 therefore collects a periodic frequency signal depending on the cut-off position of the circuit 1 closest to the coil 2. As shown in FIG. 3, this signal is transmitted to a bandpass filter 43 provided with an output S1 which collects an output signal attenuated compared to the signal collected in So if the frequency of said signal is located outside of a pass band of the filter 43. If the signal has a frequency included in the pass band of the filter 43 , said signal is not attenuated in S 1.

 Each detector 1 1 of the TPC card has a filter 43 having a different passband, centered on a frequency corresponding to an uncut length of different circuit 1. The different passbands of the filters 43 corresponding to the different detectors 11 do not overlap, but may possibly be contiguous.

 When circuit 1 is cut at one or more points, the length of circuit 1 between coil 2 and the cutoff point closest to said coil determines an oscillation frequency of the various oscillator circuits 40 of detectors 11.

A periodic signal of frequency f is therefore transmitted to the respective filters 43 of the various detectors 11. The signal at the output of the filters 43 is maximum for the filter whose passband covers or is closest to the frequency f. At the output of the filter 43, the signal is transmitted in S1 to an operational amplifier 44 of adjustable gain, having an output S2, the gain of which is adjusted during the installation of the device for locating the cut-off point so that the signal in S2 take a continuous value Vo when the circuit 1 is cut at a point such that the oscillation frequency f is close to or included in the pass band of said filter. From S2, the signal is transmitted to the component 12 for dialogue with the CPS card, which in turn transmits the information to the central supervision system via the local network. The central supervision system generally comprises a means of display allowing to display a message designating the location of the open contact (s) corresponding to the circuit 1 cut-off point.

 It is possible that several contacts that can open to cut circuit 1 are too close to each other to be discriminated by the tracking system; in this case, if one or more of these contacts open so as to cut circuit 1, the message displayed by the supervision system will indicate the position of all of said contacts close to each other, and the operator, by going to this place, can easily locate the open contacts among this set.

 In the case where circuit I has several cut-off points, the supervision system will initially indicate the position of the cut-off point closest to the coil 2. After cancellation of the corresponding fault by the operator, the contacts having caused this cut closest to the coil 2 are closed again. The locating system then locates a possible second cut-off point for circuit 1, and so on until all the contacts are closed again and circuit 1 is itself closed again.

 In this example, the invention has been described with a particular local network connecting the electronic contact location cards open to a central supervision system; it is obvious that this connection could be achieved by any other means known in the state of the art.

Claims (5)

Claims  1.- Device for locating an opening point on an electrical circuit (1) comprising at least one coil (2), characterized in that at least one oscillator electrical circuit (40) is connected in parallel with the coil (2) by collaborating with said electrical circuit (1) to form an oscillator, an output signal of which oscillates with a frequency characteristic of the position of the opening point on the electrical circuit (1).  2.- Device according to claim 1, to identify the position of open contacts constituting an opening of the electrical circuit (1), characterized in that it further comprises detection means (43, 44) of certain oscillation frequencies of said output signal, said frequencies characterizing the opening of certain contacts.  3.- Device according to claim 2, characterized in that said detection means comprise bandpass filters (43) receiving the oscillator output signal, each filter having an output connected to an operational amplifier (44) of adjustable gain producing a continuous signal taking a first value when certain contacts are open, and taking a second value when said contacts are closed.  4.- Device according to claim 3, characterized in that it comprises as many oscillator circuits (40) as bandpass filters (43), said oscillator circuits being connected in parallel with the coil (2) of the electrical circuit ( 1).  5.- Device according to one of claims 2 to 4, characterized in that said detection means (43, 44) are connected to a central supervision system programmed to display messages indicating at least the location of open contacts in the electrical circuit (1) when said detection means (43, 44) detect an oscillation frequency characterizing the opening of said contacts.