JPH04344116A - Discontinuity monitor for trip circuit - Google Patents

Abstract

PURPOSE:To prevent an erroneous detection of a discontinuity by detecting an open signal of a switch interposed between both ends of a breaker and a line, and locking a discontinuity detection signal. CONSTITUTION:Open/close signals of switches LS-A, LS-B, LS-C interposed between both ends of a breaker CB and a system line are input to an input circuit 11, and a decision signal of a discontinuity detector by a suppressing element 17 is locked by a decision of opening of one end of the breaker CB by logic elements 15, 16. A detection signal of opening of both switches LS-A and LS-B or opening of the switch LS-C is decided by the elements 15, 16, and an output of a decision element 12 is locked by a suppressing element 17 by the decision. Thus, an erroneous detection of a discontinuity can be prevented while eliminating an operation of a monitoring lock switch SW1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disconnection monitoring device for a trip circuit in a digital relay.

0002

[Prior Art] Digital relays capture voltage and current detection signals from power systems and equipment as digital signals.
A protection calculation is performed using these, and when an accident determination is obtained as a result of the calculation, the circuit breaker is tripped (tripped) in accordance with a predetermined sequence. In addition to such protection processing functions, various processing functions such as function inspection and function monitoring of each part are attached.

Among these devices, the disconnection monitoring device for a trip circuit detects a disconnection by passing a weak monitoring current of several milliamperes through a trip coil and detecting conduction or interruption of the current. This conventional device will be explained in detail below.

FIG. 2 shows a configuration for monitoring disconnection of a trip circuit in a conventional digital relay. The main detection unit 1 and the accident detection unit 2 input a detection signal from a protection target, perform protection calculations, and output a trip signal for disengaging the breaker to be protected. For example, the main detection unit 1 performs differential relay calculation of the protection system, and performs undervoltage detection for fault detection.

The trip signals from these detection units 1 and 2 are converted into ON control signals for trip output switches 31 and 32, respectively, in a trip circuit 3, and
The trip coil 34 is energized, that is, the breaker is disconnected, through the two series circuits. A normally-on inspection switch 33 is also provided in series with the trip circuit 3, and the main detection unit 1
The switch 33 is turned off in response to an inspection signal from the trip circuit, and the trip circuit is inspected for disconnection.

[0006] The trip circuit 3 also includes each switch 31.
~33 on/off status as an answer signal (FS answer, M
The main detection unit 1 uses the signal as a constant monitoring signal. Further, the result of detecting a disconnection in the trip circuit through inspection is output as a disconnection answer signal, and the main detection unit 1 monitors the disconnection based on this signal, the device use signal, the trip coil input signal, and the monitoring lock switch on signal.

The specific circuit configuration of the trip circuit 3 is shown in FIG.
Shown below. Trip signals FS and M are photocoupler PC1,
It is insulated by PC2 and taken in. The inspection signal is sent to the photocoupler PC as a signal inverted by INV.
It is incorporated into 3. The output signals of the photocouplers PC1 to PC3 are made into on/off control signals for the FET switches 31 to 33, and the on/off states of the switches 31 to 33 are taken out as answer signals from the photocouplers PC4 to PC6.

A device use/device lock changeover switch 35, a lock terminal 36, and a normally open contact 37 are provided in series between the series circuit of switches 31 to 33 and the trip coil 34. An on/off switch 38 for the breaker is also provided. The above-mentioned trip coil input signal is taken into the main detection unit 1 as an operation signal of the contact 37.

When the monitoring lock switch SW1 is turned on, it energizes the relay MX, and the output contacts MX1 and MX2 of the relay are turned on.
performs a supervisory lock. The disconnection detection circuit that obtains the disconnection answer signal branches off from the trip coil side from the switches 31 to 33, takes it out as an on/off signal for the photocoupler PC7 via current limiting resistors R1 and R2, and outputs the disconnection answer signal to the photocoupler PC8. get.

In the above configuration, disconnection monitoring of the trip circuit is performed by sending the main detection unit 1 a disconnection answer signal, a signal of the device use/lock switch 35, an on/off signal of the trip coil 34, and an on/off signal of the monitoring lock switch 38. is taken in by the input circuit 11 and determined by the judgment circuit 12 based on the logic of each signal.
A disconnection is detected in the output circuit 14 through continuous confirmation by the timer 13.

Normally, the switches 31 and 32 are off, the switch 33 is on, the switch 37 is "on", the lock terminal 36 is closed, the supervisory lock switch SW1 is "open", and the photocouplers PC9, PC10 and switch A monitoring current of several milliamperes is caused to flow through the trip coil 34 via the trip coil 33, so that no current flows to the disconnection answer circuit side (PC7, etc.), and the disconnection answer signal is OFF ("0").

[0012] A break occurs in the trip circuit or the switch 3
5, 37, etc., the monitoring current does not flow to the trip coil 34 side, but flows to the disconnection circuit side (PC7, etc.), and the disconnection answer signal turns on (“1”). This disconnection answer signal causes the main detection unit 1 to use the device/lock switch 3.
5 is on (used), contact 37 is "on", and monitoring lock switch SW1 is locked (off).
2, obtain a disconnection detection signal.

[0013]

[Problem to be Solved by the Invention] In the conventional disconnection monitoring device, the trip coil 3 is
When the power supply terminal N of No. 4 is intentionally lost, the disconnection answer signal becomes "1" and it is erroneously determined that the trip circuit is disconnected. Therefore, when inspecting the breaker, use the monitoring lock switch SW1.
This required work to turn on the power, making inspection work cumbersome.

An object of the present invention is to provide a wire breakage monitoring device that prevents erroneous wire breakage detection without operating a monitoring lock switch.

[0015]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a digital relay that flows a disconnection monitoring current to a trip coil of a breaker and monitors disconnection of the trip circuit based on whether or not the current is interrupted. A monitoring locking means for locking a disconnection detection signal of the trip circuit when it is determined that at least one terminal of the breaker is opened by inputting a switching signal of a switch that opens and closes between both ends of the breaker and the system line. It is characterized by having the following.

[0016]

[Operation] According to the present invention having the above structure, when inspecting a breaker, opening the switches installed at both ends of the breaker is used, and a disconnection detection signal is obtained by obtaining a switch open signal. By locking, it is possible to eliminate the need to operate the monitoring lock switch and prevent erroneous disconnection detection.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention, and shows the software structure of a main detection unit 1A. This figure differs from the disconnection monitoring device in the main detection unit 1 of FIG. 2 in that it includes a disconnection monitoring locking means consisting of elements 15 to 17.

The input circuit 11 includes switches LS-A, LS-B, and LS interposed between both ends of the breaker CB and the system line.
-C open/close signal is taken in, and the determination signal of disconnection detection by the inhibiting element 17 is locked by the open/open determination of one end of the circuit breaker CB by the logic elements 15 and 16.

That is, the breaker CB in the actual system has switches LS-A, LS-B, LS-C, etc. interposed in connection with the line, and when inspecting the breaker CB, all the switches connected to one end of the breaker CB are connected to the line. Open the switch. Taking advantage of this, in the illustrated example, both switches LS-A and LS-B are opened, or switch LS-B is opened.
- determine the open detection signal of C by logic elements 15 and 16;
Based on this determination, the inhibiting element 17 locks the output of the determining element 12. As a result, the monitoring lock switch SW
To prevent erroneous disconnection detection while eliminating the need for operation 1.

In the embodiment, the combination of the logic elements 15 and 16 is changed depending on the manner of connection between both ends of the breaker and the system line.

[0021]

[Effects of the Invention] As described above, according to the present invention, the disconnection detection signal is locked by detecting the open signal of the switch interposed between both ends of the breaker and the line. This eliminates the possibility of erroneously detecting a disconnection without operating the monitoring lock switch, which has the effect of facilitating inspection of the circuit breaker.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of main parts showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional disconnection monitoring device.

FIG. 3 is a circuit breaker trip circuit diagram.

[Explanation of symbols]

1, 1A... Main detection unit, 11... Input circuit, 12... Judgment circuit, 13... Timer, 14... Output circuit, 15, 16...
Logic element, 17... Deterrent element, CB... Circuit breaker, 34... Trip coil, SW1... Monitoring lock switch, 35... Device use/lock switch.

Claims (1)

[Claims] 1. A digital relay that flows a disconnection monitoring current through a trip coil of a breaker and monitors disconnection of the trip circuit based on the presence or absence of interruption of the current, wherein a switch that opens and closes between both ends of the breaker and a system line is provided. A disconnection monitoring device for a trip circuit, comprising a monitoring locking means for locking a disconnection detection signal of the trip circuit when it is determined that at least one terminal of the breaker is opened by inputting a switching signal.