KR100960495B1 - Digital protective relay - Google Patents

Abstract

The present invention allows a digital protection relay that protects the electric shock system by driving a circuit breaker when the power system has an abnormality to isolate the trunk from the bus, so that it can also be used for the signal. For this purpose, the circuit connected to the output contact can be freely transitioned to the closed or open circuit state as needed. Accordingly, it is possible to satisfy the demands of consumers who want to use the digital protective relay not only for protection but also for signaling.

Relay, Breaker, Relay, Protection, Control, Signaling, Closed Circuit, Open Circuit

Description

Digital Protective Relay

The present invention relates to a digital protective relay, and in particular, it is possible to always monitor the state of the electrical circuit configured between the relay and the circuit breaker or the breaking coil installed inside the circuit breaker without having to drive the circuit breaker, as well as the digital protective relay for signals. It is also intended to be used.

In general, there are a variety of potential accidents in the power system. For example, there are many risks such as damage caused by natural disasters such as lightning strikes, short circuit accidents caused by birds such as magpies, voltage drops due to system overload, damage to equipment, accidents caused by leakage of load such as electric motors, etc.

If these accidents are left unattended, the loss of human and material resources becomes very serious. Therefore, by adopting system protection devices such as relays in general, the accident system can be quickly separated from other normal systems to prevent the spread of accidents to other systems. It is taking measures to prevent the spread of accidents in the country.

Referring to the example of the general power system with reference to Figure 1, assuming that the terminal block 11 of the motors (M1, M2) connected to the trunk line branched from the bus line is short-circuited, Overcurrent flows through the track, which immediately disrupts the C system's power supply. Therefore, if such a situation is left unattended, it will affect not only the accident or fire hazard of the B system but also the facilities of the C system, resulting in damage to all equipment and systems connected to the bus.

In this case, if there is a relay in the B system, the accident current of the B system can be detected quickly and the B system can be separated from the bus to prevent the expansion of the accident.

On the other hand, the circuit breaker driving relay operates only in the event of a system accident. The relay contact (A contact) of the relay is continuously exposed to air, which causes corrosion when it is old. Burnout of the relay contact may occur. In addition, the relay may not operate in case of short circuit or short circuit of the circuit breaker driving relay coil, and even if the electric circuit which drives the circuit breaker driving relay is disconnected or short-circuited due to an error in the internal circuit of the relay, try to operate the circuit breaker. Until now, there is no way to monitor for abnormalities.

In other words, when the electric circuit is applied to the circuit breaker driving relay to check the circuit breaker driving relay, the breaker operates at the same time, there is an inconvenience that must cut off the power of the trunk.

In order to solve this problem, Patent Publication No. 2002-74689 proposes the following 'relay monitoring apparatus and method'.

Referring to FIG. 2, the relay monitoring device selects and cuts the supply of power to the trunk branch branched from the bus and applies a power to the load 21, a current flowing through the breaker 21 and a voltage applied to the predetermined ratio. Instrument transformer 22 for releasing to the secondary side of the furnace, photocouplers 23 connected to both ends of resistor elements R1, R2, R3, R4, and resistor elements R2 and R4 respectively for limiting and distributing current of AC power source (AC). And the output of the analog / digital converter 24, the analog / digital converter 24, and the output of the instrument transformer 22, which convert the output voltage of the photocoupler 23 into digital values, respectively, And a control unit 25 for outputting the relay control signal, and an output amplifier 26 for amplifying the relay control signal and transmitting the relay control signal to the relays RLY1 and RLY2.

That is, the relay RLY1 is used for driving the circuit breaker, and is usually turned off, and the RLY2 used as the auxiliary relay is turned on. Then, a current flows along the path formed by the AC power source AC, the resistor elements R1, R2, the relay RLY2, the circuit breaker trip coil C, and the AC power source AC, and a voltage of a predetermined magnitude or more is detected by the photocoupler PC1. Therefore, the operating state of the circuit breaker driving circuit can be monitored.

In addition, to check the circuit breaker driving relay RLY1, the relay RLY2 is turned off once (current flows through the resistor elements R1, R2, R3, and R4), and then the circuit breaker driving relay RLY1 is turned on. Then, the current flows along a path formed by AC power source AC, RLY1, resistance elements R3 and R4, circuit breaker trip coil C, and AC power source AC, so that a voltage of a predetermined magnitude or more is detected by photocoupler PC2. The operating state of the circuit breaker drive circuit can be monitored.

In addition, when both the relays RLY1 and RLY2 are in the on state, current flows without passing through the resistance element to drive the circuit breaker.

Due to such a configuration, the voltage output through each photocoupler 23 varies according to the on / off states of the relays RLY1 and RLY2, so that the state in the circuit breaker driving circuit can be checked without driving the circuit breaker 21.

However, in the example shown in Fig. 2, since the circuit breaker driving circuit always maintains the closed circuit regardless of the states of the relays RLY1 and RLY2, there is a problem that such a device cannot be used for signals. In other words, if you want to use the signal for other devices connected to the output contact can be signaled to the open or closed state to be able to transmit the signal, because you have to keep the closure at all times will not have any meaning of signal transmission.

Accordingly, an object of the present invention is to provide a digital protection relay that can be used as a signal as needed while checking the state in the circuit breaker driving circuit without driving the circuit breaker. .

In order to achieve the above object, the digital protective relay according to the present invention, the output contact used for the control or signal; An input contact for receiving a signal from the instrument transformer; A path determining unit forming a current path flowing between both terminals of the output contact; An analog / digital converter converting the voltage induced by the current flowing through the routing unit into a digital value; And calculating a digital value converted by the analog / digital converter and a signal input through the input contact, and controlling a current path flowing through the routing determiner according to whether to use the output contact for a control or a signal. It includes a control unit.

The routing part includes a first relay part and a second relay part connected in series between both terminals of the output contact, the first relay part is connected in parallel with a series of resistance elements R1 and R2, and both ends of the first relay part are connected to the first relay part. The operation mode setting relay unit, one end of which is connected to the common terminal with the relay unit, and the resistor elements R3 and R4 may be configured to be connected in series.

In this embodiment, the analog / digital converter comprises a first analog / digital converter and a second converter for converting the output voltages of the first photocoupler and the second photocoupler respectively connected to both ends of the resistor elements R2 and R4 into digital values. It may be configured to include an analog / digital converter.

In this case, the controller calculates the digital value converted by the first analog / digital converter and the second analog / digital converter and the signal input through the input contact, and uses the output contact as a control or a signal. And control the first relay unit, the second relay unit, and the operation mode setting relay unit depending on whether the first relay unit and the second relay unit are used.

The control unit may be configured to control the operation mode setting relay unit in a short state when the digital protection relay is to be used for a circuit breaker control connected to the output contact.

The control unit controls the operation mode setting relay unit to an open state when the digital protection relay is to be used for a signal, and controls one of the first relay unit and the second relay unit to an open state and the other to a short circuit state. It can be configured to.

The digital protection relay according to the present invention can monitor all the circuit breaker driving circuits such as the circuit breaker driving relay and the relay driving circuit without disconnection of power supply to the system.

Accordingly, the breaker inoperable state due to a failure of the breaker driving relay or an abnormality in the relay drive circuit can be prevented in advance.

In addition, if necessary, since the digital protection relay can also be used for signals through simple relay control, it is possible to appropriately cope with the reality that the use of signals becomes increasingly important.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 3A, the digital protective relay 30 according to the present invention has an output contact 31 used for control or signal. When the output contact 31 is used for control, it is connected to the AC power source and the breaker 21 as shown in the example shown in FIG. 2, and when used for a signal, another device (shown) Is not connected).

In addition, the digital protective relay 30 has an input point 32 for receiving a signal from the instrument transformer 22. The instrument transformer 22 serves to induce the current flowing through the trunk line and the applied voltage to the secondary side at a predetermined ratio.

The routing section includes components such as a first relay section 33-1, a second relay section 33-2, an operation mode setting relay section 33-3, and resistance elements R1, R2, R3, and R4. Can be done.

Each relay unit 33-1 to 33-3 includes an output amplifier and a relay element for amplifying the relay control signal transmitted from the controller 36.

Specifically, the first relay unit 33-1 and the second relay unit 33-2 are connected in series between both terminals of the output contact 31. The first relay unit 33-1 is connected in parallel to the resistance elements R 1 and R 2 in series, and one end of the second relay unit 33-2 is connected to a common terminal with the first relay unit 33-1. The operation mode setting relay unit 33-3 and the resistance elements R3 and R4 are connected in series.

Photocouplers 34-1 and 34-2 are connected to both ends of the resistor elements R2 and R4, and the analog / digital converters 35-1 and 35-2 are each photocouplers 34-1 and 34-. Convert the voltage output from 2) to digital value.

The controller 36 calculates a signal input from the instrument transformer 22 through the digital value converted by each analog / digital converter 35-1 and 35-2 and the input contact point 32. In addition, the control unit 36 may use the first relay unit 33-1, the second relay unit 33-2, depending on whether the output contact 31 is to be used for control or signal, and the calculation result. The relay control signal is output to the operation mode setting relay unit 33-3.

An example of configuring the control unit 36 is illustrated in FIG. 3B, and the PC1 signal input unit 36-6 and PC2 receiving the digital values converted by the analog / digital converters 35-1 and 35-2, respectively. Arithmetic unit 36-1 for calculating the digital value input through the signal input unit 36-4, the PC1 signal input unit 36-6, and the PC2 signal input unit 36-4 and the signal input from the instrument transformer 22. ), The RLY1 drive signal output unit 36-5, the RLY2 drive signal output unit 36-3, and the RLY3 drive signal output unit 36- that output drive signals for the respective relays RLY1 to RLY3 as relay control signals. 2) and the like.

On the other hand, when the control unit 36 intends to use the digital protection relay 30 for a signal, the control unit 36 controls the relay RLY3 to be turned off through the RLY3 driving signal output unit 36-2. The relays RLY1 and RLY2 are controlled to be in opposite states.

Referring to FIG. 4A, when the relay RLY3 is in the off state and the relay RLY1 is in the off state and the relay RLY2 is in the on state, the circuit is closed, whereas the relay RLY2 is in the off state and the relay RLY1 is in the open circuit. That is, it has a meaning of sending a signal to another device through the output contact 31 of the digital protective relay 30.

In addition, the controller 36 controls the relay RLY3 to the ON state when the digital protection relay 30 is to be used for the breaker control connected to the output contact 31.

The operation when the digital protective relay 30 is used for the breaker control will be described. In this case, although not separately illustrated in FIG. 3, the AC contact point AC and the breaker 21 are connected to the output contact 31 as shown in the example of FIG. 2.

Usually, the relay contact of the first relay unit 33-1 is in an off state and the relay contact of the second relay unit 33-2 is in an on state.

The current flowing in the AC power source AC flows through the contacts of the resistor elements R1, R2, and the second relay unit 33-2, and the resistance value of the resistor element R1 is set to be much larger than that of the resistor element R2. The voltage and current applied to the resistor element R2 become large enough to be used as an input signal of the photocoupler PC1 34-1 for small signal transfer.

At this time, the trip coil driving current of the breaker 21 is usually about several amperes, but the trip coil of the breaker cannot be driven because the current is limited by the resistance element R1.

The current flowing through the resistor element R1 is distributed to the resistor element R2 at the input terminal of the photocoupler PC1 34-1 so that the emitter and collector terminals of the output terminal of the photocoupler PC1 34-1 can be energized.

Then, the first analog / digital converter 35-1 corresponding to the photocoupler PC1 34-1 converts the output voltage of the photocoupler PC1 34-1 into a digital value, and the converted value is It is input to the control part 36 via the PC1 signal input part 36-6. That is, when there is a signal coming through the first analog-to-digital converter 35-1, it may be determined that there is no abnormality in the circuit breaker driving circuit and the circuit breaker trip coil.

This is because the output of the photocoupler PC1 34-1 does not occur when the circuit breaker drive circuit is disconnected or shorted or the circuit breaker trip coil is disconnected.

Through such an operation process, as shown in the example of FIG. 4B, the first relay unit 33-1 and the second relay unit 33-2 may be controlled to determine various states of the circuit breaker driving circuit and the circuit breaker trip coil. Will be.

Now let's look at the process of monitoring the state of the breaker drive circuit without shutting down the power system.

First, the relay RLY2 of the second relay section 33-2 is turned off. At this time, the current flows through the AC power source (AC) and the resistors R1, R2, R3, and R4. Therefore, the photocoupler PC1 34-1 and the photocoupler PC2 34-2 are both in an activated state, so that the first analog / digital converter 35-1 and the second analog / digital converter 35-2 are activated. May output a digital value of a predetermined size or more, and the controller 36 may recognize that both of the contacts of the first relay 33-1 and the second relay 33-2 are open.

Now, to check the state of the first relay section 33-1, the relay RLY1 is turned on. The current then flows through AC power supply AC, relay RLY1, resistor elements R3, R4. Accordingly, the photocoupler PC2 34-2 generates an output value by the voltage applied to the resistor element R4, and the second analog / digital converter 35-2 transfers a digital value of a predetermined size or more to the controller 36. As a result, the control unit 36 can confirm that the relay RLY1 of the first relay unit 33-1 is normal.

That is, when the contact of the relay RLY1 is opened and closed while the relay RLY2 is turned off, the relay RLY1 is normal if a value of a predetermined size or more passes through the first analog / digital converter 35-1 and then disappears. .

However, if the relay RLY1 is opened and closed while the relay RLY2 is turned off, but the output value of the first analog / digital converter 35-1 remains constant, this indicates that there is a problem in the relay RLY1 or the corresponding current path. .

Each embodiment described above is intended to help the understanding of the present invention, the present invention is not limited to the above embodiments and can be variously modified and implemented by those skilled in the art without departing from the technical spirit of the present invention. Of course.

1 is an example for explaining an accident of a power system;

2 is an example of a conventional digital protection relay,

3 is an embodiment of a digital protective relay according to the present invention;

4 is a table showing a circuit state according to each relay state.

DESCRIPTION OF THE REFERENCE NUMERALS

21: breaker AC: AC power

22: instrument transformer 30: digital protective relay

31: Output contact 32: Input contact

33-1 to 33-3: relay section 34-1, 34-2: photocoupler

35-1,35-2: Analog-to-digital converter

36: control unit R1 to R4: resistance element

RLY1 ~ RLY3: Relay

Claims (5)

Output contacts used for control or signaling; An input contact for receiving a signal from the instrument transformer; A path determining unit forming a current path flowing between both terminals of the output contact; An analog / digital converter converting the voltage induced by the current flowing through the routing unit into a digital value; And A controller for calculating a digital value converted by the analog / digital converter and a signal input through the input contact, and controlling a current path flowing through the routing determiner according to whether to use the output contact for control or for a signal Including, The routing part includes a first relay part and a second relay part connected in series between both terminals of the output contact, the first relay part is connected in parallel with a series of resistance elements R1 and R2, and both ends of the second relay part And an operation mode setting relay unit having one end connected to a common terminal with the first relay unit and a resistor R3 and R4 connected in series. delete The method of claim 1, The analog / digital converting unit includes a first analog / digital converting unit and a second analog / digital converting unit configured to convert output voltages of the first photocoupler and the second photocoupler respectively connected to both ends of the resistor elements R2 and R4 into digital values. Including wealth, The controller calculates the digital value converted by the first analog / digital converter and the second analog / digital converter and the signal input through the input contact, and according to whether to use the output contact for control or signal. And the first relay unit, the second relay unit, and an operation mode setting relay unit. The method of claim 3, wherein And the control unit is configured to control the operation mode setting relay unit in a short circuit state when the digital protection relay intends to use the circuit breaker control connected to the output contact. The method of claim 3, wherein The control unit controls the operation mode setting relay unit to an open state when the digital protection relay is to be used for a signal, and controls one of the first relay unit and the second relay unit to an open state and the other to a short circuit state. And a digital protection relay.

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