KR101503314B1 - Protective relay - Google Patents

Abstract

The present invention relates to a protective relay. More specifically, the protective relay is capable of: promptly and flexibly responding to an accident by reducing a trip counter which determines relaying operation and relaying return due to inverse time; and allowing suitable relaying operation and relaying return for circumstances in an accident by increasing/decreasing the trip counter inversely proportional to a size of a relaying element, thereby improving lifespan and efficiency of a protective device including a relay. Also, the protective relay can be widely and flexibly applied to the protective device with return properties as well as operation properties, thereby preparing itself against various accidents. The protective relay comprises: a detecting unit to detect a relaying element which is an operation base of a relay; a calculating unit to control increase/decrease of a trip counter which displays a time limit for relaying operation and relaying return based on detection results detected by the detecting unit; and an operating unit to perform the relaying operation and the relaying return based on the increase/decrease of the trip counter.

Description

Protection Relay {PROTECTIVE RELAY}

The present invention relates to a protection relay, and more particularly, to a protection relay having a return curve characteristic by reducing a trip counter to an inverse characteristic.

Relay means an electrical device designed to respond in a prescribed manner if the specified conditions are met due to an action or similar unexpected change in the associated electrical control circuit and the protective relay is connected to an unusual or dangerous device or a faulty line ≪ / RTI > or other power system, and operates the appropriate control circuitry.

1 is a flowchart showing a flow of relay operation of a conventional protection relay.

1, the relay operation of the conventional protection relay senses an input signal, compares the detected input current with an operation value, and when a comparison result indicates that the input current is greater than the operation value, a trip counter The relay element outputs an operation and a trip signal when the trip counter is equal to or longer than the time set in time, and after the relay operation is performed, or when the detected input current is equal to or less than the operation value, .

In case of a relay operating with the above characteristics, the breaker trips after a certain time due to an accident. When the accident is temporarily released and the breaker trips again, the trip counter of the relay is reset to 0 And it takes a long time for the relay operation to be performed again.

In such a case, it is impossible to immediately take protective measures against the recurrence of accidents, and there is a problem that the burden is accumulated in the facilities causing accidents, and thus the facilities are burned down and the safety is reduced, and also there is a problem in that flexible coping is difficult .

Therefore, in the present specification, the trip counter is reduced to the return curve characteristic at the time of the return of the relay, so that it can respond immediately to the accident recurrence, and the trip counter is increased or decreased in inverse proportion to the size of the relay element, And to provide a protective relay capable of performing proper relay operation and return to the relay.

The protection relay described in this specification for realizing the above-mentioned problems includes a detection unit for detecting a relay element that is a basis for operation of a relay, a trip unit for detecting a relay operation based on the detection result detected by the detection unit, An operation unit for controlling an increase / decrease of a trip counter, and an operation unit for performing the relay operation and the relay return based on an increase / decrease of the trip counter, wherein the trip counter is reduced to a return curve characteristic, The curve characteristic is a characteristic in which the decrease time of the trip counter changes in accordance with the detection result.

In an embodiment, the relay element may be a current element.

In an embodiment, the detector may detect the relay element from any one of a CT (Current Transformer) and a ZCT (Zero Current Transformer).

In the embodiment, the relaying operation may be an operation in which the opening / closing device or the breaker is opened and closed.

In an embodiment, the relay return may be a return to a state before the relay operation is performed.

In an embodiment, the calculation unit may increase the trip counter when the detection result is equal to or larger than a predetermined reference input value.

In an embodiment, the operation unit may reduce the trip counter when the detection result is reduced to less than or equal to the predetermined reference input value.

In an embodiment, the trip counter may be increased with either one of instantaneous or transient characteristics.

In the embodiment, the temporal characteristic may be any one of a fixed temporal characteristic and an inverse characteristic.

In an embodiment, the operation unit may send an operation signal to a trip coil to perform a relay operation.

In an embodiment, the operation unit may perform a relay return by sending a return signal to an input coil (Closing Coil).

In an embodiment, the operation section can perform the relay operation when the trip counter has reached the predetermined time input value.

In an embodiment, the operation unit can perform a relay reset when the trip counter is initialized to zero.

In an embodiment, the return curve characteristic may be a curved characteristic of any one of SI (Standard Inverse), VI (Very Inverse), EI (Extremely Inverse) and LI (Long Inverse).

According to another aspect of the present invention, there is provided a method of relaying a protective relay described in the present specification, including the steps of detecting a relay element, comparing the detection result with a predetermined reference input value, A trip counter, performing a relay operation based on the increased trip counter, re-detecting the relay element, re-comparing the re-detection result with the predetermined reference input value, Decreasing the increased trip counter to a return curve characteristic based on a result of the re-comparison, and performing a relay return based on the reduced trip counter.

In an embodiment, the step of increasing the trip counter based on the comparison result may increase the trip counter when the detection result is equal to or greater than a predetermined reference input value.

In an embodiment, performing the relaying operation based on the increased trip counter may perform the relaying operation when the increased trip counter reaches a predetermined time input value.

In an embodiment, reducing the increased trip counter to the return curve characteristic based on the re-comparison result may reduce the trip counter if the re-detection result is less than or equal to a predetermined reference input value.

In an embodiment, performing the relay reset based on the reduced trip counter may perform a relay reset if the trip counter is initialized to zero.

In an embodiment, the return curve characteristic may be a curved characteristic of any one of SI (Standard Inverse), VI (Very Inverse), EI (Extremely Inverse) and LI (Long Inverse).

The protection relay disclosed in this specification can reduce the trip counter which determines the relay operation and the relay return performance to the inverse characteristic so that it is possible to cope with the accident recurrence promptly and flexibly so that the burden on the load can be reduced, It has the effect of reducing the risk.

In addition, since the trip counter is increased or decreased in inverse proportion to the size of the relay element, proper relay operation and relay return are performed according to the situation in the event of an accident, thereby improving the life and efficiency of the protective device including the relay have.

In addition, since the relays have not only the operating characteristics but also the return characteristics, the relays can be applied to the protective devices more widely and flexibly, thereby making it possible to prepare for various accidents.

1 is a flow chart showing a flow of relay operation of a conventional protection relay.
2 is a block diagram of the protection relay disclosed in this specification;
3 is a configuration diagram according to an embodiment of the protective relay disclosed herein;
4 is a graph showing an SI return curve applied to an embodiment of the protective relay disclosed herein.
5 is a graph showing a VI return curve applied to an embodiment of the protective relay disclosed herein.
6 is a graph showing an EI return curve applied to an embodiment of the protective relay disclosed herein.
7 is a graph showing an LI return curve applied to an embodiment of the protective relay disclosed herein.
FIG. 8 is a flow chart illustrating the relay operation and relay return operation of the protection relay disclosed herein. FIG.
Figure 9 is a flow diagram illustrating the relaying method of the protective relay disclosed herein.

The techniques disclosed herein can be applied to protective relays. However, the technology disclosed in this specification is not limited thereto, and can be applied to all relays, circuit breakers, controllers, switches, power protection devices, and other protection relay systems to which the technical idea of the above-described technology can be applied.

It is noted that the technical terms used herein are used only to describe specific embodiments and are not intended to limit the scope of the technology disclosed herein. Also, the technical terms used herein should be interpreted as being generally understood by those skilled in the art to which the presently disclosed subject matter belongs, unless the context clearly dictates otherwise in this specification, Should not be construed in a broader sense, or interpreted in an oversimplified sense. In addition, when a technical term used in this specification is an erroneous technical term that does not accurately express the concept of the technology disclosed in this specification, it should be understood that technical terms which can be understood by a person skilled in the art are replaced. Also, the general terms used in the present specification should be interpreted in accordance with the predefined or prior context, and should not be construed as being excessively reduced in meaning.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In this specification, the terms "comprising ", or" comprising "and the like should not be construed as necessarily including the various elements or steps described in the specification, Or may be further comprised of additional components or steps.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, wherein like reference numerals denote like or similar elements, and redundant description thereof will be omitted.

Further, in the description of the technology disclosed in this specification, a detailed description of related arts will be omitted if it is determined that the gist of the technology disclosed in this specification may be obscured. It is to be noted that the attached drawings are only for the purpose of easily understanding the concept of the technology disclosed in the present specification, and should not be construed as limiting the spirit of the technology by the attached drawings.

First, the terms used in the description of the construction and the embodiment of the protection relay disclosed in this specification will be described.

The terms used in describing the construction of the protection relays disclosed in this specification and the description of the embodiments include relays, protective relays, relay elements, trip counters, relay operations and relaying.

The relay means an electrical device designed to respond in a prescribed manner if the specified conditions are met due to an operation or similar unexpected change in the associated electrical control circuit and the protective relay is a device or fault of an unusual or dangerous nature Means a protective device that senses conditions such as a line or other power system and operates the appropriate control circuitry.

The protection relay may refer to all relays used for various purposes such as an overcurrent relay, an overvoltage relay, an undervoltage indicator, an undercurrent detector, a power relay, an active power relay, and a reactive power relay.

In addition, the protection relay may mean all relays used in a circuit breaker, a controller, an actuator, a power protection device, and other protection relay systems for protecting the power system and the power equipment.

The relay element means an electrical value that is a basis for performing the relay operation and the relay return of the protection relay.

The relay element is set according to the application field and the application of the protection relay, and can be applied to the protection relay.

For example, as a protection relay for protecting the line from a short-circuit current of 1 [KA] or more generated in the line, an overcurrent relay to which an overcurrent relay element is applied may be used so that an overcurrent of 1 [KA] or more can be detected.

That is, the protection relay classifies the application field and the application according to the relay element.

The protection relay detects the relaying element, so that the relaying operation and the relaying of the protection relay can be performed.

The trip counter means a time taken for the protection relay to perform the relay operation and the relay return.

The trip counter can be counted by detecting the relay element.

For example, when the relay element is detected in the state of the initial 0 [s], the counting of the trip counter is started and the counter Counter is increased in units of [s], and after 10 seconds, The trip counter value can be set to 10 [s].

Here, the unit may be set according to the characteristics of the relay element from the microsecond [us] unit to the second [s] unit.

Further, the trip counter can be DisCounted by stopping the detection of the relay element.

For example, when the relay element is detected in the initial 0 [s] state of the trip counter and counting is started and the counter is increased to 10 [s], if the detection of the relay element is stopped, 10 [s], and after 10 seconds, the value of the trip counter can be initialized to 0 [s].

That is, the trip counter can be increased or decreased depending on whether or not the relay element is detected.

When the relay element is detected, the trip counter is incremented, and when the detection of the relay element is stopped, the trip counter is decremented.

The trip counter is increased, and when the predetermined time input value is reached, the relay operation of the protection relay can be performed.

The trip counter is increased to reach the predetermined time input value and the relay operation of the protection relay is performed. When the detection of the relay element is stopped, the trip counter is decremented and initialized to 0 [s] , The relay return of the protection relay can be performed.

The relaying operation may be performed when the protection relay detects the relaying element and the trip counter reaches the predetermined time input value.

The relaying operation may be performed in such a manner that the circuit connection portion is blocked or linked.

For example, in the case of a protection relay consisting of an a-contact opened at normal time and closed at the time of relaying, if the relay operation is performed, the circuit connection portion can be closed, and the protection made up of b- In the case of a relay, when the relay operation is performed, the circuit connection portion may be opened.

The relaying is stopped after the relaying element detects the relay element and the trip counter reaches the predetermined time input value and the relaying operation is performed, the relay element detection is stopped, the trip counter is reduced, . ≪ / RTI >

The relay return may be performed by restoring the state in which the relay operation is performed to the original state.

For example, in the case of the protection relay made up of the a-contact, the relay operation can be performed and the circuit connection part can be returned to the open state when the circuit connection part is closed. In the case of the protection relay made up of the b- The relay operation may be performed and the circuit connection portion may be opened to return to the original closed state.

Hereinafter, the configuration of the protection relay disclosed in this specification will be described with reference to Figs. 2 and 3. Fig.

2 is a block diagram of the protection relay disclosed in this specification.

3 is a configuration diagram according to an embodiment of the protective relay disclosed herein.

As shown in FIGS. 2 and 3, the protection relay 100 includes a detection unit 10 for detecting a relay element that is an operation basis of the relay, An operation unit (20) for controlling an increase / decrease of a trip counter indicating a time limit for return, and an operation unit (30) for performing the relay operation and the relay return based on increase / decrease of the trip counter, , And the return curve characteristic is a characteristic in which the decrease time of the trip counter changes in accordance with the detection result.

The relay element may be a current element.

The relay element may be a current element for a full-phase overcurrent and a ground-fault overcurrent, and the protection relay 100 may be a relay that detects and operates the overcurrent and the ground-fault overcurrent.

The detection unit 10 may detect the relay element from any one of a CT (Current Transformer) 40 and a ZCT (Zero Current Transformer).

Here, the CT 40 refers to a current transformer included in the instrument transformer, and the ZCT refers to a video current transformer capable of detecting a video current.

The CT 40 can transform a large current into a small current and supply the same to an instrument or a relay.

That is, a large current flowing in a circuit provided with the protective relay 100 is transformed into a small current so that the protection relay 100 can measure the current value, and the reduced current is supplied to the protection relay 100 I can do it.

The modified small current supplied from the CT 40 is detected through the detection unit 10, and the current value for the detected current can be measured.

For example, when the current changed by the CT 40 is 5 [A], the detection unit 10 detects the current when the modified current is supplied to the protection relay 100, The current value 5 [A] can be measured.

The operation unit 20 can increase the trip counter when the detection result is equal to or greater than a predetermined reference input value.

The predetermined reference input value means a reference value at which the protection relay 100 performs the relay operation.

For example, when the predetermined reference input value is 50 [A], when the detecting section 10 detects a current value of 51 [A], the calculating section 20 calculates the current value The result is compared. As a result of the comparison, since the detection result is larger than the predetermined reference input value, the operation unit 20 increases the trip counter.

The operation unit 20 may reduce the trip counter when the detection result is decreased to a predetermined reference input value or less.

For example, when the predetermined reference input value is 50 [A], the detection unit 10 detects a current value of 51 [A], and the operation unit 20 detects the current value of the [ The current value of 49 [A] is detected again by the detecting unit 10, the calculating unit 20 compares the preset reference value and the re-detection result with each other And the comparison result indicates that the re-detection result is smaller than the predetermined reference input value, the operation unit 20 reduces the trip counter.

That is, if the detection result detected by the detection unit 10 is larger than the predetermined reference input value, the operation unit 20 increases the trip counter. If the re-detection result is smaller than the predetermined reference input value, (20) reduces the trip counter.

In the case where an instantaneous short-circuit fault occurs in a circuit, for example, when a short-circuit fault occurs and a short-circuit current of a large current flows, the detecting unit 10 detects the occurrence of a short- And the trip counter is increased. When the short-circuit current is attenuated, the reduced current is detected again by the detecting unit 10, and in the calculating unit 20, the re-detection result compares the predetermined reference input value The trip counter is decreased.

The trip counter may be increased to either one of instantaneous or transient characteristics.

The instantaneous characteristic means that the trip counter increases without delay.

For example, if the relay element is detected and the detection result is larger than the preset reference value, the trip counter can be increased to a set value without a time delay.

The time characteristic may be any one of a definite time and an inverse time characteristic.

The predetermined time means that the trip counter is increased at a certain rate, and the inverse time means that the trip counter is increased in inverse proportion to the magnitude of the current.

For example, when the trip counter is increased to the set time characteristic, the current counter is constantly counted regardless of the size, and when the trip counter is increased to the inverse time characteristic, if the detected current is large, And the smaller the magnitude of the detected current, the slower the counting proceeds and the increased speed can be reduced.

That is, as the fault current increases, the trip counter increases rapidly, and the relay operation of the protection relay 100 is performed quickly.

The operation unit 30 can perform a relay operation by sending an operation signal to a trip coil (50).

The trip coil 50 means a coil for operating the trip mechanism when the opening / closing device or the breaker 60 is opened.

When the operation signal is transmitted to the trip coil 50, the trip mechanism of the breaker 60 or the trip mechanism of the breaker 60 is operated by the magnetic force of the trip coil 50 to open the open / close device and the breaker 60 have.

In addition, the operation unit 30 can perform a relay return by sending a return signal to the closing coil (Closing Coil).

The closing coil means a coil for returning the trip mechanism when the opening / closing device or the circuit breaker 60 is closed.

When the return signal is transmitted to the closing coil, the trip mechanism of the opening / closing device or the breaker (60) is returned by the magnetic force of the closing coil to close the opening / closing device and the breaker (60).

The operation signal and the return signal may be generated based on an increase / decrease of the trip counter.

The operation unit 30 can perform the relay operation when the trip counter reaches the predetermined time input value.

The operation unit 30 may perform a relay operation by opening and closing an a contact or a b contact included in the protection relay 100 or opening and closing the opening and closing device or the circuit breaker 60.

When the trip counter reaches the predetermined time input value, the operation unit 30 generates the operation signal and transmits the operation signal to the opening / closing device or the breaker 60 to perform the relay operation.

When the trip counter is initialized to 0, the operation unit 30 can perform the reset operation.

The operation unit 30 may perform the relay reset by opening or closing the a contact or the b contact included in the protection relay 100 or opening or closing the opening or closing device 60 or the breaker 60. [

When the trip counter is initialized to 0, the operation unit 30 generates the return signal and sends the return signal to the opening / closing device or the breaker 60 to perform the relay return.

Hereinafter, the return curve characteristic of the protection relay disclosed in this specification will be described with reference to Figs.

4 is a graph showing an SI return curve applied to an embodiment of the protective relay disclosed herein.

5 is a graph showing a VI return curve applied to an embodiment of the protective relay disclosed herein.

6 is a graph showing an EI return curve applied to an embodiment of the protective relay disclosed herein.

7 is a graph showing an LI return curve applied to an embodiment of the protective relay disclosed herein.

The return curve characteristic may be a curve characteristic of any one of SI (Standard Inverse), VI (Very Inverse), EI (Extremely Inverse) and LI (Long Inverse).

The return curve characteristic means a characteristic in which the trip counter is reduced.

The return curve may be a characteristic in which the trip counter is reduced in inverse proportion to the magnitude of the current in the inverse time characteristic.

For example, if the magnitude of the detected current is large, the trip counter is slowly reduced, and if the magnitude of the detected current is small, the trip counter can be quickly reduced.

Due to the return curve characteristic, the trip counter can not be immediately initialized to zero even after the fault current has been attenuated, and can be discounted at a rate that is inversely proportional to the magnitude of the detected current.

That is, even after the protection relay 100 performs the relay operation, the trip counter is not immediately initialized to 0 and the counter is maintained for a predetermined time, so that the relay operation can be performed again in response to the accident recurrence .

SI is a standard inverse characteristic, and a return curve is shown in Fig. 4, and can be expressed by the following equation (1).

[Equation 1]

T represents the time taken for the trip counter to be initialized to zero.

And I denotes a current detected by the detection unit 10. [

The I _s means the predetermined reference input value.

TL is a time lever, which means the set value of t.

Referring to Equation (1), since the value of t increases as the I increases, the time for decreasing the trip counter may become longer.

That is, the larger the magnitude of the detected current is, the slower the trip counter is reduced.

The above characteristics are also shown in the following equations (2) to (4).

The above-mentioned VI is a strong inverse characteristic, and a return curve is shown in FIG. 5 and can be expressed by the following equation (2).

&Quot; (2) "

The EI is the time characteristic of the second half, and the return curve is shown in Fig. 6, and can be expressed by the following equation (3).

&Quot; (3) "

The LI is a long time characteristic, and the return curve is shown in FIG. 7, and can be expressed by the following equation (4).

&Quot; (4) "

At least one of the inverse time characteristics expressed by the above Equations (1) to (4) can be set according to the installed position and the purpose of application to the protection relay 100, The trip counter may be reduced to the return curve characteristic.

Hereinafter, with reference to Fig. 8, the flow of the relay operation and the relay return operation of the protection relay disclosed in the above-mentioned specification will be described.

FIG. 8 is a flow chart illustrating the relay operation and relay return operation of the protection relay disclosed in this specification. FIG.

8, the protection relay detects a relay element (S1), compares the detection result with a preset reference value (S2), and increases the trip counter when the detection result is equal to or higher than the preset reference value (S3), the trip counter is incremented and compared with a predetermined time set value (S4). When the trip counter is equal to or larger than the predetermined time set value, the relay operation and the Trip signal are outputted (S5) After the trip signal output (S5), the trip counter can be reduced according to the return curve characteristic.

The protection relay detects the relay element (S1), compares the detection result with a preset reference value (S2), and decreases the trip counter according to the return curve characteristic when the detection result is equal to or less than the preset reference value , The relay element may be re-detected (S1).

The protection relay detects the relay element (S1), compares the detection result with a preset reference value (S2), increases the trip counter (S3) when the detection result is equal to or greater than the preset reference value, The trip counter is increased and compared with a preset time set value (S4), and the relay element can be re-detected (S1) when the trip counter is equal to or less than the preset time set value.

The above-described flow of the relay operation and the relay return execution can be repeatedly performed while the protection relay is operated.

Hereinafter, the relaying method of the protection relay disclosed in this specification will be described with reference to Fig.

9 is a flowchart showing a relaying method of the protection relay disclosed in this specification.

As shown in FIG. 9, the relaying method of the protection relay includes a step of detecting a relay element (S10), a step of comparing the detection result with a predetermined reference input value (S20) (S30) a step of incrementing a counter (S30), performing a relay operation based on the incremented trip counter (S40), re-detecting the relay element (S50) (S70) of decreasing the increased trip counter to a return curve characteristic based on the result of the re-comparison, and performing a relay return based on the reduced trip counter (S80) .

The step of increasing the trip counter based on the comparison result (S30) may increase the trip counter when the detection result is equal to or greater than a predetermined reference input value.

The step of performing the relaying operation based on the increased trip counter may perform the relaying operation when the increased trip counter reaches the predetermined time input value.

The step of decreasing the increased trip counter to the return curve characteristic based on the result of the re-comparison (S70) may reduce the trip counter when the re-detection result is less than a predetermined reference input value.

The step of performing the relay reset based on the reduced trip counter (S80) may perform the relay reset when the trip counter is initialized to zero.

Embodiments of the protection relays disclosed herein can be applied to electronic relays, including mechanical and digital systems.

Embodiments of the protection relay disclosed in this specification can be implemented by being applied to a circuit breaker including a relay, a switch, a controller, and the like.

Embodiments of the protection relays disclosed herein may be implemented in a software manner by programming the relaying method and may be implemented in one or more combinations of the embodiments.

The protection relay disclosed in this specification can reduce the trip counter which determines the relay operation and the relay return performance to the inverse characteristic so that it is possible to cope with the accident recurrence promptly and flexibly so that the burden on the load can be reduced, It has the effect of reducing the risk.

In addition, since the trip counter is increased or decreased in inverse proportion to the size of the relay element, proper relay operation and relay return are performed according to the situation in the event of an accident, thereby improving the life and efficiency of the protective device including the relay have.

In addition, since the relays have not only the operating characteristics but also the return characteristics, the relays can be applied to the protective devices more widely and flexibly, thereby making it possible to prepare for various accidents.

It will be apparent to those skilled in the art that various modifications and changes can be made in the present invention without departing from the spirit or scope of the present invention as defined by the appended claims. And such modifications and the like should be considered to fall within the scope of the following claims.

10; Detection section 20:
30: Operation part 40: CT
50: Trip coil 60: Switchgear or circuit breaker
S1: Relay element detection
S2: Comparison of detection results and reference values
S3: Increase Trip Counter
S4: Comparison of Trip Counter and Time Set Point
S5: Relay operation and trip signal output
S10: Relay element detection step
S20: a step of comparing the detection result with a predetermined reference input value
S30: Increasing the Trip Counter based on the comparison result
S40: Performing the relay operation based on the increased trip counter
S50: Relay element re-detection step
S60; And re-comparing the re-detection result with a predetermined reference input value
S70: Reduce the Trip Counter, which is increased based on the result of the re-comparison, to the return curve characteristic
S80: Performing the relay return based on the reduced Trip Counter

Claims (8)

A detection unit for detecting a relay element that is an operation basis of the relay;
An operation unit for controlling the increase / decrease of a trip counter indicating a time limit for relay operation and relay return based on the detection result detected by the detection unit; And
And an operation unit for performing the relay operation and the relay return based on the increase / decrease of the trip counter,
The trip counter includes:
Is reduced to a return curve characteristic,
Wherein the return curve characteristic comprises:
A decrease time of the trip counter is changed according to the detection result,
The operation unit,
And increases the trip counter when the detection result is equal to or greater than a predetermined reference input value.
The method according to claim 1,
Wherein:
And the relay element is detected from any one of CT (Current Transformer) and ZCT (Zero Current Transformer).
delete The method according to claim 1,
The operation unit,
And decreases the trip counter when the detection result is less than or equal to the preset reference input value.
The method according to claim 1,
The trip counter includes:
Instantaneous < / RTI > time characteristic,
The time-
Wherein the protective relay is one of fixed time or inverse time characteristics.
The method according to claim 1,
Wherein,
And performs the relaying operation when the trip counter reaches a predetermined time input value.
The method according to claim 1,
Wherein,
And when the trip counter has been initialized to zero, the relay is reset.
8. The method according to any one of claims 1, 2, and 4 to 7,
Wherein the return curve characteristic comprises:
Wherein the curve is a curve characteristic of any one of SI (Standard Inverse), VI (Very Inverse), EI (Extremely Inverse) and LI (Long Inverse).

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