JP2009131016A - Disconnection protective relay - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a disconnection protective relay capable of solving the hot-line state of a disconnection section by opening a breaker by accurately detecting a single-line disconnection with no ground fault. <P>SOLUTION: The disconnection protective relay has an input conversion section 11 inputting the current and voltage of its own terminal, a transmission-reception section 12 transmitting and receiving current data and a current arithmetic section 13 deciding the presence of an operation on the basis of a predetermined setting condition from the current data of its own terminal and an opposite terminal. The disconnection protective relay further has an operation-circuit decision section 18 inputting the open-close state of the breaker fitted to a transmission distribution line and deciding a single-line operation state or a two-line operation state and a differential-current arithmetic section 14 deciding the presence of the operation on the basis of the predetermined setting condition from the differential current of each phase of its own terminal and the opposite terminal. The disconnection protective relay further has an accident detecting section 16 detecting an undervoltage and a ground-fault overvoltage by the voltage data of its own terminal and an operation deciding section 15 outputting a disconnection detecting signal according to a condition detecting no accident by the accident detecting section 16, a condition having no differential current in the differential-current arithmetic section 14 or a condition having no disconnection in other phases. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a disconnection protection relay that stops a power supply to a disconnection system by detecting a disconnection accident without a ground fault in a power transmission / distribution system and operating a circuit breaker.

  In recent years, insulated wires that are insulated and shielded are used for power transmission lines and distribution lines (hereinafter referred to as transmission and distribution lines) that are not only underground but also suspended in the air. For this reason, even if the wire breaks, the conductor does not come into contact with the ground due to this insulation shield, and in most cases there will be no ground fault, and no zero-phase current (Io) flowing to the ground will occur. There is a problem that the fault cannot be detected and the transmission / distribution line in the accident cannot be cut off.

  This problem will be described with reference to FIG. A general power transmission / distribution system is connected to a lower load system 38 via a transformer 37 of a substation serving as a load by a three-phase power transmission / distribution line 32 connected to a power supply 31 of a power substation. Circuit breakers 33 and 34 are inserted into the outlets of the transmission and distribution lines of each substation. In the power substation, a neutral grounding resistor 50 is provided in order to ensure that the ground fault protection relay operates in the event of a ground fault in the transmission and distribution lines. Further, a ground fault protection relay 40 that detects a ground fault and opens the corresponding circuit breaker 33 is connected via a current transformer 35. In this system, for example, when the c-phase transmission / distribution line 32c, which is an insulated wire, is disconnected, the conductor does not contact the ground and the zero-phase current (Io) does not flow, so the ground fault protection relay 40 does not operate. The corresponding circuit breaker 33 is not opened.

Conventionally, techniques for detecting this disconnection have been proposed. For example, in Patent Document 1, the current of at least one of the three-phase currents is equal to or greater than a predetermined value, and the current between certain phases is 1 because the ratio of the interphase current to the maximum interphase current is equal to or less than the predetermined value. Techniques have been proposed for detecting wire breaks. However, since there is always a difference in the interphase current in the transmission / distribution line in which an unbalanced load current flows, there is a limit in increasing the sensitivity by increasing the predetermined value of the ratio of the interphase current for detecting the one-wire disconnection. There is a problem that the detection accuracy of disconnection does not increase.
JP-A-6-253446

  The present invention has been made in view of the above-described circumstances, and accurately detects a one-wire break without a ground fault and a one-wire and a two-wire break in parallel two lines to open the circuit breaker. It aims at providing the disconnection protection relay which can eliminate the live state of a disconnection part by.

  The feature of the present invention is that the current of the disconnected phase becomes zero at the time of disconnection, the phase current becomes unbalanced, the residual current of the residual circuit of the current transformer flows, and each of the own terminal and the counterpart terminal Focusing on the fact that the phase currents are equal to each other and exchange the currents and the difference current becomes zero, the disconnection is detected.

  Specifically, the disconnection protection relay according to the present invention is provided at each terminal of the transmission / distribution line of the power system, and the current difference between the terminals is transmitted and protected between the terminals according to the measured current value of the digital signal. This is a dynamic disconnection protection relay that inputs the open / close state of the circuit breaker installed on the transmission / distribution line and determines whether it is in the 1-line operation state or 2-line operation state, and the measured self Based on the current value of each phase of the terminal and the current value of each phase of the counterpart terminal received via the transmission line, the current calculation unit that determines the condition of the disconnection phase, and the operation line determination unit Operation status of the line, the difference current value of each phase calculated from the current value of the own terminal and the current value of the counterpart terminal, the measured residual current value of the own terminal, and the counterpart terminal received via the transmission line Difference current to determine the condition of disconnection based on the residual current value of A calculation unit; and an operation determination unit that outputs a disconnection detection signal based on determination of a disconnection phase condition in the current calculation unit and determination of a disconnection condition in the difference current calculation unit. To do.

  According to the present invention, it is possible to detect a disconnection by paying attention only to the current value of the transmission / distribution line, and thus it is possible to make the disconnection protection relay relatively simple. Moreover, since the disconnection determination is performed based on the line operation state, the accurate disconnection determination can be performed.

  Further, in the disconnection protection relay according to the present invention, the determination of the condition of the disconnection phase in the current calculation unit is a necessary condition for the disconnection phase when the current value of each phase of the own terminal and the counterpart terminal is equal to or less than a set value. In the determination of the disconnection condition in the difference current calculation unit, the difference current value in each phase of the own terminal and the counterpart terminal is equal to or less than a set value, and any of the own terminal and the counterpart terminal is determined. When the value of the residual current in the phase is equal to or higher than the set value, it is determined that the requirement for disconnection is satisfied.

  Furthermore, the disconnection protection relay according to the present invention includes an accident detection unit that detects an accident of a transmission and distribution line due to an undervoltage and a ground fault overvoltage based on the measured voltage value of the terminal, and the operation determination unit includes the operation determination unit, A disconnection detection signal is output based on a disconnection phase condition by a current calculation unit, a disconnection condition by the difference current calculation unit, and a condition in which no accident is detected by the accident detection unit.

  Thereby, since the accident which does not depend on a disconnection can be excluded and a disconnection can be determined, there exists an effect of improving the precision of determination.

  The disconnection detection method using the current differential type protective relay of the present invention uses a current differential type protective relay arranged at each terminal of the transmission and distribution line of the power system, measures the current value at each terminal, A disconnection detection method that detects disconnection of transmission and distribution lines by transmitting value data, and inputs the open / close state of the circuit breaker installed in the transmission and distribution lines, and either one line operation state or two line operation The condition of the disconnection phase is determined based on the step of determining the operational state of the state, the measured current value of each phase of the own terminal, and the current value of each phase of the counterpart terminal received via the transmission line. Step, the operating state, the difference current value of each phase calculated from the current value of the own terminal and the current value of the counterpart terminal, the measured value of the residual current of the own terminal, and received via the transmission line A step of determining a disconnection condition based on the value of the residual current of the mating terminal Characterized in that it comprises the determination result of the condition of the disconnection phase, and outputting a disconnection detection signal based on the determination result of the condition of the break, the.

  According to the present invention, the disconnection can be easily detected using the existing current differential type protective relay, so that it is not necessary to newly add a protective relay for detecting the disconnection, and the cost can be reduced. .

  As described above, according to the present invention, it is possible to accurately detect all wire breakage accidents and operate the circuit breaker regardless of the presence or absence of a ground fault. Further, by adding the function of the present invention to the function of the conventional current differential type protective relay, it is possible to protect the grounding of the transmission / distribution line of the insulated wire and the disconnection accident, thereby reducing the equipment cost. .

Hereinafter, an embodiment of the present invention will be described.
FIG. 1 is a functional block diagram of a disconnection protection relay 1 according to the present embodiment. The disconnection protection relay 1 is a one-line facility that inputs the open / close state of the circuit breaker of the transmission line (line), or is a one-line operation in which only one of the circuit breakers is closed in a parallel two-line facility The operation line determination unit 18 for determining whether the circuit breakers of both lines are closed and the current signal and voltage signal of the three-phase power transmission line are input, and the current data and Input conversion unit 11 for converting to voltage data, this own terminal current data is transmitted to the disconnection protection relay of the counterpart terminal via the transmission line 41, and the transmission / reception unit 12 for receiving the current data of the counterpart terminal, for each input phase Current calculation unit 13 for calculating and detecting a phase (disconnection phase) in which the current at both ends of each phase is equal to or lower than a set value (zero) due to disconnection or the like from the self-terminal current data and the counterpart terminal current data, operation line The line operation status from the judgment unit 18 and the power at both ends of each phase A difference current calculation unit 14 for detecting a disconnection condition when the residual current of both current transformers is equal to or greater than a pre-set value when the difference is less than a set value (zero) An accident detection unit 16 that detects the occurrence of an accident other than a disconnection accident, such as an undervoltage accident in which the terminal voltage of each phase from the conversion unit 11 is less than a set value, or a ground fault in which the zero phase voltage is greater than a set value; The first disconnection condition based on the disconnection phase detected by the current calculation unit 13, the second disconnection condition detected by the differential current calculation unit 14, and finally the disconnection under other conditions without the accident detection unit 16 It is comprised with the operation | movement determination part 15 which determines with an accident and opens the applicable circuit breaker.

  The input conversion unit 11 includes a filter circuit 111 that filters a signal, a sample and hold circuit 112 that holds the signal for a certain period of time, and an A / D conversion circuit 113 that converts the analog signal into a digital signal. A sampling signal generating circuit 115 to be supplied to the circuit 112, and a current signal input processing means 114 for storing the current signal subjected to A / D conversion processing in a current data file 116 to which time data and the like are added.

  With respect to the disconnection protection relay 1 having the above configuration, the operation at the time of the disconnection accident will be described with reference to the system diagram at the time of one-line operation of FIG. 3 and the phase characteristic diagram of FIG.

  In FIG. 3, three-phase power transmission lines 32 a, 32 b, and 32 c connected from the power supply 31 are connected to a load system 38 via a load-side transformer 37. Circuit breakers 33 and 34 are inserted at both ends of each of the three-phase power transmission lines. Further, disconnection protection relays 1a and 1b are installed at the outlets of the transmission lines of the respective lines via current transformers 35 and 36 and grounding transformers 39 and 40, respectively. The disconnection protection relays 1a and 1b at both ends are connected to each other via a transmission line 41 so that mutual data can be transmitted and received. The symbols of the respective currents are the currents Ia, Ib, Ic and the currents Ia ′, Ib ′, Ic ′ flowing through the current transformers 35, 36, and the residual currents Ix, Ix ′ of the residual circuit which is the feedback circuit. .

  Changes in the phase characteristics of each phase in this system will be described with reference to FIG. During normal operation (1), the currents Ia, Ib, and Ic of each phase flow in a phase relationship of 120 degrees. In the case of a balanced load (1a), the residual current Ix does not flow, and in the case of an unbalanced load (1b), the residual current Ix flows for the unbalanced portion. When a one-wire break occurs (2), naturally, a closed circuit is formed by the remaining two phases, so that the phases are in a 180-degree relationship of opposite phases. When the disconnection protection relays 1a and 1b detect a one-wire disconnection in such a system, the circuit breakers 33 and 34 of the line are opened to stop power feeding.

Next, operation | movement of the disconnection protection relay 1a is demonstrated based on FIG.
In normal times, the disconnection protection relay 1a takes in the current signals Ia, Ib, Ic, Ix via the current transformer 35 attached to the power transmission line. The current signals Ia, Ib, and Ic are converted into digital signals through the filter circuit 111, the sample hold circuit 112, and the A / D conversion circuit 113 of the input conversion unit 11 shown in FIG. A sampling identification number (to be described later) or a time is added and stored in the current data file 116. Note that a multiplexer may be provided before the A / D conversion circuit 113 so that a plurality of current data are scanned and input in a time division manner.

  The sample hold circuit 112 and the current signal input processing means 114 operate in synchronization with the sampling signal output from the sampling signal generation circuit 115. In addition, the current data file 116 is scale-converted into a current on the system, and stored in the current data file 116, with the current value input for each sampling period. Note that the sampling period is a sampling interval. For example, sampling is performed every 30 ° with respect to the system frequency. The current data file is stored with the sampling identification number or time attached.

  In the transmission / reception unit 12, the current value of its own terminal is input from the current data file 116 A / D-converted by the input conversion unit 11 at a fixed period and transmitted to the transmission line 41, and transmitted from the counterpart terminal at a fixed period. The current value is received and output to the current calculation unit 13.

  The current calculation unit 13 calculates the current value of the own terminal from the input conversion unit 11 and the current value of the counterpart terminal from the transmission / reception unit 12 to the effective value data, and the currents at both ends of each phase are set values. Assuming that the disconnection phase condition is satisfied when it changes to the following, a “disconnection phase signal” is generated and output to the operation determination unit 15. The “disconnection phase signal” is output as a “first disconnection condition signal” by the operation determination unit 15 under condition determination described later.

  The difference current calculation unit 14 uses the current values of the own terminal and the counterpart terminal calculated by the current calculation unit 13 to generate a “no difference current signal” that is generated when the difference current of each phase is equal to or less than a set value. And the “second disconnection condition signal” is generated based on the line operation state from the operation line determination unit 18 and the “residual current signal” generated when the residual current at both ends is equal to or higher than the set value. To the operation determination unit 15.

  The accident detection unit 16 generates an “undervoltage signal” generated when the voltage of each phase from the input conversion unit 11 is equal to or lower than the set value, and an overvoltage equal to or higher than the set value of the zero phase voltage. Based on the “ground fault signal”, an “other accident signal” indicating the occurrence of an accident other than a disconnection accident is generated and output to the operation determination unit 15.

  The operation determination unit 15 detects the disconnection condition of the first and second wires based on the aforementioned “disconnection phase signal”, generates a “first disconnection condition signal” from the signal, and generates the “second disconnection condition signal”. ”And the negative logic of the“ other accident signal ”, it is finally determined that the circuit is disconnected, and a“ breaker open signal ”is generated and output to the time relay 17.

  In the system shown in FIG. 3, for example, when a one-phase disconnection of b phase occurs, as shown in the phase characteristic diagram of FIG. = Ib '= 0, Ia = Ia'> 0, Ic = Ic '> 0, and the difference currents are Ib-Ib' = 0, Ia-Ia '= 0, Ic-Ic' = 0, and the operation line is determined Is one line operation. In addition to the establishment of this condition, the disconnection protection relay 1a opens the corresponding circuit breaker 33 when the "no other accident" condition is satisfied. The disconnection protection relay 1b at the other end also opens the corresponding circuit breaker 34 by the same determination operation as described above. Note that actual comparison and determination are performed with reference to each predetermined value, taking into account measurement errors and the like.

FIG. 2 is a sequence diagram showing the operation logic of the disconnection protection relay 1 described above.
The current calculation unit 13 includes first AND circuits 13a, 13b, and 13c, and both the self-terminal currents (Ia, Ib, Ic) and the counterpart terminal currents (Ia ', Ib', Ic ') of each phase are set values. A case of the following shortage current is detected, and a “disconnection phase signal” that satisfies the condition of the disconnection phase is generated and output to the operation determination unit 15.

  The operation determination unit 15 negates the “disconnection phase signal” of each phase output from the current calculation unit 13, that is, the outputs of the AND circuits 13a, 13b, and 13c, and the remaining “disconnection phase signal” of the other two phases. By inputting logic to the second AND circuits 151a, 151b, and 151c, respectively, a one-phase disconnection condition is detected and a “one-wire disconnection signal” is generated (second AND circuits 151a, 151b, and 151c). Output). Also, a two-phase disconnection condition is detected by inputting a negative logic of a certain two-phase “disconnection phase signal” and the remaining one-phase “disconnection phase signal” to the third AND circuits 152a, 152b, and 152c. Then, a “2-wire disconnection signal” is generated (outputs of the second AND circuits 152a, 152b, and 152c). Furthermore, a “first disconnection condition signal” is generated by the first OR circuit 15 d that ORs all of them.

  In addition, the operation line determination unit 18 inputs the circuit breaker ON / OFF state of each line, inputs both state signals to the NAND circuit 18a, and “1”, 2 lines in the 1-line operation state. “0” is output in the operational state.

  Next, the difference current calculation unit 14 ANDs the negative logic of the difference currents Ida (= Ia−Ia ′), Idb (= Ib−Ib ′), and Idc (= Ic−Ic ′) of each phase. The output signal of the fourth AND circuit 14a that detects that there is no difference between the input and output currents, and the output and operation of the fifth AND circuit 14b that detects the case where the residual currents Ix and Ix 'at both ends are equal to or higher than the set value. The output signal of the second OR circuit 14d that performs an OR operation with the output of the NAND circuit 18a of the line determination unit 18 and the sixth AND circuit 14c that detects the disconnection condition by ANDing both the signals are used as “second”. Is generated.

  On the other hand, the accident detection unit 16 detects an accident other than disconnection. Specifically, the third OR circuit 16a detects the “undervoltage signal” in which the phase voltage is equal to or lower than the set value and the “ground fault signal” in the case where the zero phase voltage is the overvoltage equal to or higher than the set value. Thus, an “other accident signal” indicating an accident other than a disconnection accident is generated by ORing both signals.

Then, the operation determination unit 15 performs an AND operation on the “first disconnection condition signal”, the “second disconnection condition signal”, and the negative logic of the “other accident signal”, and a seventh AND circuit 15e. Accordingly, it is determined that the circuit is finally disconnected, and a “breaker open signal” is output to the corresponding breaker via the time relay 17 for time coordination with other protection systems and the like.
The operation of the disconnection protection relay 1 in the one-line disconnection accident in the one-line operation state has been described above.

  Next, the operation of the disconnection protection relay 1 in a one-line disconnection accident in a two-line operation state will be described using the two-line system diagram of FIG. 4, the phase characteristic diagram of FIG. 5, and the phase characteristic diagram for disconnection determination of FIG. To do.

  In FIG. 4, the same parts as those in FIG. Three-phase two-line transmission lines connected from the power source 31, that is, the first line transmission lines 32a1, 32b1, 32c1 and the second line transmission lines 32a2, 32b2, 32c2 are connected to a load system 38 via a load-side transformer 37. ing. Circuit breakers 331 and 341 and circuit breakers 332 and 342 are inserted at both ends of each of the three-phase power transmission lines. In addition, disconnection protection relays 1a and 1c are connected to the outlets of the transmission lines of the respective lines via current transformers 351 and 352 and a grounding transformer 39, and are disconnected via current transformers 361 and 362 and a grounding transformer 40. Protective relays 1b and 1d are installed respectively. The disconnection protection relays 1a and 1b at both ends and the disconnection protection relays 1c and 1d are connected by transmission lines 41 and 42, respectively.

  FIG. 5 shows the phase characteristics of each phase when the balanced load is in such a system and during normal operation and when one wire is disconnected. In the normal state shown in FIG. 5 (1), both lines show the same current value and phase. In the case of a balanced load, the residual current Ix1 of the current transformer 351 and the residual current Ix1 ′ of the current transformer 361 are zero. The residual current Ix2 of the current transformer 352 and the residual current Ix2 'of the current transformer 362 are also zero.

  For example, when the b-phase 32b1 of the first line is disconnected at the time of one-wire disconnection in the balanced load, the phase characteristics of the first line are zero when the b-phase current Ib1 and the current Ib1 'are zero as shown in FIG. And the unbalanced residual currents Ix1 = −Ib1 and Ix1 ′ = − Ib1 ′ appear with a phase angle of 180 degrees with respect to the b phase. The second line side appears as a current value obtained by adding the b-phase currents Ib1 and Ib1 ′ of the first line in normal times to the b-phase currents Ib2 and Ib2 ′ of the second line in normal times. Due to this unbalanced current, in the residual currents Ix2 and Ix2 ′, currents having the same value as the b-phase currents Ib1 and Ib1 ′ of the first line having the same phase as the b-phase appear.

  FIG. 6 shows the phase characteristics for determining the disconnection condition based on the change of the phase characteristics. This figure shows that when the phase characteristics of current or voltage are inside the circle with a shadow inside the solid circle, it is broken when it is inside the circle, and when the shadow is outside the circle, it is broken. Indicates an accident that is a condition of The conditions for determining the disconnection based on the phase characteristics of the current or voltage are as follows: (a) the current of each phase is an undercurrent of I or less (FIG. 6a), (b) the difference current between both ends of each phase is I or less (C) Residual current at both ends is I or more and is in an unbalanced state (FIG. 6c), (d) As another accident, the voltage of each phase is less than V (27 ) Or a ground fault (64V) (FIGS. 6d and 6e) where the zero-phase voltage is equal to or higher than Vo.

  When such a change in the phase characteristic is detected and all the determination conditions shown in FIG. 6 are satisfied, it is determined that the disconnection occurs according to the determination sequence of FIG. 2, and the disconnection protection relays 1a and 1b or the disconnection protection relays 1c and 1d The circuit breaker open signal "is output, the circuit breakers 331, 341 or circuit breakers 332, 342 of the line are opened, and the power supply is stopped.

  Hereinafter, the operation of the disconnection protection relay 1a and the disconnection protection relay 1c at the time of the b-phase one-line disconnection accident on the first line side will be described. The disconnection protection relay 1a on the first line side having a disconnection is in the state of the phase characteristic diagram of FIG. 5 (2) described above, and operates in the same manner as the disconnection protection relay 1a during the one-line operation described above. (B) There is no difference current Ida, Idb, Idc, (c) An unbalanced state with residual currents Ix, Ix ', (d) Ground voltage is not As a result, the breaker 331 is opened by detecting the b-phase 1 wire breakage by the sequence of FIG.

  The disconnection protection relay 1c on the second line side does not detect disconnection because the undercurrent of (A) is not detected under the determination conditions of FIG. For this reason, the corresponding circuit breaker 332 is not opened.

  Similarly, the disconnection protection relays 1b and 1d of the counterpart terminal perform the same operation as the disconnection protection relays 1a and 1c. The disconnection protection relay 1b of the first line detects the disconnection and opens the corresponding circuit breaker 341. The disconnection protection relay 1d of the second line does not detect the disconnection and does not open the corresponding circuit breaker 342.

  As described above, according to the present embodiment, changes in the current value and residual current of each phase and changes in the voltage of each phase and the zero-phase voltage, which are other accidents other than disconnection, are set in advance. By determining that the wire breaks by satisfying the value condition, the corresponding circuit breaker can be opened.

  In particular, by incorporating the differential current of each phase into the determination condition by the current differential protection relay, it is possible to detect disconnection with high accuracy using the existing configuration.

It is a functional block diagram of a disconnection protection relay according to the present invention. It is a sequence diagram of a disconnection protection relay according to an embodiment of the present invention. It is a systematic diagram which shows the connection state to the 1 circuit system | strain of the disconnection protection relay by embodiment of this invention. It is a systematic diagram which shows the connection state to the 2 circuit system of the disconnection protection relay by embodiment of this invention. It is a phase characteristic figure in 2 circuit systems of a disconnection protection relay by an embodiment of the invention. It is a phase characteristic diagram for disconnection determination of the disconnection protection relay according to the embodiment of the present invention. It is explanatory drawing of the connection state of the protection relay apparatus in the conventional electric power system. It is a phase characteristic figure which shows the connection state to the 1 circuit | line system of the disconnection protection relay by embodiment of this invention.

Explanation of symbols

1, 1a, 1b, 1c, 1d Disconnection protection relay 11 Input converter 12 Transmitter / receiver 13 Current calculator 14 Differential current calculator 15 Operation determination unit 16 Accident detection unit 17 Timed relay 18 Operation line determination unit 31 Power supply 32, 32a, 32b, 32c, 321a, ..., 322c Transmission line 33, 34, 331, 332, 341, 342 Breaker 35, 36, 351, 352, 361, 362 Current transformer 37 Transformer 38 Load side system 39, 40 Grounding transformer 41, 42 Transmission path 111 Filter circuit 112 Sample hold circuit 113 A / D conversion circuit 114 Current signal input processing means 115 Sampling signal generation circuit 116 Current data file Ia, Ib, Ic, Ix, Ia ′, Ib ′, Ic ', Ix' Current Ida, Idb, Idc Difference current

Claims (4)

A current differential type disconnection protection relay that is provided at each terminal of a power transmission / distribution line of the power system, and transmits and protects between each terminal according to the measured current value of the digital signal,
An operation line determination unit that inputs a switching state of a circuit breaker mounted on a transmission / distribution line and determines whether it is in a 1-line operation state or a 2-line operation state;
Based on the measured current value of each phase of the own terminal and the current value of each phase of the counterpart terminal received via the transmission line, a current calculation unit that determines the condition of the disconnection phase,
The operational state of the line determined by the operational line determination unit, the value of the current difference of each phase calculated from the current value of the own terminal and the current value of the counterpart terminal, the value of the measured residual current of the own terminal, A difference current calculation unit for determining a disconnection condition based on the value of the residual current of the counterpart terminal received via the transmission line;
An operation determination unit that outputs a disconnection detection signal based on the determination of the condition of the disconnection phase in the current calculation unit and the determination of the condition of the disconnection in the difference current calculation unit;
A disconnection protection relay characterized by comprising: The determination of the condition of the disconnection phase in the current calculation unit determines that the condition of the disconnection phase is provided when the current values of each phase of the own terminal and the counterpart terminal are both equal to or less than a set value.
In the determination of the disconnection condition in the difference current calculation unit, in the case of one-line operation state, the disconnection condition is provided when the value of the difference current in each phase of the own terminal and the counterpart terminal is equal to or less than a set value. In the case of a two-line operation state, the difference current value in each phase of the own terminal and the counterpart terminal is less than or equal to a set value, and the residual current values of the own terminal and the counterpart terminal are both greater than or equal to the set value. The disconnection protection relay according to claim 1, wherein the disconnection protection relay is determined to have a disconnection condition in some cases. Based on the measured voltage value of its own terminal, equipped with an accident detection unit that detects accidents in transmission and distribution lines due to undervoltage and ground fault overvoltage,
The operation determination unit outputs a disconnection detection signal based on a disconnection phase condition by the current calculation unit, a disconnection condition by the difference current calculation unit, and a condition in which no accident is detected by the accident detection unit. The disconnection protection relay according to claim 1 or 2, characterized in that: Using a current differential protection relay placed at each terminal of the power transmission and distribution line of the power system, the current value at each terminal is measured and current value data is transmitted to each other to detect disconnection of the transmission and distribution line A disconnection detection method,
A step of inputting an open / close state of a circuit breaker mounted on a transmission / distribution line and determining an operation state of a one-line operation state or a two-line operation state;
A step of determining the condition of the disconnection phase based on the measured current value of each phase of the own terminal and the current value of each phase of the counterpart terminal received via the transmission line;
The operating state, the difference current value of each phase calculated from the current value of the own terminal and the current value of the counterpart terminal, the measured value of the residual current of the own terminal, and the counterpart terminal received via the transmission line Determining a disconnection condition based on the value of the residual current;
Outputting a disconnection detection signal based on the determination result of the disconnection phase condition and the determination result of the disconnection condition;
The disconnection detection method using the current differential type protective relay characterized by including.