JP2012080700A - Current differential protective relay - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current differential protective relay which suppresses deterioration of dynamic sensitivity as much as possible and which does not malfunction even if CT induction to the other phase occurs.SOLUTION: The current differential protective relay 1 operates an operation amount and a suppression amount by using terminal currents I1 to In from a plurality of current transformers arranged in respective phases of a power system and protects the power system based on the operation amount and the suppression amount. The relay includes: an induction current information output portion 20 generating an amount KH of induction current flowing to a secondary side of the current transformer of the other phase with current flowing to a primary side of the current transformer of the self-phase based on effective values of the respective terminal currents I1 to In of the self-phase and outputting it to the current differential protective relay 1 of the other phase; and a sensitivity control portion 21 controlling a minimum sensitivity setting value K01 of a small current region of the current differential protective relay 1 of the self-phase based on the induction amount KH from the induction current information output portion 20 of the other phase.

Description

  The present invention relates to a protective relay installed for the purpose of protecting a power system, and more particularly to a current differential protective relay that protects a bus and a power transmission line by a current differential principle.

  The conventional current differential protection relay samples each terminal current detected in the power system protection target (transmission line or bus) at the same time and with a constant period, and samples these after AD (analog / digital conversion) Data (terminal current data) is used to identify internal and external accidents in the protected section, and in the event of an internal accident, the circuit breaker (Circuit Breaker: An open command is output to CB). The operation of the current differential protection will be described. The vector sum (sampled) of the relay input currents I1, I2,... In obtained from current transformers (abbreviated as CT) arranged at each terminal. The sum of the instantaneous value data, that is, the value obtained by calculating the effective value of the difference current Id = I1 + I2 +... + In, is used as the operation amount ID, and the scalar sum of the terminal currents ) As a suppression amount IR, it is determined whether it is an internal accident or an external accident based on a determination formula for an operation region in which the operation amount ID and the suppression amount IR are preset.

In general, the action judgment formula is set as follows.
ID> R1 * IR + K01 --- small current range ID> R2 * IR + K02 --- high current range However, R1 <R2, K01> K02
This is because in a region where the current is relatively small, the amount of suppression is reduced to widen the operation region (high sensitivity), and in a region where the current is large, the effect of errors due to the influence of CT (magnetic) saturation is avoided. The amount of suppression is increased to reduce the operating area (low sensitivity).

  Furthermore, CT (magnetism) saturation at the time of an external accident may occur even in a region where the accident current is relatively small because the accident current concentrates on a one-terminal CT. Therefore, the conventional current differential protection relay has a countermeasure such as controlling the minimum sensitivity of the operation region setting according to the maximum value of the suppression amount from the past for a certain period (for example, Patent Document 1 below).

JP 2000-224755 A (paragraph 0042)

  However, the conventional current differential protection relay represented by Patent Document 1 has the following problems. The conventional current differential protection relay uses the maximum difference in the amount of suppression for a certain period in the past when the CT is magnetically saturated and a secondary current different from the primary current is input to the relay due to magnetic saturation. There is a measure to control the setting of motion sensitivity (motion area) by value. However, when there is CT phase induction rather than CT (magnetic) saturation, there is a possibility that the current of CT secondary (not CT primary) may also flow in the healthy phase CT that is not the accident phase due to the induction between each phase CT. is there.

  Explaining this, even if there is a difference current (operation amount) due to error current such as CT saturation due to the accident current, the differential protection relay element of the accident phase can operate because it can expect a large amount of suppression. Absent. However, the differential protection relay element of the healthy phase has a small amount of suppression because no accident current flows, so that an operation amount by CT induction that enters the operation region of the small current region of the current differential protection relay occurred. In this case, there was a problem of malfunction.

  Regarding the induction between the above-mentioned respective phase CTs, the three-phase CTs should be arranged so as not to occur basically. However, in order to reduce the size of the substation equipment, the three-phase integrated CT is adopted. In the case, induction may easily occur because the distance between the CT phases is close. In such a case, the operation sensitivity of the current differential protection relay is reduced so that the induced amount due to the maximum external accident current is assumed and the induced amount is not detected (K01 in the small current region is changed to the CT at the maximum external accident current. A measure such as setting to an induced current generated by induction) is taken. However, this brings about a problem that the operation sensitivity is lowered, and it is impossible to detect a minute accident current (missing an accident).

  The present invention has been made in view of the above, and an object of the present invention is to obtain a current differential protection relay that suppresses a decrease in operating sensitivity as much as possible and does not malfunction even if CT induction to another phase occurs. To do.

  In order to solve the above-described problems and achieve the object, the present invention calculates an operation amount and a suppression amount using phase currents from a plurality of current transformers provided in each phase of the power system, A current differential protection relay that protects the power system based on the operation amount and the suppression amount, and based on the effective value of the phase current of the own phase, the current flowing to the primary side of the current phase current transformer An induced current information output unit for generating induced current information related to the presence or amount of induced current flowing in the secondary side of the current transformer of the other phase and outputting it to the current differential protection relay of the other phase, And a sensitivity control unit that controls the operation sensitivity of the current-phase current differential protection relay based on the induced current information from the induced current information output unit.

  According to the present invention, by controlling the operation sensitivity in the small current region of the current differential protection element of the other phase according to the effective value of each terminal current, it is possible to suppress a decrease in the operation sensitivity as much as possible, and to the other phase. Even if CT induction occurs, there is an effect that no malfunction occurs.

FIG. 1 is a diagram illustrating an overall configuration centering on a current differential protection relay according to first to third embodiments of the present invention. FIG. 2 is a configuration diagram of the current differential protection relay according to the first exemplary embodiment of the present invention. FIG. 3 is a configuration diagram of the current differential protection relay according to the second exemplary embodiment of the present invention. FIG. 4 is a configuration diagram of a current differential protection relay according to the third exemplary embodiment of the present invention.

  Embodiments of a current differential protection relay according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 shows an overall configuration centering on current differential protection relays (hereinafter also simply referred to as “relays”) 1a, 1b, and 1c common to the first to third embodiments of the present invention. FIG. FIG. 1 shows buses 30a, 30b, and 30c of each phase of a three-phase bus that is a protection target of the relays 1a, 1b, and 1c.

  Circuit breakers 34, 35, and 36 and CTs 37a, 37b, 37c, 38, and 39 are installed on lead lines (also referred to as “lines”) 31a, 31b, 31c, 32, and 33 from each bus. ing. One end of cables 40a, 40b, 40c, 41, and 42 is connected to each CT, and the other end of the cable 40a, cable 41, and cable 42 is an input converter group (not shown) installed in the relay 1a. It is connected to the. The other end of the cable 40b is connected to the relay 1b, and the other end of the cable 40c is connected to the relay 1c. In FIG. 1, the lead wires 32 and 33, the CTs 38 and 39, and the cables 41 and 42 related to the relay 1b and the relay 1c are illustrated in a simplified manner. In the following description, unless otherwise specified, the relays 1a, 1b, and 1c are simply referred to as the relay 1, and for each CT, N (N is an integer of 2 or more) CTs are arranged on each bus. This is referred to as CTn (n = 1, 2,... N).

  FIG. 2 is a configuration diagram of the current differential protection relay 1 according to the first exemplary embodiment of the present invention, and shows the configuration of the current differential protection relay 1 for a certain one of the three phases. The relay 1 mainly includes a difference current calculation circuit 3, an effective value calculation circuit 4, an effective value calculation circuits 2-1 to 2-n, a suppression amount calculation circuit 5, a maximum value calculation circuit 6, and an induction. The quantity calculation circuit 8, the maximum value selection circuit 9, the minimum operation sensitivity setting circuit 10, and the operation determination circuit 7 are configured.

  Here, the maximum value calculation circuit 6 and the induction amount calculation circuit 8 constitute an induced current information output unit 20, and this induced current information output unit 20 is based on the effective value of the phase current of the own phase. Along with the current flowing on the primary side of the CT, it is configured to generate induced current information (inductive amount KH described later) related to the induced current amount flowing on the secondary side of the CT of the other phase and output it to the relay 1 of the other phase. ing. Further, the maximum value selection circuit 9 and the minimum operation sensitivity setting circuit 10 constitute a sensitivity control unit 21, which is based on the induction amount KH from the induced current information output unit 20 of the other phase. The operation sensitivity of the relay 1 is configured to be controlled. Details will be described below.

  Each terminal current connected to the protection target (power transmission line or bus) of the electric power system passes through each CT shown in FIG. 1 for each of the three phases, CT1 current (I1), CT2 current (I2),. -It inputs into the relay 1 as CTn electric current (In).

  In the relay 1, all input terminal currents are sampled at the same time and processed as digital data by AD conversion. In FIG. 2, a function (for example, an input current conversion unit) that converts terminal currents (phase currents) I1 to In captured in the relay 1 into current values handled in the relay 1 or terminal currents I1 to In The illustration of a function (for example, a synchronization processing unit) that outputs in synchronization is omitted.

  The differential current calculation circuit 3 executes differential calculation. Specifically, the difference current calculation circuit 3 adds the same time data of the terminal currents I1 to In input to the relay 1 on an instantaneous value basis. The added data is input to the effective value calculation circuit 4, and the effective value calculation circuit 4 calculates an effective value of the difference current Id = I1 + I2 +... + In and sends it to the operation determination circuit 7 as an operation amount ID.

  On the other hand, the terminal currents I1 to In are respectively input to the effective value calculation circuits 2-1 to 2-n, and the effective value calculation circuits 2-1 to 2-n execute the effective value calculation. The effective values calculated by the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5 and the maximum value calculation circuit 6.

  The suppression amount calculation circuit 5 calculates the suppression amount IR by adding the effective values of the terminal currents I1 to In.

  The maximum value calculation circuit 6 selects the maximum terminal current (maximum value IK of the effective values of the terminal currents I1 to In) among the effective values of the terminal currents I1 to In and outputs the selected terminal current to the induction amount calculation circuit 8. . The induction amount calculation circuit 8 calculates the induction amount KH by multiplying the maximum value IK from the maximum value calculation circuit 6 by the interphase induction coefficient α of CT. Then, the induction amount KH calculated by the induction amount calculation circuit 8 is sent to the other two-phase relay 1 and used for controlling the operation region of the other phase.

  Here, the interphase induction coefficient α is the degree of the induced current that flows to the secondary side of the own-phase CT due to the magnetic induction from the other-phase CT. In other words, the amount of CT induction generated by the accident current changes to the other phase. Indicates the degree of influence. The induction amount KH is a value of the induced current to the other phase in which the interphase induction coefficient α is added, and indicates the magnitude of the induced current that may cause the other phase to malfunction due to the CT phase induction.

  The operation determination circuit 7 executes an internal / external accident determination based on the effective value (operation amount ID) calculated by the effective value calculation circuit 4 and the suppression amount IR calculated by the suppression amount calculation circuit 5. The protection characteristic (or operation characteristic) schematically shown in the operation determination circuit 7 describes the minimum sensitivity setting value (operation sensitivity) K01 in the small current region controlled by the relay 1 according to the embodiment of the present invention. This is shown for the sake of convenience, and is set by the minimum sensitivity setting value K01, the operation amount ID, and the suppression amount IR in the small current region.

  Here, the minimum sensitivity setting value K01 in the small current region set in the operation determination circuit 7 will be described. First, the maximum value selection circuit 9 takes in the induction amount KH sent from the other two-phase relay 1 and outputs the larger one of the induction amounts KH to the minimum operation sensitivity setting circuit 10. The minimum operation sensitivity setting circuit 10 adds the induction amount KH from the maximum value selection circuit 9 to the preset minimum sensitivity setting value K01 in the small current region, and sets the minimum sensitivity setting value K01 in the new small current region. Is output to the operation determination circuit 7 as follows. As described above, the minimum sensitivity setting value K01 of the small current region input to the minimum operating sensitivity setting circuit 10 is changed to K01 + KH by the minimum operating sensitivity setting circuit 10. In other words, the minimum sensitivity setting value K01 in the small current region output from the minimum operation sensitivity setting circuit 10 is changed according to the magnitude of the external accident current of the other phase.

  Next, the operation will be described.

  First, the operation in the circuit from the effective value calculation circuits 2-1 to 2-n to the induction amount calculation circuit 8 will be described. The effective values of the terminal currents I1 to In output from the effective value arithmetic circuits 2-1 to 2-n are taken into the maximum value arithmetic circuit 6, and the maximum value IK is selected. The maximum value IK is taken into the induction amount calculation circuit 8, and the induction amount KH is calculated based on the maximum terminal current (maximum value IK) and the interphase induction coefficient α of CT, and the induction amount KH is sent to the other two phases. Is done.

  Next, operations according to the maximum value selection circuit 9 and the minimum operation sensitivity setting circuit 10 will be described. In the relay 1, the induction amount KH from the phases other than the own phase (the other two phases) is compared by the maximum value selection circuit 9, and the data with the larger induction amount KH is preset by the minimum operation sensitivity setting circuit 10. The value is added to the minimum sensitivity setting value K01 of the small current region, and is taken into the operation determination circuit 7. By such an operation, for example, the minimum sensitivity setting value K01 in the small current region shown in the operation determination circuit 7 is changed to an increasing side, so that it is possible to prevent malfunction at the time of another phase external accident due to CT phase induction. it can.

  Hereinafter, explanation will be made in relation to the healthy phase and the accident phase. A general protective relay is configured to operate by determining an internal failure when the differential current exceeds a set value. For example, when a one-phase failure (accident) occurs outside, a differential current does not occur because the outflow current and the inflow current of that phase are the same in opposite phases. Therefore, the protective relay does not malfunction.

  However, for example, in the case of a three-phase collective CT, when a large accident current (for example, 50 KA) flows in the CT related to the accident phase, the healthy phase CT receives magnetic induction from the accident phase CT, and the healthy phase CT An induced current (for example, 500 to 600 A in terms of CT primary side) may flow on the secondary side of CT. In that case, the difference between the inflow and the outflow does not become zero, and a differential current is generated. Therefore, the protective relay for the healthy phase may malfunction.

  According to the relay 1 according to the present embodiment, for example, when assuming that the A phase is the accident phase and the B phase and the C phase are the healthy phases, the induced amount KH calculated by the induced amount calculating circuit 8 related to the A phase. Is transmitted to the relay 1 relating to the B and C phases, and the relay 1 relating to the B and C phases controls the operation sensitivity based on the induction amount KH from the relay 1 relating to the A phase. That is, when any of the terminal currents I1 to In input to the relay 1 related to the A phase is large, the minimum sensitivity setting value K01 of the relay 1 related to the B and C phases becomes high, and the relay 1 related to the A phase. When all of the terminal currents I1 to In inputted to are small, the minimum sensitivity setting value K01 of the relay 1 for the B and C phases is low. As described above, the relay 1 according to the present embodiment predicts the induced current caused by the CT induction from the A phase based on the magnitude of the input current, and changes the minimum sensitivity setting value K01 accordingly. By comprising, it is possible to prevent the malfunction of the relay 1 concerning the B and C phases.

  On the other hand, the conventional technology does not have the idea of taking the induction amount KH from the relay applied to the A phase into the relay applied to the B and C phases. Therefore, the relay applied to the B and C phases is in the operation region in the small current region. When an operation amount (inductive current) due to CT induction from the A phase that enters, a malfunction may occur. In the prior art, taking such an induction amount, measures such as setting the minimum sensitivity setting value K01 in the small current region to be greater than or equal to the induction current generated by CT induction at the time of the maximum external accident current are taken. In some cases, this causes a reduction in operational sensitivity, and therefore, it may not be possible to detect a minute accident current. In the relay 1 according to the present embodiment, the operation sensitivity of the B and C phases can be controlled in accordance with the A phase external fault current (effective value of each terminal current), so that the decrease in the operation sensitivity is minimized. It is possible to suppress.

  As described above, in the relay 1 according to the embodiment of the present invention, the induced current information output unit 20 has the maximum effective value (IK) and the predetermined coefficient (α) among the effective values of the phase current. Based on the induction amount KH indicating the magnitude of the induced current, and the sensitivity control unit 21 controls the operation sensitivity K01 of the self-phase relay 1 based on the induction amount KH. It is not necessary to set in advance K01 in consideration of the induced current caused by the maximum accident current, it is possible to prevent malfunction of the healthy phase relay 1 due to CT induction at the time of other phase external accident, and the relay 1 related to the healthy phase. It is possible to minimize a decrease in the operation sensitivity. Moreover, according to the relay 1 concerning embodiment of this invention, since the effective value of each terminal current I1-In is calculated, since it is comprised so that the minimum sensitivity setting value K01 of a small electric current area may be changed. Even if the effective values of the terminal currents I1 to In are small, it is possible to prevent malfunction due to CT induction.

Embodiment 2. FIG.
In the first embodiment, the induction amount KH assumed by multiplying the maximum value IK of the effective values of the terminal currents I1 to In by the interphase induction coefficient α of the CT is calculated, and a small current region is determined according to the induction amount KH. The minimum sensitivity setting value K01 was controlled. In the second embodiment, a circuit for determining whether or not the effective value of each of the terminal currents I1 to In is equal to or greater than a predetermined current value is provided instead of the induced amount calculation circuit 8 for calculating the induced amount KH. When it is determined that the relay 1 may malfunction due to the CT induction amount, the minimum sensitivity setting value K01 in the small current region is increased to prevent malfunction. Details will be described below.

  FIG. 3 is a configuration diagram of the current differential protection relay 1 according to the second exemplary embodiment of the present invention. The relay 1 shown in FIG. 3 mainly includes a difference current calculation circuit 3, an effective value calculation circuit 4, an effective value calculation circuits 2-1 to 2-n, a suppression amount calculation circuit 5, and an overcurrent determination. The circuit 11-1 to 11-n, the OR circuit 12, the OR circuit 13, the minimum operation sensitivity setting circuit 10, and the operation determination circuit 7 are configured.

  Here, the overcurrent determination circuits 11-1 to 11-n and the OR circuit 12 constitute an induced current information output unit 22, which is based on the effective value of the phase current of the own phase. Inductive current information (detection signal to be described later) related to the presence or absence of induced current flowing in the secondary side of the CT of the other phase in accordance with the current flowing in the primary side of the CT of the own phase is generated and output to the relay 1 of the other phase. It is configured as follows. The OR circuit 13 and the minimum operating sensitivity setting circuit 10 constitute a sensitivity control unit 23. The sensitivity control unit 23 is configured to control the operation sensitivity setting value K01 of the relay 1 of the own phase based on the detection signal from the induced current information output unit 22 of the other phase. Hereinafter, the same reference numerals are given to the same parts as those in the first embodiment, and the description thereof is omitted, and only different parts will be described here.

  A predetermined determination value IH is set in the overcurrent determination circuits 11-1 to 11-n. The overcurrent determination circuits 11-1 to 11-n fetch the effective values from the effective value calculation circuits 2-1 to 2-n, respectively, and when each effective value exceeds the determination value IH, the overcurrent determination circuits 11-1 to 11-n Output a detection signal. The determination value IH is set as a value with which the induced current generated by the CT phase induction has a margin that the relay 1 does not operate with respect to the preset minimum sensitivity K01. That is, when the effective values (I1 ′ to In ′) of the terminal currents I1 to In that are equal to or less than the determination value IH are input to the overcurrent determination circuits 11-1 to 11-n, the relay 1 does not operate. On the other hand, when the effective values (I1 ′ to In ′) of the terminal currents I1 to In that are larger than the determination value IH are input to the overcurrent determination circuits 11-1 to 11-n, the minimum sensitivity K01 set in advance is set. There is a possibility that the relay 1 operates.

  The OR circuit 12 takes in each detection signal from the overcurrent determination circuits 11-1 to 11-n, and when a detection signal is output from any of the overcurrent determination circuits 11-1 to 11-n, the detection signal Is sent to the other two-phase relay 1.

  The OR circuit 13 takes in the detection signal from the other two-phase relay 1, and if the detection signal is output from the relay 1 related to one of the other two phases, the detection signal is used as the minimum operating sensitivity. Output to the setting circuit 10.

  In the minimum operation sensitivity setting circuit 10 shown in FIG. 3, a minimum sensitivity setting value K01 and an induction amount KH ′ in a small current region are set in advance. For example, when the maximum external fault current flows in the other phase, the induction amount KH ′ is set as a value that does not cause the own-phase relay 1 to malfunction due to the CT induction amount from the other phase. When the detection signal is not output from the OR circuit 13, the minimum operation sensitivity setting circuit 10 outputs the minimum sensitivity setting value K01 in the small current region without adding the induction amount KH '. On the other hand, when the detection signal is output from the OR circuit 13, the minimum operation sensitivity setting circuit 10 sets the minimum sensitivity setting value K01 in the small current region set in advance to the current of the own phase by CT induction from the other phase. The value is changed to a value (new K01) in which the differential protection relay does not malfunction. That is, when the detection signal from the induced current information output unit 22 of the other phase is received, the minimum operation sensitivity setting circuit 10 changes the minimum sensitivity setting value K01 in the small current region to K01 + KH ′.

  In this way, by adding the induction amount KH ′ to the minimum sensitivity setting value K01 in the small current region, the relay 1 relating to the healthy phase malfunctions due to the induction between the CT phases from the accident phase at the time of the other phase external accident. Can be prevented.

  Next, the operation will be described. However, in FIG. 3, the circuits having the same reference numerals as those in FIG.

  First, the operation in the circuit from the effective value arithmetic circuits 2-1 to 2-n to the OR circuit 12 will be described. The effective values of the terminal currents I1 to In output from the effective value arithmetic circuits 2-1 to 2-n are taken into the overcurrent determination circuits 11-1 to 11-n, respectively. When the effective value exceeds the determination value IH, a detection signal is output from the overcurrent determination circuits 11-1 to 11-n, and the detection signal is sent to the other two-phase relay 1 via the OR circuit 12. .

  Next, operations according to the OR circuit 13 and the minimum operation sensitivity setting circuit 10 will be described. The relay 1 receives a detection signal from a phase other than its own phase (the other two phases). When a detection signal is output from the relay 1 relating to one of the other two phases, the detection signal is taken into the minimum operation sensitivity setting circuit 10 via the OR circuit 13. The minimum operation sensitivity setting circuit 10 uses the detection signal as a trigger to add the induction amount KH ′ to the minimum sensitivity setting value K01 in the small current region. By such an operation, for example, the minimum sensitivity setting value K01 in the small current region schematically shown in the operation determination circuit 7 is changed to an increasing side, and prevents malfunction at the time of another phase external accident due to CT interphase induction. Can do.

  As described above, in the relay 1 according to the embodiment of the present invention, the induced current information output unit 22 compares the maximum effective value among the effective values of the phase current with the predetermined determination value IH, respectively. If any of the effective values of the phase current is larger than the determination value IH, a detection signal indicating that the induced current may cause the current differential protection relay of the other phase to malfunction is generated, and the sensitivity control unit 23 is based on this detection signal. Since the operation sensitivity K01 of the relay 1 of the own phase is controlled, it is not necessary to set the operation sensitivity K01 in consideration of the induced current caused by the maximum accident current as in the prior art. It is possible to prevent malfunction of the relay 1 in the healthy phase due to CT induction, and it is possible to minimize the influence of the decrease in operation sensitivity of the relay 1 on the healthy phase. Further, according to the relay 1 according to the embodiment of the present invention, the minimum sensitivity setting value K01 in the small current region does not change until the effective values of the terminal currents I1 to In become equal to or higher than a predetermined current value. It is possible to facilitate the characteristic test. Further, since the maximum value calculation circuit 6 and the induction amount calculation circuit 8 shown in FIG. 2 are not required, the circuit can be simplified and the countermeasure against malfunction due to the CT phase induction can be made the same as in the first embodiment. Furthermore, unlike the relay 1 according to the first embodiment, the process of calculating the induction amount KH assumed by multiplying the interphase induction coefficient α is unnecessary, so that the minimum sensitivity setting value K01 in the small current region can be set more quickly. Can be changed.

Embodiment 3 FIG.
In the second embodiment, a circuit (overcurrent determination circuits 11-1 to 11-n) for determining whether or not the effective values of the terminal currents I1 to In are greater than or equal to a predetermined current value is provided, and CT phase induction is performed. In the third embodiment, the minimum sensitivity setting value K01 in the small current region is controlled when a current that is determined to have a possibility of malfunction due to the amount flows. In the third embodiment, the maximum of each of the terminal currents I1 to In is controlled. The overcurrent is determined for the value. Although there is a difference between the overcurrent determination of each of the terminal currents I1 to In and the maximum value calculation circuit, even when configured in this way, substantially the same effect as the second embodiment can be obtained. Details will be described below.

  FIG. 4 is a configuration diagram of the current differential protection relay 1 according to the third exemplary embodiment of the present invention. The relay 1 shown in FIG. 4 mainly includes a difference current calculation circuit 3, an effective value calculation circuit 4, an effective value calculation circuits 2-1 to 2-n, a suppression amount calculation circuit 5, and a maximum value calculation. The circuit 6 includes an overcurrent determination circuit 14, an OR circuit 13, a minimum operation sensitivity setting circuit 10, and an operation determination circuit 7.

  Here, the maximum value calculation circuit 6 and the overcurrent determination circuit 14 constitute an induced current information output unit 24. The induced current information output unit 24 is based on the effective value of the phase current of the own phase. It is configured to generate induced current information (detection signal to be described later) related to the presence or absence of induced current flowing in the secondary side of the CT of the other phase in accordance with the current flowing in the primary side of the CT and to output it to the relay 1 of the other phase. ing. The OR circuit 13 and the minimum operating sensitivity setting circuit 10 constitute a sensitivity control unit 23. The sensitivity control unit 23 is configured to control the operation sensitivity of the relay 1 of the own phase based on the detection signal from the induced current information output unit 22 of the other phase. In the following, the same parts as those in the first and second embodiments are denoted by the same reference numerals and description thereof is omitted, and only different parts will be described here.

  A predetermined determination value IH is set in the overcurrent determination circuit 14. This determination value IH is the same as the determination value IH set in the overcurrent determination circuits 11-1 to 11-n according to the second embodiment. The overcurrent determination circuit 14 outputs a detection signal when the maximum value IK from the maximum value calculation circuit 6 exceeds the determination value IH.

  Next, the operation will be described. However, in FIG. 4, circuits having the same reference numerals as those in FIGS.

  First, the operation in the circuit from the effective value arithmetic circuits 2-1 to 2-n to the overcurrent determination circuit 14 will be described. The effective values of the terminal currents I1 to In output from the effective value arithmetic circuits 2-1 to 2-n are taken into the maximum value arithmetic circuit 6, and the maximum value IK is selected. Maximum value IK is compared with determination value IH by overcurrent determination circuit 14. When the maximum value IK exceeds the determination value IH, a detection signal is output from the overcurrent determination circuit 14 and the detection signal is sent to the other two-phase relay 1. Since operations relating to the OR circuit 13 and the minimum operation sensitivity setting circuit 10 are the same as those in the second embodiment, description thereof will be omitted.

  As described above, in the relay 1 according to the embodiment of the present invention, the induced current information output unit 24 compares the maximum effective value (IK) among the effective values of the phase current with the predetermined determination value IH. At the same time, when the maximum effective value IK is larger than the determination value IH, a detection signal indicating that the induced current may cause the current differential protection relay of the other phase to malfunction is generated, and the sensitivity control unit 23 is based on this detection signal. Since the operation sensitivity K01 of the self-phase relay 1 is controlled, there is no need to set K01 in advance in consideration of the induced current caused by the maximum accident current as in the prior art. It is possible to prevent the malfunction-phase relay 1 from malfunctioning and to minimize the influence of a decrease in the operation sensitivity of the relay 1 relating to the healthy phase. Further, since the relay 1 according to the embodiment of the present invention is configured to control the minimum sensitivity setting value K01 in the small current region only at the time of a large current, the influence on the operation sensitivity at the time of an internal accident is minimized. There is an effect that can be made. Furthermore, unlike the relay 1 according to the first embodiment, the process of calculating the induction amount KH assumed by multiplying the interphase induction coefficient α is unnecessary, so that the minimum sensitivity setting value K01 in the small current region can be set more quickly. Can be changed.

  In the description of the first to third embodiments, the determination is made based on the result of the effective value calculation by the effective value calculation circuits 2-1 to 2-n. However, the same effect can be obtained by the result of the amplitude value calculation or the absolute value calculation. obtain. In the description of the first to third embodiments, as an example of the application of the present invention (the function of changing the minimum sensitivity setting value K01 of the small current region applied to the healthy phase), the transmission line or the bus is targeted for protection. Although described, it can also be applied to other protection relays based on other current differential protection operating principles.

  In addition, the current differential protection relay shown in the first to third embodiments shows an example of the contents of the present invention, and can be combined with another known technique, and the gist of the present invention. Of course, it is possible to change and configure such as omitting a part without departing from the above.

  As described above, the present invention can be applied to a current differential protection relay that protects a bus and a power transmission line by a current differential principle, and is particularly useful as an invention that does not malfunction even when CT induction to a healthy phase occurs. It is.

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c Current differential protection relay 2-1 to 2-n RMS value calculation circuit 3 Difference current calculation circuit 4 RMS value calculation circuit 5 Suppression amount calculation circuit 6 Maximum value calculation circuit 7 Operation determination circuit 8 Induction amount Arithmetic circuit 9 Maximum value selection circuit 10 Minimum operation sensitivity setting circuit 11-1 to 11-n, 14 Overcurrent determination circuit 12, 13 OR circuit 20 Inductive current information output unit 21, 23 Sensitivity control unit 22, 24 Inductive current information output Section 30a, 30b, 30c Bus 31a, 31b, 31c, 32, 33 Leader 34, 35, 36 Circuit breaker 37a, 37b, 37c, 38, 39 CT
40a, 40b, 40c, 41, 42 Cable α Correlation induction coefficient I1-In Terminal current (phase current)
Id Difference current ID Operating amount IH Judgment value IK Maximum effective value of each terminal current IR suppression amount KH, KH 'Induction amount (induction current information related to the induction current amount)
K01 Minimum sensitivity setting value for small current range (operation sensitivity)

Claims (4)

A current differential that calculates an operation amount and a suppression amount using phase currents from a plurality of current transformers provided in each phase of the power system, and protects the power system based on the operation amount and the suppression amount A protective relay,
Based on the effective value of the phase current of the own phase, an induced current related to the presence or absence of the induced current flowing in the secondary side of the current transformer of the other phase or the amount of induced current accompanying the current flowing in the primary side of the current phase current transformer An induction current information output unit that generates information and outputs it to the current differential protection relay of the other phase;
A sensitivity control unit that controls the operation sensitivity of the current-phase current differential protection relay based on the induced current information from the induced current information output unit of the other phase;
A current differential protection relay comprising: The induced current information output unit generates an induced amount indicating the magnitude of the induced current based on a maximum effective value and a predetermined coefficient among effective values of the phase current,
The current differential protection relay according to claim 1, wherein the sensitivity control unit controls the operation sensitivity of the current differential protection relay of the own phase based on the amount of induction. The induced current information output unit compares the effective value of the phase current with a predetermined determination value, and if any of the effective values of the phase current is larger than the determination value, the induced current is a current of another phase. Generate a detection signal indicating the possibility of malfunctioning the differential protection relay,
The current differential protection relay according to claim 1, wherein the sensitivity control unit controls operation sensitivity of the current differential protection relay of the own phase based on the detection signal. The induced current information output unit compares the maximum effective value of the effective values of the phase current with a predetermined determination value, and if the maximum effective value is larger than the determination value, the induced current is in another phase. Generates a detection signal indicating the possibility of malfunctioning the current differential protection relay of
The current differential protection relay according to claim 1, wherein the sensitivity control unit controls operation sensitivity of the current differential protection relay of the own phase based on the detection signal.

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