JP5697551B2 - Current differential protection relay - Google Patents

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.

  A 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 Circuit breaker installed in the protection section to identify internal and external accidents in the protected section using data (terminal current data) and to disconnect the protected section from the power system in the event of an internal accident The release command is output to. The operation of the current differential protection will be described. The vector sum (sampling) 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 difference current Id = I1 + I2 +... + In, which is calculated as an effective value, is used as the operation amount ID, and the scalar sum of the terminal currents (the respective terminal currents are calculated after calculating the effective value) Value) is set as the suppression amount IR, and it is determined whether it is an internal accident or an external accident based on the determination formula of the operation region in which the operation amount ID and the suppression amount IR are preset.

Generally, the determination formula is set to the following formula. However, R1, R2, K1, and K2 are settling values.
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 occurrence of an external accident may occur even in a region where the accident current is relatively small because the accident current concentrates on one terminal CT. Therefore, in the conventional current differential protection relay, measures 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 of time are taken (for example, Patent Document 1 below).
In addition, the above judgment formula is more easily
ID> K01 and ID> R * IR
In some cases, the maximum value among the effective values of the terminal currents may be used as the suppression amount (IR) (for example, Non-Patent Document 1 below).

JP 2000-224755 A (paragraph 0042 and the like)

2.3 (2) Remarks and Explanation Figure 6 (page 39) of JEC-2515-2005 (issued June 30, 2006 by Denki Shoin)

  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. Even if there is a difference current (operation amount) due to an error current such as CT saturation due to an external accident current, the differential protection relay element in the accident phase does not operate because a large suppression amount can be expected, but CT induction When the accident phase current is induced to only one terminal of the healthy phase, the induced current is recognized as an operation amount in the healthy phase differential protection relay element. Considering the case where there is no load current for simplicity, for example, when an external accident occurs in the A phase, a current flows through the CT2 of the healthy phase (for example, the B phase) that has received the CT induction. When the B-phase CT of another line does not receive the CT induction, there is no current in the CT secondary that does not receive the CT induction, and the current flows into only one terminal. In this case, there is a problem in that if CT induction amount = operation amount = suppression amount is established and the CT induction amount is within the operation region of the current differential protection relay, a malfunction occurs.

  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 an electric power system based on an operation amount and the suppression amount, and the self-phase current transformer is connected to the suppression amount of the own phase by interphase induction of a three-phase integrated current transformer a plurality of induction ratio determined by the arrangement of the current transformer constitutes a table and the 3-phase integral degree of induction current induced in the secondary side of the other phases of the current transformer with the current flowing through the primary side of the The induction suppression amount is calculated by multiplying a fixed ratio determined by the slope of the operation characteristic in the ratio differential calculation, and output to the current differential protection relay of the other phase, and the induction suppression amount calculation of the other phase Based on the induction suppression amount output from the unit and the suppression amount of the own phase, the ratio differential of the own phase And a suppression amount calculation unit that calculates a suppression amount used for the calculation.

  According to this invention, since the suppression amount for performing the ratio differential calculation of the own phase is controlled using the induction suppression amount output from the induction suppression amount calculation circuit of the other phase, the operation sensitivity is reduced. There is an effect that the operation is suppressed as much as possible and no malfunction occurs even if CT induction to another phase occurs.

FIG. 1 is a diagram illustrating an overall configuration centering on a current differential protection relay according to first to fourth 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. FIG. 5 is a configuration diagram of a current differential protection relay according to the fourth 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 is a diagram showing an overall configuration centering on current differential protection relays (hereinafter simply referred to as “relays”) 1a, 1b, and 1c common to the first to fourth embodiments of the present invention. FIG. 1 shows buses 30a, 30b, and 30c of each phase of a three-phase bus that is a protection target of relays 1a, 1b, and 1c. For example, bus 30a is an A-phase bus and bus 30b is a B-phase bus. The bus 30c is a C-phase bus.

  A breaker 34a and a CT 37a are installed on the lead wire 31a from the bus 30a. Similarly, a circuit breaker 35a and a CT 38a are installed on the lead line 32a from the bus bar 30a, and a circuit breaker 36a and a CT 39a are installed on the lead line 33a from the bus bar 30a. One end of each of the cables 40a, 41a, and 42a is connected to the CTs 37a, 38a, and 39a, and the other end of the cable 40a, the cable 41a, and the cable 42a is connected to an input converter group (not shown) in the relay 1a. It is connected.

  A breaker 34b and a CT 37b are installed on the lead wire 31b from the bus 30b. Similarly, the circuit breaker 35b and CT38b are installed in the lead wire 32b from the bus 30b, and the circuit breaker 36b and CT39b are installed in the lead wire 33b from the bus 30b. One end of each of the cables 40b, 41b, and 42b is connected to the CTs 37b, 38b, and 39b, and the other end of the cable 40b, the cable 41b, and the cable 42b is connected to an input converter group (not shown) in the relay 1b. It is connected.

  A breaker 34c and a CT 37c are installed on the lead wire 31c from the bus 30c. Similarly, the circuit breaker 35c and CT38c are installed in the lead wire 32c from the bus bar 30c, and the circuit breaker 36c and CT39c are installed in the lead wire 33c from the bus bar 30c. One end of each of the cables 40c, 41c, and 42c is connected to the CTs 37c, 38c, and 39c, and the other end of the cable 40c, the cable 41c, and the cable 42c is connected to an input converter group (not shown) in the relay 1c. It is connected.

  In FIG. 1, the number of lead lines from each of the buses 30a, 30b, and 30c is three in order to simplify the description. Actually, it is assumed that n lead lines (n is an integer of 2 or more) are arranged on each bus. The same applies to the number of CTs. Further, in the following description, the relays 1a, 1b, and 1c are simply referred to as the relay 1 unless otherwise specified.

  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 a configuration for one phase among 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, and a suppression amount correction calculation circuit (a suppression amount). (Calculation unit) 61, CT induction suppression amount calculation circuit (induction suppression amount calculation unit) 81, and operation determination circuit 7.

  Each terminal current (phase current) connected to an object to be protected in the power system (transmission line or bus) is passed through each CT shown in FIG. 1 as CT1 current (I1), CT2 current (I2),. -It inputs into the relay 1 as CTn electric current (In).

  In the relay 1, all the input terminal currents I1 to In are sampled at the same time and processed as digital data by AD conversion. In FIG. 2, a function of converting each terminal current I1 to In taken into the relay 1 into a current value handled in the relay 1 (for example, an input current conversion unit), and the terminal currents I1 to In are time-synchronized. Illustration of a function to output (for example, a synchronization processing unit) is omitted.

  First, the differential current calculation circuit 3 executes a 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 input to the relay 1 are also input to the effective value calculation circuits 2-1 to 2-n, respectively, and the effective value calculation circuits 2-1 to 2-n perform the effective value calculation. Run. The effective values calculated by the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5. The suppression amount calculation circuit 5 calculates the suppression amount IR1 that is the suppression amount of the own phase by adding the effective values of the terminal currents I1 to In.

  The CT induction suppression amount calculation circuit 81 calculates a suppression amount (CT induction suppression amount KH) for controlling the suppression amount IR of the other phase by multiplying the suppression amount IR1 from the suppression amount calculation circuit 5 by a certain ratio P. This CT induction suppression amount KH is a suppression for controlling the suppression amount IR1 of the other phase calculated using the induced current flowing on the CT secondary side of the other phase in accordance with the current flowing on the primary side of the CT of the own phase. Amount. The CT induction suppression amount KH calculated by the CT induction suppression amount calculation circuit 81 is transmitted to the other two-phase relay 1 and used for control of the operation region of the other phase (ratio differential calculation).

  The constant ratio P is a ratio determined by the CT induction ratio α and the slope R of the operating characteristics. The CT induction ratio α represents the degree of the phase current In induced on the secondary side of the CTs 37a to 39c of the other phases with the current flowing on the primary side of the CTs 37a to 39c of the own phase. In other words, it is the degree that the CT induction amount generated by the accident current affects the other phases. This CT induction ratio α is a value determined by the arrangement of the CTs 37a to 39c.

  The constant ratio P is obtained as follows. When CT induction occurs in the healthy phase when an external accident occurs, if the CT induction is generated by one CT, the operation amount ID of the healthy phase is as shown in equation (1). Note that “CT induction is caused by one CT” means that, for example, when an external posterior occurs in the lead line 31a shown in FIG. 1, the CT 37b is guided to the secondary side of the CT 37b along with the current flowing to the primary side of the CT 37a A current flows, but an induced current does not flow on the secondary side of a CT (for example, CT38b) disposed at another terminal.

  At this time, the suppression amount of the accident phase is twice the inflow accident current. That is, if the total current flowing into the bus at the time of an external accident is referred to as an inflow accident current, the outflow accident current is the same, and therefore the amount of suppression flows twice as much as the inflow accident current.

  Since the state with the largest induction amount is a case where only one CT receives induction, if the accident current IF is assumed to be a current flowing through the CT, the accident phase suppression amount IR1 = 2IF.

  On the other hand, since the healthy phase suppression amount IR1 increases as the load current increases, the most operable case (the most severe condition) is when the load current is 0 (A). The suppression amount IR of the healthy phase when the load current is 0 (A) is expressed by the expression (2) by the suppression amount correction calculation circuit 61 (or a suppression amount correction calculation circuit 62 described later).

  That is, a value obtained by multiplying the above-described accident phase suppression amount (2IF) by a certain ratio P is the healthy phase suppression amount IR. Here, the operation condition expression of the operation determination circuit 7 is represented by Expression (3).

  The condition of the suppression amount IR for which the healthy phase does not operate by substituting the healthy phase operation amount ID obtained by the equation (1) and the healthy phase suppression amount IR obtained by the equation (2) into the equation (3). Is obtained, the condition is as shown in equation (4).

  ΑIF in the equation (4) corresponds to the operation amount ID of the healthy phase in the equation (1). In addition, αIF <R * P * 2IF in the equation (4) becomes P> α / (2 * R). At this time, the condition of the operation determination circuit 7 is not satisfied, and malfunction can be avoided. That is, the value of the CT induction suppression amount KH obtained by multiplying the suppression amount IR1 calculated in the relay 1 related to the accident phase by a certain ratio P is more relative to the operation amount ID calculated in the relay 1 related to the healthy phase. A large value. When the suppression amount calculation method of the suppression amount calculation circuit 5 is a scalar sum suppression method, the slope of the operating characteristic is set to about R = 0.3, so that P> 1.67α (R = 0.3). Become.

  When the accident phase is assumed to be A phase and the healthy phase is assumed to be B and C phases, the CT induction suppression amount calculation circuit 81 in the relay 1a for the A phase is calculated by multiplying the suppression amount IR1 of the own phase by a constant ratio P. The suppression amount (KHA) is calculated, and this CT induction suppression amount (KHA) is transmitted to the relay 1b for the B phase and the relay 1c for the C phase.

  Next, the suppression amount correction calculation circuit 61 will be described. The suppression amount correction calculation circuit 61 includes the suppression amount IR1 output from the self-phase suppression amount calculation circuit 5 and the CT induction suppression amount KH calculated by the relay 1 of the other phase (that is, two-phase CT induction other than the self-phase). The CT induction suppression amount KH) output from the suppression amount calculation circuit 81 is taken in, and the largest of these suppression amounts (IR1, KH) is calculated as the suppression amount IR. When the accident phase is assumed to be B phase and the healthy phase is assumed to be A phase, for example, the suppression amount correction calculation circuit 61 in the relay 1a for the A phase includes the suppression amount IR1 output from the suppression amount calculation circuit 5 of the own phase. The CT induction suppression amount (KHB) output from the CT induction suppression amount calculation circuit 81 in the relay 1b for the B phase and the CT induction suppression amount calculation circuit 81 in the relay 1c for the C phase. A suppression amount (KHC) is taken in. Then, the suppression amount correction calculation circuit 61 in the relay 1a calculates the maximum (KHB) among IR1, KHB, and KHC as the suppression amount IR.

  The operation determination circuit 7 performs an internal / external accident determination based on the operation amount ID from the effective value calculation circuit 4 and the suppression amount IR from the suppression amount correction calculation circuit 61. When the accident phase is assumed to be B phase and the healthy phase is assumed to be A and C phases, for example, the suppression amount IR taken into the operation determination circuit 7 in the relay 1a is calculated by the relay 1a when an external failure occurs in the B phase. The value is relatively larger than the motion amount ID. In the operation determination circuit 7 in the relay 1a, the ratio of the suppression amount IR to the operation amount ID is relatively large, and the locus of the operation amount ID and the suppression amount IR is set in the non-operation area. The same applies to the operation determination circuit 7 in the relay 1c. As a result, the relays 1a and 1c for the healthy phase can avoid malfunction due to CT induction when a B-phase external failure occurs.

  If the accident current at the time of the occurrence of an internal accident is IF and the current of the healthy phase (load current, etc.) is IL, the accident phase suppression amount IR1 ≧ IF and the healthy phase suppression amount IR1 = 2IL, and the induction ratio α is 0. If it is less than 1, P = 1.67 * 0.1 = 0.167. In this case, the KH of the healthy phase is KH = 0.167 * 2IL = 0.33IL, and it is considered that the accident current IF> the load current IL. Therefore, the self phase (accident phase) suppression amount (IR1)> the other phase suppression amount. (KH). Therefore, since it is considered that there is little possibility that the operation sensitivity is lowered due to the influence of the other phase suppression amount (KH), the influence on the operation sensitivity when an internal accident occurs can be minimized. The reason why the suppression amount IR1 = 2IL is that the current passes through in the healthy phase, so that the inflow current to the bus line = the outflow current = the load current.

  As described above, the relay 1 according to the first embodiment induces the suppression amount IR1 of the own phase to the secondary side of the CT37a to 39c of the other phase with the current flowing to the primary side of the CT37a to 39c of the own phase. The induction suppression amount KH is calculated by multiplying the constant ratio P determined by the induction ratio α indicating the degree of induced current and the gradient R of the operating characteristic in the ratio differential calculation, and output to the relay 1 of the other phase Based on the suppression amount calculation circuit 81, the CT induction suppression amount KH output from the other-phase CT induction suppression amount calculation circuit 81, and the self-phase suppression amount IR1, the suppression amount used for the ratio differential calculation of the own phase Since the suppression amount correction calculation circuit 61 for calculating IR is provided, the relay applied to the healthy phase by predicting the induced current caused by CT induction from the accident phase and correcting the suppression amount IR accordingly. 1 To prevent malfunction.

  Next, the operation will be described. The effective values of the terminal currents I1 to In output from the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5, and the suppression amount IR1 is calculated. The suppression amount IR1 is taken into the suppression amount correction calculation circuit 61 and the CT induction suppression amount calculation circuit 81, and the CT induction suppression amount calculation circuit 81 calculates the CT induction suppression amount KH based on the suppression amount IR1 and the constant ratio P. Is calculated, and this CT induction suppression amount KH is sent to the other two phases. In the suppression amount correction calculation circuit 61 in the relay 1 related to the healthy phase, the maximum is selected from the suppression amount IR1 from the suppression amount calculation circuit 5 of the own phase and the CT induction suppression amount KH from two phases other than the own phase. A thing is calculated as the suppression amount IR. As a result, since the suppression amount IR shown in the operation determination circuit 7 of FIG. 2 is changed to an increasing side, malfunction due to CT induction at the time of another phase external accident is avoided.

  As described above, in the relay 1 according to the first embodiment, the CT induction suppression amount calculation circuit 81 calculates the induction suppression amount KH by multiplying the suppression amount IR1 of the own phase by the constant ratio P, and the suppression amount The correction calculation circuit 61 sets the maximum one of the self-phase suppression amount IR1 and the CT induction suppression amount KH transmitted from the other two-phase CT induction suppression amount calculation circuit 81 to the self-phase ratio differential calculation. Since the output is made as the suppression amount IR to be used, it is possible to suppress a decrease in operation sensitivity at the time of an internal accident as much as possible, and to prevent malfunction even if CT induction to another phase occurs. When a three-phase collective CT is used as the terminal current measuring means, a large accident current (for example, 50 KA) flows in the CT related to the accident phase, so that the healthy phase CT causes the magnetic induction from the accident phase CT. In response, an induced current (for example, 500 to 600 A in terms of CT primary side) may flow on the CT secondary side of the healthy phase. In that case, the difference between the inflow and the outflow does not become zero, and a difference current Id is generated. Therefore, CT induction amount = operation amount = suppression amount is established. That is, since the ratio between the operation amount ID and the suppression amount IR becomes equal, the locus of the operation amount ID and the suppression amount IR is set in the operation region, and as a result, the relay 1 related to the healthy phase may malfunction. . In the prior art, taking such a CT 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. The relay 1 according to the first embodiment can perform a ratio differential calculation using the CT induction suppression amount KH output from the CT induction suppression amount calculation circuit 81 of the other phase when an external accident occurs, and an internal accident At the time of occurrence, ratio differential calculation can be performed using the suppression amount IR1 calculated by the suppression amount calculation circuit 5 of the own phase. Therefore, even if the minimum sensitivity setting value K01 is not set as in the prior art, CT induction is used. In addition to preventing malfunctions, it is possible to minimize a decrease in operational sensitivity when an internal accident occurs.

Embodiment 2. FIG.
In the relay 1 according to the first embodiment, even when an induced current flows on the CT secondary side of the healthy phase due to the accident current IF when an external accident occurs, the suppression amount IR1 applied to the accident phase is multiplied by a certain ratio P. When the CT induction suppression amount KH is larger than the suppression amount IR1 as compared with the result (CT induction suppression amount KH) and the suppression amount IR1 applied to the healthy phase, the accident phase CT induction suppression amount KH is adopted as the suppression amount IR. Therefore, it is configured to prevent malfunction due to CT induction. When the larger one of the other two-phase CT induction suppression amounts KH is larger than the self-phase suppression amount IR1, the relay 1 according to the second embodiment uses the CT induction suppression amount KH as the self-phase suppression amount IR1. By adopting the suppression amount IR added to the above, it is configured to prevent malfunction due to CT induction. By adding the CT induction suppression amount KH to the self-phase suppression amount IR1, a ratio margin for CT induction can be obtained, and a more stable operation can be expected. Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 3 is a configuration diagram of the current differential protection relay 1 according to the second exemplary embodiment of the present invention, and shows a configuration for one phase among the three phases. 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 a suppression amount calculation. The unit 63, the CT induction suppression amount calculation circuit 81, and the operation determination circuit 7 are configured.

  The suppression amount calculation unit 63 includes a maximum value selection circuit 9, another phase induction suppression amount setting circuit 10, and a suppression amount correction calculation circuit (suppression amount calculation unit) 62 as main components.

  The maximum value selection circuit 9 selects the larger one of the two CT induction suppression amounts KH transmitted from the CT induction suppression amount calculation circuit 81 in the relay 1 related to the other two phases, and the selected one is the suppression amount. Output as KHM.

  The other-phase induction suppression amount setting circuit 10 compares the suppression amount KHM from the maximum value selection circuit 9 with the suppression amount IR1 calculated by the suppression amount calculation circuit 5 of the own phase, and when IR1> KMH, KHM = 0. On the other hand, when IR1 <KHM, KHM is output as it is.

  The suppression amount correction calculation circuit 62 takes in the suppression amount IR1 output from the suppression amount calculation circuit 5 and the suppression amount KHM from the other-phase induction suppression amount setting circuit 10, and uses it as the suppression amount IR1 from the suppression amount calculation circuit 5. The suppression amount KHM is added, and the addition result is calculated as the suppression amount IR.

  The operation determination circuit 7 executes internal / external accident determination based on the operation amount ID from the effective value calculation circuit 4 and the suppression amount IR from the suppression amount correction calculation circuit 62.

  As described above, the relay 1 according to the second embodiment induces the suppression amount IR1 of the own phase to the secondary side of the CT 37a to 39c of the other phase with the current flowing to the primary side of the CT 37a to 39c of the own phase. The induction suppression amount KH is calculated by multiplying the constant ratio P determined by the induction ratio α indicating the degree of induced current and the gradient R of the operating characteristic in the ratio differential calculation, and output to the relay 1 of the other phase Based on the suppression amount calculation circuit 81, the CT induction suppression amount KH output from the other-phase induction suppression amount calculation circuit 81, and the self-phase suppression amount IR1, the suppression amount IR used for the ratio differential calculation of the own phase The suppression amount calculation unit 63 that calculates the amount of the relay 1 for the healthy phase by predicting the induced current caused by CT induction from the accident phase and correcting the suppression amount IR accordingly. Malfunction To stop.

  Next, the operation will be described. The effective values of the terminal currents I1 to In output from the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5, and the suppression amount IR1 is calculated. The suppression amount IR1 is taken into the suppression amount correction calculation circuit 62 and the CT induction suppression amount calculation circuit 81. In the CT induction suppression amount calculation circuit 81, the CT induction suppression amount KH is based on the suppression amount IR1 and the constant ratio P. Is calculated, and this CT induction suppression amount KH is transmitted to the other two phases. When assuming the accident phase as B phase and the healthy phase as A and C phase, for example, in the maximum value selection circuit 9 in the relay 1a, the CT induction suppression amount (KHB) from the B phase and the CT induction suppression from the C phase The larger one (KHB) of the quantity (KHC) is selected. The selected suppression amount KHM (KHB) is compared with the suppression amount IR1 by the other-phase induction suppression amount setting circuit 10, and when the suppression amount KHM is larger than the suppression amount IR1, the suppression amount correction calculation circuit 62 indicates this suppression amount KHM. Is captured. The suppression amount KHM captured by the suppression amount correction calculation circuit 62 is added to the suppression amount IR1, and the suppression amount IR that is the addition result is captured by the operation determination circuit 7. As a result, the suppression amount IR shown in the operation determination circuit 7 of FIG. 3 is changed to an increasing side, and a malfunction due to CT induction at the time of another phase external accident is avoided. The operation of the relay 1c is the same.

  Further, when an internal accident occurs, as described in the first embodiment, in the other-phase induction suppression amount setting circuit 10, since the self-phase suppression amount (IR1)> the other-phase suppression amount (KHM), the suppression amount correction calculation The suppression amount added in the circuit 62 is zero. Therefore, since it is considered that there is little possibility that the operation sensitivity is reduced due to the influence of the other phase suppression amount (KHM), the influence on the operation sensitivity when an internal accident occurs can be minimized.

  The suppression amount calculation unit 63 according to the second embodiment is provided with the other-phase induction suppression amount setting circuit 10, but is not limited to this configuration. The other-phase induction suppression amount setting circuit 10 is not limited to this configuration. It may be omitted and the suppression amount KHM from the maximum value selection circuit 9 may be directly input to the suppression amount correction calculation circuit 62. Even in such a configuration, since the suppression amount KHM is added to the suppression amount IR1 in the suppression amount correction calculation circuit 62, malfunction due to CT induction can be prevented. In addition, when an internal accident occurs, the suppression amount KHM from the maximum value selection circuit 9 is added to the suppression amount IR1, but the suppression amount KHM is sufficiently smaller than the suppression amount IR1, so that the operation sensitivity when an internal accident occurs The impact on is minimal.

  As described above, in the relay 1 according to the second embodiment, the CT induction suppression amount calculation circuit 81 calculates the induction suppression amount KH by multiplying the suppression amount IR1 of the own phase by the constant ratio P, and the suppression amount The calculation unit 63 adds the larger one of the two CT induction suppression amounts KH transmitted from the other two-phase CT induction suppression amount calculation circuit 81 to the self-phase suppression amount IR1, and the suppression after this addition Since the amount IR is output as the suppression amount IR used for the ratio differential calculation of the own phase, the CT induction suppression amount KH from the accident phase is added to the healthy phase suppression amount IR1 and is taken into the operation determination circuit 7 The suppression amount IR becomes a large value, and a ratio margin for CT induction can be obtained. As a result, the same effect as in the first embodiment can be obtained, and more stable protection operation can be performed.

Embodiment 3 FIG.
The relay 1 according to the first and second embodiments is configured to calculate the CT induction suppression amount KH transmitted to the other phase by multiplying the suppression amount IR1 of the own phase by a certain ratio P. The relay 1 concerning the form 3 is comprised so that the CT induction | guidance | derivation suppression amount KH transmitted to another phase may be calculated | required from the maximum value of the effective value of each terminal current I1-In. Even if the CT induction suppression amount KH is calculated from the maximum effective value of each of the terminal currents I1 to In, the same effect as in the first and second embodiments can be obtained. Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  FIG. 4 is a configuration diagram of the current differential protection relay 1 according to the third exemplary embodiment of the present invention, and shows a configuration for one phase among the three phases. 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 suppression amount correction. The calculation circuit 61, the induction suppression amount calculation unit 83, and the operation determination circuit 7 are configured.

  The induction suppression amount calculation unit 83 includes a terminal current maximum value calculation circuit 11 and a CT induction suppression amount calculation circuit 82 as main components.

  The terminal current maximum value calculation circuit 11 selects the maximum terminal current (the maximum value IK of the effective values of the terminal currents I1 to In) from the effective values of the terminal currents I1 to In, and calculates the CT induction suppression amount calculation circuit. 82. The CT induction suppression amount calculation circuit 82 calculates a CT induction suppression amount KH) by multiplying the maximum current (IK) from the terminal current maximum value calculation circuit 11 by a certain ratio P1, and the result is calculated as another two-phase relay 1. Send to.

  The constant ratio P1 is obtained as follows. When CT induction occurs in the healthy phase when an external accident occurs, if the CT induction is generated by one CT, the operation amount ID of the healthy phase is as shown in Equation (5).

  The accident phase CT induction suppression amount KH at this time is the same as the inflow accident current. This is because the CT induction suppression amount calculation circuit 82 captures the maximum value of each terminal. That is, when the current flowing into the buses 30a to 30c flows into 1CT, the inflow accident current = the maximum current.

  The state where the induction amount is the largest is when only the CT at the inflow end of the accident current IF is induced. Therefore, assuming that the accident current IF is a current flowing through the CT, the accident phase suppression amount IR1 = IF. .

  On the other hand, since the healthy phase suppression amount IR1 increases as the load current increases, the most operable case (the most severe condition) is when the load current is 0 (A). Then, the suppression amount IR of the healthy phase when the load current is 0 (A) is expressed by the suppression amount correction calculation circuit 61 as shown in the equation (6).

  That is, a value obtained by multiplying the above-described accident phase suppression amount (IF) by a certain ratio P1 is the healthy phase suppression amount IR. Here, the operation condition expression of the operation determination circuit 7 is defined as expression (7).

  The condition of the suppression amount IR at which the healthy phase does not operate by substituting the healthy phase operation amount ID obtained by the equation (5) and the healthy phase suppression amount IR obtained by the equation (6) into the equation (7). Is obtained, the condition is as shown in equation (8).

  ΑIF in the equation (8) corresponds to the operation amount ID of the healthy phase in the equation (5). In addition, αIF <R * P1 * IF in the equation (8) becomes P1> α / R. At this time, the condition of the operation determination circuit 7 is not satisfied, and malfunction can be avoided. That is, the value of the CT induction suppression amount KH obtained by multiplying the suppression amount IR1 calculated in the relay 1 related to the accident phase by the constant ratio P1 is more relative to the operation amount ID calculated in the relay 1 related to the healthy phase. A large value. When the suppression amount calculation method of the suppression amount calculation circuit 5 is the scalar sum suppression method, the slope of the operating characteristic is set to about R = 0.3, so that P1> 3.4α (R = 0.3). Become.

  Next, the suppression amount correction calculation circuit 61 will be described. The suppression amount correction calculation circuit 61 takes in the suppression amount IR1 output from the suppression amount calculation circuit 5 of the own phase and the CT induction suppression amount KH calculated in the relay 1 of the other phase, and these suppression amounts (IR1, The maximum value among KH) is calculated as the suppression amount IR.

  As described above, the relay 1 according to the third embodiment has the maximum effective value among the effective values of the phase current In of the own phase, and the current of the other phase accompanying the current flowing on the primary side of the CT 37a to 39c of the own phase. The induction suppression amount KH is calculated by multiplying the constant ratio P1 determined by the induction ratio α indicating the degree of the induced current induced on the secondary side of the CT 37a to 39c and the gradient R of the operation characteristic in the ratio differential calculation, Based on the induction suppression amount calculation unit 83 to be output to the relay 1 and the CT induction suppression amount KH output from the other-phase induction suppression amount calculation unit 83 and the self-phase suppression amount IR1, Since the suppression amount correction calculation circuit 61 for calculating the suppression amount IR used for the calculation is provided, an induced current caused by CT induction from the accident phase is predicted, and the suppression amount IR is corrected accordingly. Relay 1 for the healthy phase To prevent malfunction.

  Next, the operation will be described. The effective values of the terminal currents I1 to In output from the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5 and the terminal current maximum value calculation circuit 11. The suppression amount IR1 calculated by the suppression amount calculation circuit 5 is taken into the suppression amount correction calculation circuit 61. In the terminal current maximum value calculation circuit 11, the maximum effective value IK is selected, and the selected maximum effective value IK is input to the CT induction suppression amount calculation circuit 82. The maximum effective value IK input to the CT induction suppression amount calculation circuit 82 is multiplied by a fixed ratio P1, and the resulting CT induction suppression amount KH is transmitted to the other two-phase relay 1. When assuming the accident phase as B phase and the healthy phase as A and C phases, for example, in the suppression amount correction calculation circuit 61 in the relay 1a, the suppression amount IR1 from the suppression amount calculation circuit 5 of the own phase and other than the own phase The maximum of the CT induction suppression amount KH from the two phases is calculated as the suppression amount IR. As a result, since the suppression amount IR shown in the operation determination circuit 7 of FIG. 4 is changed to an increasing side, malfunction due to CT induction at the time of another phase external accident is avoided.

  As described above, in the relay 1 according to the third embodiment, the induction suppression amount calculation unit 83 has the maximum effective value among the effective values of the self-phase phase current In and the CTs 37a to 39c of the self-phase. Multiply by a constant ratio P1 determined by the induction ratio α representing the degree of induced current induced on the secondary side of the CTs 37a to 39c of the other phases with the current flowing on the primary side and the gradient R of the operating characteristic in the ratio differential calculation. The suppression suppression amount KH is calculated, and the suppression amount correction calculation circuit 61 is the largest of the suppression suppression amount IR1 of the own phase and the CT induction suppression amount KH transmitted from the other two-phase induction suppression amount calculation unit 83. Since it is configured to output the induction suppression amount as the suppression amount IR used in the self-phase ratio differential calculation, the same effect as in the first embodiment can be obtained.

Embodiment 4 FIG.
The relay 1 according to the third embodiment obtains the CT induction suppression amount KH to be transmitted to the other phase from the maximum value of the effective values of the terminal currents I1 to In, and the suppression amount correction arithmetic circuit 61 of the first embodiment. Although the maximum amount of the suppression amount IR1 and the CT induction suppression amount KH is calculated as the suppression amount IR, the relay 1 according to the fourth embodiment includes the induction suppression amount calculation unit of the third embodiment. 83 and the suppression amount calculation unit 63 of the second embodiment are combined so that the same effects as those of the second and third embodiments can be obtained. Hereinafter, the same parts as those in the second and third embodiments are denoted by the same reference numerals, and the description thereof is omitted. Only different parts will be described here.

  FIG. 5 is a configuration diagram of the current differential protection relay 1 according to the fourth exemplary embodiment of the present invention, and shows a configuration for one phase among the three phases. The relay 1 shown in FIG. 5 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 suppression amount calculation. A unit 63, a guidance suppression amount calculation unit 83, and an operation determination circuit 7 are included.

  Further, the suppression amount calculation unit 63 includes a maximum value selection circuit 9, another phase induction suppression amount setting circuit 10, and a suppression amount correction calculation circuit 62. The induction suppression amount calculation unit 83 includes a terminal current maximum value. An arithmetic circuit 11 and a CT induction suppression amount arithmetic circuit 82 are included.

  As described above, the relay 1 according to the fourth embodiment has the maximum effective value of the effective values of the phase current In of the own phase, and the current of the other phase accompanying the current flowing on the primary side of the CTs 37a to 39c of the own phase. The induction suppression amount KH is calculated by multiplying the constant ratio P1 determined by the induction ratio α indicating the degree of the induced current induced on the secondary side of the CT 37a to 39c and the gradient R of the operation characteristic in the ratio differential calculation, Based on the induction suppression amount calculation unit 83 to be output to the relay 1 and the CT induction suppression amount KH output from the other-phase induction suppression amount calculation unit 83 and the self-phase suppression amount IR1, Since the suppression amount correction calculation circuit 63 for calculating the suppression amount IR used for the calculation is provided, an induced current caused by CT induction from the accident phase is predicted, and the suppression amount IR is corrected accordingly. Relay 1 for the healthy phase To prevent malfunction.

  Next, the operation will be described. The effective values of the terminal currents I1 to In output from the effective value calculation circuits 2-1 to 2-n are taken into the suppression amount calculation circuit 5 and the terminal current maximum value calculation circuit 11. The suppression amount IR1 calculated by the suppression amount calculation circuit 5 is taken into the suppression amount correction calculation circuit 62. In the terminal current maximum value calculation circuit 11, the maximum effective value IK is selected, and the selected maximum effective value IK is input to the CT induction suppression amount calculation circuit 82. The maximum effective value IK input to the CT induction suppression amount calculation circuit 82 is multiplied by a fixed ratio P1, and the resulting CT induction suppression amount KH is transmitted to the other two-phase relay 1. When assuming the accident phase as B phase and the healthy phase as A and C phase, for example, in the maximum value selection circuit 9 in the relay 1a, the CT induction suppression amount (KHB) from the B phase and the CT induction suppression from the C phase The larger one (KHB) of the quantity (KHC) is selected. Then, the suppression amount KHM (KHB) selected by the maximum value selection circuit 9 is compared with the suppression amount IR1 by the other-phase induction suppression amount setting circuit 10, and when the suppression amount KHM is larger than the suppression amount IR1, the suppression amount correction calculation is performed. The circuit 62 takes in this suppression amount KHM. The suppression amount KHM captured by the suppression amount correction calculation circuit 62 is added to the suppression amount IR1, and the suppression amount IR that is the addition result is captured by the operation determination circuit 7. As a result, the suppression amount IR shown in the operation determination circuit 7 of FIG. 5 is changed to an increasing side, and a malfunction due to CT induction at the time of another phase external accident is avoided. The operation of the relay 1c is the same.

  Further, when an internal accident occurs, as shown in the first embodiment, in the other-phase induction suppression amount setting circuit 10, the self-phase suppression amount (IR1)> the other-phase suppression amount (KHM). The amount of suppression KHM added at 62 becomes zero. Therefore, since it is considered that there is little possibility that the operation sensitivity is reduced due to the influence of the other phase suppression amount (KHM), the influence on the operation sensitivity when an internal accident occurs can be minimized.

  In addition, the relay 1 concerning Embodiment 4 abbreviate | omits the other phase induction | guidance | derivation suppression amount setting circuit 10 similarly to the suppression amount calculating part 63 of Embodiment 2, and is using the suppression amount KHM from the maximum value selection circuit 9. FIG. It may be configured to directly input to the suppression amount correction calculation circuit 62.

  As described above, in the relay 1 according to the fourth embodiment, the induction suppression amount calculation unit 83 has the maximum effective value among the effective values of the self-phase phase current In, and the CT 37a to 39c of the self-phase. Multiply by a constant ratio P1 determined by the induction ratio α representing the degree of induced current induced on the secondary side of the CTs 37a to 39c of the other phases with the current flowing on the primary side and the gradient R of the operating characteristic in the ratio differential calculation. The suppression amount calculation unit 63 calculates the induction suppression amount KH, and the suppression amount calculation unit 63 is the larger of the two induction suppression amounts KH transmitted from the other two-phase induction suppression amount calculation unit 83 to the self-phase suppression amount IR1. Since the suppression amount after the addition is output as the suppression amount IR used for the ratio differential calculation of the own phase, the same effect as in the second embodiment can be obtained.

  In the description of the first to fourth embodiments, the suppression amount IR1 of the own phase is calculated using the sum of the effective values of the terminal currents I1 to In. However, the maximum effective value of the terminal currents I1 to In is calculated. The same effect can be obtained even if the suppression amount IR1 of the own phase is calculated by using it. In the description of the first to fourth embodiments, the application of the present invention has been described by taking as an example the case where a power transmission line or bus is a protection target, but other protection relays based on other current differential protection operating principles. It can also be applied to.

  Moreover, the current differential protection relay shown in Embodiments 1 to 4 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.

1, 1a, 1b, 1c Current differential protection relays 2-1 2-2, 2-n 4 RMS value calculation circuit 3 Difference current calculation circuit 5 Suppression amount calculation circuit 7 Operation determination circuit 9 Maximum value selection circuit 10 Others Phase induction suppression amount setting circuit 11 Terminal current maximum value calculation circuit 30a, 30b, 30c Bus line 31a, 31b, 31c, 32a, 32b, 32c, 33a, 33b, 33c Lead line 34a, 34b, 34c, 35a, 35b, 35c, 36a, 36b, 36c Circuit breaker 37a, 37b, 37c, 38a, 38b, 38c, 39a, 39b, 39c CT (current transformer)
40a, 40b, 40c, 41a, 41b, 41c, 42a, 42b, 42c Cable 61, 62 Suppression amount correction arithmetic circuit (suppression amount calculation unit)
63 Suppression amount calculation unit 81, 82 CT induction suppression amount calculation circuit (induction suppression amount calculation unit)
83 Induction suppression amount calculation part α CT induction ratio (induction ratio)
I1 to In terminal current (phase current)
Id Differential current ID Operating amount IF Accident current IK Maximum effective value of each terminal current IR, IR1, KHM Suppression amount KH CT induction suppression amount (induction suppression amount)
K01 Minimum sensitivity setting value for small current range (operation sensitivity)
P, P1 constant ratio R slope of operating characteristics

Claims (6)

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,
Induction amount induced in the secondary side of the current transformer of the other phase due to the current flowing in the primary side of the current transformer of the own phase due to the interphase induction of the three-phase current transformer calculating a plurality of induction inhibiting amount by multiplying the constant ratio determined by the slope of the operating characteristic in the induction ratio and the ratio differential operation defined by the arrangement of the current transformer which constitutes the Table above 3-phase integral degree of current, Induction suppression amount calculation unit that outputs to the current differential protection relay of the other phase;
Based on the induction suppression amount output from the induction suppression amount calculation unit of the other phase and the suppression amount of the own phase, a suppression amount calculation unit that calculates the suppression amount used for the ratio differential calculation of the own phase;
A current differential protection relay comprising:   The suppression amount calculation unit calculates a maximum induction suppression amount among the suppression amount of the own phase and the induction suppression amount transmitted from the induction suppression amount calculation unit of the other two phases. The current differential protection relay according to claim 1, wherein the current differential protection relay is output as a suppression amount used for calculation.   The suppression amount calculation unit adds the larger one of the two induction suppression amounts transmitted from the other two-phase induction suppression amount calculation units to the suppression amount of the own phase, and after this addition The current differential protection relay according to claim 1, wherein the suppression amount is output as a suppression amount used for the ratio differential calculation of the own phase. 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,
The maximum effective value of the phase current of the self-phase current transformer, the current transformer of the other phase with the current flowing to the primary side of the current transformer of the self-phase due to the interphase induction of the three-phase current transformer of the constant ratio determined by the slope of the operating characteristics of a plurality of determined by the arrangement of the current transformer induction ratio and the ratio differential operation constituting the Table above 3-phase integral degree of induced currents induced in the secondary side An induction suppression amount calculation unit that multiplies to calculate the induction suppression amount and outputs to the current differential protection relay of the other phase;
Based on the induction suppression amount output from the induction suppression amount calculation unit of the other phase and the suppression amount of the own phase, a suppression amount calculation unit that calculates the suppression amount used for the ratio differential calculation of the own phase;
A current differential protection relay comprising:   The suppression amount calculation unit calculates a maximum induction suppression amount among the suppression amount of the own phase and the induction suppression amount transmitted from the induction suppression amount calculation unit of the other two phases. The current differential protection relay according to claim 4, wherein the current differential protection relay is output as a suppression amount used for calculation.   The suppression amount calculation unit adds the larger one of the two induction suppression amounts transmitted from the other two-phase induction suppression amount calculation units to the suppression amount of the own phase, and after this addition The current differential protection relay according to claim 4, wherein the suppression amount is output as a suppression amount used for the ratio differential calculation of the own phase.

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