JP2019165569A - Failure determination device and protective relay device - Google Patents

Abstract

To provide a failure determination device capable of detecting a failed phase with high precision.SOLUTION: The failure determination device includes: a voltage input section for receiving an input of each phase voltage of a three-phase power system; a first determination section for determining whether or not each phase voltage is less than a first threshold value; a second determination section for determining whether or not a variation in each line voltage calculated based on each phase voltage is less than a second threshold value; and a failed-phase determination section for determining a failed phase in the power system. When a phase voltage of a first one of three phases is less than a first threshold value and a variation in a line voltage between a second phase and a third phase of three phases is less than a second threshold value, the failed-phase determination section determines that a failure has occurred in the first phase.SELECTED DRAWING: Figure 7

Description

  The present disclosure relates to a failure determination device and a protective relay device.

  Conventionally, in order to operate a power system safely, various protective relays that detect a failure or abnormality occurring in the power system have been used. For example, an undervoltage relay is an example of a protective relay.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2001-16767) discloses a failure section determination device using a directional relay and an undervoltage relay. In this failure section determination device, it is considered to automatically detect a failure section when a ground fault or a short-circuit accident occurs inside the power transmission substation.

JP 2001-16767 A

  The fault section determination device according to Patent Document 1 detects a fault phase of a bus fault using an undervoltage relay. For example, FIG. 3 of Patent Document 1 describes the operation of an undervoltage relay used in a failure section determination device. According to this, it is described that when a one-wire ground fault (that is, one-phase failure) occurs, the phase voltage of the healthy phase hardly changes. Here, when the positive phase and zero phase impedances up to the failure point are equal, the phase voltage of the healthy phase does not change. However, in general, since the impedances of the positive phase and the zero phase up to the failure point are different, the phase voltage of the healthy phase often changes. Therefore, with the technology according to Patent Document 1, it may be difficult to detect a fault phase with high accuracy.

  An object of an aspect of the present disclosure is to provide a failure determination device and a protective relay device that can detect a failure phase with higher accuracy.

  A failure determination apparatus according to an embodiment includes a voltage input unit that receives an input of each phase voltage of a three-phase power system, and a first determination that determines whether the phase voltage is less than a first threshold for each phase voltage. A second determination unit that determines whether or not the amount of change in the line voltage is less than a second threshold for each line voltage calculated based on each phase voltage, and a failure phase of the power system A failure phase determination unit. A failure occurs when the phase voltage of the first phase of the three phases is less than the first threshold and the amount of change in the line voltage between the second phase and the third phase of the three phases is less than the second threshold. The phase determination unit determines that a failure has occurred in the first phase.

  According to another embodiment, a protective relay device is provided for protecting a bus of a three-phase power system. The protective relay device is based on a voltage input unit that receives an input of each phase voltage of the bus, a first determination unit that determines whether the phase voltage is less than a first threshold for each phase voltage, and each phase voltage A second determination unit that determines whether or not the amount of change in the line voltage is less than a second threshold, a failure phase determination unit that determines a failure phase of the power system, and a bus Differential relay operation unit for detecting a fault in the bus by a predetermined differential operation based on each phase current of the current and each phase current of a plurality of lines branched from the bus, and a cutoff provided in the power system And an output control unit that outputs a shut-off command to the device. A failure occurs when the phase voltage of the first phase of the three phases is less than the first threshold and the amount of change in the line voltage between the second phase and the third phase of the three phases is less than the second threshold. The phase determination unit outputs a first signal indicating that a failure has occurred in the first phase. The output control unit outputs each of the three phases when the first signal is output from the failure phase determination unit and the second signal indicating that a failure in the bus is detected by the differential relay calculation unit. Outputs a command to cut off the flowing current.

  According to the present disclosure, a failure phase can be detected with higher accuracy.

It is a figure which shows the electric power grid | system to which the protective relay apparatus according to Embodiment 1 is applied. It is a figure which shows the equivalent circuit at the time of 1 phase failure by a symmetrical coordinate method. FIG. 6 is a vector diagram showing a relationship between phase voltages at the time of one-phase failure according to the first embodiment. It is a vector diagram which shows the relationship of each phase voltage at the time of the two-phase short circuit failure according to Embodiment 1. 6 is a diagram for illustrating a failure phase determination method according to the first embodiment. FIG. FIG. 3 is a diagram showing an example of a hardware configuration of a protective relay device according to the first embodiment. It is a block diagram which shows an example of a function structure of the protection relay apparatus according to Embodiment 1. FIG. FIG. 10 is a vector diagram showing the relationship of each phase voltage at the time of one-phase failure according to the second embodiment. It is a vector diagram which shows the relationship of each phase voltage at the time of the two-phase short circuit failure according to Embodiment 2. FIG. 10 is a diagram for describing a failure phase determination method according to a second embodiment. It is a block diagram which shows an example of a function structure of the protection relay apparatus according to Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

Embodiment 1 FIG.
<Overall configuration>
FIG. 1 is a diagram showing a power system to which a protective relay device 100 according to the first embodiment is applied. Referring to FIG. 1, the electric power system according to the first embodiment includes three phases (for example, A phase, B phase, and C phase) including bus 6 and a plurality of lines (for example, feeder lines) branched from bus 6. ). FIG. 1 shows an example in which lines L1 to L4 are provided as a plurality of lines. Typically, the neutral point grounding system of the power system according to the first embodiment is a direct grounding system.

  A power source 2 behind the bus 6 is connected to the line L1 via the transformer 4. The back power supply 2 is, for example, a generator. Further, a load, a power transmission line, and the like are connected to the lines L2 to L4. The transformer 4 is connected between the load and the back power source 2 and transforms the high voltage power from the back power source 2 into low voltage power that can be used by the consumer.

  Circuit breakers 21 to 24 are inserted into the lines L1 to L4, respectively. Information on the open / closed states of the circuit breakers 21 to 24 is taken into the protective relay device 100 via an interface unit (not shown).

  The lines L1 to L4 are provided with current transformers (CT) 31 to 34. An air core transformer may be provided instead of the current transformer. Information on the value of the current flowing through the lines L <b> 1 to L <b> 4 detected by the current transformers 31 to 34 is taken into the protective relay device 100. Specifically, the current transformers 31 to 34 output the phase currents of the lines L1 to L4, respectively.

  The bus 6 is provided with a voltage transformer (VT) 8. The voltage transformer 8 detects each phase voltage of the bus 6 and outputs it to the protective relay device 100. Specifically, the voltage transformer 8 outputs phase voltages Va, Vb, and Vc of the A phase, B phase, and C phase of the bus 6.

  The protective relay device 100 is a digital protective relay device for protecting the bus 6 of the power system. The protective relay device 100 includes a failure determination unit 10, a differential relay calculation unit 12, and an output control unit 14.

  The failure determination unit 10 determines a failure phase when a failure occurs inside the bus 6 based on the voltage value of the bus 6 detected by the voltage transformer 8. The differential relay operation unit 12 determines whether or not a failure has occurred inside the bus 6 based on the current value of each line detected by the current transformers 31 to 34.

  The output control unit 14 calculates the logical product of the determination result of the failure determination unit 10 and the determination result of the differential relay operation unit 12, and outputs an open command to the circuit breakers 21 to 24 based on the calculation result.

  Here, problems and the like in the related art will be described for understanding the present embodiment. The current differential protection relay according to the related technology uses the current detected by the CT provided in each line connected to the protection target (for example, bus) of the power system to detect internal and external failures in the protection target section. In the case of an internal failure, an open command is output to a circuit breaker provided in the protection section in order to disconnect the protection target section from the power system.

  In such a current differential protection relay, when there is an interphase induction of CT, a one-phase fault occurs outside the bus 6 (for example, outside the current transformer 32 provided on the line L2 as viewed from the bus 6). When a large current flows in the failure phase, there is a possibility that a current not in the primary side of the CT flows in the secondary side of the CT even in the healthy phase CT that is not the failure phase. In addition, for the induction between CTs of each phase, three-phase CT should be arranged so that it does not occur basically. However, in order to reduce the size of the substation equipment, the three-phase integrated CT is adopted. Alternatively, depending on the configuration of GIS (Gas Insulated substation), induction may be likely to occur because the distance between CTs of each phase is close.

  For example, a case where an external failure occurs in the protection target section is assumed. In this case, even if there is a difference current (that is, an operation amount) due to an error current such as CT saturation due to the failure current, the failure phase ratio differential element does not operate because a large suppression amount can be expected. However, in the healthy phase ratio differential element, when the current due to the induction between the CTs is generated only in one set of CTs, the induced current becomes a difference current and a suppression amount is also generated. In this case, when a large difference current that falls within the operating range of the current differential protection relay occurs, the healthy phase ratio differential element malfunctions.

  Therefore, in the present embodiment, an opening command is output to the circuit breakers 21 to 24 based on the determination result by the failure determination unit 10 and the determination result of the differential relay operation unit 12. Failure determination unit 10 according to the present embodiment can determine not only the presence / absence of failure of bus 6 but also the failure phase of bus 6 with high accuracy. Therefore, even if the differential relay operation unit 12 makes an erroneous determination in a phase other than the failure phase due to induction between the respective phase CTs due to an external failure, the determination to the circuit breakers 21 to 24 depends on the determination result of the failure determination unit 10. The output of the opening command (that is, malfunction of the protective relay device 100) can be prevented.

<Failure phase judgment method>
Next, the failure phase determination method will be described. It is assumed that the neutral point grounding method of the power system is a direct grounding method.

(Single phase failure)
FIG. 2 is a diagram showing an equivalent circuit at the time of one-phase failure by the symmetric coordinate method. Here, a case where a one-phase ground fault of the A phase of the bus 6 occurs will be described.

  Referring to FIG. 2, Ea, Z1, Z2, and Z0 represent a power supply voltage, a positive phase impedance, a negative phase impedance, and a zero phase impedance, respectively. V1, V2, V0, and I0 represent a positive phase voltage, a negative phase voltage, a zero phase voltage, and a zero phase current, respectively.

  The relationship between the symmetric coordinate component and each phase voltage of the bus 6 is expressed by the following equation (1). Here, Va, Vb, and Vc are the respective phase voltages detected by the voltage transformer 8 at the time of the A-phase ground fault, and Va0, Vb0, and Vc0 are voltages before the A-phase ground fault if the load current is ignored. This corresponds to each phase voltage detected by the transformer 8. “A” is a vector operator.

  A method for deriving the B-phase voltage Vb shown in Expression (1) will be described. Here, from FIG. 2, since I0 = Ea / (Z1 + Z2 + Z0), V1 = Ea−Z1 × I0, V2 = −Z2 × I0, and V0 = −Z0 × I0, the voltage Vb is expressed by the following equation (2). It is expressed as

In Expression (2), “a ² Ea” represents a phase rotation of “a ² = 240 °”, and therefore “a ² Ea” represents a B-phase voltage Vb 0 that is 120 ° before the A-phase. In general, since Z1 = Z2, the following expression (3) is derived.

Furthermore, “(a ² + a)” in Expression (3) can be expanded as shown in Expression (4).

  Therefore, substituting equation (4) into equation (3) leads to the following equation (5).

  Similarly, the C-phase voltage Vc is represented by the following formula (6).

  Since the B-phase voltage Vb and the C-phase voltage Vc at the time of the A-phase ground fault are expressed by the above-described equations (5) and (6), the relationship between the phase voltages Va, Vb, and Vc is shown in FIG. It is expressed as 3.

  FIG. 3 is a vector diagram showing the relationship between the phase voltages at the time of one-phase failure according to the first embodiment. Referring to FIG. 3, the A phase voltage changes from Va0 to Va before and after the failure, and the phase voltages of B phase and C phase, which are healthy phases, also change. Specifically, since the positive phase impedance is different from the zero phase impedance, (Z0-Z1) does not become zero. Therefore, the B phase voltage changes from Vb0 to Vb before and after the failure, and the C phase voltage changes from Vc0 to Vc before and after the failure.

  However, the line voltage between the B phase and the C phase, which are healthy phases, does not change before and after the failure. That is, the line voltage Vbc0 before the A-phase failure is almost the same as the line voltage Vbc after the A-phase failure, and the line voltage change amount ΔVbc is almost zero.

  Thus, in the case of a one-phase failure, the voltage of the failure phase is greatly reduced, and the two-phase line voltage that is a healthy phase does not change. Therefore, for example, the magnitude of the A-phase voltage Va (that is, | Va |) is less than the threshold value K1G (for example, about 70% to 80% of the rated phase voltage), and the line voltage Vbc between the BC phases is If the magnitude change amount (ie, Δ | Vbc |) is less than a threshold K2G (eg, about 5% of the rated line voltage), an A-phase fault (ie, a single-phase fault of A phase) occurs. Can be determined. Δ | V | is a vector of the amount of change in the magnitude of the voltage V.

(Two-phase failure)
FIG. 4 is a vector diagram showing the relationship between the phase voltages at the time of a two-phase short circuit failure according to the first embodiment. Here, a short-circuit fault in the BC phase is assumed. Referring to FIG. 4, at the time of BC phase failure, the phase voltages of B phase and C phase, which are faulty phases, are reduced, but the phase voltage of A phase, which is a healthy phase, does not change before and after the failure ( That is, Va0 = Va). Further, the line voltages Vab, Vbc, Vca between the two phases (that is, between the AB phase, the BC phase, and the CA phase) are decreased.

  Thus, in the case of a two-phase failure, the voltage of the healthy phase does not change, and the line voltage between the two phases changes. Therefore, for example, the magnitude of the line voltage Vbc between the BC phases (that is, | Vbc |) is less than a threshold value K1S (for example, about 70% to 80% of the rated line voltage), and the A-phase voltage Va Is smaller than a threshold K2S (for example, about 5% of the rated phase voltage), a BC phase failure (that is, a B-phase and C-phase two-phase failure) ) Has occurred.

(3-phase failure)
When a three-phase failure occurs, all of the three-phase voltages and the line voltages between the two phases change. Therefore, for example, the change amount of each phase voltage is larger than the threshold value K3G (for example, about 5% of the rated phase voltage), and the change amount of each line voltage is the threshold value K3S (for example, about 5% of the rated line voltage). If it is larger than that, it can be determined that a three-phase failure has occurred.

  In addition, the system voltage at the time of healthy changes according to a load condition. Therefore, there are cases where the transformer 4 is a transformer with a tap that can adjust the voltage to be as close to the rated voltage as possible by voltage ratio operation, but in general, there are many cases where the voltage is higher or lower than the rated voltage. In this case, the threshold values K1G, K2S, and K3G may be set using “phase voltage before failure”, and the threshold values K2G, K1S, and K3S may be set using “line voltage before failure”. May be. When the pre-failure voltage is 100%, the threshold values K1G and K1S can be set to 90% of the pre-failure voltage, for example, and a more sensitive determination is possible.

(Summary)
FIG. 5 is a diagram for explaining a failure phase determination method according to the first embodiment. Referring to FIG. 5, failure determination unit 10 includes determination circuits 101-118, AND gates 131-137, and OR gates 141-143.

  If it is determined that | Va | <K1G is satisfied, the determination circuit 101 outputs the output value “1” to the AND gate 131; otherwise, the determination circuit 101 outputs the output value “0” to the AND gate. It outputs to 131. The operations of the determination circuits 103 and 105 regarding | Vb | and | Vc | are the same.

  If the determination circuit 102 determines that Δ | Vbc | <K2G is satisfied, the determination circuit 102 outputs the output value “1” to the AND gate 131, and if not, outputs the output value “0” to the AND gate 131. Output to the gate 131. The operations of the determination circuits 104 and 106 regarding Δ | Vca | and Δ | Vab | are the same.

  The AND gate 131 performs an AND operation on the output value of the determination circuit 101 and the output value of the determination circuit 102. Specifically, when | Va | <K1G and Δ | Vbc | <K2G are satisfied (that is, when the output values of the determination circuits 101 and 102 are “1”), the AND gate 131 has a one-phase fault in the A phase. Is output to the OR gate 141 (ie, the output value “1”). Otherwise, the AND gate 131 outputs the output value “0” to the OR gate 141.

  When satisfying | Vb | <K1G and Δ | Vca | <K2G, the AND gate 132 outputs a signal indicating a one-phase failure of the B phase (that is, an output value “1”) to the OR gate 142. When satisfying | Vc | <K1G and Δ | Vab | <K2G, the AND gate 133 outputs a signal indicating a C-phase one-phase failure (that is, an output value “1”) to the OR gate 143.

  If it is determined that | Vab | <K1S is satisfied, the determination circuit 107 outputs the output value “1” to the AND gate 134, and if it is not, the determination circuit 107 outputs the output value “0” to the AND gate. It outputs to 134. The operations of the determination circuits 109 and 111 regarding | Vbc | and | Vca | are the same.

  If it is determined that Δ | Vc | <K2S is satisfied, the determination circuit 108 outputs the output value “1” to the AND gate 134, and if it is not, the determination circuit 108 ANDs the output value “0”. Output to the gate 134. The operations of the determination circuits 110 and 112 regarding Δ | Va | and Δ | Vb | are the same.

  The AND gate 134 performs an AND operation on the output value of the determination circuit 107 and the output value of the determination circuit 108. Specifically, when | Vab | <K1S and Δ | Vc | <K2S are satisfied (that is, when the output values of the determination circuits 107 and 108 are “1”), the AND gate 134 has a two-phase fault in the AB phase. Is output to the OR gates 141 and 142 (that is, the output value “1”).

  When satisfying | Vbc | <K1S and Δ | Va | <K2S, the AND gate 135 outputs a signal indicating a two-phase failure in the BC phase (that is, an output value “1”) to the OR gates 142 and 143. When AND gate 136 satisfies | Vca | <K1S and Δ | Vb | <K2S, the AND gate 136 outputs a signal indicating a two-phase failure of the CA phase (ie, output value “1”) to the OR gates 141 and 143.

  If the determination circuit 113 determines that Δ | Va |> K3G is satisfied, the determination circuit 113 outputs the output value “1” to the AND gate 137, and if not, outputs the output value “0” to the AND gate 137. Output to the gate 137. The operations of the determination circuits 114 and 115 regarding Δ | Vb | and Δ | Vc | are the same.

  If the determination circuit 116 determines that Δ | Vab |> K3S is satisfied, the determination circuit 116 outputs the output value “1” to the AND gate 137, and otherwise determines that the output value “0” is AND. Output to the gate 137. The operations of the determination circuits 117 and 118 regarding Δ | Vbc | and Δ | Vca | are the same.

  The AND gate 137 outputs a signal indicating a three-phase failure (that is, the output value “1”) to the OR gates 141, 142, and 143 when all the output values of the determination circuits 113 to 118 are “1”. .

  The OR gate 141 performs an OR operation on the output values of the AND gates 131, 134, 136, and 137. Specifically, when at least one of these output values is “1”, the OR gate 141 outputs a signal indicating that a failure has occurred in the A phase.

  The OR gate 142 outputs a signal indicating that a failure has occurred in the B phase when at least one of the output values of the AND gates 132, 134, 135, and 137 is "1". If at least one of the output values of the AND gates 133, 135, 136, and 137 is “1”, the OR gate 143 outputs a signal indicating that a failure has occurred in the C phase.

<Hardware configuration>
FIG. 6 is a diagram showing an example of a hardware configuration of protection relay device 100 according to the first embodiment. Referring to FIG. 6, protection relay device 100 includes an auxiliary transformer 51, an AD (Analog to Digital) conversion unit 52, and an arithmetic processing unit 70.

  The auxiliary transformer 51 takes in the amount of electricity from each detector, converts it into a voltage suitable for the relay internal circuit, and outputs it. The AD converter 52 takes in the voltage output from the auxiliary transformer 51 and converts it into digital data. Specifically, the AD conversion unit 52 includes an analog filter, a sample and hold circuit, a multiplexer, and an AD converter.

  The analog filter removes high-frequency noise components from the current and voltage waveform signals output from the auxiliary transformer 51. The sample-and-hold circuit samples the current and voltage waveform signals output from the analog filter at a predetermined sampling period. Based on the timing signal input from the arithmetic processing unit 70, the multiplexer sequentially switches the waveform signal input from the sample hold circuit in time series and inputs the waveform signal to the AD converter. The AD converter converts the waveform signal input from the multiplexer from analog data to digital data. The AD converter outputs the digitally converted waveform signal (digital data) to the arithmetic processing unit 70.

  The arithmetic processing unit 70 includes a CPU (Central Processing Unit) 72, a ROM 73, a RAM 74, a DI (digital input) circuit 75, a DO (digital output) circuit 76, an input interface (I / F) 77, and communication. And an interface (I / F) 78. These are connected by a bus 71.

  The CPU 72 controls the operation of the protective relay device 100 by reading and executing a program stored in the ROM 73 in advance. The ROM 73 stores various information used by the CPU 72. The CPU 72 is, for example, a microprocessor. The hardware may be an FPGA (Field Programmable Gate Array) other than the CPU, an ASIC (Application Specific Integrated Circuit), a circuit having other arithmetic functions, or the like.

  The CPU 72 takes in digital data from the AD conversion unit 52 via the bus 71. The CPU 72 executes control calculation using the acquired digital data according to the program stored in the ROM 73.

  The CPU 72 outputs a control command to an external device via the DO circuit 76 based on the control calculation result. Further, the CPU 72 receives a response to the control command via the DI circuit 75. The input interface 77 is typically various buttons or the like, and accepts various setting operations from the system operator. Further, the CPU 72 transmits / receives various information to / from other devices via the communication interface 78.

<Functional configuration>
FIG. 7 is a block diagram showing an example of a functional configuration of the protective relay device 100 according to the first embodiment. Referring to FIG. 7, protective relay device 100 includes a failure determination unit 10, a differential relay calculation unit 12, and an output control unit 14 as main functional configurations. Each of these functions is realized, for example, when the microprocessor of the protective relay device 100 executes a program stored in the memory. Note that some or all of these functions may be implemented by hardware.

  Failure determination unit 10 includes a voltage input unit 201, a line voltage change amount calculation unit 203, a phase voltage change amount calculation unit 205, determination units 211 to 216, and a failure phase determination unit 220.

  Voltage input unit 201 accepts input of phase voltages Va to Vc of bus 6 output from voltage transformer 8.

  The line voltage change amount calculation unit 203 includes a change amount ΔVab of the line voltage Vab between the A phase and the B phase, a change amount ΔVbc of the line voltage Vbc between the B phase and the C phase, and a line interval between the C phase and the A phase. A change amount ΔVca of the voltage Vca is calculated. For example, the change amount of the line voltage is calculated by subtracting the line voltage several cycles (for example, 1 to 2 cycles) before the current line voltage.

  The phase voltage change amount calculation unit 205 calculates a change amount ΔVa of the A phase voltage Va, a change amount ΔVb of the B phase voltage Vb, and a change amount ΔVc of the C phase voltage Vc. For example, the change amount of the phase voltage is calculated by subtracting the phase voltage several cycles (for example, 1 to 2 cycles) before the current phase voltage.

  The determination unit 211 determines, for each phase voltage Va, Vb, Vc, whether the phase voltage is less than the threshold value K1G. Specifically, the determination unit 211 corresponds to the determination circuits 101, 103, and 105 shown in FIG.

  The determination unit 212 determines, for each line voltage Vab, Vbc, Vca, whether the change amount of the line voltage is less than the threshold value K2G. Specifically, the determination unit 212 corresponds to the determination circuits 102, 104, and 106 shown in FIG.

  The determination unit 213 determines, for each line voltage Vab, Vbc, Vca, whether the line voltage is less than the threshold value K1S. Specifically, the determination unit 213 corresponds to the determination circuits 107, 109, and 111 illustrated in FIG.

  The determination unit 214 determines, for each phase voltage Va, Vb, Vc, whether the change amount of the phase voltage is less than the threshold value K2S. Specifically, the determination unit 214 corresponds to the determination circuits 108, 110, and 112 shown in FIG.

  The determination unit 215 determines, for each phase voltage Va, Vb, Vc, whether the change amount of the phase voltage is larger than the threshold value K3G. Specifically, the determination unit 215 corresponds to the determination circuits 113 to 115 illustrated in FIG.

  The determination unit 216 determines, for each line voltage Vab, Vbc, Vca, whether or not the amount of change in the line voltage is greater than the threshold value K3S. Specifically, the determination unit 216 corresponds to the determination circuits 116 to 118 illustrated in FIG.

  The failure phase determination unit 220 determines the failure phase of the power system (for example, the failure phase of the bus 6) based on the determination results of the determination units 211 to 216. Here, for the determination by the failure phase determination unit 220, a change amount obtained by subtracting the phase voltage several cycles before from the current phase voltage is used. The failure phase determination unit 220 outputs a signal indicating the determination result for a period longer than several cycle periods. For example, the failure phase determination unit 220 is configured to output a signal indicating the determination result for a predetermined time T (for example, a time required for external failure removal) or more using a return timer.

  In one aspect, the phase voltage of the first phase (for example, the A phase) of the three phases is less than the threshold K1G, and the second phase (for example, the B phase) and the third phase (for example, of the three phases) , C phase) is smaller than the threshold value K2G, the failure phase determination unit 220 determines that a failure has occurred in the first phase, and outputs a signal indicating the determination result. In this case, the failure phase determination unit 220 corresponds to the AND gates 131 to 133 and the return timer.

  In another aspect, the line voltage between the first phase (eg, A phase) and the second phase (eg, B phase) is less than the threshold K1S, and the phase voltage of the third phase (eg, C phase) When the amount of change in is less than the threshold value K2S, the failure phase determination unit 220 determines that a failure has occurred in the first phase and the second phase, and outputs a signal indicating the determination result. In this case, the failure phase determination unit 220 corresponds to the AND gates 134 to 136 and the return timer.

  In yet another aspect, when the amount of change in each phase voltage is greater than threshold value K3G and the amount of change in each line voltage is greater than threshold value K3S, failure phase determination unit 220 determines that a failure has occurred in all three phases. Then, a signal indicating the determination result is output. In this case, the failure phase determination unit 220 corresponds to the AND gate 137 and the return timer.

  The differential relay operation unit 12 detects a failure in the bus 6 by a predetermined differential operation based on each phase current of the bus 6 and each phase current of the lines L1 to L4. Specifically, the differential relay calculation unit 12 includes a current input unit 250, a differential current calculation unit 252, a suppression current calculation unit 254, and a differential determination unit 256.

  The differential current calculation unit 252 calculates a vector sum of the currents I1 to I4 of the lines L1 to L4 detected by the current transformers 31 to 34, and outputs the magnitude of the calculated vector sum as a differential current ID. .

  The suppression current calculation unit 254 outputs the largest current I1 to I4 of the lines L1 to L4 detected by the current transformers 31 to 34. Instead of the maximum value suppression method, a scalar sum suppression method may be used. That is, the detected scalar sum of the currents I1 to I4 of the lines L1 to L4 may be used as the suppression current IR.

  The differential determination unit 256 determines whether or not the relationship between the suppression current IR and the differential current ID satisfies a predetermined relationship. Specifically, the differential determination unit 256 multiplies the suppression current IR by a constant α and determines whether or not the differential current ID is larger than a value obtained by adding the constant β, that is, the following expression (7) is established. It is determined whether or not to do.

ID> α · IR + β (7)
Note that the differential determination unit 256 may perform determination using only the differential current ID without using the suppression current IR. Specifically, the differential determination unit 256 determines whether or not the differential current ID is larger than the threshold value IP, that is, whether or not the following formula (8) is satisfied.

ID> IP (8)
The differential determination unit 256 outputs a signal indicating the determination result to the output control unit 14.

  The output control unit 14 outputs an opening command for opening the circuit breakers 21 to 24 based on the determination result of the failure phase by the failure determination unit 10 and the determination result by the differential relay operation unit 12.

  For example, a determination result indicating that the failure phase is the first phase is output by the failure phase determination unit 220, and the above formula (7) or (8) is established for the first phase by the differential relay operation unit 12. Is output (that is, the result of detecting the failure of the first phase), the output control unit 14 outputs a command for interrupting the current flowing through the first phase.

  Specifically, since the protective relay device 100 targets the bus 6 as a protection target, the output control unit 14 breaks down the current that flows in each of the three phases as well as the first phase, which is a faulty phase. An open command is output to 21-24. That is, the output control unit 14 outputs an opening command to the circuit breakers 21 to 24 provided in each phase.

<Advantages>
According to the first embodiment, the failure phase is determined in consideration of not only the magnitude of the phase voltage and the line voltage but also the magnitude of the change amount, so the failure phase determination of the one-phase failure and the two-phase failure is more accurate. Can perform well. Therefore, even in the case of a ground fault with a high fault point impedance such as an arc fault, the fault phase can be determined with high sensitivity. In addition, since the failure phase can be determined with high accuracy, it is possible to prevent malfunction due to induction between the CTs of the protective relay device, and a highly reliable protection system can be configured.

Embodiment 2. FIG.
In the second embodiment, a failure phase determination method different from that in the first embodiment will be described. <Overall configuration> and <hardware configuration> are the same as those in the first embodiment, and thus detailed description thereof will not be repeated. Note that the neutral point grounding system of the power system is a direct grounding system.

<Failure phase judgment method>
(Single phase failure)
From the equations (5) and (6) described above, the relationship with the voltages Va, Vb, Vc at the time of the A-phase ground fault is expressed as shown in FIG.

  FIG. 8 is a vector diagram showing the relationship between the phase voltages at the time of one-phase failure according to the second embodiment. Referring to FIG. 8, before and after the A phase failure, the line voltage of the AB phase and the CA phase including the failure phase has changed, but the line voltage of the BC phase that is a healthy phase has not changed. That is, the AB phase line voltage variation ΔVab and the CA phase line voltage variation ΔVca are equal to or greater than a certain value, and the BC phase line voltage variation ΔVbc is substantially zero.

  By utilizing this, for example, when Δ | Vbc | is less than the threshold value K2G and Δ | Vca | and Δ | Vab | are equal to or greater than the threshold value K2G, it can be determined that a one-phase failure of the A phase has occurred.

(Two-phase failure)
FIG. 9 is a vector diagram showing the relationship between the phase voltages at the time of a two-phase short-circuit failure according to the second embodiment. Here, B-phase and C-phase short-circuit faults are assumed. Referring to FIG. 9, before and after the BC phase failure, the phase voltages of the B phase and the C phase that are the failure phases have changed, but the phase voltage of the A phase that is the healthy phase has not changed. That is, the change amount ΔVb of the B phase voltage and the change amount ΔVc of the C phase voltage are equal to or greater than a certain value, and the change amount ΔVa of the A phase voltage is substantially zero.

  Using this, for example, when Δ | Va | is less than the threshold value K2S and Δ | Vb | and Δ | Vc | are equal to or greater than the threshold value K2S, it can be determined that a BC-phase two-phase failure has occurred.

(3-phase failure)
The determination method of the three-phase failure is the same as the determination method of the first embodiment.

(Summary)
FIG. 10 is a diagram for explaining a failure phase determination method according to the second embodiment. Referring to FIG. 10, failure determination unit 10 according to the second embodiment includes determination circuits 102, 104, 106, 108, 110, 112, 113 to 118, AND gates 137, 151 to 156, and OR gates 161 to 161. 163. The operations of the determination circuits 102, 104, 106, 108, 110, 112, 113 to 118 and the operation of the AND gate 137 are the same as those described with reference to FIG.

  The AND gate 151 performs an AND operation on the output value of the determination circuit 102, the value obtained by inverting the logical level of the output of the determination circuit 104, and the value obtained by inverting the logical level of the output of the determination circuit 106. Specifically, Δ | Vbc | <K2G is satisfied, Δ | Vca | <K2G is not satisfied (that is, Δ | Vca | ≧ K2G is satisfied), and Δ | Vab | <K2G is not satisfied (that is, Δ | When Vab | ≧ K2G is satisfied), the AND gate 151 outputs a signal indicating the one-phase failure of the A phase (that is, the output value “1”) to the OR gate 161.

  The AND gate 152 satisfies the condition Δ | Vca | <K2G, and does not satisfy Δ | Vbc | <K2G and Δ | Vab | <K2G, a signal indicating a B-phase one-phase failure (ie, an output value “1”) ) Is output to the OR gate 162. The AND gate 153 satisfies the condition Δ | Vab | <K2G, and does not satisfy Δ | Vbc | <K2G and Δ | Vca | <K2G, the signal indicating the C-phase one-phase failure (ie, the output value “1”) ) Is output to the OR gate 163.

  The AND gate 154 performs an AND operation on the output value of the determination circuit 108, the value obtained by inverting the logical level of the output of the determination circuit 110, and the value obtained by inverting the logical level of the output of the determination circuit 112. Specifically, Δ | Vc | <K2S is satisfied, Δ | Va | <K2S is not satisfied (that is, Δ | Va | ≧ K2S is satisfied), and Δ | Vb | <K2G is not satisfied (that is, Δ | When Vb | ≧ K2S is satisfied), the AND gate 154 outputs a signal indicating the AB phase two-phase failure (that is, the output value “1”) to the OR gates 161 and 162.

  The AND gate 155 satisfies the condition Δ | Vc | <K2S, and when Δ | Va | <K2S and Δ | Vc | <K2S are not satisfied, the signal indicating the two-phase failure of the BC phase (that is, the output value “1”) ) Is output to the OR gates 162 and 163. The AND gate 156 satisfies the condition Δ | Vb | <K2S, and does not satisfy Δ | Vc | <K2S and Δ | Va | <K2S, a signal indicating a CA-phase two-phase failure (ie, an output value “1”) ) Is output to the OR gates 161 and 163.

  The OR gate 161 performs an OR operation on the output values of the AND gates 151, 154, 156 and 137. Specifically, when at least one of these output values is “1”, the OR gate 161 outputs a signal indicating that a failure has occurred in the A phase.

  When at least one of the output values of the AND gates 152, 154, 155, 137 is “1”, the OR gate 162 outputs a signal indicating that a failure has occurred in the B phase. If at least one of the output values of the AND gates 153, 155, 156, and 137 is “1”, the OR gate 163 outputs a signal indicating that a failure has occurred in the C phase.

<Functional configuration>
FIG. 11 is a block diagram showing an example of a functional configuration of protective relay device 100A according to the second embodiment. Referring to FIG. 11, protection relay device 100A includes a failure determination unit 10A, a differential relay operation unit 12, and an output control unit 14 as main functional configurations. The functions of differential relay operation unit 12 and output control unit 14 are the same as those described with reference to FIG. 7, and therefore detailed description thereof will not be repeated.

  Failure determination unit 10A includes voltage input unit 201, line voltage change amount calculation unit 203, phase voltage change amount calculation unit 205, determination units 215 and 216, change amount determination units 271 and 272, and failure phase determination. Part 220A. The functions of the voltage input unit 201, the line voltage change amount calculation unit 203, the phase voltage change amount calculation unit 205, and the determination units 215 and 216 are the same as those described with reference to FIG. Detailed description will not be repeated.

  For each of the change amount ΔVab of the line voltage Vab, the change amount ΔVbc of the line voltage Vbc, and the change amount ΔVca of the line voltage Vca, the change amount determination unit 271 determines whether or not the change amount is less than K2G. judge. Specifically, the change amount determination unit 271 corresponds to the determination circuits 102, 104, and 106 illustrated in FIG. In other words, the change amount determination unit 271 has substantially the same function as the determination unit 212 illustrated in FIG.

  The change amount determination unit 272 determines, for each of the change amount ΔVa of the phase voltage Va, the change amount ΔVb of the phase voltage Vb, and the change amount ΔVc of the phase voltage Vc, whether the change amount is less than K2S. Specifically, the change amount determination unit 272 corresponds to the determination circuits 108, 110, and 112 shown in FIG. In other words, the change amount determination unit 272 has substantially the same function as the determination unit 214 illustrated in FIG.

  The failure phase determination unit 220A determines the failure phase of the power system based on the determination results of the determination units 215 and 216 and the change amount determination units 271 and 272, and outputs a signal indicating the determination result for time T or more. In one aspect, the amount of change in the line voltage between the first phase (eg, A phase) and the second phase (eg, B phase), and the line voltage between the third phase (eg, C phase) and the first phase. Is greater than or equal to the threshold value K2G, and the amount of change in the line voltage between the second phase and the third phase is less than the threshold value K2G, the failure phase determination unit 220 determines that a failure has occurred in the first phase. Determination is made and a signal indicating the determination result is output. In this case, the failure phase determination unit 220A corresponds to the AND gates 151 to 153 and the return timer.

  In another aspect, the change amount of the phase voltage of the first phase (for example, the A phase) and the change amount of the phase voltage of the second phase (for example, the B phase) are equal to or greater than the threshold value K2S, and the third phase (for example, , C phase) when the amount of change in the phase voltage is less than the threshold K2S, the failure determination unit 10A determines that a failure has occurred in the first phase and the second phase, and outputs a signal indicating the determination result . In this case, the failure phase determination unit 220 corresponds to the AND gates 154 to 156 and the return timer.

  In yet another aspect, when the amount of change in each phase voltage is greater than threshold K3G and the amount of change in each line voltage is greater than threshold K3S, failure phase determination unit 220A determines that a failure has occurred in all three phases. Then, a signal indicating the determination result is output. In this case, the failure phase determination unit 220A corresponds to the AND gate 137 and the return timer.

<Advantages>
According to the second embodiment, the failure phase determination unit can be constructed with simple logic. Other advantages are the same as those of the first embodiment.

Other embodiments.
(1) In the above-described embodiment, the configuration in which the protective relay device includes the failure determination unit, the differential relay calculation unit, and the output control unit is described, but the configuration is not limited thereto. For example, the above-described failure determination device having the function of the failure determination unit is provided separately, and the protection relay device is realized by combining the failure determination device with a device having a differential relay operation unit and an output control unit. It may be configured to. In this case, the hardware configuration of the failure determination apparatus may be the same as the hardware configuration illustrated in FIG.

  (2) In the above-described embodiment, the configuration in which the failure determination unit determines a bus failure has been described, but the configuration is not limited thereto. For example, when the protective relay device targets a transmission line as a protection target, the failure determination unit may be configured to determine a failure of the transmission line. Further, when the failure phase is the first phase, the output control unit may output an opening command to the circuit breakers 21 to 24 provided in the first phase, or the current flowing through each of the three phases. An open command may be output to the circuit breakers 21 to 24 in order to shut off. It is arbitrarily determined by the system operator whether to cut off only the current flowing in the failure phase or to cut off all the current flowing in the failure phase and the healthy phase.

  (3) In the embodiment described above, the failure determination unit performs the three-phase failure based on the comparison result of the change amount of each phase voltage and the threshold value K3G, and the comparison result of the change amount of each line voltage and the threshold value K3S. Although the configuration for determination has been described, the configuration is not limited thereto. For example, the failure determination unit may be configured to determine a three-phase failure based on a comparison result of each phase voltage and threshold K1G and a comparison result of each line voltage and threshold K1S.

  In this case, instead of the determination circuit 113, a determination circuit that outputs an output value “1” when | Va | <K1G is satisfied and outputs an output value “0” otherwise is used. Similarly, an alternative determination circuit is used for the determination circuits 114 and 115. Instead of the determination circuit 116, a determination circuit that outputs an output value “1” when | Vab | <K1S is satisfied and outputs an output value “0” otherwise is used. Similarly, an alternative determination circuit is used for the determination circuits 117 and 118.

  (4) The configuration exemplified as the above-described embodiment is an example of the configuration of the present invention, and can be combined with another known technique, and a part thereof does not depart from the gist of the present invention. It is also possible to change and configure such as omitting.

  In the above-described embodiment, the process and configuration described in the other embodiments may be adopted as appropriate.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  2 Back power supply, 4 Transformer, 6 Bus, 8 Voltage transformer, 10, 10A Fault determination unit, 12 Differential relay operation unit, 14 Output control unit, 21-24 Breaker, 31-34 Current transformer, 51 Auxiliary transformer, 52 AD converter, 70 arithmetic processing unit, 71 bus, 72 CPU, 73 ROM, 74 RAM, 75 DI circuit, 76 DO circuit, 77 input interface, 78 communication interface, 100, 100A protective relay device, 101-118 determination circuit, 131-137, 151-156 AND gate, 141-143, 161-163 OR gate, 201 voltage input unit, 203 line voltage change amount calculation unit, 205 change amount calculation unit, 211-216 determination Unit, 220, 220A failure phase determination unit, 250 current input unit, 252 differential current calculation unit, 254 suppression Suppression current calculation unit, 256 differential determination unit, 271, 272 change amount determination unit.

Claims (7)

A voltage input unit for receiving the input of each phase voltage of the three-phase power system;
For each phase voltage, a first determination unit that determines whether the phase voltage is less than a first threshold;
For each line voltage calculated based on each phase voltage, a second determination unit that determines whether the amount of change in the line voltage is less than a second threshold;
A failure phase determination unit for determining a failure phase of the power system,
The phase voltage of the first phase of the three phases is less than the first threshold value, and the amount of change in the line voltage between the second phase and the third phase of the three phases is less than the second threshold value. In some cases, the failure phase determination unit determines that a failure has occurred in the first phase. For each line voltage, a third determination unit that determines whether the line voltage is less than a third threshold;
A fourth determination unit that determines whether or not the change amount of the phase voltage is less than a fourth threshold for each phase voltage;
When the line voltage between the first phase and the second phase is less than the third threshold value, and the amount of change in the phase voltage of the third phase is less than the fourth threshold value, the failure phase determination unit The failure determination device according to claim 1, wherein it is determined that a failure has occurred in the first phase and the second phase. A voltage input unit for receiving the input of each phase voltage of the three-phase power system;
A first change amount of a line voltage between the first phase and the second phase of the three phases; a second change amount of the line voltage between the second phase and the third phase of the three phases; and A first change amount determination unit that determines whether or not the change amount is less than a first reference value for each of the third change amounts of the line voltage between the three phases and the first phase;
A failure phase determination unit for determining a failure phase of the power system,
When the first change amount and the third change amount are greater than or equal to the first reference value and the second change amount is less than the first reference value, the failure phase determination unit determines that the first phase A failure determination device that determines that a failure has occurred. Whether each of the change amount of the phase voltage of the first phase, the change amount of the phase voltage of the second phase, and the change amount of the phase voltage of the third phase is less than a second reference value. A second change amount determination unit that determines whether or not
The change amount of the phase voltage of the first phase and the change amount of the phase voltage of the second phase are not less than the second reference value, and the change amount of the phase voltage of the third phase is less than the second reference value. 4. The failure determination device according to claim 3, wherein the failure phase determination unit determines that a failure has occurred in the first phase and the second phase.   The failure determination apparatus according to any one of claims 1 to 4, wherein the voltage input unit receives an input of each phase voltage of a bus of the power system. A protective relay device for protecting a bus of a three-phase power system,
A voltage input unit for receiving an input of each phase voltage of the bus;
For each phase voltage, a first determination unit that determines whether the phase voltage is less than a first threshold;
For each line voltage calculated based on each phase voltage, a second determination unit that determines whether the amount of change in the line voltage is less than a second threshold;
A failure phase determination unit for determining a failure phase of the power system;
A differential relay operation unit for detecting a failure in the bus by a predetermined differential operation based on each phase current of the bus and each phase current of a plurality of lines branched from the bus;
An output control unit that outputs a shutoff command to a circuit breaker provided in the power system,
The phase voltage of the first phase of the three phases is less than the first threshold value, and the amount of change in the line voltage between the second phase and the third phase of the three phases is less than the second threshold value. If there is, the failure phase determination unit outputs a first signal indicating that a failure has occurred in the first phase,
The output control unit, when the first signal is output by the failure phase determination unit, and when the second signal indicating that a failure in the bus is detected by the differential relay operation unit, A protective relay device that outputs a command for interrupting a current flowing through each of the three phases. A protective relay device for protecting a bus of a three-phase power system,
A voltage input unit for receiving an input of each phase voltage of the bus;
A first change amount of a line voltage between the first phase and the second phase of the three phases; a second change amount of the line voltage between the second phase and the third phase of the three phases; and A first change amount determination unit that determines whether or not the change amount is less than a reference value for each of the third change amount of the line voltage between the three phases and the first phase;
A failure phase determination unit for determining a failure phase of the power system;
A differential relay operation unit for detecting a failure in the bus by a predetermined differential operation based on each phase current of the bus and each phase current of a plurality of lines branched from the bus;
An output control unit that outputs a shutoff command to a circuit breaker provided in the power system,
When the first change amount and the third change amount are greater than or equal to the reference value and the second change amount is less than the reference value, the failure phase determination unit causes a failure in the first phase. Output a first signal indicating that
The output control unit, when the first signal is output by the failure phase determination unit, and when the second signal indicating that a failure in the bus is detected by the differential relay operation unit, A protective relay device that outputs a command for interrupting a current flowing through each of the three phases.

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