JP6739384B2 - Failure point locator - Google Patents

Description

The present disclosure relates to a fault point locating device for locating a fault point of a power transmission line, and is preferably used particularly when a series capacitor for compensation is connected to the power transmission line.

In a long-distance transmission line, the impedance of the transmission line (in particular, the reactance component) increases and the voltage drop at the receiving end increases. Therefore, by installing a series capacitor on the power transmission line and compensating the reactance component of the impedance with this series capacitor, it is possible to suppress the voltage drop at the power receiving end and improve the power transmission efficiency. For this reason, the series capacitor for compensation is mainly applied to long-distance transmission lines.

When a series capacitor is installed on a transmission line, the line impedance suddenly changes by the capacitance of the capacitor at the installation point, which makes it difficult to locate a fault point. A failure point locating method for a power transmission line to which a series capacitor is connected is disclosed, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 53-105109).

Specifically, in the method of Patent Document 1, the system voltage and the system current of the self end and the other end at the same time are taken into the processing device. The processor calculates the impedance value calculated from the voltage and current at its own end and the current at the other end and the impedance angle of the transmission line both when the failure point is on the other end side or on the other end side than the capacitor. The reactance from the self-end to the failure point is calculated by correcting with. Furthermore, the processing device uses the impedance value calculated from the voltage and the current at the other end as the current and the power transmission line of the other end both in the case where the failure point exists on the own end side or the other end side of the capacitor. By reacting with the impedance angle, the reactance from the other end to the failure point is calculated. The processor calculates the sum of the combined results of these reactances and selects the calculated value when the reactance corresponds to the line length as the line reactance up to the fault point.

Patent Document 2 (Japanese Unexamined Patent Publication No. 2010-19625) does not relate to fault localization in a transmission line having a series capacitor, but does not require complete synchronization for measuring current and voltage between the self-end and the other end. A fault location method is disclosed.

Specifically, in Patent Document 2, the square value of the failure point voltage is calculated from the current and voltage at the self end and the transmission line constant, with the distance x from the self end to the failure point as an unknown. Similarly, the square value of the fault point voltage is calculated from the current and voltage at the other end and the transmission line constant. The unknown value x is calculated on the assumption that the calculated square values of the fault point voltages are equal.

JP-A-53-105109 JP, 2010-19625, A

Yoshiura Oura, "Protective Relay System Engineering", First Edition, The Institute of Electrical Engineers of Japan, March 2002, p. 111

The techniques disclosed in Patent Documents 1 and 2 described above have the following problems.
First, in the fault point locating method disclosed in Patent Document 1, in order to calculate the reactance from each end of the transmission line to the fault point, the self-end current and the other end current are combined (that is, the vector sum is calculated). There is a need to. Therefore, it is necessary to use a synchronization signal such as a GPS signal from a communication satellite to accurately synchronize the timing of detecting the current at the self-end of the power transmission line with the timing of detecting the current at the other end of the power transmission line.

However, since GPS signals from communication satellites are easily affected by the weather and the like, there is no guarantee that the substations at both ends of the transmission line, which are distant from each other, can receive the GPS signal correctly when a failure occurs in the transmission line.

As a method of not using the GPS signal, there is a method of realizing sampling synchronization at both ends of the power transmission line by exchanging data with each other via a signal transmission path connecting between substations at both ends of the power transmission line. However, this method is based on the premise that the signal transmission delay time from the own end to the other end and the signal transmission delay time from the other end to the own end are equal to each other. Actually, an error of about several hundreds of microseconds may occur in the transmission delay time in both directions. An error of this degree does not cause a problem in protection by adjusting the characteristic value in the case of the current differential type protection relay calculation, but it greatly affects the calculation result in the case of fault location.

In the fault point locating method described in Patent Document 2, it is not necessary to completely synchronize the detection timings of current and voltage at both ends of the transmission line. However, the method of Patent Document 2 is premised on that the transmission line constant is uniform, and is applied to the case where the impedance suddenly changes as in the case where a series capacitor is provided in the transmission line. , No teaching or suggestion.

This disclosure takes the above problems into consideration, and its purpose is to relatively easily locate faults in a transmission line provided with a series capacitor without requiring sampling synchronization at both ends of the transmission line. It is to provide a failure point locating device.

The fault point locating device according to one embodiment is used for fault point locating of a transmission line having a series capacitor on a line, and includes a coordinate conversion unit, a fault section determination unit, a terminal voltage compensation unit, and a fault point determination unit. Prepare The coordinate conversion unit converts the time series data of the three-phase current and the three-phase voltage of each terminal of the power transmission line into the time series data of the positive-phase current and the positive-phase voltage. The failure section determination unit determines, for each terminal of the transmission line, whether the terminal is a first terminal having no failure point with the series capacitor or a second terminal having a failure point with the series capacitor. To do. The terminal voltage compensator compensates the positive phase voltage of the first terminal by adding the voltage generated by the impedance of the series capacitor. The fault point determination unit determines the amplitude of the positive phase voltage of the fault point based on the positive phase current of the first terminal and the compensated positive phase voltage and the positive point of the fault point based on the positive phase current and the positive phase voltage of the second terminal. The position of the failure point is determined assuming that the amplitude of the phase voltage is equal.

A fault point locating device according to another embodiment is used for fault point locating of a transmission line having a series capacitor on a line, and includes a coordinate conversion unit, a fault section determination unit, a terminal voltage compensation unit, and a fault point determination unit. Equipped with. The coordinate conversion unit performs coordinate conversion of the time-series data of the three-phase current and the three-phase voltage of each terminal of the power transmission line into the time-series data of the current and voltage of the α circuit when the power transmission line has one line failure, and the power transmission line is When there is a two-wire fault, the time-series data of the three-phase current and three-phase voltage of each terminal of the power transmission line is converted into the time-series data of the current and voltage of the β circuit, and when the power transmission line has a three-phase fault, The time-series data of the three-phase current and the three-phase voltage of each terminal are converted into time-series data of the current and voltage of one of the α circuit and the β circuit. The failure section determination unit determines, for each terminal of the transmission line, whether the terminal is a first terminal having no failure point with the series capacitor or a second terminal having a failure point with the series capacitor. To do. The terminal voltage compensator compensates the voltage of the first terminal after the coordinate conversion by adding the voltages generated by the impedance of the series capacitor. The failure point determination unit determines the amplitude of the voltage of the failure point based on the current after the coordinate conversion of the first terminal and the compensated voltage, and the amplitude of the voltage of the failure point based on the current and the voltage after the coordinate conversion of the second terminal. Assuming that and are equal, the position of the failure point is determined.

According to the fault point locating device of the above-described embodiment, the amplitude of the positive phase voltage at the fault point based on the positive phase current at the first terminal and the compensated positive phase voltage, the positive phase current at the second terminal, and the positive phase current. Since the fault location is performed assuming that the amplitude of the positive phase voltage of the fault point based on the phase voltage is equal, the fault location can be performed relatively easily without requiring sampling synchronization at both ends of the transmission line. Further, according to the fault point locating device of the other embodiment, the amplitude of the voltage at the fault point based on the current after the coordinate conversion of the first terminal and the compensated voltage, and the coordinate after the coordinate conversion of the second terminal. Since the fault location is performed on the assumption that the amplitude of the voltage at the fault point based on the current and the voltage is equal, the fault location can be performed relatively easily without requiring sampling synchronization at both ends of the transmission line.

FIG. 3 is a configuration diagram of an electric power system in which the failure point locating device according to the first embodiment is installed. It is a block diagram which shows an example of the hardware constitutions of each fault location device 106 of FIG. FIG. 6 is a circuit diagram when an a-phase ground fault occurs at a failure point F when the series capacitor 103 is in the protection section of the power transmission line 102. 4 is an equivalent circuit according to the symmetric coordinate method corresponding to the circuit diagram of FIG. 3. It is an equivalent circuit by the symmetric coordinate method when a bc phase 2 wire ground fault occurs at a fault point F in FIG. 4 is an equivalent circuit based on the symmetric coordinate method when a bc phase 2 wire short-circuit fault occurs at fault point F in FIG. It is a positive-phase circuit when a three-phase ground fault occurs at a fault point F in FIG. FIG. 8 is a diagram showing a simplified equivalent circuit by a positive phase circuit and a distribution of a positive phase voltage when a series capacitor 103 is provided between an A terminal and a failure point F. FIG. 7 is a diagram showing a distribution of a simple equivalent circuit and a positive phase voltage when a series capacitor 103 is provided between the B end and a failure point F. FIG. 9 is an impedance diagram in the simple equivalent circuit of FIG. FIG. 10 is an impedance diagram in the simple equivalent circuit of FIG. FIG. 3 is a functional block diagram of the fault point locating device according to the first embodiment. 6 is a flowchart showing a fault point locating procedure according to the first embodiment. 14 is a flowchart showing the procedure of step S104 of FIG. 13 in more detail. It is a timing chart for explaining the data storage period of the second storage area RAM2. It is a figure for demonstrating the phase shift calculation method of 120 degrees and 240 degrees. It is a figure which shows the other structural example of the electric power system provided with the fault location device. FIG. 3 is a circuit diagram showing a series capacitor SC in which a protection circuit MOV is connected in parallel and a voltage-current characteristic of the protection circuit MOV. FIG. 19 is a diagram showing an equivalent circuit of the circuit shown in FIG. 18A and its characteristics. 4 is an equivalent circuit based on the Clark coordinate method when a one-line ground fault occurs at a fault point F in FIG. 4 is an equivalent circuit based on Clark coordinates when a two-wire ground fault occurs at a fault point F in FIG. 4 is an equivalent circuit based on Clark coordinates when a two-wire short circuit fault occurs at fault point F in FIG. 3. 4 is an equivalent circuit based on Clark coordinates when a three-phase failure occurs at failure point F in FIG. 4 is a simple equivalent circuit based on Clark coordinates when a failure occurs at a failure point F in FIG. It is the figure which put together the conversion formula by Clark conversion in tabular form. It is a functional block diagram of the fault location device of Embodiment 3. 9 is a flowchart showing a fault point locating procedure according to the third embodiment. It is a functional block diagram which shows the more detailed structure of the coordinate conversion part 123A of FIG.

Hereinafter, each embodiment will be described in detail with reference to the drawings. Note that the same or corresponding parts will be denoted by the same reference symbols, and the description thereof will not be repeated.

Embodiment 1.
[Schematic configuration of power system]
FIG. 1 is a configuration diagram of an electric power system in which the failure point locating device according to the first embodiment is installed. Referring to FIG. 1, a power system includes a power transmission line 102, a current transformer (CT: Current Transformer) 104_1 and a voltage transformer (VT: Voltage Transformer) 105_1 connected to the power transmission line 102 at an A-end substation. The B-end substation includes CT 104_2 and VT 105_2 connected to the power transmission line 102, and a series capacitor 103 connected in the middle of the power transmission line 102. Let C be the capacitance value of the series capacitor. The section between CT 104_1 and 104_2 is the protection section of the power transmission line 102.

Since the power system is a three-phase circuit, the power transmission line 102, the series capacitor 103, and the CTs 104 and VTs 105 provided at the substations of the respective terminals actually have three phases. In FIG. 1, only one phase is schematically shown for ease of illustration.

A three-phase back power supply 101_1 is provided far from the A end of the power transmission line 102, and a three-phase back power supply 101_2 is provided far from the B end of the power transmission line 102. The voltage amplitude of each phase of the back power supply 101_1 is Ea, and the voltage amplitude of each phase of the back power supply 101_2 is Eb.

Further, the power system includes a fault point locating device 106_1 provided at the A-end substation, a fault point locating device 106_2 provided at the B-end substation, and communication devices 108_1 and 108_2. Each fault point locating device 106 samples and captures a current value from the CT 104 at its own end and samples and captures a voltage value from the VT 105 at its own end. Each fault point locating device 106 generates digital current data and voltage data by A/D (Analog to Digital) converting the captured current value and voltage value.

The communication devices 108_1, 108, 2 are connected to the fault point locating devices 106_1, 106_2 at their own ends, respectively. Each communication device 108 receives input of current data and voltage data from the failure point locating device 106 of its own end, and inputs the input current data and voltage data of its own end to the communication device 108 of the other end via the transmission path 107. Send. Each communication device 108 outputs the current data and the voltage data of the other end received via the transmission path 107 to the failure point locating device 106 of its own end.

Each fault point locating device 106 performs a synchronization process using the current data and voltage data sampled by the fault point locating device 106 at the other end. Then, each failure point locating device 106 obtains voltage data and current data sampled at both ends of the power transmission line 102 at substantially the same time by delaying the data at its own end by the transmission time of the transmission path 107. Each fault point locating device 106 uses the voltage data and the current data to perform a current differential type protection relay operation.

A supplementary explanation will be given on the method of the above synchronization processing. Specifically, the fault point locating devices 106_1 and 106_2 perform synchronization processing by transmitting current and voltage data as serial data at a constant cycle. The transmission data from the communication device 108 connected to each failure point locating device 106 includes, in addition to the current and voltage data, a timing signal indicating the transmission timing of the data and a timing signal transmitted from the other end. The signal that represents the time difference until the timing signal is received is included. Each failure point locating device 106 adjusts the transmission timing at either terminal (for example, B end) so that the time difference Ta measured at the A end and the time difference Tb measured at the B end are equal to each other. You can

When the transmission delay time from the A end to the B end is equal to the transmission delay time from the B end to the A end, synchronization is obtained by the above synchronization processing method. However, when there is a difference in the transmission delay time in both directions, a synchronization error corresponding to (Ta-Tb)/2 occurs. The practical size of the error is about 250 μsec to 500 μsec at the maximum in a general-purpose communication device. However, if the error is within this range, it is possible to prevent a problem in the protection operation by adjusting the operation characteristics of the current differential relay.

Synchronous processing is not necessary when a failure occurrence in the protection section is detected by a method other than the current differential relay. In this case, the fault point locating device 106_1 at one end, for example, the A end, performs fault point locating. The B-end fault point locator 106_2 has a function of detecting the B-end current and voltage and a function of transmitting A/D converted B-end current data and voltage data to the A-end fault point locator 106_1. It is enough to have. In this case, the A-point fault point locator 106_1 does not need to transmit the A/D converted current data and voltage data of the A-end to the B-point fault point locator 106_2.

However, even when a failure occurrence in the protection section is detected by a method other than the current differential relay, the current and voltage data at both ends when the protection section is in failure are necessary in order to locate the failure point. .. Therefore, even if the sampling synchronization with the accuracy required for the current differential relay calculation is not required, the synchronization in the millisecond order is necessary.

[Example of hardware configuration of fault location device]
FIG. 2 is a block diagram showing an example of the hardware configuration of each failure point locating device 106 of FIG. The fault point locating device 106 of FIG. 2 has the same configuration as a so-called digital relay device. Specifically, referring to FIG. 2, the fault point locating device 106 includes an input conversion unit 201, an A/D conversion unit 211, an arithmetic processing unit 221, and an I/O (Input and Output) unit 231. ..

The input conversion unit 201 includes auxiliary transformers 202_1, 202_2,... For each input channel. The input conversion unit 201 is an input unit to which the current signal of each phase output from the CT 104 of FIG. 1 and the voltage signal of each phase output from the VT 105 of FIG. 1 are input. Each auxiliary transformer 202 converts the current signal and the voltage signal from the CT 104 and the VT 105 into a signal of a voltage level suitable for signal processing in the arithmetic processing unit 221 and the arithmetic processing unit 221.

The A/D converter 211 includes an analog filter (AF: Analog Filter) 212_1, 212_2,..., a sample hold circuit (S/H: Sample Hold Circuit) 213_1, 213_2,..., and a multiplexer (MPX: Multiplexer) 214. , A/D converter 215. The analog filter 212 and the sample hold circuit 213 are provided for each channel of the input signal.

Each analog filter 212 is a low-pass filter provided to remove a folding error during A/D conversion. Each sample hold circuit 213 samples and holds the signal that has passed through the corresponding analog filter 212 at a specified sampling frequency. The sampling frequency is, for example, 4800 Hz. The multiplexer 214 sequentially selects the voltage signals held in the sample hold circuits 213_1, 213_2,.... The A/D converter 215 converts the signal selected by the multiplexer 214 into a digital value.

The arithmetic processing unit 221 includes a CPU (Central Processing Unit) 222, a RAM (Random Access Memory) 223, a ROM (Read Only Memory) 224, and a bus 225 connecting these. The CPU 222 controls the entire operation of the fault point locating device 106. The RAM 223 and the ROM 224 are used as a main memory of the CPU 222. The ROM 224 can store programs and setting values for signal processing by using a nonvolatile memory such as a flash memory.

The I/O unit 231 has an interface (I/F: Interface) circuit 232 for connecting to the communication device 108 at its own end, a digital input (D:I: Digital Input) circuit 234, and a digital output (D/O). : Digital Output) circuit 235. The digital input circuit 234 and the digital output circuit 235 are interface circuits for performing communication between the CPU 222 and an external device other than the communication device 108.

[About fault location method]
Hereinafter, the principle of the fault location method according to the first embodiment will be described.

<1. Expression by simple equivalent circuit>
FIG. 3 is a circuit diagram when an a-phase ground fault occurs at the failure point F when the series capacitor 103 is in the protection section of the power transmission line 102. The fault resistance is R. The fault resistance is the arc resistance. FIG. 3 shows a case where the series capacitor 103 exists between the A end and the failure point F.

In FIG. 3, when the length of the transmission line 102 between the A-end substation and the B-end substation is set to “1”, the ratio of the distance from the A-end substation to the fault point F is set to “X”, The ratio from the B-end substation to the fault point F is “1-X”. In the fault point locating method according to the present embodiment, the current and voltage at the A terminal and the B terminal of the power transmission line 102 and the line constant of the power transmission line 102 are coordinate-transformed using the symmetric coordinate method.

FIG. 4 is an equivalent circuit according to the symmetrical coordinate method corresponding to the circuit diagram of FIG. As shown in FIG. 4, the positive phase voltage at the A end is VA1 and the positive phase voltage at the B end is VB1. It is assumed that the positive-phase current at the A end is IA1, the negative-phase current is IA2, and the zero-phase current is IA0. The positive phase current at the B end is IB1, the negative phase current is IB2, and the zero phase current is IB0. The positive phase voltage output from the rear power supply 101_1 at the A terminal is EA, and the positive phase voltage output from the rear power supply 101_2 at the B terminal is EB. The anti-phase impedance of the power transmission line 102 from the rear power source 101_1 at the A end to the fault point F is ZA2, and the negative phase impedance of the power transmission line 102 from the back power source 101_2 at the B end to the fault point F is ZB2. The zero-phase impedance of the power transmission line 102 from the rear power supply 101_1 at the A terminal to the fault point F is ZA0, and the zero-phase impedance of the power transmission line 102 from the rear power supply 101_2 at the B terminal to the fault point F is ZB0. The antiphase impedance ZA2 includes the capacitance of the antiphase capacitor of the series capacitor 103. The zero-phase impedance ZA0 includes the zero-phase capacitance of the series capacitor 103.

The equivalent circuit of the a-phase ground fault has a configuration in which a positive-phase circuit, a negative-phase circuit, and a zero-phase circuit are connected in series at a fault point F, as shown in FIG. In this case, the anti-phase circuit, the zero-phase circuit, and the ground fault resistance 3·R can be combined into one as the impedance ZF of the following expression (1).

ZF=ZA2//ZB2+ZA0//ZB0+3·R (1)
In the above formula (1), the symbol // represents the impedance of parallel connection. Therefore, the equivalent circuit of the a-phase ground fault can be represented by a simple equivalent circuit of only the positive phase circuit as shown in FIG. 8A by using the impedance ZF of the above equation (1). The same applies to the b-phase ground fault and the c-phase ground fault.

Although the simple equivalent circuit in the case of the 1-line ground fault has been described with reference to FIGS. 3 and 4, other types of the 2-line ground fault, 2-wire short-circuit fault, 3-phase ground fault, and 3-phase short-circuit fault are described. Even in the case, it can be represented by a similar simple equivalent circuit. Hereinafter, a brief description will be given with reference to FIGS.

FIG. 5 is an equivalent circuit based on the symmetric coordinate method when a bc phase 2 wire ground fault occurs at the fault point F in FIG. Let r be the ground resistance of each of the b-phase and the c-phase, and let R be the common ground resistance. As shown in FIG. 5, the equivalent circuit of the two-wire ground fault has a configuration in which a negative phase circuit and a zero phase circuit are connected in parallel at a fault point F of the positive phase circuit. Therefore, the impedance ZF represented by the following equation (2), that is,
ZF=r+(r+ZA2//ZB2)//(r+3R+ZA0//ZB0) (2)
By using, the equivalent circuit of the bc-phase two-wire ground fault can be represented by the simple equivalent circuit of FIG. The same applies to the case of the ca phase 2 wire ground fault and the case of the ab phase 2 wire ground fault.

FIG. 6 is an equivalent circuit based on the symmetric coordinate method when a bc phase 2 wire short circuit fault occurs at the fault point F in FIG. As shown in FIG. 6, the equivalent circuit of the two-wire short circuit fault has a configuration in which the negative phase circuit is connected in parallel to the fault point F of the positive phase circuit. Therefore, the impedance ZF represented by the following equation (3), that is,
ZF=ZA2//ZB2 (3)
By using, the equivalent circuit of the bc-phase two-wire short-circuit fault can be represented by the simple equivalent circuit of FIG. The same applies to the case of a ca phase 2 wire short circuit failure and the case of an ab phase 2 wire short circuit failure.

FIG. 7 shows a positive-phase circuit in the case where a three-phase ground fault occurs at the fault point F in FIG. In the positive-phase circuit in the case of a three-phase short circuit failure, the ground fault resistance r becomes 0 in FIG. Therefore, even in the case of the three-phase short-circuit fault and the three-phase ground fault, the impedance ZF can be used to represent the simple equivalent circuit of FIG.

<2. Fault Locating Method-When the series capacitor is located between the end A and the fault point F>
FIG. 8 shows a case where the series capacitor 103 is provided between the A end and the failure point F (that is, the failure point F does not exist between the A end and the series capacitor 103, and the B end and the series capacitor 103 are provided. 6 is a diagram showing a simplified equivalent circuit by a positive-phase circuit and a distribution of the positive-phase voltage in the case where a fault point F exists between and. In this specification, the A end in the above case may be referred to as the first end, and the B end may be referred to as the second end.

FIG. 8A shows a simple equivalent circuit according to the symmetrical coordinate method corresponding to FIG. As described above, the power system can be represented by a simple equivalent circuit in which the impedance ZF is added to the fault point F of the positive phase circuit as shown in FIG. 8A for almost all fault types. In FIG. 8A, “*” is a symbol representing multiplication.

FIG. 8B shows the distribution of the positive phase voltage at each point in the simplified equivalent circuit of FIG. The positive phase voltage at the A terminal is VA1 and the positive phase current is IA1. The positive phase voltage at the B end is VB1 and the positive phase current is IB1. The positive phase voltage at the failure point F is VF.

8A and 8B, the length of the power transmission line 102 from the A end to the B end is 1, the distance from the A end to the failure point F is X, and the failure from the B end occurs. The distance to the point F is 1-X. 0≦X≦1 holds. Further, the distance from the end A to the installation position of the series capacitor 103 is X1, and the distance from the installation position of the series capacitor 103 to the failure point F is X2. In this case, X=X1+X2 holds.

Further, the impedance of the length of the transmission line 102 from the A end to the B end is Z. In this case, the impedance from the A end to the fault point F not including the series capacitor 103 is represented by X*Z, and the impedance from the B end to the fault point F is represented by (1-X)*Z. Further, the impedance of the power transmission line 102 from the A end to the series capacitor 103 is X1*Z, and the impedance of the power transmission line 102 from the series capacitor 103 to the failure point F is X2*Z.

As shown in FIG. 8(B), the positive phase voltage increases by VC at the installation point of the series capacitor 103. This positive phase voltage VC is a voltage increase due to the capacitance C of the series capacitor 103. The impedance ZC of the series capacitor 103 has an imaginary unit of j, a system frequency of f, and
ZC=-j (1/ωC), ω=2πf (4)
It is represented by. Therefore, when the current IA1 flows through the series capacitor 103, its voltage VC becomes
VC=ZC*IA1=-j(1/ωC)*IA1 (5)
It is represented by. At the installation point of the series capacitor 103, the positive phase voltage increases by this voltage VC.

Here, a voltage VA1′ obtained by compensating the positive phase voltage VA1 at the A end with the above voltage VC, that is,
VA1'=VA1+VC (6)
think of. Then, the positive phase voltage VF at the fault point F is calculated by using the compensation voltage VA1′ at the A terminal and the positive phase current IA1.
VF=VA1'-X*Z*IA1 (7)
Represented by

Further, the positive phase voltage VF at the fault point F is calculated by using the positive phase voltage VB1 at the B end and the positive phase current IB1.
VF=VB1-(1-X)*Z*IB1 (8)
Represented by

The above equations (7) and (8) are established by vector operations, respectively, but if the current and voltage data at the A terminal and the current and voltage data at the B terminal do not have the same time, then according to the equation (7), The calculated positive phase voltage VF and the positive phase voltage VF calculated according to the equation (8) are not equal to each other because of a time difference. However, since the amplitude value of the positive phase voltage VF of the expression (7) and the amplitude value of the positive phase voltage V failure point F of the expression (8) do not need the same time, they are equal to each other.

Specifically, when the amplitude value is represented by the symbol “amp”, the relational expression of the amplitude value corresponding to the expression (7) is
VFamp=(VA1'-X*Z*IA1) amp (9)
It is represented by. Further, the relational expression of the amplitude value corresponding to the expression (8) is
VFamp=(VB1-(1-X)*Z*IB1) amp (10)
It is represented by. Therefore,
(VA1'-X*Z*IA1) amp = (VB1--(1-X)*Z*IB1) amp …(11)
Is established. Here, since all the equations (11) except X are known, X can be calculated. The distance from the A end to the failure point F can be calculated by multiplying the calculated X by the actual length of the power transmission line 102 between the A end and the B end.

In the equation (11), a known method can be used as the method of calculating the amplitude value using the data sampled in time series. For example, Yoshifumi Oura, "Protective Relay System Engineering", First Edition, The Institute of Electrical Engineers of Japan, March 2002, p. Various amplitude value calculation methods described in Table 5.2 of 111 (Non-Patent Document 1) can be applied (but not limited to this).

<3. Fault Locating Method-When the series capacitor is located between the end B and the fault point F>
9 shows a case where the series capacitor 103 is provided between the B end and the failure point F (that is, the failure point F exists between the A end and the series capacitor 103, and the B end and the series capacitor 103 are connected). FIG. 8 is a diagram showing a simplified equivalent circuit and a distribution of a positive phase voltage when a fault point F does not exist between the two. In this specification, the B end in the above case may be referred to as the first end, and the A end may be referred to as the second end.

As shown in FIG. 9A for almost all types of failure, the power system can be represented by a simple equivalent circuit in which the impedance ZF is added to the failure point F of the positive phase circuit. FIG. 9B shows the distribution of the positive phase voltage at each point of the simple equivalent circuit of FIG. 9A.

With reference to FIGS. 9A and 9B, the length of the power transmission line 102 from the A end to the B end is 1, the distance from the A end to the failure point F is X, and the failure occurs from the B end. The distance to the point F is 1-X. 0≦X≦1 holds. Furthermore, the distance from the B end to the installation position of the series capacitor 103 is X1, and the distance from the installation position of the series capacitor 103 to the failure point F is X2. In this case, 1-X=X1+X2 holds.

When the current IB1 flows through the series capacitor 103, the voltage VC generated in the series capacitor 103 is
VC=ZC*IB1=-j(1/ωC)*IB1 (12)
It is represented by. At the installation point of the series capacitor 103, the positive phase voltage increases by this voltage VC.

Here, a voltage VB1′ obtained by compensating the positive phase voltage VB1 at the B end with the above voltage VC, that is,
VB1'=VB1+VC (13)
think of. Then, the positive phase voltage VF at the failure point F is calculated by using the compensation voltage VB1′ at the B end and the positive phase current IB1.
VF=VB1'-(1-X)*Z*IB1 (14)
Represented by

The positive phase voltage VF at the fault point F is calculated by using the positive phase voltage VA1 at the A terminal and the positive phase current IA1.
VF=VA1-(1-X)*Z*IA1 (15)
Represented by

In order to eliminate the need for simultaneity between the current and voltage data at the A terminal and the current and voltage data at the B terminal, the amplitude value calculation of the above equations (14) and (15) is performed.
VFamp=(VB1'-(1-X)*Z*IB1) amp (16)
VFamp=(VA1-(1-X)*Z*IA1) amp (17)
Is established. Therefore,
(VA1−X*Z*IA1) amp=(VB1′−(1-X)*Z*IB1) amp …(18)
Is established. Here, since all the equations (18) except X are known, X can be calculated. The distance from the A end to the failure point F can be calculated by multiplying the calculated X by the actual length of the power transmission line 102 between the A end and the B end.

<4. Relationship between installation position of series capacitor and failure point F>
Next, a method of simply determining whether the fault point F exists between the A terminal and the series capacitor 103 or between the B terminal and the series capacitor 103 will be described.

FIG. 10 is an impedance diagram in the simple equivalent circuit of FIG. FIG. 10A shows an impedance diagram seen from the A end, and FIG. 10B shows an impedance diagram seen from the B end.

With reference to FIGS. 8A and 10A, the impedance calculated using the positive phase voltage VA1 and the positive phase current IA1 at the A end is VA1/IA1, and the phase angle is φA. The impedance VA1/IA1 is the impedance X1*Z of the power transmission line 102 from the A end to the series capacitor 103, the impedance ZC of the series capacitor 103, and the impedance X2*Z of the power transmission line 102 from the series capacitor 103 to the failure point F. , And the impedance ZF of the fault point F is combined (that is, vector addition) and is equal to the value.

With reference to FIGS. 8A and 10B, the impedance calculated using positive phase voltage VB1 and positive phase current IB1 at the B end is VB1/IB1 and its phase angle is φB. The impedance VB1/IB1 is equal to a value obtained by combining the impedance (1-X)*Z of the power transmission line 102 from the B end to the fault point F and the impedance ZF of the fault point F.

Comparing FIG. 10A and FIG. 10B, because the impedance ZC=−j(1/ωC) of the series capacitor 103, the phase angle φA of the impedance VA1/IA1 seen from the A end is the B end. The impedance is apparently smaller than the phase angle φB of VB1/IB1. That is, φA<φB.

FIG. 11 is an impedance diagram in the simple equivalent circuit of FIG. FIG. 11A shows an impedance diagram seen from the A end, and FIG. 11B shows an impedance diagram seen from the B end.

With reference to FIGS. 9A and 11A, the impedance calculated using the positive phase voltage VA1 and the positive phase current IA1 at the A end is VA1/IA1 and the phase angle is φA. The impedance VA1/IA1 is equal to a value obtained by combining the impedance X*Z of the power transmission line 102 from the A end to the failure point F and the impedance ZF of the failure point F.

With reference to FIGS. 9A and 11B, the impedance calculated using positive phase voltage VB1 and positive phase current IB1 at the B end is VB1/IB1 and its phase angle is φB. The impedance VB1/IB1 is the impedance X1*Z of the power transmission line 102 from the B end to the series capacitor 103, the impedance ZC of the series capacitor 103, and the impedance X2*Z of the power transmission line 102 from the series capacitor 103 to the failure point F. , And the impedance ZF of the fault point F is combined (that is, vector addition) and is equal to the value.

Comparing FIG. 11A and FIG. 11B, since the impedance ZC=−j(1/ωC) of the series capacitor 103, the phase angle φA of the impedance VA1/IA1 seen from the A end is the B end. The impedance is apparently larger than the phase angle φB of VB1/IB1. That is, φA>φB.

From the above, the phase angle φA of the impedance VA1/IA1 seen from the A end is compared with the phase angle φB of the impedance VB1/IB1 seen from the B end. When φA<φB, the failure point F is the B end. Can be determined to exist between the end A and the series capacitor 103. On the other hand, when φA>φB, it can be determined that the failure point F exists between the A end and the series capacitor 103 and does not exist between the B end and the series capacitor 103.

When it is determined that the fault point F exists between the B end and the series capacitor 103, the positive phase voltage at the A end is compensated according to the above equations (5) and (6), and the above ( The unknown X can be calculated according to the equation (11). On the other hand, when it is determined that the fault point F exists between the A terminal and the series capacitor 103, the positive phase voltage at the B terminal is compensated according to the above equations (12) and (13), and the above ( The unknown X can be calculated according to the equation 18).

[Specific procedure for fault location]
In the following, a specific procedure for fault low localization will be described by summarizing the above description.

FIG. 12 is a functional block diagram of the fault point locating device according to the first embodiment. FIG. 13 is a flowchart showing a fault point locating procedure according to the first embodiment. FIG. 14 is a flowchart showing the procedure of step S104 of FIG. 13 in more detail.

With reference to FIG. 12, the failure point locating device 106, when viewed functionally, the current/voltage data input/output unit 120, the synchronization processing unit 121, the first storage area RAM1, and the second storage area RAM2. The transmission line failure detection unit 122, the coordinate conversion unit 123, the failure section determination unit 124, the terminal voltage compensation unit 125, and the failure point determination unit 126 are included.

The current/voltage data input/output unit 120 corresponds to the input conversion unit 201 of FIG. 2 and the interface circuit 232 of the I/O unit 231 connected to the communication device 108. The first storage area RAM1 and the second storage area RAM2 are storage areas provided in the RAM 223 of the arithmetic processing unit 221 in FIG. Each function of the synchronization processing unit 121, the transmission line failure detection unit 122, the coordinate conversion unit 123, the failure section determination unit 124, the terminal voltage compensation unit 125, and the failure point determination unit 126 is performed by the CPU 222 of the arithmetic processing unit 221 in FIG. It is realized by executing the program. Note that these functions can be realized by a dedicated circuit configured by an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit) instead of the CPU 222 in FIG. 2. The operation of each component of the fault point locating device 106 of FIG. 12 will be described below with reference to the flowcharts of FIGS. 13 and 14.

Referring to FIGS. 12 and 13, in step S100, current/voltage data input/output unit 120 (specifically, input conversion unit 201) receives the current value of its own end from CT 104, and receives the current value from VT 105. Receives the input voltage value at the end. The A/D conversion unit 211 in FIG. 2 samples the input current value and voltage value at a specified sampling frequency (for example, 4800 Hz), and A/D converts the sampled current value and voltage value into a digital value.

In the next step S101, the current/voltage data input/output unit 120 (specifically, the interface circuit 232 connected to the communication device 108 in FIG. 2) transmits the current data and voltage data after A/D conversion. It transmits to the failure point locator 106 of the other end via the path 107 and the communication devices 108_1 and 108_2. Further, in step S102, the current/voltage data input/output unit 120 (specifically, the interface circuit 232 connected to the communication device 108 in FIG. 2) causes the other end point sampled by the failure point locating device 106 at the other end. It receives current data and voltage data of.

In the next step S103, the synchronization processing unit 121 of each failure point locating device 106 performs synchronization processing on the current data and voltage data of its own end. Specifically, each failure point locating device 106 determines that the transmission time of the transmission path 107 from its own end to the other end is equal to the transmission time of the transmission path 107 from the other end to its own end, and the transmission delay time of the transmission path 107. By delaying the sampling time of the current data and the voltage data of the self-end by (usually several milliseconds), the sampling time of the data of the self-end and the sampling time of the data of the other end are made approximately the same time.

In the next step S104, the power transmission line failure detection unit 122 performs protection relay calculation by a current differential method or the like in the protection section of the power transmission line 102 (between the A end and the B end in the present embodiment). It detects the presence or absence of a failure and also detects sudden changes in current data and voltage data.

FIG. 14 is a flowchart showing the procedure of step S104 of FIG. 13 in more detail. FIG. 15 is a timing chart for explaining the data storage period of the second storage area RAM2.

12, 14, and 15, in step S200, first storage area RAM1 and second storage area RAM2 receive current data and voltage data of their own ends and the other end after synchronization processing. receive.

In the next step S201, the first storage area RAM1 and the second storage area RAM2 store the latest current data and voltage data of its own end and the latest current data and voltage data of the other end. At this time, the stored data in the first storage area RAM1 and the second storage area RAM2 are replaced with the oldest data each time the latest data is acquired by the current/voltage data input/output unit 120. To be updated. The data storage period of the first storage area RAM1 is a period required for a protection relay calculation such as a current differential relay. The data storage period of the second storage area RAM2 is a period required for fault point localization and is the T1 period of FIG.

In the next step S202, the power transmission line failure detection unit 122 detects whether or not the current data or the voltage data at its own end (or the other end) has changed suddenly. As the sudden change detection processing, for example, it is detected whether the difference between the current data and the data one cycle before exceeds a threshold value, or whether the sum of the current data and the data half cycle before exceeds a threshold value. It Such a process is generally called a current (or voltage) change width relay and can detect an abnormality earlier than a protection relay calculation such as a current differential relay.

As a result, when a sudden change in the current data or the voltage data is detected (YES in step S202), the second storage area RAM2 in the next step S205 has a T2 period (T2 is longer than T1) from the sudden change detection time t2. (Small) also stops updating the data. As a result, the data in the T1 period (from time t1 to time t4 in FIG. 15) before and after time t2 when the sudden change in the current data or the voltage data is detected is stored in the second storage area RAM2 (step in FIG. 13). S105). The data stored in the second storage area RAM2 is used for fault point localization after step S106 in FIG. After the fault point is located, the update of the data stored in the second storage area RAM2 is restarted.

In parallel with this step S202, in step S203, the power transmission line failure detection unit 122 performs a protection relay calculation by a current differential method or the like, and thereby, the protection section of the power transmission line 102 (in this embodiment, the A end and the B end). It detects the presence or absence of a fault between the edge). As a result, when a failure of the power transmission line 102 is detected in the protection section (YES in step S204), the process proceeds to the next step S106 and subsequent steps, and the fault point localization is executed.

On the other hand, if a failure in the protection section of the power transmission line 102 is not detected even after the T3 period has elapsed from the time t2 when the sudden change of the current or the voltage is detected (NO in step S204), it is determined in step S105. The data stored in the second storage area RAM2 is invalidated, and the update of the data stored in the second storage area RAM2 is restarted.

In FIG. 15, as a general time setting example, the T1 period is set to 2 to 3 cycles, the T2 period is set to about 1 to 2 cycles, and the T3 period is set to 3 cycles or more (these setting values are set). Is not limited to).

Referring again to FIG. 12 and FIG. 13, in the next step S106, the coordinate conversion unit 123 causes the amplitude value in the period corresponding to the fault section in the data of the T1 period stored in the second storage area RAM2. The data of about one cycle required for the calculation is taken out. This is because the data stored in the second storage area RAM2 may include data after the circuit breaker is opened, that is, after the fault is removed, and the data cannot be used for fault location. The coordinate conversion unit 123 calculates the time series data of the positive phase voltage VA1 at the A terminal by using the extracted time series data of the a phase voltage Va, the b phase voltage Vb, and the c phase voltage Vc at the A terminal. Similarly, the coordinate conversion unit 123 calculates the time series data of the positive phase current IA1 at the A end by using the time series data of the a-phase current Ia, the b-phase current Ib, and the c-phase current Ic at the A end. Further, the coordinate conversion unit 123 calculates the time series data of the positive phase voltage VB1 at the B end by using the time series data of the a-phase voltage Va, the b-phase voltage Vb, and the c-phase voltage Vc at the B end, The time series data of the positive phase current IB1 at the B end is calculated using the time series data of the a-phase current Ia, the b-phase current Ib, and the c-phase current Ic.

Hereinafter, the positive phase voltages at the A terminal and the B terminal will be collectively referred to as V1, and the positive phase currents at the A terminal and the B terminal will be collectively referred to as I1. The positive phase voltage V1 and the positive phase current I1 are calculated according to the following equations (19) and (20).

V1=(Va+a*Vb+(a^2)*Vc)/3 (19)
I1=(Ia+a*Ib+(a^2)*Ic)/3 (20)
Here, “^” is a symbol representing a power, a represents a phase shift of 120°,
a=(1-j√3)/2 (21)
Defined by Therefore, a^2 represents a 240° phase shift.

FIG. 16 is a diagram for explaining a phase shift calculation method for 120° and 240°. Referring to FIG. 16, the phase shift operation of 120° and 240° can be calculated by using the electrical angle of the sampling data, for example, 60° before.

Specifically, in FIG. 16, voltage data at the current time point is V(t), and voltage data at an electrical angle of 60° before the current time point is V(t-60°). Then, the voltage data V∠120° obtained by phase-shifting the current voltage data V(t) by 120° and the voltage data V∠240° obtained by phase-shifting 240° are
V∠120°=−V(t−60°) (22)
V∠240°=V(t−60°)−V(t) (23)
It is represented by.

Therefore, a*Vb and (a^2)*Vc in equation (19) are
a*Vb=Vb∠120°=−Vb(t−60°) (24)
(A^2)*Vc=Vc∠240°=Vc(t−60°)−Vc(t) (25)
Can be calculated according to. The same applies to the case of the positive phase current I1.

In the next step S107, the failure section determination unit 124 determines that the phase angle φA=Arg(VA1/IA1) of the impedance VA1/IA1 of the power transmission line 102 viewed from the A end and the impedance VB2 of the power transmission line 102 viewed from the B end. The phase angle φB of /IB2=Arg(VB2/IB2) is calculated.

Next, in step S108, the failure section determination unit 124 determines the magnitude of the phase angles φA and φB. When φA<φB, the failure section determination unit 124 determines that the failure point F is between the B end and the series capacitor 103 (step S109). In this case, the terminal voltage compensating unit 125 calculates the compensation voltage VA1′ that compensates the positive phase voltage VA1 at the A end according to the above-described equations (5) and (6), and the failure point determination unit 126 causes the above-mentioned ( 11) The unknown number X of the equation is obtained. By multiplying the calculated X by the actual length of the power transmission line 102, the distance from the A end to the failure point F can be determined.

On the other hand, when φA>φB, the failure section determination unit 124 determines that the failure point F is between the A-terminal series capacitor 103 (step S111). In this case, the terminal voltage compensating unit 125 calculates the compensation voltage VB1′ that compensates the positive phase voltage VB1 at the B end according to the above equations (12) and (13), and the failure point determining unit 126 determines the above ( The unknown number X of the equation 18) is calculated. By multiplying the calculated X by the actual length of the power transmission line 102, the distance from the A end to the failure point F can be determined.

When φA=φB, the failure section determination unit 124 determines that the failure point F is the arrangement position of the series capacitor 103 (step S113), and ends the process. Alternatively, in the case of φA=φB, it is determined that the determination is not possible, and the unknown number X is obtained by both the equations (11) and (18) to obtain the distance from the A end to the failure point F and the B end to the failure point F. The distance may be displayed as a reference value.

[Modification]
In steps S101 and S102 of FIG. 13, the fault point locating devices 106_1 and 106_2 mutually exchange the three-phase current and the three-phase voltage via the transmission line 107. Instead of this, each fault point locating device 106 may first perform coordinate conversion into a positive phase current and a positive phase voltage, and transmit the positive phase voltage and the positive phase current to the fault point locating device 106 at the other end. As a result, the amount of data transmitted via the transmission path 107 can be reduced, and the amount of data stored in the first storage area RAM1 and the second storage area RAM2 can be reduced.

In step S202 of FIG. 14, the current data or the voltage data of the self end before the synchronization processing may be used as it is to determine whether or not the current or the voltage suddenly changes. Since the synchronization process is not performed, a sudden change in current or voltage can be detected earlier.

The synchronization processing in step S103 of FIG. 13 is performed because the current differential method is used for detecting the failure of the power transmission line 102. Therefore, when the failure of the power transmission line 102 is detected by another method, it suffices that the data in the same failure state can be exchanged, and accurate synchronization processing is not necessary.

FIG. 17: is a figure which shows the other structural example of the electric power system provided with the fault location device. The electric power system of FIG. 17 is provided with current differential type protection relay devices 110_1 and 110_2 in place of the fault point locating devices 106_1 and 106_2 of FIG. The fault point locating device 111 receives the current data and the voltage data detected from each protection relay device.

In this case, the fault point locating device 111 includes the arithmetic processing unit 221 of FIG. 2 and the digital input circuit 234 and the digital output circuit 235 of the I/O unit 231 as a hardware configuration. The steps up to step S105 in FIG. 13 are executed by each protection relay device 110 and the communication device 108, and the failure point locating device 111 is configured to execute each step after step S106 in FIG.

[effect]
As described above, the fault point locating devices 106 and 111 of the first embodiment are preferably used for fault point locating of the transmission line 102 having the series capacitor 103.

Specifically, the fault point locators 106 and 111 compare the impedance angle φA obtained from the positive phase voltage and positive phase current at the A end with the impedance angle φB obtained from the positive phase voltage and positive phase current at the B end. Thus, it is first determined whether the fault point F is closer to the A end or the B end than the series capacitor 103. When the failure point F is closer to the B end than the series capacitor 103, the series capacitor voltage is used to compensate the positive phase voltage at the A terminal, and the compensation voltage at the A terminal and the positive phase current at the A terminal are used. Then, the positive phase voltage VF at the fault point F is calculated. Further, the positive phase voltage VF at the failure point F is calculated using the positive phase voltage at the B end and the positive phase current at the B end. Assuming that the amplitude values of the positive phase voltage VF are equal by these two kinds of calculations, the distances from the A end and the B end to the failure point are obtained. Even when the fault point F is closer to the end A than the series capacitor 103, the fault point can be located by the same calculation.

As described above, in the fault point locating method according to the first embodiment, it is not necessary to combine (vector operation) the voltage and current at the A terminal and the voltage and current at the B terminal, so that accurate sampling synchronization of the data at both ends is achieved. It is unnecessary. Therefore, accurate fault location can be performed without performing highly accurate synchronization processing using GPS. Further, the fault point locating method of the first embodiment has an advantage that the same arithmetic expression can be used regardless of the fault type.

Embodiment 2.
In the second embodiment, a case where the series capacitor 103 of FIG. 1 is provided with a protection circuit will be described. Hereinafter, a metal oxide varistor (MOV) will be described as an example of the protection circuit.

FIG. 18 is a circuit diagram showing a series capacitor SC in which the protection circuit MOV is connected in parallel and a voltage-current characteristic of the protection circuit MOV. A circuit diagram is shown in FIG. The voltage applied to the parallel circuit of the series capacitor SC and the protection circuit MOV is V _V, and the current flowing in the parallel circuit is I _V. FIG. 18B shows the relationship between the voltage v _MOV of the protection circuit _MOV and the current i _MOV . As shown in FIG. 18B, since the voltage v _MOV generated in the protection circuit _MOV is limited even if the current i _MOV increases, the voltage V _{V in} FIG. 18A is also limited. This makes it possible to protect the voltage applied to the series capacitor SC from exceeding the rated voltage.

FIG. 19 is a diagram showing an equivalent circuit of the circuit shown in FIG. 18A and its characteristics. The parallel connection circuit of the series capacitor SC and the protection circuit MOV shown in FIG. 18A is shown as a series circuit of the resistor R _V and the reactance X _V in FIG. 19A. FIG. 19B shows the impedance characteristic (that is, the characteristic of the resistance R _V and the reactance X _V ) of the series capacitor SC with the protection circuit with respect to the absolute value |I _V | of the current I _V.

As shown in FIG. 19B, the series capacitor SC having the protection circuit MOV can be characterized as an element whose impedance (that is, resistance and reactance) changes according to the current. Therefore, by storing the resistance and reactance characteristics with respect to the current in the memory, the voltage VC generated in the series capacitor shown in FIGS. 8 and 9 can be calculated.

Specifically, the resistance of the series capacitor with the protection circuit connected to the a-phase power transmission line is Rva, and the reactance is Xva. The resistance of the series capacitor with the protection circuit connected to the b-phase transmission line is Rvb, and the reactance is Xvb. The resistance of the series capacitor with the protection circuit connected to the c-phase power transmission line is Rvc, and the reactance is Xvc. In this case, as the voltage VC generated in the series capacitor with the protection circuit, a=(1−j√3)/2, the a phase current Ia, the b phase current Ib, and the c phase current Ic in the above equation (21) are used. hand,
VC=((Xva+Rva)*Ia+a*(Xvb+Rvb)*Ib+(a^2)*(Xvc+Rvc)*Ic) (26)
It is represented by. The above equation (26) is used instead of the above equation (5) or equation (12).

To summarize the above, the series capacitor with a protection circuit provided in each phase of the power transmission line 102 has a characteristic that the impedance changes according to the current flowing through itself. In this case, the terminal voltage compensation unit 125 calculates and calculates the voltage generated in the series capacitor with the protection circuit of each phase based on the currents Ia, Ib, Ic of each phase and the impedance characteristics of the series capacitor with the protection circuit. The positive phase voltage VC generated in the series capacitor with the protection circuit is calculated from the voltage of each phase.

Since the other points of the fault point locating device of the second embodiment are the same as those of the first embodiment, the description will not be repeated.

Embodiment 3.
In the fault point locating device 106 of the first embodiment, the three-phase voltage and the three-phase current at both ends of the power transmission line 102 are converted into the positive-phase voltage and the positive-phase current by using the symmetrical coordinates, and the positive-phase voltage and the positive-phase current are converted. Was used for fault location. The fault point locating device 106 according to the third embodiment uses the Clark transform (α-β-0 method) to convert the three-phase voltage and the three-phase current across the transmission line 102 into an α voltage and an α current or a β voltage or a β current. Then, the fault point is located using the α voltage and the α current or the β voltage or the β current. As described below, when using the Clark transform, it is necessary to determine the failure phase, and it should be noted that the conversion formula is different depending on the failure phase.

[About fault location method]
The principle of the fault location method according to the third embodiment will be described below.

<1. Expression by simple equivalent circuit>
FIG. 20 is an equivalent circuit based on the Clark coordinate method when a one-line ground fault occurs at the fault point F in FIG. The voltage of the α circuit at the A end is VAα, and the current of the α circuit is IAα. The voltage of the α circuit at the B end is VBα, and the current of the α circuit is IBα. Further, the zero-phase current at the A end is IA0, and the zero-phase current at the B end is IB0. The output voltage in the α circuit of the rear power supply 101_1 at the A terminal is EAα=Ea, and the output voltage in the β circuit is EAβ=−jEa. The output voltage in the α circuit of the rear power supply 101_2 at the B end is EBα=Eb, and the output voltage in the β circuit is EBβ=−jEb.

As shown in FIG. 20, the equivalent circuit based on the Clark coordinate method in the case of a one-line ground fault has a configuration in which an α circuit and a zero-phase circuit are connected in series at a fault point F.

FIG. 21 is an equivalent circuit based on Clark coordinates when a two-wire ground fault occurs at the fault point F in FIG. The voltage of the β circuit at the A terminal is VAβ, and the current of the β circuit is IAβ. The voltage of the β circuit at the B end is VBβ, and the current of the β circuit is IBβ.

As shown in FIG. 21, in the equivalent circuit based on the Clark coordinate method in the case of the two-wire ground fault, the α circuit and the zero-phase circuit are connected in parallel at the fault point F, and the β circuit is short-circuited at the fault point F. It has a different configuration.

22 is an equivalent circuit based on Clark coordinates when a two-wire short-circuit fault occurs at fault point F in FIG. As shown in FIG. 22, the equivalent circuit based on the Clark coordinate method in the case of a two-wire short-circuit fault has a configuration in which the β circuit is short-circuited at the fault point F.

FIG. 23 is an equivalent circuit based on Clark coordinates when a three-phase failure occurs at the failure point F in FIG. As shown in FIG. 23, the Clarke coordinate equivalent circuit in the case of a three-phase fault has a configuration in which the α circuit is short-circuited at the fault point F and the β circuit is short-circuited at the fault point F.

FIG. 24 is a simple equivalent circuit based on Clark coordinates when a failure occurs at the failure point F in FIG. FIG. 24A shows a simple equivalent circuit of the α circuit, and shows a configuration in which the impedance ZFα is added to the fault point F. The voltage at the failure point F is VFα. The simple equivalent circuit of FIG. 24A can be applied to the case of a one-line ground fault and a three-phase fault.

FIG. 24B shows a simple equivalent circuit of the β circuit, which shows a configuration in which the impedance ZFβ is added to the fault point F. The voltage at the fault point F is VFβ. The simple equivalent circuit of FIG. 24(B) can be applied to the case of a 2-wire ground fault, a 2-wire short-circuit fault, and a 3-phase fault. As described above, in the case of Clark conversion, the simple equivalent circuit to be applied differs depending on the type of failure.

<2. Conversion formula of Clark conversion>
FIG. 25 is a diagram in which conversion formulas by the Clark conversion are summarized in a table format. The failure types are classified into a 1-line short-circuit fault, a 2-line short-circuit fault, a 2-line ground fault, and a 3-phase fault.

With reference to FIG. 25, in the case of a one-line ground fault, a simple equivalent circuit using an α circuit is used. However, it should be noted that the Clark transform formula differs depending on the failure phase.

In the case of a two-wire ground fault or a two-wire short-circuit fault, a simple equivalent circuit using a β circuit is used. However, it should be noted that the Clark transform formula differs depending on the failure phase.

In the case of a three-phase failure, FIG. 25 shows the conversion formula in the case of the bc phase failure in the β circuit. However, in this case, a conversion formula of another phase may be used, or a conversion formula of the α circuit may be used.

Coordinate conversion of the voltage and current of each terminal of the power transmission line 102 is performed according to the conversion formula shown in FIG. The procedure for locating the fault point thereafter is almost the same as that in the first embodiment. Hereinafter, description will be given with reference to FIGS. 26 and 27.

[Specific procedure for fault location]
FIG. 26 is a functional block diagram of the fault point locating device according to the third embodiment. FIG. 27 is a flowchart showing a fault point locating procedure according to the third embodiment.

The configuration of the fault point locating device 106 shown in FIG. 26 is almost the same as that of the fault point locating device 106 of FIG. However, the coordinate conversion unit 123A in FIG. 26 uses the time-series data of the voltage and current of each terminal of the power transmission line 102 to determine the voltage and current of the α circuit according to the failure phase output from the power transmission line failure detection unit 122. Convert to time series data or time series data of β circuit voltage and current. When the transmission line failure detection unit 122 detects a failure by the current differential method, it is easy to identify the failure phase.

26 and 27, steps S100 to S104 of FIG. 27 are similar to those described with reference to FIGS. 13 and 14, and therefore description thereof will not be repeated.

In the next step S105A, the second storage area RAM2 stores the current and voltage time series data of the A terminal and the B terminal in a predetermined period (that is, T1 period in FIG. 15) before and after the current or voltage sudden change detection time. save. The second storage area RAM2 also stores information on the failure phase.

In the next step S106A, the coordinate conversion unit 123A determines which one of the α circuit and the β circuit should be applied based on the information of the failure phase, and also determines the Clark conversion formula.

FIG. 28 is a functional block diagram showing a more detailed configuration of the coordinate conversion unit 123A of FIG. FIG. 28 also shows the configuration of the transmission line failure detection unit 122.

Referring to FIG. 28, the transmission line failure detection unit 122 includes an a-phase failure detection unit 130, a b-phase failure detection unit 131, and a c-phase failure detection unit 132. The a-phase failure detection unit 130 determines whether or not there is a failure in the protection section of the a-phase transmission line by the current differential method, and outputs the determination result to the coordinate conversion unit 123A. The b-phase failure detection unit 131 determines whether there is a failure in the protection section of the b-phase transmission line by the current differential method, and outputs the determination result to the coordinate conversion unit 123A. The c-phase failure detection unit 132 determines whether or not there is a failure in the protection section of the c-phase transmission line by the current differential method, and outputs the determination result to the coordinate conversion unit 123A.

The coordinate conversion unit 123A includes logical operation units 133 to 139 that specify a failure phase based on the outputs of the a-phase failure detection unit 130, the b-phase failure detection unit 131, and the c-phase failure detection unit 132, and voltage-current coordinate conversion. And arithmetic units 140 to 145 for performing.

The logical operation unit 133 determines whether or not a three-phase failure has occurred. The logical operation unit 134 determines whether or not there is an a-phase 1-line fault. The logical operation unit 135 determines whether or not there is a bc-phase two-wire fault. The logical operation unit 136 determines whether or not there is a b-phase 1-line fault. The logical operation unit 137 determines whether or not there is a ca-phase two-wire fault. The logical operation unit 138 determines whether or not there is a c-phase 1-line fault. The logical operation unit 139 determines whether or not there is an ab phase two-wire fault.

The calculation units 140 to 145 perform coordinate conversion of the voltage and current across the power transmission line 102 according to the conversion formulas shown in the table of FIG. 25 based on the calculation results of the logical calculation units 133 to 139, respectively. That is, in the case of a one-line failure, the arithmetic unit corresponding to the detected failure phase uses the conversion formulas according to the failure phase, and the α voltage VAα and the α current IAα at the A terminal and the α voltage VBα at the B terminal and The α current IBα is calculated. In the case of a two-wire failure, the arithmetic unit corresponding to the detected failure phase uses the conversion formula according to the failure phase, and uses the β voltage VAβ and β current IAβ at the A terminal and the β voltage VBβ and β current at the B terminal. Calculate IBβ. In the case of a three-wire failure, the operation unit 133 uses, for example, the same formula as in the case of the bc phase failure of the β circuit, the β voltage VAβ and the β current IAβ at the A terminal, and the β voltage VBβ and the β current IBβ at the B terminal. And are calculated (step S106A in FIG. 27).

In the next step S107A of FIG. 27, the failure section determination unit 124 uses the α voltage VAα and the α current IAα at the A end calculated in step S106A (or the β voltage VAβ and the β current IAβ at the A end) to calculate A The phase angle φA of the impedance VAα/IAα (or the impedance VAβ/IAβ) viewed from the end is calculated. Furthermore, the failure section determination unit 124 uses the α voltage VBα and the α current IBα at the B end (or the β voltage VBβ and the β current IBβ at the B end) calculated in step S106A to measure the impedance VBα/ The phase angle φB of IBα (or impedance VBβ/IBβ) is calculated.

In the next step S108, the failure section determination unit 124 determines the magnitude of the phase angles φA and φB. When φA<φB, the failure section determination unit 124 determines that the failure point F is between the B end and the series capacitor 103 (step S109). In this case, the terminal voltage compensating unit 125 calculates the compensation voltage VAα′ (or VAβ′) that compensates the α voltage VAα (or β voltage VAβ) at the A terminal according to the above equations (5) and (6), The failure point determination unit 126 obtains the unknown number X in the above equation (11). However, in the above equations (5), (6), and (11), the positive phase voltage is changed to α voltage (or β voltage), and the positive phase current is changed to α current (or β current). ..

In the case of the series capacitor 103 with the protection circuit described in the second embodiment, it is necessary to change the above equation (26). Specifically, in the case of an a-phase ground fault, the voltage VC generated in the series capacitor 103 with a protection circuit is
VC=[2*(Xva+Rva)*Ia-(Xvb+Rvb)*Ib-(Xvc+Rvc)*Ic]/3 (27)
Becomes In the case of a short circuit (ground fault) fault and a three-phase fault of the bc phase, the voltage VC generated in the series capacitor 103 with the protection circuit is Ib=-Ic.
VC=[(Xvb+Rvb)*Ib-(Xvc+Rvc)*Ic]/√3
=(2/√3)*(Xvb+Rvb)*Ib …(28)
Becomes In the case of a failure in another phase, the voltage VC can be calculated in the same manner as above.

Subsequent calculations are performed in the same manner as in the first embodiment. Briefly described below, the A terminal voltage VAα(β)′ after the capacitor compensation of the α circuit (or β circuit) is
VAα(β)'=VAα(β)+VC (29)
Becomes Therefore, the voltage VFα(β) at the failure point F calculated using the A-terminal voltage VAα(β)′ after the capacitor compensation and the A-terminal current is
VFα(β)=VAα(β)′−X*Z*IAα(β) (30)
Given in.

Similarly, the voltage VFα(β) at the fault point F calculated using the B-terminal voltage VBα(β) and the B-terminal current VBα(β) is
VFα(β)=VBα(β)-(1-X)*Z*IBα(β) (31)
Given in.

In order to eliminate the need for perfect simultaneousness of the voltage and current at the A terminal and the voltage and current at the B terminal, the amplitude values of the above equations (30) and (31) are calculated and the voltage VFα(β at the failure point F is calculated. ), the calculation results of the amplitude value VFα(β)amp are equal to each other. by this,
(VAα(β)′-X*Z*IAα(β))amp
=(VBα(β)-(1-X)*Z*IBα(β))amp (32)
Is established. In the above equation (32), all the values other than the unknown number X are known, so X can be calculated. By multiplying the calculated X by the actual length of the power transmission line 102, the distance from the A end to the failure point F can be located.

On the other hand, when φA>φB, the failure section determination unit 124 determines that the failure point F is between the A-terminal series capacitor 103 (step S111). In this case, the terminal voltage compensating unit 125 calculates the compensation voltage VBα′ (or VBβ′) that compensates the α voltage VBα (or β voltage VBβ) at the B end according to the above equations (12) and (13), The failure point determination unit 126 obtains the unknown number X in the above equation (18). However, in the above equations (12), (13), and (18), the positive phase voltage is changed to α voltage (or β voltage), and the positive phase current is changed to α current (or β current). .. In the case of the series capacitor 103 with the protection circuit, the voltage VC generated in the series capacitor 103 is replaced by the above-mentioned formula (27) or (28). By multiplying the calculated X by the actual length of the power transmission line 102, the distance from the A end to the failure point F can be determined.

When φA=φB, the failure section determination unit 124 determines that the failure point F is the arrangement position of the series capacitor 103 (step S113), and ends the process. Alternatively, in the case of φA=φB, it is determined that the determination is not possible, and the unknown number X is obtained by both the equations (11) and (18) to obtain the distance from the A end to the failure point F and the B end to the failure point F. The distance may be displayed as a reference value.

[effect]
In this way, when the Clark coordinate method is used, unlike the symmetrical coordinate method, 120° and 240° phase shift calculations are unnecessary. Therefore, the detection period of data required for calculation (T1 period in FIG. 15) can be shortened. In particular, when using a series capacitor with a protection circuit, it is necessary to consider that the voltage of the series capacitor changes according to the current, but by shortening the detection period of the data required for calculation, the calculation error Can be reduced.

Further, in the case of the first embodiment using the symmetric coordinate method, when the system frequency deviates from the rated frequency, if the phase shift calculation is performed using the data 60 electrical degrees before, an error occurs in the phase shift calculation. .. On the other hand, since the Clark transform uses only the latest data at the current time, there is an advantage that it is not necessary to consider the error due to the coordinate transform.

[Modification]
The failure point locating devices of the first to third embodiments can be incorporated in a power transmission line protection relay device that protects the power transmission line based on the current and voltage at both ends of the power transmission line like a current differential relay.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope.

101 Rear Power Supply, 102 Power Transmission Line, 103 Series Capacitor, 106, 111 Fault Locator, 107 Transmission Line, 108 Communication Device, 120 Voltage Data Input/Output Unit, 121 Synchronization Processing Unit, 122 Transmission Line Fault Detection Unit, 123, 123A Coordinate conversion unit, 124 failure section determination unit, 125 terminal voltage compensation unit, 126 failure point determination unit, 201 input conversion unit, 211 A/D conversion unit, 221 arithmetic processing unit, 222 CPU, 231 I/O unit, F failure point.

Claims (7)

A fault locator for a transmission line having a series capacitor on the line,
A coordinate conversion unit that converts time-series data of three-phase current and three-phase voltage of each terminal of the power transmission line into time-series data of positive-phase current and positive-phase voltage;
A failure that determines, for each terminal of the power transmission line, whether the terminal is the first terminal having no failure point with the series capacitor or the second terminal having the failure point with the series capacitor. A section determination unit,
A terminal voltage compensator for compensating the positive phase voltage of the first terminal by adding the voltage generated by the impedance of the series capacitor;
The amplitude of the positive phase voltage at the fault point based on the positive phase current at the first terminal and the compensated positive phase voltage, and the positive phase voltage at the fault point based on the positive phase current and the positive phase voltage at the second terminal. A fault point locating device that determines the position of the fault point assuming that the amplitudes of the fault points are equal. The failure section determination unit,
The impedance phase angle calculated from the positive phase voltage and the positive phase current of one terminal of the transmission line is compared with the impedance phase angle calculated from the positive phase voltage and the positive phase current of the other terminal of the transmission line. ,
The fault location device according to claim 1, wherein the terminal having the smaller calculated phase angle is the first terminal and the terminal having the larger calculated phase angle is the second terminal. .. By including a protection circuit in the series capacitor, the series capacitor provided in each phase of the transmission line has a characteristic that impedance changes according to the current flowing through itself,
3. The terminal voltage compensator calculates a voltage to be added to the positive phase voltage of the first terminal based on the current of each phase of the first terminal and the impedance characteristic of the series capacitor. The fault location device described in. A fault locator for a transmission line having a series capacitor on the line,
When the power transmission line has a one-line fault, the time-series data of the three-phase current and the three-phase voltage of each terminal of the power transmission line are coordinate-converted into the time-series data of the current and voltage of the α circuit, and the power transmission line has two lines. When there is a failure, the time-series data of the three-phase current and the three-phase voltage of each terminal of the power transmission line are converted into the time-series data of the current and voltage of the β circuit, and when the power transmission line has a three-phase failure, the transmission is performed. A coordinate conversion unit that converts the time-series data of the three-phase current and the three-phase voltage of each terminal of the electric wire into the time-series data of the current and voltage of one of the α circuit and the β circuit,
A failure that determines, for each terminal of the power transmission line, whether the terminal is the first terminal having no failure point with the series capacitor or the second terminal having the failure point with the series capacitor. A section determination unit,
A terminal voltage compensator for compensating the coordinate-converted voltage of the first terminal by adding the voltage generated by the impedance of the series capacitor;
Of the amplitude of the voltage at the fault point based on the coordinate-transformed current at the first terminal and the compensated voltage, and the voltage at the fault point based on the coordinate-transformed current and voltage at the second terminal. A fault point locating device, comprising: a fault point determination unit that determines the position of the fault point assuming that the amplitudes are equal. The fault point locating device according to claim 4, further comprising a transmission line fault detection unit that detects a fault phase of the transmission line. The failure section determination unit,
The impedance phase angle calculated from the voltage and current after the coordinate conversion of one terminal of the power transmission line, and the phase angle of the impedance calculated from the voltage and current after the coordinate conversion of the other terminal of the power transmission line. Compare
The failure point according to claim 4 or 5, wherein the terminal having the smaller calculated phase angle is the first terminal and the terminal having the larger calculated phase angle is the second terminal. Orientation device. By including a protection circuit in the series capacitor, the series capacitor provided in each phase of the transmission line has a characteristic that impedance changes according to the current flowing through itself,
The terminal voltage compensator calculates a voltage to be added to the coordinate-converted voltage of the first terminal based on the current of each phase of the first terminal and the impedance characteristic of the series capacitor. The fault point locating device according to any one of 4 to 6.

Images