JP2018163065A - Fault locator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relatively simply perform fault location in a power line having a series capacitor without the need of sampling synchronization at both ends of the power line.SOLUTION: In a fault locator 106 for a power line having a series capacitor, a coordinate conversion part 123 converts a time series data of a three-phase current and a three-phase voltage at every terminal of the power line into time series data of a positive-phase current and a positive-phase voltage. A fault section determination part 124 determines whether every terminal of the power line is a first terminal having a series capacitor between a fault point and the terminal or a second terminal not having a series capacitor between a fault point and the terminal. A terminal voltage compensation part 125 compensates for the positive-phase voltage of the first terminal by adding a voltage generated due to an impedance of the series capacitor. A fault point determination part 126 determines the position of the fault point, assuming that the amplitude of a positive-phase voltage of the fault point based on the positive-phase current and the positive-phase voltage after the compensation of the first terminal is equal to the amplitude of the positive-phase voltage of the fault point based on the positive-phase current and the positive-phase voltage of the second terminal.SELECTED DRAWING: Figure 12

Description

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

  In a long-distance transmission line, the transmission line impedance (particularly the reactance component) increases and the voltage drop at the power receiving end increases. Therefore, by installing a series capacitor on the transmission line and compensating the reactance component of the impedance with this series capacitor, voltage drop at the power receiving end can be suppressed and transmission efficiency can be increased. For this reason, compensation series capacitors are mainly applied to long-distance transmission lines.

  When a series capacitor is installed on the transmission line, the line impedance changes abruptly by the capacitance of the capacitor at the installation point, making it difficult to determine the fault point. For example, Patent Document 1 (Japanese Patent Laid-Open No. 53-105109) discloses a fault location method for a transmission line to which a series capacitor is connected.

  Specifically, in the method of Patent Document 1, the system voltage and system current of the local end and the counterpart end at the same time are taken into the processing device. The processor treats the impedance value calculated from the voltage and current at its own end and the current and the transmission line impedance angle for both the case where the failure point exists on its own side or the other end side from the capacitor. The reactance from the self end to the failure point is calculated by correcting by the above. Further, the processing device determines the impedance value calculated from the voltage and current of the other end for both the case where the failure point exists on the own end side or the other end side of the capacitor, and the current and transmission line of the own end and the other end. By reacting with the impedance angle, the reactance from the other end to the failure point is calculated. The processing device calculates a sum obtained by combining the calculation results of these reactances, and selects the calculated value when the reactance corresponding to the line length is coincident as the line reactance up to the failure point.

  Patent Document 2 (Japanese Patent Application Laid-Open No. 2010-19625) does not relate to fault location in a transmission line having a series capacitor, but does not require complete synchronization for current and voltage measurement between its own end and the other end. A fault location method is disclosed.

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

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

Supervised by Yoshifumi Ohura, “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 location method disclosed in Patent Document 1, in order to calculate the reactance from each end of the transmission line to the fault point, the own 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 synchronize the timing for detecting the current at the own end of the transmission line and the timing for detecting the current at the other end of the transmission line with high accuracy by using a synchronization signal such as a GPS signal from the communication satellite.

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

  As a method that does not use a GPS signal, there is a method of realizing sampling synchronization at both ends of the transmission line by exchanging data with each other via a signal transmission path connecting the substations at both ends of the transmission line. However, this method is based on the premise that the signal transmission delay time from the own end to the other end is equal to the signal transmission delay time from the other end to the other end. Actually, an error of about several hundred μs may occur in the transmission delay time in both directions. If the error is such a level, there is no problem in terms of protection by adjusting the characteristic value in the case of current differential type protection relay calculation, but in the case of fault location, the calculation result is greatly affected.

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

  This disclosure takes the above-mentioned problems into consideration, and its purpose is to relatively easily determine the fault point of a transmission line provided with a series capacitor without requiring sampling synchronization at both ends of the transmission line. It is to provide a fault location device.

  A fault location apparatus according to an embodiment is used for fault location 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 transmission line into the time-series data of the positive phase current and the positive phase voltage. The failure section determination unit determines whether each terminal of the transmission line is a first terminal that does not have a failure point between the series capacitor and a second terminal that has a failure point between the terminal and the series capacitor. To do. The terminal voltage compensation unit 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 is configured to detect the positive phase voltage amplitude 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 on the assumption that the amplitude of the phase voltage is equal.

  A fault location apparatus according to another embodiment is used for fault location 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. Is provided. The coordinate conversion unit converts the time-series data of the three-phase current and voltage of each terminal of the transmission line into the time-series data of the current and voltage of the α circuit when the transmission line has a one-line failure. In the case of a two-wire failure, the time-series data of the three-phase current and voltage of each terminal of the transmission line is coordinate-converted to the time-series data of the current and voltage of the β circuit. The coordinate conversion is performed on the time-series data of the three-phase current and the three-phase voltage of each terminal to the time-series data of the current and voltage of one of the α circuit and the β circuit. The failure section determination unit determines whether each terminal of the transmission line is a first terminal that does not have a failure point between the series capacitor and a second terminal that has a failure point between the terminal and the series capacitor. To do. The terminal voltage compensation unit compensates the voltage after the coordinate conversion of the first terminal by adding the voltage generated by the impedance of the series capacitor. The failure point determination unit includes a failure point voltage amplitude based on the current after the first terminal coordinate conversion and the compensated voltage, and a failure point voltage amplitude based on the current and voltage after the second terminal coordinate conversion. Are determined to be equal, the position of the failure point is determined.

  According to the fault location apparatus of the above 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 on the assumption that the amplitude of the positive phase voltage at the fault location based on the phase voltage is equal, the fault location can be performed relatively easily without the need for sampling synchronization at both ends of the transmission line. In addition, according to the failure point locating device of the other embodiment described above, the amplitude of the voltage at the failure 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 assuming that the amplitude of the voltage at the fault location based on the current and the voltage is equal, the fault location can be performed relatively easily without the need for sampling synchronization at both ends of the transmission line.

It is a block diagram of the electric power system in which the failure point location apparatus by Embodiment 1 was installed. It is a block diagram which shows an example of the hardware constitutions of each failure point location apparatus 106 of FIG. 6 is a circuit diagram when an a-phase ground fault occurs at a fault point F when the series capacitor 103 is in the protection section of the transmission line 102. FIG. FIG. 4 is an equivalent circuit by a symmetric coordinate method corresponding to the circuit diagram of FIG. 3. FIG. 4 is an equivalent circuit based on a symmetric coordinate method when a bc-phase two-wire ground fault occurs at the fault point F in FIG. 3. 4 is an equivalent circuit based on a symmetric coordinate method when a bc-phase two-wire short-circuit fault occurs at the fault point F in FIG. 3. FIG. 4 is a normal phase circuit when a three-phase ground fault occurs at the fault point F in FIG. 3. FIG. When a series capacitor 103 is provided between an A end and a failure point F, it is a diagram illustrating a simple equivalent circuit using a positive phase circuit and a distribution of positive phase voltages. FIG. 6 is a diagram illustrating a simple equivalent circuit and a distribution of positive phase voltages when a series capacitor 103 is provided between a 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 simplified equivalent circuit of FIG. 2 is a functional block diagram of the failure point locating device according to Embodiment 1. FIG. 3 is a flowchart illustrating a failure point location procedure according to the first embodiment. It is a flowchart which shows the procedure of step S104 of FIG. 13 in more detail. FIG. 10 is a timing chart for explaining a data storage period of the second storage area RAM2. It is a figure for demonstrating the phase-shifting calculation method of 120 degrees and 240 degrees. It is a figure which shows the other structural example of the electric power grid | system provided with the failure point location apparatus. FIG. 3 is a circuit diagram showing a series capacitor SC in which a protection circuit MOV is connected in parallel, and a diagram showing 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 Clarke coordinate method when a one-line ground fault occurs at the fault point F in FIG. 3. 4 is an equivalent circuit based on Clarke coordinates when a two-wire ground fault occurs at the fault point F in FIG. 3. 4 is an equivalent circuit based on Clarke coordinates when a two-wire short-circuit fault occurs at the fault point F in FIG. 3. FIG. 4 is an equivalent circuit based on Clarke coordinates when a three-phase fault occurs at the fault point F in FIG. 3. FIG. 4 is a simplified equivalent circuit based on Clarke coordinates when a failure occurs at the failure point F in FIG. 3. It is the figure which put together the conversion type | formula by Clark conversion in a tabular form. FIG. 10 is a functional block diagram of a failure point locating device according to a third embodiment. 10 is a flowchart illustrating a failure point locating procedure according to the third embodiment. It is a functional block diagram which shows the more detailed structure of the coordinate transformation part 123A of FIG.

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

Embodiment 1 FIG.
[Schematic configuration of power system]
FIG. 1 is a configuration diagram of an electric power system in which a failure point locating device according to Embodiment 1 is installed. Referring to FIG. 1, an electric power system includes a transmission line 102, a current transformer (CT) 104_1 and a voltage transformer (VT) 105_1 connected to the transmission line 102 at an A-terminal substation, CT 104_2 and VT105_2 connected to the power transmission line 102 at the B terminal substation, and a series capacitor 103 connected in the middle of the power transmission line 102 are provided. Let C be the capacitance value of the series capacitor. A section between the CTs 104_1 and 104_2 is a protection section of the transmission line 102.

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

  A three-phase back power supply 101_1 is provided far from the A end of the 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 failure point locating device 106_1 provided at the A-end substation, a failure point locating device 106_2 provided at the B-end substation, and communication devices 108_1 and 108_2. Each failure point locating device 106 samples and takes in a current value from its own CT 104 and samples and takes in a voltage value from its own VT 105. Each failure point locator 106 generates digital current data and voltage data by performing A / D (Analog to Digital) conversion on the acquired current value and voltage value.

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

  Each failure point locating device 106 performs a synchronization process using the current data and voltage data sampled by the counterpart failure point locating device 106. Each failure point locating device 106 obtains voltage data and current data sampled at almost the same time at both ends of the transmission line 102 by delaying the data at its own end by the transmission time of the transmission path 107. Each failure point locating device 106 performs a current differential protection relay calculation using these voltage data and current data.

  It supplements about the method of said synchronous processing. Specifically, the failure point locating devices 106_1 and 106_2 perform synchronization processing by transmitting current and voltage data as serial data at a constant period. In addition to current and voltage data, the transmission data from the communication device 108 connected to each failure point locating device 106 includes a timing signal indicating the transmission timing of the data, and from the other end after transmitting the timing signal. A signal representing a time difference until the timing signal is received is included. Each failure point locating device 106 is synchronized by adjusting the transmission timing at one of the terminals (for example, the B end) so that the time difference Ta measured at the A end is equal to the time difference Tb measured at the B end. Can do.

  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 can be achieved by the above-described synchronization processing method. However, when there is a difference between the transmission delay times in both directions, a synchronization error corresponding to (Ta−Tb) / 2 occurs. The actual error size is about 250 μsec to 500 μsec at the maximum in a general-purpose communication device. However, if the error is such a level, it is possible to prevent a problem in the protection operation by adjusting the operation characteristics of the current differential relay.

  When detecting the occurrence of a failure in the protection section by a method other than the current differential relay, the synchronization process is not necessary. In this case, fault location is performed only at the fault location device 106_1 at one end, for example, the A end. The B-end fault location device 106_2 has a function of detecting the current and voltage of the B end, and a function of transmitting A / D converted B-end current data and voltage data to the A-end fault location device 106_1. Having it is enough. In this case, the A-end fault location device 106_1 does not need to transmit A / D converted A-end current data and voltage data to the B-end fault location device 106_2.

  However, even when the occurrence of a fault in the protection zone is detected by a method other than the current differential relay, current and voltage data at both ends when the protection zone is faulty are necessary to determine the fault location. . Therefore, even if sampling synchronization with the accuracy required for the current differential relay operation is not required, 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 a hardware configuration of each failure point locating device 106 in FIG. 2 has the same configuration as a so-called digital relay device. Specifically, referring to FIG. 2, failure point locating apparatus 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 each phase current signal output from the CT 104 in FIG. 1 and each phase voltage signal output from the VT 105 in FIG. 1 are input. Each auxiliary transformer 202 converts the current signal and voltage signal from CT 104 and VT 105 into a signal of a voltage level suitable for signal processing in arithmetic processing unit 221 and arithmetic processing unit 221.

  The A / D converter 211 includes analog filters (AF) 212_1, 212_2,..., Sample hold circuits (S / H) 213_1, 213_2,. And an 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 aliasing errors during A / D conversion. Each sample and 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 for connecting them. The CPU 222 controls the overall operation of the failure point location device 106. The RAM 223 and the ROM 224 are used as the main memory of the CPU 222. The ROM 224 can store programs, setting values for signal processing, and the like by using a nonvolatile memory such as a flash memory.

  The I / O unit 231 includes an interface (I / F) circuit 232 for connecting to its own communication device 108, a digital input (D / I) 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 fault point F when the series capacitor 103 is in the protection section of the transmission line 102. Let R be the failure point resistance. The failure point resistance is arc resistance. FIG. 3 shows the 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 terminal substation and the B terminal substation is “1”, the ratio of the distance from the A terminal substation to the failure point F is “X”. The ratio from the B terminal substation to the failure point F is defined as “1-X”. In the fault location method according to the present embodiment, the current and voltage at the A and B ends of the transmission line 102 and the line constant of the transmission line 102 are coordinate-converted using a symmetric coordinate method.

  FIG. 4 is an equivalent circuit by the symmetric 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. The positive phase current at the A end is IA1, the reverse phase current is IA2, and the zero phase current is IA0. The positive phase current at the B end is IB1, the reverse phase current is IB2, and the zero phase current is IB0. The positive phase voltage output from the A-side rear power supply 101_1 is EA, and the positive-phase voltage output from the B-end rear power supply 101_2 is EB. The reverse phase impedance of the transmission line 102 from the A-side rear power supply 101_1 to the failure point F is ZA2, and the reverse-phase impedance of the transmission line 102 from the B-end rear power supply 101_2 to the failure point F is ZB2. The zero-phase impedance of the transmission line 102 from the A-side rear power supply 101_1 to the failure point F is ZA0, and the zero-phase impedance of the transmission line 102 from the B-end rear power supply 101_2 to the failure point F is ZB0. The negative phase impedance ZA2 includes the capacitance of the negative phase of the series capacitor 103. The zero-phase impedance ZA0 includes a zero-phase capacitance of the series capacitor 103.

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

ZF = ZA2 / ZB2 + ZA0 // ZB0 + 3 · R (1)
In the above equation (1), symbol // indicates the impedance of parallel connection. Therefore, the equivalent circuit of the a-phase ground fault can be expressed by a simple equivalent circuit having only a 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.

  3 and 4, the simple equivalent circuit in the case of a one-wire ground fault has been described. However, other types of faults, such as a two-wire ground fault, a two-wire short-circuit fault, a three-phase ground fault, and a three-phase short-circuit fault, are described. The case can also be expressed 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 two-wire ground fault occurs at the fault point F in FIG. The single ground fault resistance of the b phase and the c phase is r, and the common ground fault resistance is R. 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 to the fault point F of the positive phase circuit. Therefore, the impedance ZF represented by the following formula (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 expressed by the simple equivalent circuit of FIG. The same applies to the ca-phase 2-wire ground fault and the ab-phase 2-wire ground fault.

FIG. 6 is an equivalent circuit based on the symmetric coordinate method when a bc-phase two-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 a 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 formula (3), that is,
ZF = ZA2 // ZB2 (3)
By using, the equivalent circuit of the bc-phase two-wire short-circuit fault can be expressed by the simple equivalent circuit of FIG. The same applies to the ca-phase 2-wire short-circuit failure and the ab-phase 2-wire short-circuit failure.

  FIG. 7 is a normal phase circuit when 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 is 0 in FIG. Therefore, even in the case of a three-phase short-circuit fault and a three-phase ground fault, it can be represented by the simple equivalent circuit of FIG. 8A by using the impedance ZF.

<2. Failure point location method-When the series capacitor is between the A end and the failure 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 present. Is a diagram showing the distribution of the positive phase voltage and the simple equivalent circuit by the positive phase circuit in the case where the fault point F exists between the In this specification, the A end in the above case may be referred to as a first end, and the B end may be referred to as a second end.

  FIG. 8A shows a simple equivalent circuit based on the symmetric 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 failure point F of the normal phase circuit as shown in FIG. In FIG. 8A, “*” is a symbol representing multiplication.

  FIG. 8B shows the distribution of positive phase voltages at each point of 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. Let the positive phase voltage at the failure point F be VF.

  8A and 8B, the length of the transmission line 102 from the A end to the B end is set to 1, the distance from the A end to the failure point F is set to X, and the failure is started from the B end. The distance to the point F is 1-X. 0 ≦ X ≦ 1 holds. Further, the distance from the A 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, X = X1 + X2 holds.

  Further, let Z be the impedance of the transmission line 102 from the A end to the B end. In this case, the impedance not including the series capacitor 103 from the A end to the failure point F is represented by X * Z, and the impedance from the B end to the failure point F is represented by (1-X) * Z. Furthermore, 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. 8B, the positive phase voltage is increased 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 is assumed that j is an imaginary unit and f is a system frequency.
ZC = −j (1 / ωC), ω = 2πf (4)
It is represented by Therefore, when the current IA1 flows through the series capacitor 103, the voltage VC is
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, the voltage VA1 ′ obtained by compensating the A-phase positive phase voltage VA1 with the voltage VC, that is,
VA1 ′ = VA1 + VC (6)
think of. Then, the positive phase voltage VF at the failure point F is obtained by using the compensation voltage VA1 ′ at the A end and the positive phase current IA1.
VF = VA1′−X * Z * IA1 (7)
Represented by

Further, the positive phase voltage VF at the failure point F is obtained by using the positive phase voltage VB1 and the positive phase current IB1 at the B end,
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 end and the current and voltage data at the B end do not have the same time, The calculated positive phase voltage VF and the positive phase voltage VF calculated according to the equation (8) are not equal because of a time difference. However, the amplitude value of the positive phase voltage VF in the equation (7) and the amplitude value of the positive phase voltage V fault point F in the equation (8) are equal to each other because the same time property is not necessary.

Specifically, when the amplitude value is represented by the symbol “amp”, the relational expression of the amplitude value corresponding to the equation (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 of the expressions (11) are known except for X, 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 transmission line 102 between the A end and the B end.

  In Equation (11), a known method can be used as a method for calculating the amplitude value using data sampled in time series. For example, supervised by Yoshifumi Oura, “Protection 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 (not limited to this).

<3. Fault location method-When the series capacitor is between the B end and the fault F>
FIG. 9 shows a case where the series capacitor 103 is provided between the B end and the fault point F (that is, the fault point F exists between the A end and the series capacitor 103, and the B end and the series capacitor 103 5 is a diagram showing the distribution of the simple equivalent circuit and the positive phase voltage in the case where no fault point F exists between the two. In this specification, the B end in the above case may be referred to as a first end, and the A end may be referred to as a 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 an impedance ZF is added to the failure point F of the positive phase circuit. FIG. 9B shows the positive phase voltage distribution at each point of the simplified equivalent circuit of FIG.

  Referring to FIGS. 9A and 9B, the length of the transmission line 102 from the A end to the B end is set to 1, the distance from the A end to the failure point F is set to X, and the failure is started from the B end. The distance to the point F is 1-X. 0 ≦ X ≦ 1 holds. Further, 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 voltage VC, that is,
VB1 ′ = VB1 + VC (13)
think of. Then, the positive phase voltage VF at the failure point F is obtained 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 failure point F is obtained by using the positive phase voltage VA1 and the positive phase current IA1 at the A end.
VF = VA1- (1-X) * Z * IA1 (15)
Represented by

In order to eliminate the need for the same time between the current and voltage data at the A end and the current and voltage data at the B end, 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 Expression (18) is already known except for X, 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 transmission line 102 between the A end and the B end.

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

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

  Referring to FIGS. 8A and 10A, the impedance calculated using positive phase voltage VA1 and 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 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 transmission line 102 from the series capacitor 103 to the failure point F. , Equal to the value obtained by combining (that is, vector addition) the impedance ZF of the failure point F.

  Referring 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 the phase angle is φB. The impedance VB1 / IB1 is equal to a value obtained by combining the impedance (1-X) * Z of the transmission line 102 from the B end to the failure point F and the impedance ZF of the failure 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 viewed from the A end is Is apparently smaller than the phase angle φB of the impedance VB1 / IB1. That is, φA <φB.

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

  Referring to FIGS. 9A and 11A, the impedance calculated using positive phase voltage VA1 and 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.

  Referring 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 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 transmission line 102 from the series capacitor 103 to the failure point F. , Equal to the value obtained by combining (that is, vector addition) the impedance ZF of the failure point F.

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

  Thus, the phase angle φA of the impedance VA1 / IA1 viewed from the A end is compared with the phase angle φB of the impedance VB1 / IB1 viewed from the B end. If φA <φB, the failure point F is And the series capacitor 103, and not between the A terminal 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 terminal and the series capacitor 103 and does not exist between the B terminal and the series capacitor 103.

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

[Specific procedure for fault location]
Hereinafter, the above description will be summarized and a specific procedure for fault low orientation will be described.

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

  Referring to FIG. 12, functionally, fault location apparatus 106 includes current / voltage data input / output unit 120, synchronization processing unit 121, first storage area RAM1, and second storage area RAM2. A power line failure detection unit 122, a coordinate conversion unit 123, a failure section determination unit 124, a terminal voltage compensation unit 125, and a failure point determination unit 126.

  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. The functions of the synchronization processing unit 121, the power 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 performed by the CPU 222 of the arithmetic processing unit 221 in FIG. This is realized by executing the program. Note that these functions can also 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 of FIG. Hereinafter, the operation of each component of the failure point locator 106 in FIG. 12 will be described with reference to the flowcharts in 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 input of the current value from CT 104 and receives the current value from VT 105. Receives the voltage value at the end. The A / D converter 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. The data is transmitted to the fault location device 106 at the other end via the path 107 and the communication devices 108_1 and 108_2. 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) Current data and voltage data are received.

  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 at its own end. Specifically, each fault location device 106 assumes 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 own-end current data and voltage data by (usually several milliseconds), the sampling time of the own-end data and the sampling time of the other-end data are made substantially the same time.

  In the next step S104, the power transmission line failure detection unit 122 performs a protection relay operation using a current differential method or the like, thereby performing a protection section of the power transmission line 102 (between the A end and the B end in this embodiment). The presence or absence of a failure is detected, and a sudden change in current data and voltage data is detected.

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

  Referring to FIG. 12, FIG. 14, and FIG. 15, in step S200, first storage area RAM1 and second storage area RAM2 receive the current data and voltage data of their own and other ends after the 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 at its own end and the latest current data and voltage data at the other end. At this time, the stored data in the first storage area RAM1 and the second storage area RAM2 is replaced with the oldest data every time the latest data is acquired by the current / voltage data input / output unit 120. It is updated by being done. The data storage period of the first storage area RAM1 is a period necessary for a protection relay operation such as a current differential relay. The data storage period of the second storage area RAM2 is a period necessary for fault location, and is the T1 period in FIG.

  In the next step S202, the power transmission line failure detection unit 122 detects whether or not current data or voltage data at its own end (or the other end) has changed suddenly. As this 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 a cycle before exceeds a threshold value. The Such a process is generally referred to as a current (or voltage) change width relay, and can detect an abnormality earlier than a protective relay operation such as a current differential relay.

  As a result, when a sudden change in the current data or voltage data is detected (YES in step S202), in the next step S205, the second storage area RAM2 has a period T2 from the sudden change detection time t2 (T2 from T1). The update of the data is stopped after the elapse of time. As a result, data in the T1 period (from time t1 to time t4 in FIG. 15) around time t2 when the sudden change in current data or 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 location after step S106 in FIG. Note that the update of the data stored in the second storage area RAM2 is resumed after the fault location.

  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, thereby the protection section of the power transmission line 102 (in this embodiment, the A end and the B Detect the presence or absence of a fault (between the edges). As a result, when a failure of the power transmission line 102 is detected within the protection section (YES in step S204), the process proceeds to the next step S106 and the failure point location is executed.

  On the other hand, if a failure in the protection section of the transmission line 102 is not detected even after the lapse of the period T3 from the time t2 at which the sudden change in current or voltage is detected (NO in step S204), the process proceeds to 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 resumed.

  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 set values). Not limited to).

  Referring to FIGS. 12 and 13 again, in the next step S106, the coordinate conversion unit 123 sets the amplitude value in the period corresponding to the failure section among the data in the T1 period stored in the second storage area RAM2. Data of about one cycle necessary for 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 fault removal, and the data cannot be used for fault location. The coordinate conversion unit 123 calculates time-series data of the A-phase positive phase voltage VA1 by using the time-series data of the A-phase voltage Va, b-phase voltage Vb, and c-phase voltage Vc extracted. Similarly, the coordinate converter 123 calculates time-series data of the A-phase positive phase current IA1 using the time-series data of the A-phase current Ia, b-phase current Ib, and c-phase current Ic. Further, the coordinate conversion unit 123 calculates time-series data of the positive-phase voltage VB1 at the B end 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 and B ends are collectively referred to as V1, and the positive phase currents at the A and B ends are 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 phase shift of 240 °.

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

Specifically, in FIG. 16, the current voltage data is V (t), and the voltage data 60 electrical degrees before the current time is V (t-60 °). Then, the voltage data V∠120 ° shifted by 120 ° and the voltage data V∠240 ° shifted by 240 ° from the current voltage data V (t) 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 sets the phase angle φA = Arg (VA1 / IA1) of the impedance VA1 / IA1 of the transmission line 102 viewed from the A end and the impedance VB2 of the transmission line 102 viewed from the B end. / IB2 phase angle φB = 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. The failure section determination unit 124 determines that the failure point F is between the B end and the series capacitor 103 when φA <φB (step S109). In this case, the terminal voltage compensator 125 calculates a compensation voltage VA1 ′ obtained by compensating 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 11) Find the unknown X in the equation. By multiplying the calculated X by the actual length of the 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-series series capacitor 103 (step S111). In this case, the terminal voltage compensator 125 calculates the compensation voltage VB1 ′ compensated for the positive phase voltage VB1 at the B end according to the above-described equations (12) and (13). 18) Find the unknown X in the equation. By multiplying the calculated X by the actual length of the transmission line 102, the distance from the A end to the failure point F can be determined.

  If φA = φB, the failure section determination unit 124 determines that the failure point F is an 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 impossible, and the unknown X is obtained by both the equations (11) and (18), so that the distance from the A end to the failure point F and the B end to the failure point F are obtained. The distance may be displayed as a reference value.

[Modification]
In step S101 and step S102 of FIG. 13, the failure point locating devices 106_1 and 106_2 exchange a three-phase current and a three-phase voltage with each other via the transmission line 107. Alternatively, each failure point locating device 106 may first convert the coordinates into a positive phase current and a positive phase voltage, and transmit the positive phase voltage and the positive phase current to the failure 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, it may be determined whether or not the current or voltage has suddenly changed using the current data or voltage data at the end before the synchronization processing as it is. Since no synchronization processing is performed, a sudden change in current or voltage can be detected more quickly.

  The synchronization process in step S103 in FIG. 13 is performed in order to use the current differential method for detecting a failure in the power transmission line 102. Therefore, when the failure detection of the power transmission line 102 is performed by another method, it is only necessary to exchange data in the same failure state, and accurate synchronization processing is not necessary.

  FIG. 17 is a diagram illustrating another configuration example of the power system including the failure point locating device. The power system of FIG. 17 is provided with current differential type protection relay devices 110_1 and 110_2 instead of the fault location devices 106_1 and 106_2 of FIG. The fault location device 111 receives current data and voltage data detected from each protection relay device.

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

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

  Specifically, the failure point locating devices 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 failure point F is closer to the A end or closer to 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 positive voltage at the A end is compensated by the series capacitor voltage, and the compensation voltage at the A end and the positive phase current at the A end are used. Thus, the positive phase voltage VF at the failure 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 by these two kinds of calculations are equal, the distances from the A end and the B end to the failure point are obtained. Even when the failure point F is closer to the A end than the series capacitor 103, the failure point can be determined by the same calculation.

  As described above, in the fault location method according to the first embodiment, it is not necessary to synthesize (vector operation) the voltage and current at the A end and the voltage and current at the B end. It is unnecessary. Therefore, accurate fault location can be performed without performing high-accuracy synchronization processing using GPS. Furthermore, the failure point locating method of the first embodiment has an advantage that the same arithmetic expression can be used regardless of the failure type.

Embodiment 2. FIG.
In the second embodiment, a case where a protection circuit is provided in the series capacitor 103 in FIG. 1 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 a protection circuit MOV is connected in parallel, and a diagram showing 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 through the parallel circuit is I _V. FIG. 18B shows the relationship between the voltage v _MOV and the current i _MOV of the protection circuit MOV. As shown in FIG. 18B, even if the current i _MOV increases, the voltage v _MOV generated in the protection circuit _MOV is limited, so the voltage V _{V in} FIG. 18A is also limited. Thereby, it is possible to protect the voltage applied to the series capacitor SC so as not to exceed 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 impedance characteristics of the series capacitor SC with a protection circuit (that is, characteristics of the resistance R _V and the reactance X _V ) 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 current. Therefore, the voltage VC generated in the series capacitor shown in FIGS. 8 and 9 can be calculated by storing the resistance against the current and the reactance characteristic in the memory.

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

  In summary, 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 the series capacitor. In this case, the terminal voltage compensator 125 calculates the voltage generated in the series capacitor with the protection circuit of each phase based on the currents Ia, Ib, and 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 a protection circuit is calculated from the voltage of each phase.

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

Embodiment 3 FIG.
In the failure point locating device 106 according to the first embodiment, the three-phase voltage and the three-phase current at both ends of the transmission line 102 are converted into the positive-phase voltage and the positive-phase current using the symmetric coordinates, and the positive-phase voltage and the positive-phase current are converted. Used to determine the fault location. The failure point locating device 106 according to Embodiment 3 uses the Clark transformation (α-β-0 method) to convert the three-phase voltage and the three-phase current at both ends of the transmission line 102 into an α voltage, an α current, a β voltage, or a β current. And fault location is performed using α voltage and α current or β voltage or β current. As will be described below, when using Clark conversion, it is necessary to determine the failure phase, and it is necessary to note that the conversion formula differs depending on the failure phase.

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

<1. Expression by simple equivalent circuit>
FIG. 20 is an equivalent circuit based on the Clarke 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 terminal is VAα, and the current of the α circuit is IAα. The voltage of the α circuit at the B terminal is VBα, and the current of the α circuit is IBα. Further, the zero-phase current at the A end is assumed to be IA0, and the zero-phase current IB0 at the B end is assumed to be IA0. The output voltage in the α circuit of the A-side rear power supply 101_1 is EAα = Ea, and the output voltage in the β circuit is EAβ = −jEa. The output voltage in the α circuit of the power source 101_2 behind the B terminal 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 Clarke coordinate method in the case of a one-wire ground fault has a configuration in which an α circuit and a zero-phase circuit are connected in series at the fault point F.

  FIG. 21 is an equivalent circuit based on Clarke 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 terminal is VBβ, and the current of the β circuit is IBβ.

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

  FIG. 22 is an equivalent circuit based on Clarke coordinates when a two-wire short-circuit fault occurs at the fault point F in FIG. As shown in FIG. 22, the equivalent circuit based on the Clarke 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 Clarke coordinates when a three-phase fault occurs at the fault point F in FIG. As shown in FIG. 23, the equivalent circuit based on Clarke coordinates in the case of a three-phase failure has a configuration in which the α circuit is short-circuited at the failure point F and the β circuit is short-circuited at the failure point F.

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

  FIG. 24B shows a simple equivalent circuit using a β circuit, and shows a configuration in which an impedance ZFβ is added to the failure point F. Let VFβ be the voltage at the failure point F. The simple equivalent circuit of FIG. 24B can be applied to a case of a two-wire ground fault, a two-wire short-circuit failure, and a three-phase failure. Thus, in the case of Clark conversion, the simplified equivalent circuit to be applied differs depending on the type of failure.

<2. Clarke conversion formula>
FIG. 25 is a table summarizing conversion formulas by Clark conversion in a tabular form. There is a distinction between failure types: 1-wire short-circuit failure, 2-wire short-circuit failure, 2-wire ground fault, and 3-phase failure.

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

  In the case of a three-phase failure, FIG. 25 shows a conversion formula in the case of a 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 an α circuit may be used.

  According to the conversion formula shown in FIG. 25, the voltage and current coordinates of each terminal of the transmission line 102 are converted. The procedure for performing the subsequent fault location is almost the same as in the first embodiment. Hereinafter, a description will be given with reference to FIGS. 26 and 27. FIG.

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

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

  Referring to FIGS. 26 and 27, steps S100 to S104 in FIG. 27 are the same as 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 at the A end and the B end in a predetermined period (that is, the T1 period in FIG. 15) before and after the current or voltage sudden change detection time. save. The second storage area RAM2 further stores fault phase information.

  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 failure phase information, 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 power transmission line failure detection unit 122.

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

  The coordinate conversion unit 123A includes logic operation units 133 to 139 that specify a failure phase based on 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 coordinate conversion of voltage and current. And arithmetic units 140 to 145 that perform the above.

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

  The calculation units 140 to 145 perform coordinate conversion of the voltage and current at both ends of the transmission line 102 according to the conversion formula shown in the table of FIG. 25 based on the calculation results of the logic calculation units 133 to 139, respectively. In other words, in the case of a one-line failure, the arithmetic unit corresponding to the detected failure phase uses the conversion formula corresponding to the failure phase, and the α voltage VAα and α current IAα at the A end and the α voltage VBα at the B end and The α current IBα is calculated. In the case of a two-wire fault, the arithmetic unit corresponding to the detected fault phase uses the conversion formula corresponding to the fault phase to use the β voltage VAβ and β current IAβ at the A end and the β voltage VBβ and β current at the B end. IBβ is calculated. In the case of a three-wire failure, the arithmetic unit 133 uses, for example, the same formula as in the case of the bc phase failure of the β circuit, and the β voltage VAβ and β current IAβ at the A end and the β voltage VBβ and β current IBβ at the B end Are calculated (step S106A in FIG. 27).

  In the next step S107A of FIG. 27, the failure section determination unit 124 uses the A-terminal α voltage VAα and α-current IAα (or A-terminal β voltage VAβ and β-current IAβ) calculated in step S106A to The phase angle φA of the impedance VAα / IAα (or impedance VAβ / IAβ) viewed from the end is calculated. Further, the failure section determination unit 124 uses the B-terminal α voltage VBα and α-current IBα (or the B-terminal β voltage VBβ and β-current IBβ) calculated in step S106A to generate an 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. The failure section determination unit 124 determines that the failure point F is between the B end and the series capacitor 103 when φA <φB (step S109). In this case, the terminal voltage compensation unit 125 calculates a compensation voltage VAα ′ (or VAβ ′) obtained by compensating the α voltage VAα (or β voltage VAβ) at the A end according to the above-described equations (5) and (6), The failure point determination unit 126 obtains the unknown number X in the above-described equation (11). However, 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 above formulas (5), (6), and (11). .

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

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

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

In order to eliminate the need for complete synchronicity between the voltage and current at the A end and the voltage and current at the B end, the amplitude values of the above equations (30) and (31) are calculated, and the voltage VFα (β ) Of amplitude values 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), since all except the unknown X are known, X can be calculated. By multiplying the calculated X by the actual length of the 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-series series capacitor 103 (step S111). In this case, the terminal voltage compensation unit 125 calculates a compensation voltage VBα ′ (or VBβ ′) obtained by compensating the α voltage VBα (or β voltage VBβ) at the B end in accordance with the above-described equations (12) and (13). The failure point determination unit 126 obtains the unknown X in the above equation (18). However, 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 above equations (12), (13), and (18). . In the case of the series capacitor 103 with a protection circuit, the voltage VC generated in the series capacitor 103 is replaced with the above-described equation (27) or (28). By multiplying the calculated X by the actual length of the transmission line 102, the distance from the A end to the failure point F can be determined.

  If φA = φB, the failure section determination unit 124 determines that the failure point F is an 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 impossible, and the unknown X is obtained by both the equations (11) and (18), so that the distance from the A end to the failure point F and the B end to the failure point F are obtained. The distance may be displayed as a reference value.

[effect]
Thus, when the Clarke coordinate method is used, unlike the symmetric coordinate method, the phase shift calculation of 120 ° and 240 ° is not necessary. For this reason, the detection period (T1 period of FIG. 15) of the data required for calculation 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 it is possible to reduce the calculation error by shortening the detection period of the data required for the calculation. Can be reduced.

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

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

  The embodiment disclosed this time must 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.

  DESCRIPTION OF SYMBOLS 101 Back power supply, 102 Transmission line, 103 Series capacitor, 106,111 Fault location device, 107 Transmission path, 108 Communication device, 120 Voltage data input / output unit, 121 Synchronization processing unit, 122 Transmission line failure 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 location device for a transmission line having a series capacitor on the line,
A coordinate conversion unit that converts time-series data of the three-phase current and the three-phase voltage of each terminal of the transmission line into time-series data of a positive-phase current and a positive-phase voltage;
For each terminal of the power transmission line, a failure to determine whether it is a first terminal that does not have a failure point with the series capacitor or a second terminal that has the failure point with the series capacitor An interval determination unit;
A terminal voltage compensator that compensates for 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 failure point locating device comprising a failure point determination unit that determines the position of the failure point on the assumption that the amplitude of the failure point is equal. The failure section determination unit
The impedance phase angle calculated from the positive phase voltage and positive phase current of one terminal of the transmission line is compared with the phase angle of impedance calculated from the positive phase voltage and positive phase current of the other terminal of the transmission line. ,
The fault location apparatus 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. . When the series capacitor includes a protection circuit, the series capacitor provided in each phase of the transmission line has a characteristic that impedance changes according to a current flowing through the series capacitor,
The terminal voltage compensator calculates a voltage to be added to a positive phase voltage of the first terminal based on a current of each phase of the first terminal and an impedance characteristic of the series capacitor. Fault location device as described in 1. A fault location device for a transmission line having a series capacitor on the line,
When the power transmission line has one line failure, the time series data of the three-phase current and voltage of each terminal of the power transmission line is coordinate-converted to the time series data of the current and voltage of the α circuit, and the power transmission line has two lines. In the case of a failure, the time-series data of the three-phase current and voltage of each terminal of the transmission line is coordinate-converted into the time-series data of the current and voltage of the β circuit. A coordinate conversion unit for converting 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;
For each terminal of the power transmission line, a failure to determine whether it is a first terminal that does not have a failure point with the series capacitor or a second terminal that has the failure point with the series capacitor An interval determination unit;
A terminal voltage compensator that compensates the voltage after the coordinate transformation of the first terminal by adding a voltage generated by the impedance of the series capacitor;
The amplitude of the voltage at the failure point based on the current after the coordinate conversion of the first terminal and the compensated voltage, and the voltage at the failure point based on the current and the voltage after the coordinate conversion of the second terminal. A failure point locating device comprising a failure point determination unit that determines the position of the failure point on the assumption that the amplitudes are equal.   The failure point locating device according to claim 4, further comprising a transmission line failure detection unit that detects a failure phase of the transmission line. The failure section determination unit
The phase angle of the impedance calculated from the voltage and current after the coordinate conversion of one terminal of the 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 transmission line Compare and
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. When the series capacitor includes a protection circuit, the series capacitor provided in each phase of the transmission line has a characteristic that impedance changes according to a current flowing through the series capacitor,
The terminal voltage compensator calculates a voltage to be added to the voltage after the coordinate conversion of the first terminal based on a current of each phase of the first terminal and an impedance characteristic of the series capacitor. The fault location apparatus of any one of 4-6.

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