JPH10132890A - Method and device for locating failure point - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the location of failure points and improve accuracy based on normal phase, reverse phase and zero phase equivalent circuit by the method of symmetrical component coordinates. SOLUTION: During an accident of three-phase alternating current transmission line 3, a failure point locating device 100 periodically samples the voltage and current of each phase measuring with data collection terminals 10A and 10B at electric sites A and B with a data acquisition part 101, which are maintained during the accident. A symmetrical component signal converter 103 converts the voltage and current of each phase into symmetrical component voltage and symmetrical component current in each circuit of normal phase, reverse phase and zero phase of a symmetrical component equivalent circuit. An accident kind judgment par 104 selects the phase of symmetrical component equivalent circuit used in failure point locating operation according to the accident scheme judged by the symmetrical component current and the like. A failure point location operation part 105 calculates failure point of the symmetrical component equivalent circuit of selected phase by utilizing the fact that the symmetrical component voltage of the failure point become the same value in both sides of electric sites A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for locating a short-circuit or ground fault in a three-phase AC transmission line.

[0002]

2. Description of the Related Art As a method of locating a fault in a transmission line, for example, an arithmetic method described in a paper "Development of a transmission line accident aspect identification apparatus (IEEJ Transactions on Communications, Vol. 114, No. 7/8, 1994)" Etc. are known.

In these conventional fault locating methods, the voltage of each phase of a transmission line is calculated in order to calculate a voltage drop in an actual system.
An arithmetic expression is configured using the current signal, the self-impedance of each phase, and the mutual impedance between the phases.

[0004]

Since the conventional fault locating operation is based on an actual system, the target circuit is three-phase, the line impedance is large, and the operation formula is complicated. Also, depending on the type of accident, such as a short-circuit fault or a single-line ground fault, even if there are a plurality of independent information items for locating, it takes a long time to perform the calculation because the calculation method is based on those information items. Not only that, the accuracy when viewed for each accident type is reduced. Furthermore, since there are many line constants used for calculation, it takes time to set constants when newly establishing or changing the system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for overcoming the problems of the prior art and for locating a fault point of a three-phase AC transmission line with high speed and high accuracy by using a simple arithmetic expression.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a fault point locating method for determining a fault point of an accident occurring in a three-phase AC transmission line as a distance from a reference terminal A or B on both sides thereof. At the time of an accident, the voltages and currents of each of the three-phase alternating current phases measured at each of the reference terminals A and B are compared with those of the reference terminals A and B in the positive-phase, reverse-phase, and zero-phase circuits of the symmetric equivalent circuit. This is achieved by converting into a symmetrical component voltage and a symmetrical component current and calculating the fault point by utilizing that the symmetrical component voltages at the fault point have the same value as viewed from both sides of the reference terminals A and B.

[0007] The fault point is calculated by a voltage drop from both sides of the reference terminals A and B with a symmetrical line impedance being uniform.

[0008] The calculation of the fault point is performed by calculating a symmetric component equivalent circuit of a phase in which the symmetric component current in each of the positive phase, the negative phase, and the zero phase is increased to a predetermined value exceeding an unbalance component generated in a normal state. It is characterized by performing using.

Alternatively, an accident type is specified from an accident phase in which the three-phase AC current greatly changes, and a phase of a symmetrical equivalent circuit applicable to the calculation of the fault point corresponding to the accident type is selected. It is characterized by. The fault phase can be determined based on whether or not the combined value of the currents measured at both terminals A and B at the same time has exceeded a predetermined threshold.

When the type of fault is a one-wire ground fault or a two-wire ground fault, the fault point calculated by each of the positive-phase, negative-phase, and zero-phase circuits or an average value thereof is obtained. Obtains a fault point calculated in each of the positive-phase and negative-phase circuits or an average value thereof, and obtains a fault point calculated in the positive-phase circuit when a three-wire short circuit or a three-wire ground fault occurs. It is characterized by.

A fault point locating apparatus to which the method of the present invention is applied is a data collection unit that periodically samples the voltage and current of each phase measured at electric stations A and B and holds the voltage and current for a predetermined period; A symmetrical signal converter for converting a voltage and a current into a symmetrical component voltage and a symmetrical component current in each of the positive-phase, reverse-phase, and zero-phase circuits of the symmetrical equivalent circuit; The applied circuit discriminating unit that selects the symmetrical equivalent circuit of the phase in question and the symmetrical equivalent circuit of the selected phase have the same symmetrical voltage at the fault point when viewed from both sides of the electric stations A and B. And a failure point locating operation unit for calculating a failure point by utilizing the above method.

Further, storage means for setting the line impedance between the electric stations A and B with a uniform distribution is provided for each of the positive phase, the negative phase and the zero phase of the symmetrical equivalent circuit.
And calculating the voltage drop from both sides to the fault point to calculate the fault point.

Instead of the applied circuit discriminating unit, the type of the fault is discriminated by detecting the phase in which the current of each phase or its symmetrical current has changed from the steady state, and the fault current flows according to the type of the fault. An accident type determination unit for selecting a phase symmetrical equivalent circuit may be provided.

According to the configuration of the present invention, the fault point of the three-phase AC transmission line is located based on the symmetric equivalent circuit of the three-phase AC circuit by the symmetric coordinate method. That is, by using the symmetrical equivalent circuit, the fault point can be easily calculated from the voltage drop due to the symmetrical component voltage and the symmetrical component current in each of the positive phase, the negative phase, and the zero phase, and the fault location can be speeded up.

The phases of the symmetrical equivalent circuits that can be used differ depending on the type of the fault. This is because the connection state of the symmetrical equivalent circuit changes depending on the type of accident, and basically a circuit through which a fault current flows is selected. By the way,
1-phase ground fault or 2-wire ground fault, positive-phase, negative-phase, and zero-phase circuits; 2-wire short-circuit, positive-phase and reverse-phase circuits; 3-wire short-circuit or 3-wire ground fault A positive-phase circuit can be used. When a fault point is calculated by a plurality of circuits, the accuracy can be improved by obtaining the average value.

[0016]

Embodiments of the present invention will be described in detail with reference to the drawings. The same symbols are given to the same circuit elements and signals throughout the figures.

FIG. 1 shows an overall configuration of a fault locating apparatus according to an embodiment applied to a three-phase AC transmission line. The transmission line 3 and the power sources EA and EB of the power system are respectively a
It is formed by a three-phase alternating current of a phase, a b-phase, and a c-phase, but is simplified in a single diagram. F is a symbol indicating an example of a failure point.

ZPA and ZPB indicate impedances from the electric stations A and B to the power sources EA and EB. Impedances ZPA and ZPB also exist in each phase. ZNA, Z
NB is the neutral point ground impedance of the three-phase AC circuit. Depending on the voltage class of the system, the neutral point ground impedance has a form such as direct grounding or resistance grounding. Although not shown, the impedance of the transmission line 3 is regarded as a uniform distribution between the electric stations A and B, and the positive-phase impedance Z
1, negative phase Z2, and zero-phase impedance Z0.

The voltage transformers 1A and 1B are connected to the substation A and the substation B, respectively, so that the a-phase voltage Va, the b-phase voltage Vb,
The c-phase voltage Vc is measured. The current transformers 2A and 2B measure the three-phase a-phase current Ia, b-phase current Ib, and c-phase current Ic at the electric stations A and B, respectively.

The data collection terminals 10A and 10B collect voltage and current signals measured at the electric stations A and B. Further, the three-phase AC voltages Va, Vb, Vc and the currents Ia, Ia
For example, b and Ic are converted from analog quantities to digital quantities and transmitted to the fault point locating apparatus 100 via the data transmission lines 20A and 20B.

The fault point locating operation device 100 includes a data collecting unit 101 for receiving data from the data collecting terminals 10A and 10B, an operation starting unit 102 for determining whether or not to execute a fault point locating operation, and an input three-phase AC. Is provided with a symmetrical signal conversion unit 103 for converting the voltage and current data into a positive-phase component, a negative-phase component, and a zero-phase component based on the symmetric coordinate method. Further, an accident type discriminating unit (applied circuit discriminating unit) 104 for selecting a symmetrical equivalent circuit to be subjected to a fault point locating operation, an error point locating calculating unit 105, and an output display unit 106 are provided.

When an accident such as a ground fault or a short circuit occurs at the fault point F of the transmission line 3, the data collecting unit 101 accumulates data of voltage and current signals during the fault in a time series. The duration of system failure depends on the voltage class and the type of accident, such as short-circuit or ground-fault.
Since there can be about 0 to 100 ms, it is assumed that data of this degree can be held.

The calculation starting unit 102 detects the possibility that a fault has occurred in the transmission line 3 and determines a start condition for starting a fault locating calculation. For example, undervoltage detection, overcurrent detection, or the difference between the current signals of the substation A and the substation B for each of the three phases (this is called a current differential system in a protection relay).
The start condition is determined by the following method. In addition, transmission line 3
For the failure detection, a protection relay (not shown) may be used.

The symmetrical component signal converter 103 has a three-phase AC a
The input data of the phase, b-phase, and c-phase voltage or current signals are converted into positive-phase, negative-phase, and zero-phase components based on the symmetric coordinate method. The basic conversion formulas are shown in Expressions 1 and 3. “A” and “a ^2” in the formula are vector operators, and their contents are shown in Equation 2.

[0025]

(Equation 1)

[0026]

(Equation 2)

[0027]

(Equation 3)

Equation 1 shows the current signal.
1 indicates a positive phase component, I2 indicates a negative phase component, and I0 indicates a zero phase component. Number 3
Is the same for voltage signals. Equations (1) and (3) are examples in which the signal of the a-phase is converted into the reference, but the b-phase reference or the c-phase reference may be used in the same order of the phase order.

The fault type determination unit 104 is a determination unit for determining whether the fault point locating operation can be performed by using a positive phase, a negative phase, or a zero phase symmetrical equivalent circuit. In other words, this is a means for utilizing the fact that the connection configuration of the symmetrical equivalent circuit is determined by the fault type of the three-phase AC circuit. The connection configuration of the accident type and the symmetrical equivalent circuit will be described later.

The fault point locating operation section 105 performs a fault point locating operation in accordance with the operation target of the symmetrical equivalent circuit determined by the accident type. If the input data is a sample value converted into a digital quantity, it can be calculated by a digital computer.

The output display unit 106 is a device for displaying a result solved by the fault location calculation, and is constituted by a CRT display, a line printer, or the like.

Next, the connection configuration of the accident type and the symmetrical equivalent circuit will be described. FIG. 2 shows the system shown in FIG.
The connection configuration of the symmetrical equivalent circuit at the time of the phase 1 line ground fault is shown. A and B at the end of the symbols in the illustration are the substation A side or B respectively.
Side signal or impedance.

Assuming that the distance between the substations A and B is 1, the distance from the substation A to the value of x from the substation A is assumed. E1
A indicates the positive-phase component voltage of the power source EA in FIG. 1, and E1B indicates the positive-phase component voltage of the power source EB.

Although the impedance of the transmission line between the electric stations A and B is not shown, it is assumed that the positive phase component is Z1, the negative phase component is Z2, and the zero phase component is Z0. The impedance between the substation A and the generating power source EA is equal to the positive phase, the negative phase, and the zero phase, and is ZPA, and the substation B side is similarly indicated by ZPB. Since the neutral point ground impedance is determined to be tripled when converted to a zero-phase circuit by the symmetrical coordinate method, 3ZN
A, 3ZNB.

As is apparent from FIG. 2, when an a-phase 1-line ground fault occurs, a current due to a fault flows through each of the positive-phase, reverse-phase, and zero-phase circuits. Can be. That is, the voltage drop equation of Equation 4 is established from the positive-phase circuit, and the distance x to the fault point F can be calculated by Equation 5.

[0036]

(Equation 4)

[0037]

(Equation 5)

Here, the voltage signals V1A and V1B and the current signals I1A and I1B are the positive phase converted by the equations (1) and (3) based on the three-phase voltages and the line currents measured at the substations A and B, respectively. Minute signal.

Similarly, the equation (6) is also established in the reverse phase circuit, and the distance x to the fault point can be calculated from the equation (7).

[0040]

(Equation 6)

[0041]

(Equation 7)

Further, also in the zero-phase circuit, equation (8) holds, and equation (9) can be used to calculate the distance x to the fault point.

[0043]

(Equation 8)

[0044]

(Equation 9)

FIG. 2 shows the case of the a-phase ground fault.
Even at the time of a single-line ground fault of the b-phase or the c-phase, the generated voltage and current signals are only displaced by 120 degrees according to the phase order, and the distance x to the fault point can be calculated in the same manner as in the a-phase. .

FIG. 3 shows a connection configuration of a symmetrical equivalent circuit at the time of a bc phase two-line ground fault. At the time of a two-line ground fault, the positive-phase circuit, the negative-phase circuit, and the zero-phase circuit are connected in parallel at the fault point. Can be calculated.

The fault location at the time of the two-line ground fault can also be performed by a calculation formula other than Equations 4 to 9. In other words, at the time of the complete ground fault, the positive phase, the negative phase, and the zero phase are connected in parallel at the fault point F, so that the equivalent voltage of the failure point F is symmetrical with the positive phase voltage V1F, the negative phase voltage V2F, and the zero phase voltage V0F. Respectively equal. Accordingly, a total of six voltage drop equations for obtaining the target voltage at the fault point F are established from both the A terminal side and the B terminal side, and a calculation equation other than Equations 4 to 9 is made possible by combining these. . For example, calculation of x from Expression 10 to Expression 11, Expression 1
It is possible to calculate x from 2 to 13 and to calculate x from 14 to 15. X can be calculated by a plurality of formulas by the combination of these simultaneous formulas.

[0048]

(Equation 10)

[0049]

[Equation 11]

[0050]

(Equation 12)

[0051]

(Equation 13)

[0052]

[Equation 14]

[0053]

(Equation 15)

However, when an arc resistance or the like enters the failure point F, the magnitudes of the positive-phase voltage V1F, the negative-phase voltage V2F, and the zero-phase voltage V0F generated at the failure point F differ. In this case, Equations (10) to (15) do not hold unless they are completely grounded, so that the calculation result involves an error due to the degree of failure.

FIG. 3 shows an equivalent circuit at the time of the bc-phase two-wire ground fault. However, even at the time of the ab-phase or the ca-phase two-wire ground fault, the respective symmetrical voltage and current signals follow the phase order and the phase is changed. Is shifted by 120 degrees, it is possible to calculate x from Equations 4 to 9.

FIG. 4 shows a symmetrical equivalent circuit when the bc phase two-wire is short-circuited. In this case, no fault current flows through the zero-phase circuit.
And 2 are obtained from Equation (7).

Similarly, for the ab-phase short-circuit and the ca-phase short-circuit, two x's can be calculated respectively by the positive-phase and negative-phase circuits deviated by 120 degrees according to the phase order.

FIG. 5 shows a connection state of a symmetrical equivalent circuit when a three-wire short circuit or a three-wire ground fault occurs. Since a fault current flows only in the positive phase circuit in the case of a three-wire short circuit or ground fault, x can be obtained only by the positive phase circuit. That is, only Equation 4 is satisfied, and the distance x to the failure point F can be calculated from Equation 5.

The relationship between the accident type and the symmetric sub-circuit used in the fault point locating operation described above is stored in the accident type corresponding operation circuit table 107 and is referred to by the accident type discriminating unit 104. FIG. 6 shows the contents of the accident type corresponding arithmetic circuit table.

FIG. 7 shows a calculation flow of the fault location according to one embodiment of the present invention. This calculation is started by the detection of a fault in the transmission line by the calculation starting unit 102.

The symmetric component signal conversion processing 210 performs an operation of converting the three-phase voltage and current signals input by the measuring instrument into respective positive-phase, reverse-phase, and zero-phase symmetric components according to Equations 1 and 3. The zero-phase current I0 can be obtained by simply adding values obtained by sampling at the same time of the respective phase currents Ia, Ib, and Ic and reducing the value to one third.

The positive-phase current I1 is obtained by adding the sample value of Ib before the electrical angle of 240 degrees and the sample value of Ic before the electrical angle of 120 degrees on the basis of the sample value of Ia. can get. The negative-phase current I2 is obtained, for example, by adding a sample value of the electrical angle of 120 degrees or less of Ib and a sample value of 240 degrees or less of Ic on the basis of the sample value of Ia to make it 1/3. The conversion can be similarly performed for the symmetric component of the voltage signal.

Process 230 for selecting a fault point locating target arithmetic circuit
Determines which x-phase symmetrical circuit can be used to calculate x. For this reason, the magnitudes of the currents I1, I2, and I0 converted into the symmetric components of the positive phase, the negative phase, and the zero phase are determined, and are determined to be equal to or more than a predetermined value exceeding the unbalance generated in the normal state.
That is, a symmetrical equivalent circuit of the phase in which the fault current flows is selected. For example, in the case of a three-wire short circuit, only the positive phase circuit I1 increases, so that the positive phase circuit is selected.

The location calculation processing 240 calculates x for fault location using an arithmetic expression corresponding to the selected operation target circuit. Since the operations of Expressions 5, 5, and 9 are vector operations of an AC signal, both the voltage signal and the current signal are obtained by converting sample values into complex numbers. Since the symmetric equivalent impedance of the line is known in advance from the state of the equipment, it is set in a memory as a complex constant. Techniques for converting sample values to complex numbers are well known,
Description is omitted.

When a plurality of values of x are obtained by one fault, the output display process 250 performs a process for specifying the fault point to the outside, such as averaging the values, and outputs the result to the printer or CRT. indicate.

The type of fault can be determined by comparing the magnitude of each phase current, detecting the abnormally changed phase, and specifying the fault phase. That is, for each phase current signal of both the A and B terminals taken in as input data, a data composite value at the same time is obtained, and if it exceeds a predetermined threshold value, it is determined that an accident phase has occurred. In setting the threshold value, a charging current between the A and B terminals of the transmission line 3 and a measurement error are considered. In addition, you may make it receive the accident phase discrimination signal by the protection relay not shown from the electric stations A and B.

When the type of an accident is determined, an accident type determination process 220 indicated by a dotted line in FIG. 6 is first performed, and the result is used in process 230 by referring to the accident type corresponding arithmetic circuit table 107 in a process 230. Select the equivalent circuit for the target.

In the above-described embodiment, the location calculation of the accident point is performed based on one sampling point. However, the location can be determined by using the calculation results at a plurality of sampling points.

[0069]

According to the present invention, each phase-based equivalent circuit based on the symmetrical coordinate system of three-phase alternating current, which is used for protection and control of a power system, and the like, is provided for each phase. Since the fault location calculation can be performed, the calculation is simplified and the speed is increased. In addition, it is easy to set the line constants, and the system configuration is easy when a new system is installed or changed.

In addition, depending on the type of accident, a plurality of arithmetic expressions are established in one accident, and the likelihood of a solution is determined based on the variation of the plurality of fault location values, or the accuracy is improved by an average value. Performance is improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fault point locating apparatus according to a position embodiment of the present invention.

FIG. 2 is a symmetrical equivalent circuit at the time of a-phase 1-line ground fault.

FIG. 3 is a symmetrical equivalent circuit at the time of a bc phase two-line ground fault.

FIG. 4 is a symmetrical equivalent circuit when a bc phase two-wire is short-circuited.

FIG. 5 is a symmetrical equivalent circuit at the time of a three-wire short circuit and a three-wire ground fault.

FIG. 6 is an explanatory diagram of an accident type corresponding arithmetic circuit table used for fault point location.

FIG. 7 is a flowchart of a fault point location calculation process.

[Explanation of symbols]

1A, 1B: voltage transformer, 2A, 2B: current transformer, 3: transmission line, 10A, 10B: data transmission device, 20A, 20
B: data transmission line, 100: fault point locating device, 101
... Data collection unit, 102 ... Operation start unit, 103 ... Symmetric component signal conversion unit, 104 ... Fault type determination unit (applicable circuit determination unit), 105 ... Failure point location calculation unit, 107 ... Fault type correspondence calculation circuit table, A , B ... electric station (reference terminal), V
a ... a phase voltage, Vb ... b phase voltage, Vc ... c phase voltage, Ia
... a-phase current, Ib ... b-phase current, Ic ... c-phase current, V1 ...
Positive phase component voltage, V2 ... Negative phase component voltage, V0 ... Zero phase component voltage, I
1: positive phase current, I2: negative phase current, I0: zero phase current.

Claims (7)

[Claims] 1. A method for locating a fault point of an accident occurring in a three-phase AC transmission line as a distance from a reference terminal A or B on both sides thereof. The voltage and current of each phase of the three-phase alternating current measured by the above are converted into the symmetrical component voltage and the symmetrical component current of the reference terminals A and B in the positive phase, the negative phase and the zero phase of the symmetric equivalent circuit, and the fault point A fault point is calculated from a voltage drop in the symmetrical equivalent circuit using the fact that the symmetrical component voltages have the same value as viewed from both sides of the reference terminals A and B. 2. The method according to claim 1, wherein the calculation of the fault point is performed by increasing a symmetrical current in each of the positive phase, the negative phase, and the zero phase to a predetermined value that exceeds an unbalanced portion generated in a normal state. A fault point locating method characterized in that the method is performed using a symmetrical equivalent circuit of a certain phase. 3. The fault detection method according to claim 1, wherein when detecting a fault in the transmission line, the fault type is specified from the phase in which the three-phase AC current greatly changes, and the fault type is calculated according to the fault type. A fault locating method characterized by selecting a phase of a simple symmetric equivalent circuit. 4. The fault point according to claim 3, wherein when the fault type is a one-line ground fault or a two-wire ground fault, a fault point calculated by each of the positive-phase, negative-phase, and zero-phase circuits or an average value thereof is acquired. In the case of a two-wire short circuit, the fault point calculated in each of the positive-phase and negative-phase circuits or the average value thereof is obtained. In the case of a three-wire short circuit or a three-wire ground fault, the fault is calculated in the positive-phase circuit. A fault point locating method characterized by acquiring a failed point. 5. The voltage and current of each phase of a three-phase AC transmission line are measured at a plurality of electric stations, and a fault point of an accident occurring between the electric stations is determined as a distance from the electric station A or B on both sides thereof. In the fault locating device, a data collection unit that periodically samples the voltage and current of each phase measured at the electric stations A and B and holds the voltage and current for a predetermined period; A symmetrical component signal converter for converting into a symmetrical component voltage and a symmetrical component current in each of the phase, reverse phase and zero-phase circuits, and a symmetrical component equivalent circuit of the phase in which the symmetrical component current has increased to a predetermined value or more. A fault point for calculating a fault point using the fact that the symmetrical component voltage of the fault point has the same value as viewed from both sides of the electric stations A and B for the symmetrical equivalent circuit of the selected phase. Failure point location characterized by providing a location calculation unit Location. 6. A voltage and a current of each phase of a three-phase AC transmission line are measured at a plurality of electric stations, and a fault point of an accident occurring between the electric stations is determined as a distance from the electric station A or B on both sides thereof. In the fault locating device, a data collection unit that periodically samples the voltage and current of each phase measured at the electric stations A and B and holds the voltage and current for a predetermined period; A symmetrical component voltage in each of the negative-phase and zero-phase circuits, a symmetrical component signal converting unit that converts the symmetrical component current into a symmetrical component current; An accident type determination unit that determines the type of the fault and selects a symmetrical equivalent circuit of a phase through which a fault current flows according to the type of the fault. From both sides A and B Fault point locating system which characterized in that a fault point locating calculator for calculating the fault point by using the. 7. The storage device according to claim 5, wherein a line impedance between the electric stations A and B is set in a uniform distribution in each of the positive phase, the negative phase, and the zero phase of the symmetric component equivalent circuit. A fault point locating device which calculates a fault point by calculating a voltage drop from both sides of the electric stations A and B to the fault point.