JP2795128B2 - Ground fault distance relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground fault distance relay and, more particularly, to a digital ground fault distance relay used for back-up protection of a digital current differential relay for protecting transmission lines of a power system.

[0002]

2. Description of the Related Art FIG. 3 shows the general configuration of a parallel two-line transmission line of a general power system, and FIG. 4 shows a connection portion of a ground fault distance relay. In FIG. 3, 17 is a generator, 18 and 19 are electrical stations, 22 and 23 are lines 1 and 2 which are parallel two-line transmission lines, and 24 is a ground fault accident point. Also, 25 and 26 are instrument transformers for detecting the voltage of each transmission line, 20 and 21 are current transformers for detecting the current of each line, 32 and 33 are circuit breakers for interrupting power supply to each line, 1, 2 are ground fault points 2 based on the voltage and current values from the instrumentation transformers 25, 26 and the current transformers 20, 21.
4 is a ground fault distance relay for controlling the corresponding circuit breakers 32 and 33.

In FIG. 4, a ground fault distance relay 1 has an analog input unit 27 for A / D converting an analog voltage value from an instrument transformer 25 and an analog current value from a current transformer 20.
A digital operation unit 28 for deriving an electrical distance to the ground fault point 24 based on each digital electric quantity from the analog input unit 27, and an external unit for outputting a trip signal in accordance with the output of the digital operation unit 28 An interface 29 is provided. Reference numeral 30 denotes a circuit breaker tripping circuit for breaking the circuit breaker 32 in response to the trip signal.

[0004] Reference numeral 31 denotes an optical fiber for data transmission connecting the ground fault distance relays 1 and 2. The amount of electricity input to the analog input unit 27 of the ground fault distance relays 1 and 2 and A / D converted is: Through this optical fiber group 31,
Are mutually transmitted and exchanged between the ground fault distance relays 1 and 2,
It is used for deriving the electrical distance to the ground fault point 24 in the digital operation unit 28. The internal configuration and connection of the ground fault distance relay 2 omitted in FIG. 4 are the same as those of the ground fault distance relay 1.

Now, in the parallel two-line transmission line shown in FIG.
When an a-phase ground fault occurs at a certain point 24 on the line 22, the voltage and current of the line 1 change. The analog input unit 27 of the ground fault distance relay 1 is connected to the
5 and the current transformer 20 to detect changes in the voltage and current of the line 1, and a digital operation unit 28 performs digital arithmetic processing based on these data and data from the earth fault distance relay 2, thereby obtaining a ground fault. The electrical distance to the accident point 24 is derived.

That is, when a ground fault occurs, the a-phase current flowing through the line 1 is I _a , the zero-phase current is I ₀ , the zero-phase current of the line 2 is I ₀ ′, and the positive current of the line 1 is positive. The phase impedance is Z ₁ , the zero-phase impedance is Z ₀ , the mutual impedance between lines is Z _m , the distance between the electric stations 18 and 19 is 1, and the distance from the relay installation point to the ground fault point 24 is X. If a (0 ≦ X ≦ 1), a phase voltage V _a at the relay installation point of line 1 22 can be represented by the number 1.

[0007]

(Equation 1)

Here, in order to accurately derive the electrical distance from the relay installation point to the ground fault point 24 according to Equation 1, the zero-phase current I ₀ of the own line and the zero-phase current of the adjacent line are required.
It is understood that it is necessary to consider I ₀ ′ , that is, to compensate for zero-phase current. Therefore, it is necessary to exchange the zero-phase current I ₀ ′ between the ground-fault distance relays 1 and 2 connected to each line, and furthermore, to perform digital arithmetic processing, the zero-phase current I ₀ ′ is used as the adjacent line zero-phase current I ₀ ′. , The instantaneous value at the same time as the a-phase current I _a and the zero-phase current I ₀ is required, and it is necessary to synchronize the timing of sampling each electric quantity between the two ground fault distance relays 1 and 2.

FIG. 5 is a functional block diagram showing a data transmission portion between the conventional ground fault distance relays 1 and 2. The analog input section 27 of the ground fault distance relay 1 includes an analog input circuit 34 for its own line and an adjacent circuit. Line analog input circuit 36
The analog input section 27 of the ground fault distance relay 2 has an analog input circuit 35 for its own line and an analog input circuit 37 for an adjacent line.
1. Here, they are connected by optical fibers 38 and 40 for transmitting the sampling synchronization signal and optical fibers 39 and 41 for transmitting the _zero- phase current values I ₀ and I ₀ ′ , respectively.

In FIG. 5, when the zero-phase current value I ₀ ′ detected by the ground fault distance relay 2 is transmitted to the ground fault distance relay 1, the analog input circuit 35 for the adjacent line on the ground fault distance relay 2 side is used.
Samples the zero-phase current I ₀ ′ of the No. 2 line 23 based on the sampling synchronization signal received from the ground-fault distance relay 1 side own line analog input circuit 34 via the optical fiber 38, The signal is transmitted to the analog input circuit 34 for the own line of the short distance relay 1 side. The ground-fault distance relay 1 side own line analog input circuit 34 outputs the adjacent line zero-phase current I ₀ ′ sampled by the ground-fault distance relay 2.
Of the digital arithmetic unit 28 based on the
Performs zero-phase current compensation. The same applies to the case where the zero-phase current value I ₀ of the first line 22 sampled in the ground fault distance relay 1 is transmitted to the ground fault distance relay 2.

Therefore, when the data transmission method shown in FIG. 5 is used, the timing of sampling each electric quantity in the own line and the adjacent line is synchronized, and as shown in FIG. In the case where a one-line ground fault has occurred, the impedance Z _a (= X · Z ₁ ) viewed from the ground fault distance relay 1 (a phase) of the No. 1 line is based on the aforementioned equation ( ₁ ) and Can be directly derived by

[0012]

(Equation 2)

Incidentally, the zero-phase current value of the adjacent line is delayed by the data transmission delay time between the two ground fault distance relays 1 and 2. However, in a normally used sampling interval, the sampling frequency is about two times. since delay and is, accurate impedance Z _a is derived of

[0014]

Accordingly, in such a conventional ground fault distance relay, analog input circuits for the own line and for the adjacent line are separately provided as analog input sections, and high-speed synchronous data via an optical fiber is provided. Because it is configured to perform transmission, the number of hardware of the analog input unit increases, especially when the precision of the analog input unit is improved for the purpose of increasing the accuracy of the derived impedance. However, there has been a problem that the scale of the analog input section becomes enormous, and it becomes difficult to mount the analog input section on a relay panel .

The present invention has been made to solve such a problem.
Without reducing the operation accuracy of the relay.
Digital ground fault distance relay that can simplify hardware
The purpose is to provide a vessel.

[0016]

Means for Solving the Problems To achieve such an object
To this end, the ground fault distance relay according to the present invention uses an admittance equivalent value calculated from a voltage value and a current value sampled from a line to which a ground fault distance relay is connected, as an amount of electricity transmitted to each other. is there.

[0017]

[Action] Therefore, admittance equivalent value from the sampled voltages and currents from the own access in the ground fault distance relay is calculated, and transmitted to each other.

[0018]

Next, the present invention will be described with reference to the drawings. FIG. 1 is a functional block diagram showing a data transmission portion between ground fault distance relays for protecting parallel two-line transmission lines according to one embodiment of the present invention. In FIG. 1, the configuration of the parallel two-line transmission line to which the short-distance relays are connected to each other is the same as that described above (FIGS. 3 and 4), and is omitted here.

In FIG. 1, reference numeral 1 denotes a digital ground fault distance relay for protecting line 1 (see FIG. 3), reference numeral 2 denotes a digital ground fault distance relay for protecting line 2, and reference numerals 3 and 4 denote ground distance relays. An analog input unit provided for the own line and the adjacent line provided in 1 and 2, an optical fiber 5 for supplying a sampling synchronization signal from the ground fault distance relay 1 to the ground fault distance relay 2, 6 is provided from the ground fault distance relay 1. An optical fiber for transmitting the zero-phase current value I ₀ of Line 1 to the ground fault distance relay 2, and 6 is an optical fiber from the ground fault distance relay 2 to the ground fault distance relay 1.
This is an optical fiber for transmitting the zero-phase current value I ₀ ′ of the line.

Next, referring to FIG. 1, data transmission performed between the ground fault distance relays 1 and 2 will be described as an operation of the present invention. Now, when the ground fault distance relay 1 is set as a master and the ground fault distance relay 2 is set as a slave,
A sampling synchronization signal is transmitted from the ground fault distance relay 1 to the ground fault distance relay 2 via the optical fiber 5. Thereby, the ground fault distance relay 2 on the slave side is subordinately synchronized with the ground fault distance relay 1 on the master side,
The ground fault distance relay 2 samples the zero-phase current I ₀ ′ based on the sampling synchronization signal and transmits it to the ground fault distance relay 1 via the optical fiber 7, and the ground fault distance relay 1 is generated internally. The zero-phase current I ₀ is sampled based on the sampling synchronization signal and transmitted to the ground fault distance relay 2 via the optical fiber 6.

Therefore, according to this data transmission method, the master side, that is, the ground fault distance relay 1 does not need to receive the sampling synchronization signal from the ground fault distance relay 2 of the adjacent line, and the slave side, that is, the ground fault distance relay 1 Since the distance relay 2 does not need to generate and transmit a high-precision sampling synchronization signal, the analog input unit for the own line and the analog input unit for the adjacent line can be partially shared, and the number of hardware of the analog input unit is reduced. Decrease. Further, similarly to the conventional data transmission method shown in FIG. 5 described above, for example, the impedance Z _a viewed from the ground fault distance relay 1 (a phase) can be directly derived by the equation shown in Expression 2. The operation of the short-circuit relays 1 and 2 at high speed becomes high-speed and high-precision.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a functional block diagram showing a data transmission portion between ground fault distance relays for protecting parallel two-line transmission lines according to one embodiment of the present invention. In FIG. 1, the configuration of the parallel two-line transmission line to which the short-distance relays are connected to each other is the same as that described above (FIGS. 3 and 4), and is omitted here.

In FIG. 2, reference numeral 1 denotes a digital ground fault distance relay for protecting line 1 (see FIG. 3), reference numeral 2 denotes a digital ground fault distance relay for protecting line 2, and reference numerals 8 and 9 denote ground distance relays 1 for each area. , 2 are provided with an analog input section for own line and adjacent line, and an admittance-equivalent value (I ₀ / V) based on the zero-phase current value I ₀ of Line 1 from the ground fault distance relay 1 to the ground fault distance relay 2. _a ) An optical fiber for transmitting _a ), 11 is an optical fiber from ground fault distance relay 2 to ground fault distance relay 1
This is an optical fiber for transmitting an admittance equivalent value (I ₀ ′ / V _a ′) based on the zero-phase current value I ₀ ′ of the line.

Here, a description will be given of a case where the electrical distance to the ground fault point 24 is derived by using the admittance equivalent value in place of the zero-phase current I ₀ ′ of the adjacent line in the ground fault distance relay 1. In FIG. 3, the a-phase voltage at the point where the ground fault distance relay 1 is disposed on the first line 22 is represented by V _a ,
The a-phase voltage at the ground fault distance relay 2 arrangement point of No. 3 is V _a '
Then, the voltage of each phase at these points is equal,
That is, it may be considered that V _a = V _a ', the number 3 is established.

[0025]

(Equation 3)

Therefore, the above-mentioned equation (2) can be modified as equation (4).

[0027]

(Equation 4)

Here, the term of I ₀ ′ / V _a ′ in Equation 4 is obtained from the adjacent line zero-phase current I ₀ ′ and the a-phase voltage V _a ′ at the point where the ground fault distance relay 2 is arranged. This can be obtained from the ground fault distance relay 2 using only data that can be directly obtained by the relay itself.

[0029] Thus, in deriving the impedance Z _a in the ground fault distance relay 1, the ground fault distance relay 1 of sampled a phase voltage V _a and the zero-phase current I ₀ synchronized with neighboring line zero-phase current I _It is not necessary to sample ₀ ' by the ground fault distance relay 2 and transmit it to the ground fault distance relay 1. Further, I ₀ ′ / V _a is an admittance-equivalent value that is considered to have a considerably small temporal change during the continuation of the system fault, and the sampling time difference has little effect on impedance. It becomes possible to transmit.

[0030] Therefore, the ground fault distance relay 2, line 2 23
Then, a digital operation unit (not shown) calculates an admittance equivalent value based on the voltage and current values sampled at the timing of the own apparatus, and sends out the value from the analog input unit 9 asynchronously. The ground fault distance relay 1 derives an impedance based on an adjacent line admittance equivalent value received via the optical fiber 11 and various electric quantities sampled from the own line, and based on the result, a circuit breaker 32.
Control the protection operation. As a result, it is possible to reduce the configuration for sampling synchronization in the analog input units of the short-distance relays 1 and 2, the optical fiber for transmitting the sampling synchronization signal, and the like, and further simplify the apparatus.

When this admittance-equivalent value is transmitted, since it is actually transmitted by being divided into a conductance component and a susceptance component, six data (for three phases) are transmitted in one direction. Also, as a feature of this method, there is no operation delay in an accident that can operate without neighboring line information (near-end accident).

[0032]

As described above, the present invention provides a parallel 2
Te ground fault distance relay smell to protect the circuit transmission line, since so as to transmit the admittance equivalent value as next line electric quantity, it is not necessary to be sampled synchronously at both relays unnecessary configuration of the analog input section corresponding thereto Becomes Therefore, in the digital ground fault distance relay, there is a special effect that the hardware can be simplified without reducing the operation accuracy of the relay.

[Brief description of the drawings]

FIG. 1 is a functional block diagram illustrating a data transmission portion between ground fault distance relays according to an embodiment of the present invention.

FIG. 2 is a functional block diagram showing a data transmission portion between ground fault distance relays according to a second embodiment of the present invention.

FIG. 3 is a connection system diagram showing the entire configuration of a general power system parallel two-circuit transmission line.

FIG. 4 is a connection system diagram showing a connection portion of the ground fault distance relay of FIG. 3;

FIG. 5 is a functional block diagram showing a data transmission portion between conventional ground fault distance relays.

[Explanation of symbols]

 1, 2 Ground fault distance relay 3, 4 Analog input section 5, 6, 7 Optical fiber 8, 9 Analog input section 10, 11 Optical fiber 17 Generator 18, 19 Electric station 20, 21 Current transformer 22 Parallel two-line transmission line Line 1 23 Line 2 of a parallel two-circuit transmission line 24 Ground fault point 25, 26 Instrument transformer 27 Analog input unit 28 Digital operation unit 29 External interface 30 Circuit breaker trip circuit 31 Optical fiber group 32, 33 Circuit breaker

Claims (1)

(57) [Claims] 1. Two parallel transmission lines of a power system
The amount of electricity placed and sampled from each line
Are transmitted to each other, and digital processing
Derive the electrical distance to the ground fault
In the ground fault distance relay that performs protection of each transmission line according to the result , the amount of electricity transmitted to each other is determined by the ground fault distance relay.
And the voltage value sampled from the line to which
A ground fault distance relay characterized by an admittance equivalent value calculated from a current value and a current value .