JPH04319672A - Method for locating fault point - Google Patents

Abstract

PURPOSE:To restore perfect data and to locate a fault point, in a case locating one circuit earth fault point in a resistance ground type three-terminal parallel two-circuit transmission line to which a power supply having one resistance- grounded transmission terminal and not having load or neutral earthing at the other terminals thereof is connected, by compensating the data of the other terminals when the data of the transmission terminal is omitted. CONSTITUTION:The zero phase difference currents I0', I0'' at two terminals B, C and zero phase voltage V0', VI0'' at any other terminals B, C are detected. The omitted zero phase difference current I0 at a transmission terminal is estimated on the basis of formula I0=k¦V0'¦- I0'- I0'' or I0=k¦V0''¦- I 0'- I0'' using the ratio (k) of the zero phase fault current and zero phase voltage rating and an one-circuit earth fault point is located using the zero phase difference currents I0, I0', I0''.

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 ground fault point at one point on each line in a three-terminal parallel two-circuit power transmission line having resistance-grounded power transmission ends.

0002

2. Description of the Related Art In order to improve the reliability of power supply, power transmission lines between substations are generally constructed using a parallel two-circuit system. Compared to substations, etc., which are maintained and managed inside buildings, these power transmission lines are susceptible to failures caused by external sources (insulation breakdown due to lightning strikes, contact with birds or trees, etc.). Therefore, when a failure occurs, it is necessary to search for a failure point, and searching for a failure point may be extremely difficult, especially in mountainous areas.

[0003] Therefore, the range of failure points is specified in advance by calculation (
Once the location is established, the failure point can be searched for within that range, leading to more efficient work. Conventionally, as a method for locating the ground fault fault point at one point per circuit in a resistance-grounded three-terminal parallel two-circuit power transmission line, a method of calculating the shunt ratio using the difference current between the two circuits at each terminal (Japanese Patent Application Laid-Open No. 2002-20012-1) has been proposed. 15416
(Refer to Publication No. 8) has been adopted.

This method will be explained for a three-terminal parallel two-circuit power transmission line as shown in FIG. Each power transmission line is 1L, 2L
The three terminals are designated as A end, B end, and C end, respectively, and the branch point is represented by T. Let the distances between AT, BT, and CT be d1, d2, and d3, respectively. A power source (a transformer may be used) whose neutral point is grounded is connected to the A terminal. A general load or a power source without a neutral point (not shown) is connected to the B terminal and the C terminal. At the A, B, and C ends, the zero-sequence currents of each line I10, I20, I10', I20', I
10'' and I20'' are measured respectively, and the difference currents ΔI=|I10−I20|, ΔI′=|I10′−I20′|, ΔI″=|I10″−I20″|, are calculated. In this specification, the notation "I"
” is a vector

[0005]

[Outside 1]

0006. According to this method,
formula

[0007]

[Math 1]

[0008]

[Math 2]

[0009]

[Math 3]

x, x', x'' are calculated by
1, then x is the distance from end A to the failure point, and when x is greater than d1, x' and d2 are
and if x' is smaller than d2, x
' is the distance from the B end to the fault point, and if x' is larger than d2, x'' is the distance from the C end to the fault point.As described above, the current at each end is detected. This allows the fault point to be located.

[0011]

[Problem to be solved by the invention] In the above system, the A end,
It is necessary to collect all data from end B and end C,
If data at the power transmission end is lost due to a defect in the detection means, a defect in the data transmission line, etc., calculations will no longer be possible. Therefore, the present invention provides one line in a resistance-grounded three-terminal parallel two-circuit power transmission line that has one resistance-grounded power transmission end A, and the other ends B and C are connected to a load or a power source without neutral point grounding. When locating the ground fault point,
An object of the present invention is to provide a failure point locating method that can restore complete data by supplementing data from the other two ends when data is missing, thereby locating the failure point.

0012

[Means for Solving the Problems] The method of the present invention provides a three-terminal resistance-grounded type having one resistance-grounded power transmission end, and the other two ends connected to a power source without a load or neutral point grounding. In a parallel two-circuit transmission line, when current data at the transmission end is missing, the zero-sequence difference currents ΔI0' and Δ at the other two ends
I0 ″ as well as the zero-sequence voltage V0 ′ at either other end.
Or detect V0'' and use the ratio k of the zero-sequence fault current and zero-sequence voltage rating at the time of a complete ground fault in the transmission line, and use the following formula ΔI0 = k | V0 ′ | − ΔI0 ′ − ΔI0 ″ or ΔI0 = The zero-sequence difference current ΔI0 at the missing transmitting end is estimated based on k|V0 ″|−ΔI0 ′−ΔI0 ″, and these zero-sequence difference currents ΔI0 , ΔI0 ′, and Δ
This is a method of locating a single line ground fault fault point using I0''.

[0013]

[Operation] This will be explained with reference to FIG. FIG. 1 shows a resistive grounding type three-terminal parallel two-line power transmission line circuit to which the invention is applied. A three-terminal parallel two-circuit power transmission line is installed between power transmitting end A, power receiving end B, and power receiving end C. The distance between power transmitting end A and branch point T is d1, and the distance between power receiving end B and branch point T is 1. The distance between the receiving end C and the branch point T is d2, and the distance between the receiving end C and the branch point T is d3.
shall be.

Assume that a ground fault occurs on the 1L line side at point F, and a zero-sequence ground fault current Iof begins to flow. Ground fault resistance is expressed as Rf. The zero-sequence ground fault current Iof is
Iof=I10+I10′+I10″

(4) It is expressed as Since there is no failure on the 2L line side, 0=I20+I20′+I20″

(5) It is expressed as Subtracting equation (5) from equation (4), Iof=(I10-I20)
+(I10'-I20')+(I10''-I20'')(
6) It becomes. Since the currents at each terminal are almost in phase, (
6) The formula is |Iof|=|I10-I20|+|
I10′-I20′｜+｜I10″-I20″｜
=ΔI0 +ΔI0′+ΔI0″
(7
) can be written as

On the other hand, using the zero-sequence voltage rating of the line (the voltage that appears at the neutral point in the case of a complete ground fault) and the zero-sequence ground fault current in the case of a complete ground fault, the zero-sequence ground fault current Iof is | Iof｜=｜V
0 | × (Zero-sequence ground fault current at complete ground fault) / (Zero-sequence voltage rating). Here, V0 is the zero-sequence voltage generated on the bus bar at the time of failure. Since both the zero-sequence ground fault current and the zero-sequence voltage rating at the time of a complete ground fault are system-specific values, this ratio is set as a constant k as follows.

k=(Zero-sequence ground fault current at complete ground fault)/(Zero-sequence voltage rating) Since the zero-sequence impedance of the line is sufficiently small compared to the ground resistance R at the neutral point, the transmission end A and the reception end B , the zero-sequence voltage V0 is assumed to take approximately the same value regardless of whether it is measured at the power receiving end C. That is, the zero-sequence voltage V0 measured at the sending end A, the zero-sequence voltage V0' measured at the receiving end B,
It is assumed that the zero-sequence voltages V0'' measured at the power receiving end C are equal.Then, the above equation becomes |Iof|=k|V0 |=k|V0'|=k|
V0″| (8)

Now, assuming that the current and voltage data at the power transmitting end A are missing, the zero-sequence voltage V0 measured at the power receiving end B
' or using the zero-sequence voltage V0'' measured at the receiving end C,
k｜V0 ′｜=k｜V0 ″｜=ΔI0 +ΔI
0'+ΔI0''. Transforming this equation, ΔI0 = k|V0'|-ΔI0'-ΔI0
″ (9)
or ΔI0 = k | V0 ″ | −ΔI0 ′−ΔI0
″ (10)
Then, the difference current at the sending end A is expressed as the difference current at the receiving end B and the receiving end C.
It can be seen that it can be estimated using the difference current and zero-sequence voltage at .

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The failure point locating method of the present invention will be explained in detail below with reference to the accompanying drawings. Note that the same reference numerals are used for the same parts as in FIG. 1 described above. FIG. 2 is a diagram showing a three-terminal parallel two-circuit power transmission line and a fault point calculation device that implements the fault point locating method according to the present invention. A power source or a transformer grounded by a power source is disposed, and a load or an ungrounded power source (not shown) is disposed on the power receiving end B and power receiving end C sides. The failure point calculation device 3A is arranged on the power transmission end A side.

At the power transmission end A, current transformers CT1 are connected to the a phase, b phase, and c phase of the 1L line, 2L line, respectively.
A and CT2A, and connected to the bus bar on the power transmission end A side,
A transformer 4A for detecting line voltage is connected. The failure point calculation device 3A includes an input section 31A that converts the values read through the current transformers CT1A, CT2A and the transformer 4A into voltage signals of predetermined levels representing the voltages and currents of each phase;
The voltage signal of the input section 31A is set at a predetermined electrical angle (for example, 30 degrees).
Sample and hold circuits 32A and 32A sample each time
A/D converter 33A, a receiver 34A that receives data of measured values at power receiving ends B and C via radio, light, etc., and an A/D converter 33A.
A fault detection unit 36A (for example, configured with 64 relays) detects a ground fault based on the digital value converted by the converter 33A and the digital value of the measured value at the power receiving ends B and C read through the receiver 34A. ,3
It memorizes the ratio k between the zero-sequence ground fault current and the zero-sequence voltage rating when a terminal is completely grounded, and also stores the ratio k of the zero-sequence ground fault current and zero-sequence voltage rating when the terminal is completely grounded, and when the current data at the A terminal is missing in the event of a ground fault, the Measured zero-sequence voltage V0' or V0'', zero-sequence current I10', I20', I10'' and I20'' measured at terminal B and terminal C
Based on the equation (9) above, calculate the difference current ΔI′=|I10′−I20′|, ΔI″=|I10″−I20″|,
Data restoration unit 3 calculates I and supplies it to distance detection unit 37A.
5A, a distance calculation unit 37A that calculates the distance to the failure point based on the data supplied from the data restoration unit 35A, and a display unit 3 that displays the occurrence of a failure, the distance to the failure point, etc.
8A is provided.

[0020] In addition, current transformers CT1B and CT2B are connected to the a-phase, b-phase, and c-phase of the 1L line, 2L line, and the bus bar on the power receiving end B side, and the line voltage A transformer 4B for detecting is connected. The measuring device 3B includes current transformers CT1B, CT2B and transformer 4B.
an input section 31B that converts the values read through the input section 31B into voltage signals of predetermined levels representing voltages and currents of each phase;
A sample hold circuit 32B that samples the voltage signal at every predetermined electrical angle (for example, 30 degrees), and an A/D converter 3
3B, and a transmitter 34B that transmits data of the measured value at the power receiving end B via wireless, optical, etc. is provided.

[0021] In addition, the power receiving end C has current transformers CT1C and CT2C connected to the a phase, b phase, and c phase of the 1L line, 2L line on the power receiving end C side, and a line connected to the bus bar on the power receiving end C side. A transformer 4C is connected to the measuring device 3C, and the measuring device 3C has an input section that converts the values read through the current transformers CT1C, CT2C, and the transformer 4C into voltage signals at predetermined levels representing the voltages and currents of each phase. 31C, a sample hold circuit 32C that samples the voltage signal of the input section 31C at every predetermined electrical angle (for example, 30 degrees), an A/D converter 33C, and transmits the data of the measured value at the power receiving end C via radio, light, etc. A transmitter 34C is provided.

Note that the sample and hold circuits 32A, 32
Sampling synchronization is provided between B and 32C, as will be described later, to prevent calculation errors from occurring. The operation of the failure point calculation device 3A is as follows. When the failure detection unit 36A detects a failure, it causes the distance calculation unit 37A to start a failure point locating operation. The distance calculation unit 37A extracts zero-sequence current and voltage data from the data restoration unit 35A.

The distance calculation unit 37A takes in the above data and detects the zero-sequence current ΔI of the power transmitting end A, the zero-sequence current ΔI' of the power receiving end B, and the zero-sequence current ΔI'' of the power receiving end B. Then, The well-known formulas (1), (2), and (3) already shown
The distance from either end A, B or C to the failure point is calculated numerically based on the formula. In this case, when a ground fault occurs, A
Even if the current data at one end is missing, the zero-sequence difference current at the A end can be restored based on the zero-sequence voltage data and zero-sequence current data measured at the other end, so there is no problem in calculating the distance. I won't give anything.

Therefore, current transformers CT1A and CT2A, transformer 4A, input section 31A,
It is also possible to omit the sample and hold circuit 32A and A/D converter 33A from the beginning. Note that high speed and high reliability are required for data transmission between the failure point calculation device 3A, measurement device 3B, and measurement device 3C. Therefore, it is preferable to use, for example, the PCM transmission method as the data transmission method, and to use a communication path with a large capacity. In particular, if the data sampling synchronization is not accurately achieved, errors will occur in the calculation results, so the so-called S
P-synchronization control technology (a technology that sends a signal back and forth between the transmitter 13 and receiver 12, measures the time taken for the round trip, and corrects the sampling time difference. Mitsubishi Electric Technical Report Vol. 63,
No. 8, 1989, p. p. 27-31) is preferable.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, transmitters may be installed at the power transmitting end A and power receiving ends B and C to transmit data, and power can also be received from the power transmitting end A. Failure point calculation device 3A is located far away from ends B and C.
It is also possible to install Various other changes may be made without departing from the gist of the present invention.

[0026]

As described above, according to the present invention, when current data at the power transmission end is missing, the missing data can be restored by using the measured data of the current and voltage at the other end. Therefore, since it is possible to determine where the ground fault point is located, it is possible to search for the fault point with less effort.

[Brief explanation of drawings]

[Fig. 1] Three terminal parallel 2 terminals for explaining the principle of the present invention.
It is a circuit diagram of a line power transmission line.

FIG. 2 is a diagram showing a fault point calculation device that implements a fault point locating method in a three-terminal parallel two-circuit power transmission line.

FIG. 3 is a circuit diagram of a general three-terminal parallel two-circuit power transmission line.

[Explanation of symbols]

1L, 2L 3-terminal parallel 2-circuit power transmission line 3A Fault point calculation device 3B, 3C Measuring device 35A Data restoration section 37A Distance calculation section 4A, 4B, 4C Transformer A, B, C Transmission end CT1A, CT2A Current transformer CT1B, CT2B Current transformer CT1C, CT2C Current transformer

Claims (1)

[Claims] Claim 1: Single-line ground fault in a resistance-grounded three-terminal parallel two-circuit power transmission line that has one resistance-grounded power transmission end and the other two ends connected to a load or a power source without neutral point grounding. In the method of locating the fault point, if current data at the transmission end is missing, the zero-sequence difference current ΔI0' at the other two ends
and ΔI0 ″, and the zero-sequence voltage V0 ′ or V0 ″ at either other end, and using the ratio k of the zero-sequence fault current to the zero-sequence voltage rating at the time of a complete earth fault of the transmission line, Formula ΔI
Based on 0 = k | V0 ′ | − ΔI0 ′ − ΔI0 ″ or ΔI0 = k | Zero-sequence difference current ΔI0, ΔI0'
and ΔI0″ to locate the ground fault point.