JPH01153976A - Investigating method for accident point of multiple earth distribution line - Google Patents

Abstract

PURPOSE:To easily investigate a leak position by comparing the polarities of secondary currents of a current transformer and a return circuit current detecting current transformer in order, and investigating the accident point while deciding the direction of the accident point. CONSTITUTION:The outputs of the return circuit current detecting current transformer 10 and a zero-phase current detecting current transformer are supplied to waveform shaping circuits 17 and 18 for waveform shaping through amplifying circuits 15 and 16. Then their waveform-shaping outputs are inputted to a counter 20 through a NAND circuit 19. A proper pulse signal is sent out of an oscillator 21 to the counter 20, which counts the pulse signal. Then a comparator 23 is connected between the counter 20 and a register 22 and the output of the comparator 23 is outputted to a display part 24, which performs such a display that the direction of the accident point is decided erroneously.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for detecting a fault location in a multi-grounded distribution line.
Specifically, the present invention relates to a method of searching for a leakage point based on the phase relationship between a leakage current flowing in a grounding wire of a power distribution line and a leakage current flowing in the distribution line.

[Conventional technology]

Phases of overhead low-voltage distribution lines that are undergoing type 2 grounding work are:
In addition to the location where the transformer is installed, grounding work is carried out at various locations, so if there is a leakage point, the leakage current will be detected anywhere on the distribution line, so it takes a lot of effort to locate the leakage point. It often requires effort and time.

Conventionally, when such a leakage occurred, the power was cut off and a mega-
A method was used to perform insulation measurements.

In addition, conventional exploration methods have used methods such as comparing the phase difference between zero-sequence voltage and zero-sequence current to determine the direction of the fault point, but extracting the zero-sequence voltage is troublesome. There are drawbacks such as the need for operation and it is not easy, and those skilled in the art have developed a technique that can shorten the time required for leakage detection and perform earth leakage detection using a simple and labor-saving method in terms of equipment. That was what was desired.

[Problem that the invention seeks to solve]

With this technical background, the present invention can relatively easily search for a leakage point, thereby shortening the time required to search for a leakage point and performing the search in a manner that saves labor in terms of equipment. The aim is to provide technology that can

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

In the present invention, the leakage current (
This method attempts to detect the location of an earth leakage based on the phase relationship between the fault current (fault current) and the earth leakage current flowing through the distribution line using the grounding wire as a return path.

Current transformers will be installed on the distribution lines, but they will be moved one by one.
Detects the zero-sequence current flowing through the distribution line.

A current transformer is also installed on the ground wire, and this current transformer detects the return current. An exploration device capable of phase discrimination (comparison) is connected to these current transformers, and the phase of the current detected by the zero-sequence current detection current transformer and the return path current detection current transformer moved along the distribution line are detected. The location of the electrical leakage is identified while distinguishing the phase relationship of the current with the above-mentioned exploration device.

[Operation] If there is a leakage (point) in the distribution system of a multi-grounded distribution line, the leakage current will pass through the grounding wire and the return current will return to the distribution line.

Move the zero-sequence current detection current transformer along the distribution line to the customer's measurement point, and check the phase of the secondary current and the phase of the secondary current of the return current detection current transformer installed on the ground wire. When observing these current transformers with a detection device connected to them, you will find places where the current changes from the same phase to the opposite phase, or from the opposite phase to the same phase, so for example, there is a leakage point in the middle of the phase change. It turns out that there is something.

According to the present invention, since the phase difference between the currents is compared as described above, the structure is simple, the exploration time is short, and the zero-sequence voltage measurement which requires troublesome operations is avoided without causing a power outage at the leakage point. To enable the detection of a leakage point without the need for a power source.

[Example] Next, embodiments of the present invention will be described with reference to the drawings.

The principle of the method of the present invention will be explained using an example shown in FIG.

The transformer l is connected to a low voltage distribution line (hereinafter simply referred to as a distribution line) U,
Power is supplied to V and W.

Grounding wires 2A, 2B, 2G, one line W of distribution lines u, y, w,
Shared with 2D.

Multiple grounding 3A, 3B, 3C13D is performed on the ground line common line W.

The ground resistances of each ground 3A to 3D are RA, RB, and R, respectively.
C, RD.

Now, when a fault (leakage) M occurs with the ground g as shown in the diagram on the distribution line ■, the ground fault current 1g flows in the direction of the arrow as a return current IA through the grounding wire 2A with the grounding resistance of RA. Return to distribution line W.

Similarly, a return current IB is applied to the grounding wire 2B having a grounding resistance of RB, and a grounding wire 2C having a grounding resistance of RC is supplied as a return current IB.
Then, the return current IC returns to the distribution line W in the opposite direction to the ground fault current 1g as the return current ID to the ground line 2D having a ground resistance of RD.

A current transformer 4 is installed on the distribution line. Although three current transformers 4 are shown in FIG. 1, it is sufficient to move one current transformer 4 in an appropriate direction along the distribution lines U, V, and W.

The current transformer 4 is a current transformer (zero-sequence current detection current transformer, hereinafter simply referred to as a current transformer) that detects the zero-sequence current flowing in the distribution lines U, V, and W, and is, for example, a three-phase distribution line or a three-phase current transformer. The zero-sequence current generated by the total current flowing through the distribution line consisting of a combination of single phase and single phase is detected.

For example, the zero-sequence current can be detected by magnetically linking all the distribution lines U% and W together as described later, or by detecting the zero-sequence current of each phase U,
(2) Detect the zero-sequence current from the sum of the currents flowing through W.

FIG. 2 shows an example of a current transformer 4, which includes a main body 5, a split core 6, and a bird 7. Split core 6
The magnetic path 6A and the magnetic path 6B open and close at the upper center cutting position 8 thereof. The clamp type current transformers 4 are sequentially moved to the distribution lines U, V, and W. The zero-phase current is detected by operating the four current transformers 7 to detect each phase U%V.
, W can be magnetically linked to each other.

A conductive wire 9 is drawn out from the lower part of the main body 5 for connection to an exploration device to be described later.

On the other hand, as shown in FIG. 1, an arbitrary number of current transformers 10 are also installed on the ground wire. FIG. 1 shows an example in which the wires are installed on the ground wire 2B and the ground wire 2C. This current transformer 10 is fixed to the ground wire. This current transformer IO detects the current (return current) flowing through multiple earths 3A to 3D.

This return current detection current transformer (hereinafter referred to as auxiliary current transformer) 10
has the same structure as the current transformer 4, and is a similar clamp type current transformer.

It is preferable that the current transformer 4 and the auxiliary current transformer 10 be labeled to indicate the fault point side and the ground side. The display is not necessarily specified to the L side or KIIll of these current transformers 4.10, but is specified to either side depending on the polarity with the exploration device.

Examples of such indications include, for example, writing letters indicating the accident point side directly on the surface of the current transformer, pasting a label on the current transformer, or attaching an arrow painted in red. Preferably, the display 11 is placed on an easily visible part of the body 5 of the current transformer 4.10.

An exploration device 12 is connected to the conductive wire 9 drawn out from the ends of the current transformer 4 and the auxiliary current transformer IO, as illustrated in FIG.

The exploration device 12 may be a cathode ray tube oscilloscope or the like as long as it can discriminate the phase relationship between the currents of the current transformers 4 and 1O, but since the device is large, it is preferable to use the following discrimination device which can be made small. preferable.

FIG. 3 is a system diagram of the phase discrimination device 12.

The output of the auxiliary current transformer 10 (detected return current) is input from the input terminal 13 for the auxiliary current transformer 10 of the phase discriminator 12 . In addition, from the input terminal 14 for the current transformer 4, the current transformer 4
The output (detected zero-sequence current) is input.

Each output is amplified so that there is no waveform distortion when inputted to the primary waveform shaping circuit via the respective amplifier circuits 15 and 16, and is waveform-shaped by the respective waveform shaping circuits 17 and 18.

Both waveform-shaped outputs are input to a NAND circuit 19.

NAND circuit 19 is connected to counter 20 .

Appropriate pulse signals are sent to the counter 20 from the 1 oscillator 21, and the pulse signals are appropriately counted.

A comparator 23 is connected between the counter 20 and the digit register 22 to compare the contents thereof, and the comparator 23 is connected to a display section 24, and the display section 24. Then, necessary indications such as the fact that the direction of the accident point has been incorrectly determined are displayed.

An example of how to search for the accident point M will be explained according to these figures.
Prior to exploring the accident point M, a virtual accident point is temporarily determined,
Estimate one accident direction.

The current transformer 4 and the auxiliary current transformer 10 are respectively connected to the distribution line U,
Install on V, W and ground wire 2B (2C). At this time, the fault point side display of the current transformer 4 is directed toward the virtual fault point, and the ground side (display) of the auxiliary current transformer 10 is grounded 1i12B.
(2C) (7) Make sure to face the grounding point 3B (3C). In other words, the polarity of these current transformers 4.10 is fixed.

The current transformer 4 is moved to positions X, Y, and Z without changing the direction of the virtual fault point.

The phase of the zero-sequence current detected by current transformer 4 and the phase of the ground current detected by auxiliary current transformer 10 are compared at each position X, Y, and Z. At this time, a ground fault current of 1 g flows from the distribution line V to the ground g, and the ground fault current is 3 A.
~3D, and return to distribution lines U, V, and W via grounding wires 2A to 2D.

That is, the fault current 1g and the return currents IA to ID all return in the direction of the fault point M, which is equivalent to inserting a current source at the fault point M.

From the above, the current flowing through the current transformer 4x installed at position X is I
The phase of the secondary current at A is in phase with that of IB, and the current flowing through current transformer 4Y moved to position Y is Ig-(ID+I
In C), the phase of the secondary current is in phase with IB. Position Z
The current flowing through the current transformer 4Z that has been moved to is ID+IC, and the phase of the secondary current is opposite to Ic.

Therefore, if current transformer 4x is installed at current transformer positions X and Y with the direction of fault point M being on the right side of the diagram, and it is moved to position Y, current transformers 4x and 4Y induced 2
The polarity of the secondary current is the same as the polarity of the secondary current induced in the auxiliary current transformer 10, and when the polarities of the current transformers 4x, 4Y and the auxiliary current transformer 10 are the same, the current transformer 4Y Since it is determined that the fault point M is in the display direction indicating the fault point side of
Since the phase is reversed and the polarity is different, it can be seen that there is a fault point M at an intermediate point between these two points.

The phase discriminator 12 is connected to the current transformer 4 and the auxiliary current transformer 10 at positions X, Y, and Z to determine the phase relationship as described above. A voltage signal proportional to the detected alternating current of the current transformers 4 and 10 is input to the terminals 13 and 14.

The amplifier circuit (amplifier) 15.16 connects to this terminal 13.14.
Amplify the voltage signal input to the The respective output waveforms at this time are sine waves as shown by a and b in FIG.

Waveform shaping circuits (waveform shapers) 17 and 18 detect zero-crossings of input AC signals a and b, and convert them into logical rectangular wave signals c and d that are inverted at the zero-crossing points (FIG. 4).

The NAND circuit 19 does not send out a reset signal for the counter 20 and opens the counting window of the counter 20 only when both input rectangular wave signals c and d are present.

The counter 20 counts the pulse signals sent by the first oscillator 21 during the time when the reset signal is not sent.

In the timing chart shown in FIG. 4, e output indicates the output from the NAND circuit 19, and T
1. T2 indicates the counting time of the counter. From the same timing chart, it can be seen that the counting time of the counter is the longest when there is no phase difference between the a input and the b input to the waveform shaping circuits 17 and 18. At this time, the counting time becomes shorter as the phase difference becomes larger. At a phase difference of 180°, the counting time becomes zero.

When either of the input signals C and d of the NAND circuit 19 disappears, the NAND circuit 19 resets the counter 20, and the counter 20 stops counting. The contents of the counter 20 and the contents of the digit register 22 at this time are compared.

Move current transformer 4 to positions X, Y, and Z.

Discriminating the direction of the ground fault fault, at positions X and Y, the polarities of the secondary induced voltages of current transformers 4x and 4Y and auxiliary current transformer lO are equal and almost in phase, and the count value of counter 20 is large. Become. Therefore, the contents of the counter 20 are
is larger than the content of , and the display unit 24 does not display that the direction is incorrect.

As shown in FIG. 3, it is preferable to connect a polarity switching switch 25 to the waveform shaping circuit 18.

This switch 25 inverts the output waveform d of the waveform shaper 18. It is possible to check whether the phase discrimination device 12 is operating normally.

Therefore, when this normal operation confirmation switch 25 is pressed, the output waveform d of the waveform shaping circuit 18 is reversed, and the indicator light on the display section 24 lights up, indicating that the 1-phase discriminator 12 is operating normally. It can be confirmed.

When the current transformer is moved to position 2, the current ID+IC returning to the distribution lines U, V, and W flows through the current transformer 4z from the illustrated cloth to the left in the direction of the fault point M, resulting in the secondary induction of the current transformer 4z. The polarity of the current and the polarity of the secondary induced current of the auxiliary current transformer lO are approximately 180°
Produces a phase difference. Therefore, the contents of the counter 20 are smaller than the contents of the digit register 22, and the comparator 23 is
is driven to display that the estimated direction is incorrect, and the accident point M can be identified as described above.

Even in the case of the above-mentioned error display, by suppressing (turning on) the switch 25, it can be confirmed whether the operation is being performed normally.

In the above embodiments, a method of phase discrimination using the exploration device shown in FIG. Since this has been made possible as a result of intensive study, the device will now be explained with reference to FIGS. 5 and 6.

As shown in FIG. 5, the exploration device +2'' includes an amplifier circuit 26 that amplifies the input signal from the zero-phase current detection current transformer (current transformer) 4, and extracts harmonic components from the amplified output signal. a filter 27 for removing the current, a phase inversion circuit 28 for inverting the phase of the filter output from the zero-phase current detection current transformer 4, and a waveform shaping circuit 29 for shaping the phase of the phase-inverted output.
, an amplifier circuit 20 that amplifies the human input signal from the return current detection current transformer (auxiliary current transformer) 10, a filter 31 that removes harmonic components from the amplified output signal, and a return current detection current transformer. It comprises a waveform shaping circuit 32 that shapes the filter output from the IO, and a flip-flop circuit 33 that flip-flops the outputs of the waveform shaping circuits 29 and 32.

To explain the operation of this exploration device +2', the output of each current transformer 4.10 is amplified by an amplifier circuit 26.30, and harmonic components are removed by a filter 27.31.

The output from the filter 27 is delayed in phase by 90@ in the phase inversion circuit 28.

The outputs of the filter 31 and phase inversion circuit 28 are converted into positive half waves (or negative half waves) by waveform shaping circuits 29 and 32, respectively.
The signal is shaped into a square wave that becomes [H] (High) only when , and is then input to a D-type flip-flop circuit (hereinafter referred to as F, F circuit) 33.

In the case of the same phase (when the output on the current transformer 4 side leads and lags 90 degrees with respect to the output on the auxiliary current transformer 10 side), the FF
When the 0 human power of circuit 33 is [H], the cp human power is [L]
(Low) to [I]], the output Q becomes [H
].

If they are not in phase, when the D input is [L], the CP large input [
[L] becomes [H], and the Q output becomes [L].

In this way, phase discrimination can be performed based on the output of the FF circuit 33.

This exploration device 12' enables exploration of electrical leakage locations in the same manner as the exploration device 12 described above.

Fig. 6 (a) to (f) respectively show the exploration device 12'.
A timing chart diagram of each product output is shown.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a technique that allows easy exploration of an earth leakage point, shortens the exploration time, and allows exploration to be performed in a manner that saves labor in terms of equipment. Ta.

[Brief explanation of the drawing]

Fig. 1 is a principle diagram showing an embodiment of the present invention, Fig. 2 is a configuration diagram of an example of a current transformer used in the present invention, Fig. 3 is a system diagram of an exploration device showing an embodiment of the present invention, FIG. 4 is a waveform diagram showing an embodiment of the present invention, FIG. 5 is a system diagram of an exploration device showing another embodiment of the invention, and FIG. 6 is a timing chart of output in the same device. l...Transformer, 2A~2D...Grounding wire, 3A~
3 f)...multiple grounding, 4...zero-phase current detection current transformer, 5...main body, 6...divided iron core, 7-...
Trigger, 10...Return current detection current transformer, 11...
・Display, 12.12'...Exploration device, 13
．． 14...Input terminal, 15.16...Amplifier,
17.18...Waveform shaping circuit, 19...NAN
D circuit, 2゜... counter, 21... oscillator,
22... digit register, 23... comparator, 24...
・Display device, 26... Amplification circuit, 27... Filter, 28... Phase inversion circuit, 29... Waveform shaping circuit, 30
...Amplification circuit, 31.. Filter, 32.. Waveform shaping circuit, 33. Self-flip-flop circuit.

Claims (1)

[Claims] 1. In a method of searching for a fault point while determining the direction of the fault point using an appropriate number of grounding points of a multi-grounded distribution line as boundaries, a zero-sequence current flowing in the distribution line is provided. A zero-sequence current detection current transformer is installed to detect the zero-phase current, and a return current detection current transformer is installed on the ground wire to detect the return current flowing through the ground wire, and the current detected by both current transformers is A detection device for comparing polarities is provided, the direction of one fault point is estimated first, the zero-sequence current detection current transformer is installed on the distribution line with its polarity fixed, and the zero-sequence current detection current transformer is installed on the distribution line with its polarity fixed. The direction of the fault point is determined by comparing the polarity of the secondary current of the current transformer with the polarity of the secondary current of the return current detection current transformer whose polarity is determined and fixedly installed on one of the grounding wires. Then, with the polarity of the zero-sequence current detection current transformer fixed, the current transformer is moved to the next fault point direction determination position, and the polarity of the secondary current of the current transformer and the return path current detection are determined. A fault point detection method for a multi-grounded distribution line, characterized in that the fault point is searched while determining the direction of the fault point by sequentially comparing the polarity of the secondary current of a current transformer. 2. The zero-phase current detection current transformer is a clamp-type current transformer that includes a split core, a main body, and a trigger, and by operating the trigger, it magnetically links each phase of the distribution line and generates a zero-phase current. The fault point detection method for a multi-grounded distribution line according to claim 1, which is a current transformer for detecting phase current. 3. The exploration method according to claim 2, wherein the zero-sequence current detection current transformer has a character display indicating the fault point side on its main body. 4. The exploration method according to claim 1, wherein the return current detection current transformer is a clamp type current transformer comprising a split core, a main body, and a trigger. 5. The exploration method according to claim 4, wherein the return current detecting current transformer has a character indicating the ground side on its main body. 6. The exploration device includes an amplifier circuit that amplifies the respective input signals from the zero-sequence current detection current transformer and the return current detection current transformer, a waveform shaping circuit that shapes the respective outputs after the amplification, and the waveform shaping circuit. A logic circuit connected to the circuit, a counter connected to the logic circuit, an oscillator that sends a pulse signal to the counter, a comparator that compares the contents of the counter with the contents of a digitizer described later, and a digitizer. The exploration method according to claim 1, comprising a container and a display section. 7. The exploration device includes an amplifier circuit that amplifies the input signal from the zero-phase current detection current transformer, a filter that removes harmonic components from the amplified output signal, and an inverter that inverts the phase of the filter output. A phase circuit, a waveform shaping circuit that shapes the phase-inverted output, an amplifier circuit that amplifies the input signal from the return current detection current transformer, and a filter that removes harmonic components from the amplified output signal. 2. The exploration method according to claim 1, comprising: a waveform shaping circuit that shapes the filter output into a waveform; and a flip-flop circuit that flip-flops the output of each of the waveform shaping circuits.