JPH09105765A - Method for searching earth fault point and method for detecting earth fault phase of distribution line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for searching an earth fault point and a method for detecting an earth fault phase which can be easily performed by anyone with a simple method and device. SOLUTION: In a distribution line 41, a signal voltage of a specified frequency is applied from a transmitter 10 between the distribution line 41 and the ground, the voltage applied to the earth line 44 of each pole of the distribution line, and the pole to which the maximum voltage is applied is detected, thereby, an earth fault point is searched.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a ground fault point on a distribution line.

[0002]

2. Description of the Related Art Conventionally, when a ground fault occurs on a distribution line, the circuit breaker of a substation is first interrupted in order to disconnect the accident section and to transmit power to a sound section early, and after a certain period of time, the circuit breaker is restarted. Make a circuit. Then, the division switches installed on the distribution line are sequentially turned on. When power is re-transmitted to a healthy section and then re-transmitted to the ground fault section, the circuit breaker at the substation shuts off again. At this time, the classification switch that has closed the ground fault accident section is locked and the closing operation is not performed even if the power is applied next time.

After a certain period of time, when the circuit breaker of the substation is closed again, the section switches are sequentially turned on in a healthy section to transmit power. On the other hand, since the classification switch is locked in the accident section, power is not transmitted and only the accident section is separated. In this way, the accident section is detected and separated. When the detection and disconnection of the accident section is completed, turn off the manual switch installed in the accident section to divide it into smaller sections,
The ground fault accident point was investigated by measuring the insulation resistance or measuring the insulation resistance of equipment such as transformers installed on each utility pole.

[0004]

As described above, conventionally, after detecting and disconnecting the ground fault accident section, the ground fault accident section is further divided into smaller parts to measure the insulation resistance, and various types of electric poles installed on each utility pole are used. Since the insulation resistance of the equipment was measured, there was a problem that it took time and exploration of the accident point took a lot of time and labor. The problem to be solved by the present invention is to provide a method for anyone to easily search for a ground fault accident point and a method for detecting a ground fault accident phase by a simple device and method in order to eliminate these problems. Especially.

[0005]

In order to solve the above-mentioned problems, a method for detecting a ground fault in a distribution line according to the present invention is applied to a distribution line by applying a signal voltage of a specific frequency between the distribution line and the ground. It is characterized in that the ground fault point is searched by detecting the voltage applied to the ground wire of each utility pole of the line and detecting the utility pole to which the maximum voltage is applied. In this method, by applying the signal input electrode of the receiver to the ground terminal of the utility pole, the voltage applied to the ground terminal can be detected. Further, the distribution line ground fault accident phase detection method of the present invention, in the distribution line, by applying a signal voltage of a specific frequency between the distribution line and the ground, by detecting the current flowing to the distribution line or the ground, ground fault. It is characterized by detecting the phase in which an accident has occurred.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A transmitter 1 connected between a distribution line 41 and ground as shown in FIG. 2 after a section in which a ground fault has occurred is separated by a section switch installed on a distribution line.
When 0, the search signal is transmitted. The exploration signal flows from the transmitter 10 through the distribution line 41 and from the ground fault accident point to the ground through the ground wire in the utility pole.

Since there is a ground resistance between the ground wire and the ground, assuming that the search signal current is I _S and the ground resistance is r ₄ , V ₄ = I _S
A voltage drop of × r ₄ occurs. FIG. 3 is a rewrite of FIG. 2 in an electrically understandable manner. Since the exploration signal current flows only in the ground wire 44 of the electric pole in which the ground fault accident occurs, only the electric pole receives the voltage in the ground wire 44. Therefore, if the voltage applied to the ground wire 44 of each utility pole is detected, the ground fault accident point can be easily searched.

Next, a power distribution line in which the overhead ground wire 42 is installed will be described. As shown in FIG. 4, in the case of the distribution line in which the ground wire 44 of each utility pole is connected by the overhead ground wire 42,
The exploration signal current sent from the transmitter 10 flows through the distribution line 41 and the earth line 44 inside the pole from the ground fault point to the ground, and at the same time from the ground line 44 inside the pole through the overhead ground line 42 to the adjacent pole. It also flows to the ground wire. As a result, a voltage drop will occur in the ground wire other than the power pole where the ground fault occurred.

FIG. 5 is a diagram obtained by rewriting FIG. 4 so as to be electrically understandable. If the ground wire of each utility pole is connected by the overhead ground wire 42 as shown in FIG. 5, the resistance of the overhead ground wire 42 is very small, and the voltage drop of the ground wire in each utility pole will be substantially the same. This makes it difficult to search the ground fault accident point, but since the overhead ground wire 42 has an inductance component, if a high frequency signal is used as the search signal,
Exploration becomes easy.

FIG. 1 is a drawing in which the portion of the overhead ground wire in FIG. 5 is rewritten as an inductance. In FIG. 1, the exploration signal current I _S flows into the ground wire of each utility pole through the ground fault resistance r _g , but part of it flows into the ground wire of the utility pole in which the ground fault has occurred as a current I ₄ . Thereby, No. A voltage drop of V ₄ = I ₄ × r ₄ occurs on the ground wire of the telephone pole of No. ₄ .

[0011] The frequency of the probing signal is f, and the current flowing in L ₃ and I _3, causes a voltage drop of the L ₃ 2πfL ₃ × I _3. Voltage V ₃ is therefore _{V 3 = V 4 -2πfL 3 ×} I
It becomes ₃ . Similarly, the voltages of V ₂ and V ₁ are V ₂ = V ₃ -2πfL ₂ I ₂ = V ₄ -2πfL ₃ I ₃ -2πfL ₂ I ₂ V ₁ = V ₂ -2πfL ₁ I ₁ = V ₄ -2πfL ₃ I ₃ −2πfL ₂ I ₂ −2πfL ₁ I ₁ . Similarly, the voltages of V ₅ and V ₆ are V ₅ = V ₄ -2πfL ₅ I ₅ V ₆ = V ₅ -2πfL ₆ I ₆ = V ₄ -2πfL ₅ I ₅ -2πfL ₆ I ₆ .

That is, the voltage applied to the ground wire of the utility pole in which the ground fault has occurred is the highest, and the voltage decreases due to the voltage drop due to the inductor next to the ground wire and next to the ground wire. For example, if the frequency of the high-frequency exploration signal is 10 kHz and the level of the voltage applied to the ground line at the ground fault accident point is 10, the level is 3 to 4 next to it and the levels of 0 to 2 for other utility poles (Fig. 6). As described above, according to the present exploration method, since there is a clear difference between the electric pole at the ground fault accident point and the other electric pole, the exploration can be performed easily and in a short time.

Next, regarding the method of measuring the voltage applied to the ground wire, generally, when a current is passed through the ground wire, the potential rises due to the ground resistance. Since the electric current flows radially toward the earth, the potential of the earth around the earth wire also rises. As shown in FIG. 7, this potential is highest at the ground point and becomes lower as the distance from the ground point increases. Since the conventional measurement of the voltage applied to the ground wire is the voltage measurement between the ground wire and the ground, as the electrode between the ground, as shown in FIG. 8, in addition to the normal ground rod 51, another ground rod, that is, an auxiliary electrode. 52 is required.

When used to search for a ground fault point, the absolute value of the voltage of the ground wire is not required, and it is only necessary to search for the highest point. For example, even at a distance where the potential rises by ΔV, such as the point A in FIG. 7, it is possible to search without problems.
In fact, it may be said that it is a comparatively simple method as long as the auxiliary electrode is driven at a distance of 2 to 3 m from the electric pole and the voltage of the ground wire is measured. However, it becomes easier if the search can be performed without driving the auxiliary electrode 52. The method will be described below.

A ground terminal 50 as shown in FIG. 9 is installed on the electric pole of the electric power company. In the figure, the grounding wire 44 in the utility pole is cut off midway so that the grounding resistance can be regularly measured, and two grounding terminals 50 are connected. The ground terminal is an insulator base 46
A conductive rod that is threaded is fixed to the screw (thread 4
8). Two ground wires 44 are inserted into the screw portion 48, and tightened with a tightening nut 49 for connection.
The base 46 is fastened and fixed to the electric pole 43 with a mounting screw 47. Mounting screw 47 when measuring earth resistance
To loosen the ground terminal portion 50 to the outside of the utility pole 43, loosen the tightening nut 49 to remove the wire connected to the ground, and measure the ground resistance.

As shown in FIG. 9, the ground fault accident point search method according to the present invention includes a receiver 20 from the outside to a ground terminal 50 of a utility pole.
It is possible just by hitting the tip of. An electrode 11 is provided at the tip of the receiver 20, and the voltage of the ground wire 44 is detected by this electrode 11. FIG. 10 is a rewrite of this situation in an electrically understandable manner, and the ground terminal 50 has a screw portion to which a ground voltage is applied. The measurer uses the insulator of the grounding terminal 50 to receive the electrode 11 of the receiver.
The ground wire 44 and the electrode 1 of the receiver 20
1 is connected by the capacitance C ₁ between them. Further, since the receiver 20 is held by hand, the minus side of the receiver 20 and the hand are connected by the electrostatic capacitance C ₂ therebetween. Similarly, since the measurer is standing on the ground, the foot and the ground are connected by the capacitance C ₃ therebetween.

The input impedance of the receiver 20 is Z _in ,
Assuming that the internal resistance of the human body is R _m , the voltage of the ground wire 44 is divided by C ₁ , Z _in , C ₂ , R _m and C ₃ and the voltage at Z _in is applied. This voltage is amplified by the amplifier circuit 12 and displayed on the display unit 14 as a voltage value or a voltage level. As described above, in the exploration of the ground fault accident point, the voltage at the ground fault accident point and the other points are about three times as different as shown in FIG. 6, and therefore the exploration can be performed without any problem.

Next, an embodiment of the transmitter 10 is shown in FIG.
In FIG. 11, reference numeral 1 denotes an oscillator, which oscillates at a specific frequency. This output is given to the power amplifier 2 for power amplification. The output of the power amplifier 2 is given to the transformer 3,
Boosted. The output of the transformer 3 is connected to the ground and the distribution line 41, and a signal voltage is applied between the distribution line 41 and the ground.

Next, an embodiment of the receiver is shown in FIG. In the figure, 11 is an input electrode, 12 is an amplifier, 13 is a bandpass filter, and 14 is a display IC. The signal input to the input electrode 11 is amplified by the amplifier 12. The output of the amplifier 12 is selected by the bandpass filter 13 as a signal having only a specific frequency. The output of the bandpass filter 13 is applied to the display IC 14, and the LED is turned on or displayed as a value according to the input voltage. Since the input electrode 11, the amplifier 12, and the bandpass filter 13 all output in proportion to the input voltage, the number of LEDs lit or the display value is applied to the voltage applied to the input electrode 11, that is, the ground terminal 50. It will be proportional to the voltage.

Next, a method of detecting the accident phase will be described. When exploring a ground fault, it is first necessary to identify the accident phase. It is assumed that a ground fault has occurred in the T phase of the distribution line 41 as shown in FIG. In this case, it seems that in order to detect the accident phase, the resistance to ground of each phase may be measured, but the transformer 45 or the like is connected to the actual distribution line 41 as shown in the figure, and the resistance to ground is measured. Is almost the same in any of R, S, and T phases. Therefore, measurement is performed with an AC signal so that there is no influence of the transformer 45 or the like. In FIG. 13, an AC signal is used for the accident phase detector 30. This makes the transformer 4
5. The flowing current becomes small, and the influence of the transformer 45 can be almost ignored. In FIG. 13, when the output of the accident phase detector 30 is sequentially connected to R, S, and T, the largest amount of current flows when connected to the T phase. It turns out that

FIG. 13 shows an embodiment of the accident phase detector. In the figure, 21 is an oscillator, 22 is a power amplifier, 23 is a transformer, 24 is a resistor for detecting an output current value, 25
Is an amplifier, 26 is a bandpass filter, and 27 is a display I.
C. The AC signal of a certain frequency oscillated by the oscillator 21 is amplified by the power amplifier 22. Power amplifier 2
The output of 2 is applied to the transformer 23 and boosted. The output of the transformer 23 is connected to the ground and the distribution line 41, and a signal voltage is applied between the distribution line 41 and the ground. This allows
Although a signal current flows through the distribution line 41, since the current detecting resistor 24 is connected in the circuit, a voltage proportional to the signal current is generated across the resistor 24. This voltage is amplified by the amplifier 25, applied to the bandpass filter 26, and selected as a signal having only a specific frequency.

The output to the bandpass filter 26 is a display I.
It is applied to C27 and turns on or displays the LED according to the input voltage. Since the amplifier 25 and the bandpass filter 26 output the output in proportion to the input signal, the LED
The number of lights of is displayed in proportion to the terminal voltage of the resistor 24, that is, the current flowing through the distribution line 41. Therefore, if the phase showing the maximum is searched, it is found that the phase is the accident phase.

[0023]

As described above, according to the present invention, the ground fault accident point can be easily searched with a relatively simple device.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a connection relationship between a distribution line in which an overhead ground wire is rewritten as an inductance and a transmitter.

FIG. 2 is an explanatory diagram showing a state in which a search signal is transmitted from a transmitter connected between a distribution line and the ground according to the present invention.

FIG. 3 is a circuit diagram for electrically explaining the state of FIG.

FIG. 4 is an explanatory diagram showing a state in which a transmitter is transmitting a search signal to a distribution line having an overhead ground wire.

FIG. 5 is a circuit diagram for electrically explaining the state of FIG.

FIG. 6 is a graph showing the level of the voltage applied to the ground wire of the accident pole and the adjacent utility pole.

FIG. 7 is a graph showing the magnitude of increase in ground potential by the ground wire with respect to the distance from the ground point.

FIG. 8 is an explanatory diagram showing an example of installing an auxiliary electrode for measuring the voltage of a conventional ground wire.

FIG. 9 is a sectional view showing a state in which a ground terminal is attached to a utility pole.

FIG. 10 is a circuit diagram showing a state in which the voltage applied to the ground line is measured using the receiver of the present invention.

FIG. 11 is a circuit diagram showing an embodiment of a transmitter of the present invention.

FIG. 12 is a circuit diagram showing an embodiment of a receiver of the present invention.

FIG. 13 is a circuit diagram showing an embodiment of an accident phase detector of the present invention.

[Explanation of symbols]

1 oscillator, 2 power amplifier, 3 transformer, 10 transmitter, 11 electrode, 12 amplifier, 13 bandpass filter, 14 indicator, 20 receiver, 21 oscillator, 2
2 power amplifier, 23 transformer, 24 detection resistor, 2
5 amplifier, 26 band pass filter, 27 display IC, 30 accident phase detector, 41 distribution line, 42 overhead ground wire, 43 utility pole, 44 earth line, 45 transformer, 4
6 base, 47 screw, 48 screw part, 49 tightening nut, 50 ground terminal, 51 ground rod, 5
2 auxiliary electrode

Claims (3)

[Claims] 1. In a distribution line, a signal voltage of a specific frequency is applied between the distribution line and the ground, the voltage applied to the ground wire of each utility pole of the distribution line is detected, and the maximum voltage is applied to the utility pole. A ground fault accident point detection method for a distribution line, which is characterized by detecting a ground fault accident point. 2. The ground fault point of the distribution line according to claim 1, wherein the voltage applied to the ground terminal is detected by applying the signal input electrode of the receiver to the ground terminal of the utility pole. Exploration method. 3. A phase in which a ground fault has occurred by applying a signal voltage of a specific frequency between a distribution line and ground in a distribution line and detecting a current flowing to the distribution line or ground. A method of detecting a ground fault accident phase of a distribution line, characterized by: