JPH034940Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention can be applied to, for example, insulated wires buried underground.
This invention relates to a device that measures electrical leakage points in underground cables, etc.

As is well known, this type of earth leakage location measuring method includes the Murray loop method, the Burley loop method, the pulse method, the search coil method, and the like. FIG. 1 shows the Murray loop method. This is route a, b
If a fault occurs at point O, construct a Wheatstone bridge using complete lines b and c, and balance the bridge by adjusting resistances P and Q to calculate the line length from point a to fault point 0. This is to find l. Here, the line length l is P/Q=2L-l/l ∴l=2Q/P+QL [m
] It is expressed as . However, L is the length of the lines b and c.

Moreover, FIG. 2 shows the Burley loop method. In this case, under the condition of resistance P/Q = 1, adjust the resistance R to balance the bridge, and a
This is to find the line length l from the point to the fault point O. Here, the line length l is expressed as l=L-R/2r [m]. However, L is the length of lines b and c, r
is the resistance [Ω] of the unit length of the wire.

However, the Murray loop method and the Burley loop method have the following drawbacks. That is, measurement cannot be performed unless there is a complete line other than the failed line, and it is necessary to connect the ends of these two lines.
Furthermore, the pulse method and the search coil method require special measuring equipment, and the measurement methods are difficult to understand.

As described above, conventional measurement methods have had various problems.

This idea was made based on the above circumstances, and aims to provide an earth leakage point measuring device that does not require a complete electric line other than the failed electric line during measurement, and is simple in configuration and easy to measure. It is.

This invention is an application of the principle of a ground resistance meter, and first, the basic principle will be explained using FIG.

Reference numeral 11 is an AC power source for the earth resistance meter. One end and the other end of this power source 11 are respectively connected to a measurement ground electrode 12 and a fixed ground electrode 13 provided underground. Therefore, the current I supplied from the power supply 11
flows through the measurement ground electrode 12, the soil resistance 14, 15, and the fixed ground electrode 13. In this case, power supply 1
The voltage E of 1 is applied to the measuring ground electrode 12 as shown in FIG.
It is divided into Ea and Eb approximately in the middle of the fixed ground electrode 13. Therefore, since the ground resistance Ra of the measurement ground electrode 12 is Ea/I and the ground resistance Rb of the fixed ground electrode 13 is Eb/I, the measurement ground electrode 1
By measuring the voltage Ea between the measurement ground electrode 12 and the auxiliary ground electrode 16 provided between the ground electrode 2 and the fixed ground electrode 13, the ground resistance Ra of the measurement ground electrode 12 can be determined. Note that the soil resistances 14 and 15 include resistances of the conductors of the measurement grounding electrode 12 and the fixed grounding electrode 13 and the electrodes themselves, as well as contact resistance between the electrodes and the surrounding soil, but these are generally negligible and negligible. be.

Next, one embodiment of this invention will be described.
In FIG. 5, 21 is, for example, an AC power source for a ground resistance meter, and one end of this power source 21 is connected to a leakage point 2.
2, for example, a buried insulated wire 2
3 conductors are connected. Further, a fixed ground electrode 24 provided underground is connected to the other end of the power source 21, and one end of a voltmeter 25 is connected thereto.
The other end of this voltmeter 25 is connected to a moving ground electrode 26. Therefore, the alternating current I supplied from the power source 21 flows through the insulated wire 23, the leakage point 23, and the fixed ground electrode 24. The electrical equivalent circuit in this case is shown in FIG. Note that the same parts as in FIG. 5 are given the same reference numerals. The resistance 31 is the ground resistance at the leakage point, and the resistance 32 is the soil resistance between the fixed ground electrode 24 and the leakage point 22. Therefore, the voltage indicated by the voltmeter 25 is the voltage between the fixed ground electrode 24 and the moving ground electrode 26;
The closer the movable grounding electrode 26 is to the leakage point 22, the larger it becomes, and when it comes into contact with the conductor of the insulated wire 23, the voltage across the power supply 21 is measured and becomes maximum. In this way, by inserting the movable ground electrode 26 into the ground several times and determining the maximum voltage, it is possible to discover the location of the leakage.

According to the above embodiment, the voltmeter 25 is connected to the power source 21 of a commonly used earth resistance meter, and the measurement is performed by inserting the movable earth electrode 26 into the ground to determine the maximum voltage. Therefore, the leakage point can be found with a simple configuration and easy work.

In addition, since there is no need for a complete line other than the electric line where leakage occurs as in the conventional case, there is no need to connect these lines, which is convenient.

Furthermore, measurement can be performed simply by finding the maximum value with a voltmeter, which is convenient because no calculations as in the prior art are required.

Furthermore, one end of the voltmeter 25 is connected to one end of the power supply 21, and the other end of the voltmeter 25 is connected to the movable grounding electrode 26, so even if the voltage of the power supply 21 is low, there is no leakage from the other end of the power supply 21. A fixed earthing electrode 2 generated by a leakage current flowing through a point 22
4 and the movable ground electrode 26, sufficient measurement is possible, and even if the buried route of the insulated wire 23 is curved and unknown, it can be easily searched.

Note that if a high-precision voltmeter is used, it is possible to measure even if the ground resistance at the leakage point is high.

Also. Even if an electric wire installed in a space such as a tunnel is grounded, measurement is possible if the fixed ground electrode 24 and the movable ground electrode 26 can be installed.

Furthermore, in FIG. 5, the leakage point 22 is the insulated wire 2.
3 and the fixed ground electrode 24,
The fixed grounding electrode 24 connects the insulated wire 23 and the leakage point 22
It goes without saying that measurements can be made in the same manner as above even if the difference is between.

As described in detail above, according to this invention, it is possible to provide an earth leakage point measuring device that does not require a complete electric line other than the failed electric line during measurement, has a simple configuration, and is easy to measure.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams showing the conventional earth leakage point measuring method, Figure 3 is a block diagram shown to explain the basic principle of the earth leakage point measuring device according to this invention, and Figure 4 is a block diagram showing the FIG. 5 is a block diagram showing an embodiment of the leakage point measuring device according to the present invention, and FIG. 6 is an equivalent circuit diagram of FIG. 5. 21... Power source, 22... Leakage point, 23... Insulated wire, 24... Fixed grounding electrode, 25... Voltmeter, 26... Moving grounding electrode.

Claims (1)

[Scope of utility model registration request] An AC power supply having one end connected to the conductor of the electric line where the leakage occurred and the other end connected to a fixed grounding electrode to supply alternating current to these, and the other end connected to the fixed grounding electrode of this AC power supply. and a voltmeter having one end connected to a movable ground electrode and the other end connected to a movable ground electrode, and measures the leakage point of the electric line by moving the movable ground electrode and determining the maximum voltage. Earth leakage point measuring device.