JPH0470751B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a resistance leakage current measuring device for a lightning arrester.

[Conventional technology]

The equivalent circuit of a zinc oxide element used in a lightning arrester is shown in FIG. That is, the leakage current i flowing through the zinc oxide element is a combination of the resistance component ir and the capacitance component ic. this house,
It is the resistance component IR that is involved in the deterioration of zinc oxide elements. In order to measure this leakage current ir, there has been a device as shown in Utility Model Application No. 13765/1983. This is shown in FIG.

A conductive wire 50 is connected to an end plate 7 provided on the ground side of the zinc oxide element 6 and led out to the outside via a bushing 10. This conductor 50 has a leakage current.
ir+ic flows, causing a voltage drop across the resistor 12. Further, an electrode 21 is provided opposite to the head shield 5 provided on the top of the zinc oxide element 6. Due to the capacitance between the electrode 21 and the head shield 5, a capacitive component ic of the leakage current flows through the conductor 52. This current ic causes a voltage drop across resistor 13. Therefore, by changing the size of the resistor 13, the voltage drop of the capacitive component can be canceled and the resistive component ir can be observed with the oscilloscope 14 connected between the resistors 13.

[Problem that the invention seeks to solve]

In the conventional device, the electrode 21 could not be made very large due to limitations imposed by the size of the container 19, and a sufficient capacitance could not be obtained. Therefore, there was a problem in that the measurement values were affected by noise and errors occurred.

On the other hand, in order to solve the above problems, the electrode 21
If you increase the size of the container 19, the container 19 will also inevitably become larger.
This will lead to an increase in the size of the lightning arrester.

This invention was made to solve the above-mentioned problems, and aims to provide a highly accurate measuring device without increasing the size of the lightning arrester.

[Means for solving problems]

A measuring device according to the present invention includes: a metal container of a lightning arrester supported and insulated from the earth; a first resistor having a variable resistance connected between the metal container and the earth; A grounding wire connected to the installation side terminal of the zinc oxide element provided inside and led out to the outside of the metal container via an insulating bushing, and a connection between the non-grounding side terminals of the first and second resistors. It is equipped with an oscilloscope and a

[Effect]

Since the opposing area between the metal container and the head shield is sufficiently large, the capacitance component of the leakage current flowing through the first resistor is sufficiently large.

On the other hand, a resistance component and a capacitance component of the leakage current flow through the second resistor. Therefore, the first resistance and the second
The measuring means connected between the resistors detects only the leakage current of the resistive component.

〔Example〕

FIG. 1 shows an embodiment of the present invention.

A zinc oxide element 6, which is a nonlinear resistor, is housed in the metal container 19. The metal container 19 is insulated from the ground by an insulator 26 and connected to one end of the first resistor 13 via a conductive wire 52. The other end of the first resistor 13 is grounded, and a capacitive leakage current ic flows through the first resistor 13 due to the capacitance between the metal container 19 and the head shield 5. On the other hand, a conducting wire 50 is connected to an end plate 7 provided on the ground side of the zinc oxide element 6, and a bushing 10
It is derived to the outside via. A leakage current, which is a combination of the resistance component ir and the capacitance component ic, flows through the conductor 50, causing a voltage drop in the second resistor 12. An oscilloscope 14 serving as a measuring means is provided between the resistor 12 and the resistor 13. Therefore, by changing the value of resistor 13, the capacitance component
IC can be canceled and only the resistance component IR can be observed.

Further, in this embodiment, a grounding switch 11 is connected between the conducting wire 50 and the ground, and between the conducting wire 52 and the ground.
a and 11b are provided. Normally, by keeping these on, it is possible to maintain the ground potential.

〔Effect of the invention〕

As described above, according to the present invention, since the metal container of the lightning arrester is used as an electrode for electrostatic coupling, the following effects can be obtained.

First, since a sufficiently large capacitance can be obtained compared to conventional ones, accurate measurements can be made without being affected by noise or the like.

Second, there is no need to provide separate electrodes;
Not only is there no need for bushings for installing electrodes, but the container can be made smaller and lighter.

Thirdly, a leakage current measuring device can be installed on an existing lightning arrester without significantly modifying the container or the like.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, Fig. 2 shows an equivalent circuit of a zinc oxide element, Fig. 3 shows a leakage current, and Fig. 4 shows a conventional leakage current measuring device. FIG. 13 is a first resistor, 12 is a second resistor, and 14 is an oscilloscope. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A metal container of a lightning arrester supported and insulated from the earth; a first resistor with a variable resistance value connected between the metal container and the earth; and an interior of the metal container. a grounding wire connected to the grounding side terminal of the zinc oxide element provided in the metal container and led out to the outside of the metal container via an insulating bushing; and a second resistor connected between the grounding wire and the earth. , an oscilloscope connected between the non-grounded side terminals of the first and second resistors, and a resistance leakage current measuring device for a lightning arrester. 2. A resistance leakage current measuring device for a lightning arrester according to claim 1, characterized in that a grounding switch is provided in parallel with the first resistor.