Grounding device test selection scheme

1) no more than 6 years

2) It is possible to extend or shorten the cycle according to the results of the grounding network excavation inspection.

R≤2000/I or R≤0.5Ω, in the formula (I>4000A);

I- short-circuit current flowing into the ground via the grounding grid, A;

R - the maximum grounding resistance considering the seasonal variation, Ω;

1) When measuring the grounding resistance, such as the minimum necessary pole
The soil resistivity in the range is basically uniform, and various types can be used.
Compensation method, otherwise, the transport method should be adopted

2) In areas with high soil resistivity, the grounding resistance is as
The specified value requirement is allowed when the technical economy is extremely unreasonable.
There are a large number. But measures must be taken to ensure
When a ground short occurs, on the grounding network

a. The contact voltage and step voltage are not more than allowed.
Numerical value

b. Does not occur outside the high potential and low potential

C.3～10kV valve arrester does not work

3) before the preventive test or every 3 years and when necessary
Check the value/value and verify the thermal stability of the device grounding down conductor.

1) no more than 6 years

2) It is possible to extend or shorten the cycle according to the results of the grounding network excavation inspection.

1) When the grounding grid is grounded with equipment of 1kV and below, the grounding resistance R≤120/I

2) When the connection network is only above 1kV, the grounding resistance R≤250/I

3) In any of the above cases, the grounding resistance should generally not exceed 10Ω

Where: I- short-circuit current flowing into the ground via the grounding grid, A;

R- taking into account the seasonal variation of the maximum grounding resistance, R;

1) 1 to 2 years of towers within 1-2km of the power plant or substation

2) Other line towers are not more than 5 years

When the height of the tower is below 40m, according to the following requirements, if the tower height reaches or exceeds 40m, take 50% of the following values, but when the soil resistivity is greater than 2000Ω·m, the grounding resistance is difficult to reach 15Ω and can be increased to 20Ω.

For towers with a height of less than 40 m, if the soil resistivity is high and the grounding resistance is difficult to drop to 30 Ω, 6 to 8 radial grounding bodies or continuous elongated grounding bodies with a total length of not more than 500 m can be used, and the grounding resistance can be unrestricted. . However, for poles with a height of 40m or more, the grounding resistance should not exceed 20Ω.

Soil resistivity Ω·m

Grounding resistance Ω

100 and below

10

100～500

15

500～1000

20

1000～2000

25

More than 2000

30