Grading ring for HV Arrester

According to the voltage level, the grading ring of lightning arrester is divided into 110kV grading ring of lightning arrester, 220kV grading ring of arrester, 330kV grading ring of arrester, 500kV grading ring of arrester, 550kV grading ring of arrester, 750kV grading ring of arrester, grading ring of 800kV arrester, grading ring of 1000kV arrester, etc, in China. Because the high-voltage arrester has stray capacitance to the ground, the voltage distribution along the arrester is uneven, so that the place where the voltage is high is easy to be damaged, so add a lightning arrester grading ring to balance the stray capacitance to the ground, so that the voltage distribution is uniform, and no local breakdown and damage occurs. The higher the voltage level, the greater the stray capacitance to ground.

Effect of equalizing ring on arrester leakage current
When carrying out the preventive test of 500kV zinc oxide arrester, the leakage current test @ DC 1mA voltage U1mA and 0.75U1mA is an important item, which can find out whether the metal zinc oxide sheet is damp or aged in time. When the above method was used for field testing, it was found that the leakage current measured in the upper section of phase A was 223μA, and the upper section of phase A, B and C was measured several times, but there was still no obvious change. The middle and lower sections are tested using the same principle, and the test results fully meet the requirements. The test value in the previous section is obviously larger than the factory value, and the factory test of the arrester is carried out when the equalizing ring is not installed. The main reason for the analysis is that the distance between the zero-potential equalizing ring and the lower metal flange of the upper section arrester under pressure is close, which produces a strong spatial stray current, which is measured together with the leakage current, resulting in a large result.