Analysis and treatment for a insulation resistance decreasing accident of clamp to the ground in main transformer

In this paper, insulation resistance of clamp to the ground in the main transformer is reduced during the test of on-site handover. By entering the box at the scene of the substation to check the status for each part of clamp in the main transformer, the reason for insulation resistance decreasing accident of clamp to the ground in main transformer is confirmed, and two schemes of on-site treatment are proposed. Scheme one is selected and implemented after the full demonstration. And it is shown that the scheme is suitable for abnormal conditions similar to the main transformer when the test of on-site partial discharge in the main transformer and operation assessment are completed.