Poor Grounding Of Distribution Transformer

The lightning protection work for distribution transformers affected by lightning strikes has generally been done, but there are still two problems: ① poor grounding of lightning arresters; ② Only emphasizing the installation of lightning arresters on the high-voltage side and neglecting the issue of installing lightning arresters on the low-voltage side (especially in areas with frequent lightning strikes). If the grounding of the lightning arrester is poor and overvoltage occurs, the lightning arrester cannot discharge the current well, which will damage the insulation of the transformer; If a lightning arrester is not installed on the low-voltage side, when a large amount of lightning current is discharged to the ground by the high-voltage side lightning arrester, a voltage drop is generated at the grounding position. This voltage also acts on the neutral point of the low-voltage side winding while passing through the transformer casing, and the low-voltage side winding is grounded through the wave impedance of the low-voltage line. The following measures can be taken
① Identify the grounding defects related to the lightning arrester and re connect them as required. Note that the grounding wire of the lightning arrester should be directly connected to the shell of the transformer and the neutral point on the low-voltage side, and then the grounding device should be shared. Its grounding resistance shall not exceed 4 Ω; ② For areas with multiple thunderstorms, a set of low-voltage lightning arresters should be added on the low-voltage side.