... (transformers, switches, capacitors, filter resistance, transformer, generators, motors, power cables, etc. ) from over-voltage damage to electrical appliances, insulation ... 1: Low use; 2: 3 KV ~ 220KV power distribution and power plant use; 3: Transformer with neutral point; 4 ... voltage communication systems; 2: 3 KV ~ 220KV AC power distribution and power plant system with; 3: 3 KV ~ 35KV systems ...