POWER SUPPLY MAINS WITH LOW GROUND-FAULT CURRENT Russian patent published in 1998 - IPC

FIELD: electrical engineering. SUBSTANCE: 3-35 kV power mains has collecting buses connected to power-transformer through vacuum switches as well as nonlinear overvoltage limiters. Part of these limiters are connected in parallel with vacuum switches to motor loads and other part of limiters are inserted between vacuum switches and ground on side opposite collecting buses at transformer loads. On-load disconnector setting voltage is found from equation , where β = 1.7-1.8 characterizes current-voltage characteristic for on-load disconnector; a= 0.05-0.06; b=1.3-1.5 are coefficients characterizing permissible voltage rises as function of duration including energy absorption by limiter. On-load disconnector installed at power transformer load has higher setting voltage than that installed at step-down transformer side and minimal setting voltage of on-load disconnector mounted in parallel with switch contacts is lower than that of limiters installed at transformer sides. EFFECT: improved limitation of switching overvoltages and operating reliability of electrical equipment. 1 dwg