Protection method for single-phase earth fault of neutral ungrounded system

• Main Authors: SANG ZIJIE, LI YALI, YIN CHAOZHUN, LYU WENBO, YAN ZEYUAN, WANG CHUNWEI, SHEN JU, FAN QIAOLIAN, LIU AIHUA, ZHOU YUNFENG
• Format: Patent
• Language: Chinese; English
• Published: 18.11.2022
• Subjects: CONVERSION OR DISTRIBUTION OF ELECTRIC POWER; ELECTRICITY; EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS; GENERATION

The invention provides a protection method for a single-phase earth fault of a neutral point ungrounded system. The protection method comprises the following steps: step 1, continuously measuring zero-sequence current at a wire inlet switch, a wire outlet switch and a feeder switch of each substation in the neutral point ungrounded system; 2, starting zero-sequence current protection after the value and the direction of the zero-sequence current at each switch meet conditions; and 3, after the zero-sequence current protection starting condition meets the condition, starting a zero-sequence current protection action by the protection device of the switch. According to the method, the magnitude and the direction of the capacitance current when the cable and the bus of each section in the topological structure of the looped network power supply system have the single-phase earth fault are analyzed, and the magnitude and the direction characteristics of the capacitance current of the incoming line, the outgoing l