不同故障类型下具有相同灵敏度的配电网自适应电流保护

Adaptive Current Protection with Sensitivity Independent of Different Type of Faults

针对配电网电流保护的特点,提出了一种彻底消除配电网中负荷电流对保护灵敏度影响的算法,根据存在负荷电流的情况建立动作判据,将考虑负荷电流影响时的两相短路电流归算为同一点三相短路电流,然后再与定值作比较,从而克服了目前的电流保护普遍存在的由于受负荷电流的影响而使保护在两相故障时灵敏度降低的缺陷.仿真结果表明,本算法在理论上可以完全消除负荷电流的影响,使保护在两相短路时的灵敏度与三相短路时的相同.

The reliability and sensitivity of the present adaptive current protection is dropped under phase-to-phase fault due to the existence of load current in non-valid grounded power systems. This paper presents a new algorithm, which can take into account of the impact of load current under phase-to-phase fault, and can convert the measured phase-to-phase fault current to the three-phase fault current at the same fault point, then the three-phase fault current is used to compare with the setting value. This method ensures the same class of sensitivity for three-phase short circuit and phase-to-phase short circuit, and the simulation verifies the flexibility and reliability.