线路差动保护的相移制动能力研究

Studies on Phase Shift Restraint Capacity of Feeder Current Differential Protection

数据同步是基于通信的差动保护方案的首要问题。为从差动保护判据本身找到一个减小同步误差影响的途径,提出描述差动保护判据耐同步误差能力的相移制动能力指标。采用相量分析法分析常规差动保护的相移制动能力,发现常规比率制动判据的相移制动能力只能达到20°左右,而非线性差动保护的相移制动能力可以达到60°左右,这对基于软实时通信技术的使用场合非常有价值。提出一种新相差型的差动保护判据,该判据采用制动系数来调整判据的灵敏度;采用保护动作边界角来调整判据的相移制动能力,是一种新型的非线性制动判据。仿真结果表明新判据具有良好的内部故障灵敏度、抗电流互感器(current transformer,CT)饱和能力和相移制动能力,是基于软实时通信技术的差动保护的理想选择。

Data synchronization is an essential issue in digital feeder current differential protection. Synchronization tolerance leads to time shift and phase shift. A new index that defined the phase shift restraint capacity of the differential protection scheme was proposed. By analyzing the phase shift restraint capacity of traditional differential protections using phasor analysis method, it was found that the phase shift restraint capacity of the triple-bias restraint criteria only reached about 20°, while that of nonlinear restraint criteria might be up to 60°. The paper presented a new phase differential protection, a novel non-linear differential protection criterion, which adopted restraint coefficient to adjust sensitivity of the criterion and used protection action boundary angle to adjust the phase shift restraint capacity. ATP simulation results indicate the new scheme has good sensitivity to inner slight fault, fine ability against current transformers saturation and excellent phase shift restraint capacity.