针对含有移相变压器线路的距离保护策略

Distance Protection Strategies for Lines Containing Phase Shifting Transformers

受移相变压器等效内阻抗和电压移相角的影响,含移相变压器线路的距离保护测量阻抗不能正确反映故障距离,保护无法正确动作。该文基于双芯对称式移相变压器的三序等效电路分析了其对距离保护的影响机理和测量阻抗的变化特性,提出了含移相变压器线路的自适应改进距离保护方案。通过实时读取移相变压器档位信息对保护所测量的电压电流值进行相位补偿和幅值补偿,并结合原有距离保护实现了对故障位置的准确计算。该改进保护方案解决了移相变压器内阻抗和移相角对距离保护影响的问题,且不受移相变压器档位和故障位置影响、保护程序修改简便,可以适用于电网不同运行方式下对距离保护的要求。最后在PSCAD/EMTDC中建立了仿真系统模型,结果表明了该文机理和特性分析的正确性,验证了所提改进距离保护的有效性。

Affected by the equivalent internal impedance of the phase-shifting transformer and the voltage phase-shifting angle,the measured impedance of the distance protection of the line including the phase-shifting transformer cannot correctly reflect the fault distance and the protection cannot operate correctly.This paper analyzes the mechanism of its influence on the distance protection and the variation characteristics of the measured impedance based on the three-sequence equivalent circuit of the two-core symmetrical phase-shifting transformer,and proposes an adaptive improved distance protection scheme for lines containing phase-shifting transformers.The phase compensation and amplitude compensation of the voltage and current measured by the protection are carried out by reading the shift information of the phase-shifting transformer in real time,and the accurate calculation of the fault position is realized by combining the original distance protection.The improved protection scheme solves the problem of the influence of the internal impedance and phase shift angle of the phase shift transformer on the distance protection,and is not affected by the gear position and fault position of the phase shift transformer.The protection program is simple to modify,and can be applied to the requirements of distance protection under different operation modes of the power grid.Finally,a simulation system model was built in PSCAD/EMTDC,and the results showed the correctness of the mechanism and characteristics analysis in this paper and verified the effectiveness of the proposed improved distance protection.