变压器相间后备保护的改进

目前变压器相间后备保护对变压器匝间故障的灵敏度不高。低压过流保护的灵敏度不高是由于少匝数匝间短路时变压器电压下降很少。负序电流继电器的动作与电压的降落无关，因而可以获得较镐的灵敏度，距离继电器应用于变压器时其性能受Y，d接线变压器两侧电位移的影响。负序距离继电器的行为与变压器绕组的接线无关，所以它是作为变压器后备保的距离继电器的最佳选择。文中不仅讨论了负序电流和负序距离继电器的优越性能，而且提供了防止这两类继电器在电流断线和电压断线时发生误动的方法，从而得到了一个既灵敏又安全的改进的变压器后备保护。

IMPROVEMENT OF TRANSFORMER BACKUP PROTECTION FOR PHASE-TO-PHASE FAULTS

The transformer backup protection for phase- to- phase faults is not sensitive to the few turn turn- to- turn faults of transformer.The sensitivity of the low- voltage overcurrent protection is limited due to the little voltage drop in case of a few turn turn- to- turn fault. The negative sequence overcurrent relay which is ignorant of the voltage drop m ay get higher sensitivity.The behavior of the distance relay when applied to the transformer protection is much affected by the phase shift of the Y,d connection of the transformer.The negative sequence distance relay gets free from the winding connection of the transformer. So it is the best choice to use the kind of the distance relays for the transformer backup protection. In this paper,the good perform ances of the negative sequence current and distance relay are discussed and the methods to get rid of the CT and the PT failures are introduced. So an improved backup transform er protection with high sensitivity and security is recom mended.