1 000 kV特高压南阳站3/2主接线不平衡环流分析

特高压变电站1 000 kV系统采用3/2主接线，由于导电主回路电阻不平衡度较大及特高压变电站输送容量大，导致3/2主接线系统存在较大幅值的不平衡环流，极端情况下个别断路器相电流有过零甚至反相现象。结合特高压南阳站，从理论上分析不平衡环流中零序分量及其产生原因；论述了大负荷运行期间零序环流给站内二次系统带来的显著问题和严重后果；提出保护装置采用两断路器合流、单断路器最小相电流制动零序电流元件和两断路器合流制动单断路器零序电流元件的几种解决方案。以期后续交流特高压工程对此有足够的重视，供设计、施工和运行维护借鉴。

Analysis on the Unbalanced Circuit Current of the 3/2 Wiring System of 1 000 kV UHV Nanyang Substation

3/2 main wiring is used in the 1 000 kV system of UHV AC substation. Since the resistive unbalance in the main conductive circuit is significant and the power transmission capacity is large, unbalanced circulation exists in the 3/2 wiring system. In extreme case, some breakers’ single-phase current appears zero or even phase-inverted. Based on the UHV Nanyang substation, the zero-sequence of the unbalanced circulation and the cause are theoretically analyzed. The serious problems and consequences of the secondary system caused by zero-sequence circulation during large load operation are discussed and several solutions are proposed: the conflux current of two breakers is used for protection device; the minimum current of 3-phase brakes the zero-sequence module in single breaker; the conflux current of two breakers brakes single breaker zero-sequence module. This analysis is expected to call enough attention to be paid to the unbalanced circulation in the future projects.