特高压变压器的阻抗快速后备保护

摘要

研究了由三个单相变压器组成的特高压三相变压器组的后备保护，提出了用阻抗纵联保护作为特高压大容量变压器相间短路的快速后备保护的方案。分析了采用超范围允许式和超范围闭锁式阻抗纵联保护方案的可行性和优越性。说明了阻抗保护受励磁涌流影响小的原理，并用数字仿真证明了此论断的正确性。建立了特高压变压器的仿真模型，仿真结果证明在变压器空投和外部故障切除时产生的励磁涌流不会使阻抗保护误动，而在变压器出口相间短路时能够快速切除故障。采用所提出的保护方案可提高特高压变压器保护的可靠性。%The backup protection of UHV large capacity transformers consisted of three single phase transformers is studied. The overreach permissive type and the overreach blocking type impedance pilot protection scheme, used as backup protection of these transformers is proposed. The feasibility and superiority of the proposed scheme are proved. Such impedance protections are less affected by magnetizing inrush currents and the correctness of the conclusion is testified by digital simulations. The simulation model of UHV transformer is established. Simulation results prove that the magnetizing inrush current caused by transformer no-load switching and external fault clearing will not make the impedance protection maloperation, while the fault can be cleared fast at interphase short-circuit of transformer exit. The proposed protection scheme can improve the reliability of protection of large capacity UHV transformers.