基于回路平衡方程和励磁电感的特高压变压器保护

谐波制动原理的变压器差动保护受谐波影响大,动作时间过长,难以满足特高压变压器保护的需求,针对此问题,提出了基于T型等效电路的特高压变压器保护方案。建立变压器T型等效电路模型,该模型不受变压器运行状态的影响,其参数能够唯一确定,并提出基于变压器等值回路平衡方程判据和等效励磁电感判据的保护方案。使用Matlab仿真工具,依据中国第一条特高压输电线路的系统参数搭建了特高压输电模型,分别仿真了特高压变压器空载投入、区外故障、区内故障和正常运行的各种工况,验证了所提出的保护方案在特高压输电系统中运用的可行性。该保护方案不受励磁涌流的影响、动作速度快、灵敏度高。

UHV Transformer Protection Based on Equivalent Circuit Equation and Excitation Inductance

The performance of ultra-high voltage(UHV) transformer differential protection based on harmonic restraining method is seriously influenced by harmonics and its operation time is long.Aiming to solve this problem,this paper presented a novel protective scheme based on equivalent circuit model of transformer for UHV three-phase divided tank transformer.This paper established a T-type equivalent circuit model of transformer with its parameters calculated on-time.This model is not affected by transformer’s operation states,and its parameters can be uniquely determined.It proposed a transformer protection criterion,which was based on the balanced transformer equivalent circuit model equation and the variation of instantaneously measured equivalent excitation inductance.With Matlab simulation tool,this paper established a model according to the parameters of the first UHV power transmission system in China,simulated such situations as energizing,external faults,internal faults,normal operation in the model,and testified the feasibility of the proposed transformer protection in UHV transmission systems.The performance of the protection scheme is not affected by inrush currents,and the protection can operate quickly and has high sensitivity.