130. An Innovative Protective Algorithm for UHV Power Transformer

Transformer differential protection is influenced seriously by harmonics in inrush current and the operation time is long. In order to solve this problem, this paper introduces a T-type equivalent model of transformer protection. The parameters of the model can be calculated uniquely and timely at steady state. A new transformer protection algorithm is presented. The algorithm is based on the balanced equations of T-type equivalent model and the variation of the measured excitation inductance. With EMTP simulation tool, a simulation platform for the first UHV power transmission system in China is established. Situations such as energizing, external faults, internal faults and normal operations in the system are covered in the simulation. The operation time of the proposed protective scheme is short and the scheme has high sensitivity.