基于零序差流特征的变压器差动保护优化方法OA

When current transformers are not installed on the delta winding of a wye-delta transformer,the differen-tial protection must utilize currents measured outside the delta winding to calculate the differential current.To ad-dress the issue of reduced differential protection sensitivity during single-phase faults under this configuration,this paper proposes an optimal transformer differential protection method based on zero-sequence differential current characteristics.Firstly,the corrected currents on each side are calculated using a method that does not subtract the zero-sequence component from the delta side currents,from which the three-phase differential currents are derived.Secondly,based on the characteristics of the differential current during single-phase faults,an estimated value of the zero-sequence differential current is obtained.This is used to eliminate the influence of the zero-sequence com-ponent,yielding a corrected differential current.Subsequently,the protection operation decision is made by combin-ing this corrected differential current with the percentage differential characteristic,and fault phase selection is achieved based on the operated phase.Finally,simulations and actual waveform tests verify the effectiveness of the proposed method.The results demonstrate that the method increases the differential current in the faulted phase dur-ing single-phase faults while eliminating the impact of the zero-sequence component on the healthy phases,thereby improving both the sensitivity of the differential protection and the accuracy of fault phase selection.