Algorithm to identify leakage inductances of power transformer with Y-Delta connection

Algorithm to calculate leakage inductances of power transformer is proposed. Based on equivalent circuit equation, leakage inductances of power transformer with Y-Delta connection are estimated by least square method using line currents of Delta side directly and eliminating internal currents of windings in Delta side. Discrimination of leakage inductances in equivalent circuit equation and error of the algorithm are discussed. Leakage inductances can be identified effectively only when power system is in transient processes. And improved algorithm is proposed to enhance recognition precision of leakage inductances. Algorithm accuracy is verified by EMTP simulation. Result shows that leakage inductances estimated by proposed algorithm can distinguish inter fault status of transformer from a normal service operating status of transformer, which can act as criterions of transformer protection and has good project application prospect in the field of transformer protection.