With sufficient consideration to realistic application factor of UHV transformer end connecting with long-distance transmission line, and with corresponding calculation for transformer equivalent instantaneous reluctance using adaptive digital low-pass filter, this scheme is good for solving problem.

According to the mechanism of producing transformer excitation surge current caused by saturation of transformer core, the paper put forward a kind of method to discriminate excitation surge current and short-circuit current adopting calculation of equivalent instant excitation inductance average value.

Analysis of the calculation of equivalent instantaneous inductance in three-phase transformer and a new CT s configuration;

Application of equivalent instantaneous inductance algorithm to the Y/Δ three-phase transformer;

At the same time, the application based on the equivalent instantaneous inductance scheme is limited to identify the inrush.

On basis of transformer loop equation,a novel principle of transformer protection using equivalent instantaneous leakage inductance is presented.

A novel principle of transformer protection using equivalent instantaneous leakage inductance, based on the transformer model loop equation, is proposed.