Study on a New Transformer Main Protection Scheme

In the paper a new transformer main protection scheme based on the combination of generalized fundamental power and difference of loop equation is proposed. The transformer loop equations are studied, the relationship between the differential voltage and differential current is deduced and the concept of generalized fundamental power is proposed. The protection based on the generalized fundamental power reflects the changes of amplitudes and phase angles of the differential voltages and currents under different operation condition, and it is needless to discriminate inrush current. Because it is needless to calculate the leakage impedance of transformer windings accurately the proposed scheme is easy to be realized. The experiment results show that the proposed scheme has sufficient reliability and sensitivity and is superior to the differential current protection with second harmonic restraint.