Adaptive Differential Protection Method for Transformer Based on Positive Sequence Steady-State Quantity in Photovoltaic Station Access Scenario

The traditional ratio differential protection for transformer faces the problem that it’s sensitivity would be reduced or it even would refuse to trip when internal faults occur, under the scenario of the photovoltaic (PV) station access. By taking advantage of the different characteristics of positive sequence current amplitude and phase under internal and external faults, a differential protection method based on the positive sequence steady-state quantity is designed in this paper. Furthermore, to distinguish the internal faults and external faults more significantly, the calculation method of the adaptive parameter is proposed. Theoretical analysis and simulation results show that the proposed adaptive differential protection method has better internal fault sensitivity and can ensure that there is no mis-operation under external faults.