Simulation and detection of open phase for generating station auxiliary three phase transformers

This paper simulates and evaluates the terminal behavior of a nuclear generating station auxiliary transformer under an open phase condition on its primary side using electromagnetic transient simulations. The system model used in the study should represent the plant electrical system as well as the transformer, and different loads inside the plant electrical system. The simulation results can provide insight into the per phase voltage magnitude and angles as well as positive, negative, and zero sequence voltages and currents generated during the loss of one or two phases of the transformer primary side. These values are fundamental to the application of protection schemes designed to detect this condition. The transformer model implemented in PSCAD represents the magnetic and electric coupling between the phases due to the magnetic and electric coupling between the phases on both primary and secondary side as well as the magnetic core. The parameters of the model were obtained from the transformer manufacturer test reports. Different test cases with different transformer loading were conducted and each phase was open circuited. The terminal voltages and sequence voltages on all terminals of the transformer were monitored and recorded.