A digital model of a power transformer for real-time testing of protective relays

This paper presents a digital model of a three-phase three-winding power transformer for the real-time calculation of electromagnetic transients for the purpose of close-loop testing of digital relays. The model is capable of simulating turn-to-turn, inter-winding and earth internal faults. The adopted simulation technique decomposes the power system to be simulated into a number of sub-models with specified input and output signals. Thus, the model of a transformer is given as certain input-output transformation. A special procedure is proposed for iterative solution of the whole system. The paper shows how this approach enables easy decomposition of the simulation burden between processors of the multi-processor hardware. in the paper a number of simulation examples are presented and briefly discussed that validate the presented transformer model.