Hardware-in-the Loop Testing of Power Transformer Differential Relay Using RTDS and DSP

This paper presents the testing of power transformer differential relay in a hardware-in-the loop using a Real Time Digital Simulator (RTDS) and Digital Signal Processor (DSP) for all possible operating conditions of a power transformer. The Empirical Fourier Transform-based transformer differential relay (EFTDR) algorithm is implemented in DSP - TMS320F28335 which is interfaced with RTDS through its analog and digital hardware circuit. The modeling of power transformer and simulation are carried out using RSCAD. The real-time analog current signal corresponding to the simulated current signal is generated using RTDS and is fed to the analog channel of TMS320F28335. Similarly, the response of the proposed relay is fed back to the digital channel of RTDS. The relay response enables the trip of corresponding circuit breakers in the RSCAD simulation circuit. Here, the performance evaluation of EFTDR is carried out for various cases of internal faults, inrush current, current transformer saturation and possible combinations of simultaneous occurrences of the aforesaid events of power transformer in hardware-in-the loop testing using RTDS and DSP.