A TDQ-based fault detector for digital power system relaying

In this paper, a fault detector (FD) based on Park´s transformation (TDQ) for digital power system relaying application is presented. It detects faults by identifying decaying DC components and phase unbalance in current signals and, therefore, it does not require high sampling rates. To improve the FD reliability, a self-adaptive threshold is used, what overcomes the need of manual calibrations and minimizes problems due to electrical noises. The TDQ-based FD performance was compared against those of four fault detection algorithms available in the literature. In order to do so, Electromagnetic Transients Program (EMTP) simulations of faults in a 230 kV power system were carried out, through which the influence of the fault features and signal-to-noise ratio (SNR) was analyzed. The obtained results indicate that the TDQ-based FD is reliable, robust to noises and able to detect faults within a very few samples after its inception.