STATCOM modeling impacts on performance evaluation of distance protection of transmission lines

In this paper, the impact of STATCOM on the apparent impedance seen by conventional distance relay protecting a transmission line is investigated. Analytical results are presented, and verified by detailed simulations. It is shown that the implications of applying STATCOM on distance relay are highly dependent on the sophisticated modeling of STATCOM especially its control system considering practical constraints. Accurate modeling of the distance relay, particularly the analog input signals are also important in extracting reliable results. Practical constraints of the STATCOM are modeled in full details. It is demonstrated that when the STATCOM's limits are modeled in detail, i.e., the STATCOM is not considered an ideal reactive-power source the STATCOM's impact on the performance of distance protection is less severe than in the case where limits are ignored and thus ideal controllers are applied. This is a remarkable point for the utilities as not to overestimate the severity of the impact of STATCOM on conventional distance protection of transmission lines. Six different phase-to-phase and phase-to-ground measuring units of the distance relay are simulated to resemble the behavior of the relay. Different power system operating conditions, STATCOM control system settings and fault scenarios are investigated. The STATCOM effects on distance relay tripping characteristics are also analyzed. Copyright © 2010 John Wiley & Sons, Ltd.