Evaluation and testing of line protections for series-compensated transmission lines

Fundamental-frequency models of protective relays can play an important role in the testing and evaluation of the relays´ suitability in complex applications. This paper describes a process for evaluation of distance protection for application in series-compensated and adjacent lines. The process consists of the use of fundamental-frequency phasor models of relays to reduce the scope of necessary testing for a particular application. The application is a major North-South power corridor in the Ontario Hydro system, where it was proposed to install series capacitors in two parallel 500 kV lines at approximately the midpoint of the 176 km lines. (Subsequent to these studies, the plan has been cancelled). The proposed compensation was to be either 40% or 60%. Investigation of the effect of 60% compensation on the line protection on the compensated and adjacent lines is reported in this paper. Included in this investigation were studies to evaluate the suitability of existing protections and the selection of new protection equipment where deemed necessary