SWIVELLING CHARACTERISTIC FOR THE PROTECTION OF SERIES COMPENSATED LINES

The necessity for series compensation of long EHV lines is evident. Such lines are difficult to protect using either the conventional impedance or directional comparison relaying schemes. This work presents a layout of hardware with a swivelling quadrilateral characteristic to cater for the switching of the series capacitor spark gap. The characteristic swivelling through appropriate logic will encompass the measured impedance with the proper contour, according to the working conditions of the spark gap. A check for accommodating the instantaneous fault impedance at post-fault conditions is included as well. © 1990.