Transient reactance effects in static shunt reactive compensators for long ac lines

A simple equation derived from two calculable border cases and the asymptotic limits of a symmetrical multi-section transmission line is discussed in the light of experience gained from model studies on stabilisation of power transmission over distances exceeding 600 miles at 60Hz using saturated reactors. An equivalent transient reactance of a saturated reactor can be found from which the permissible product of the length of the compensated line and its power transmission capacity can be determined with satisfactory approximation. The transient reactance of saturated reactors appears to be the same as their slope reactance. Capacitive compensation of the slope reactance introduces transiently higher reactances which can be reduced but not eliminated by adequate dimensioning of the capacitor bypass filters. An empirical equation for calculating this effect is given. Combination of stabilisation by saturated reactors without slope compensation with others having it may take advantage of the differing favourable features of both and enable a desired power capability to be achieved in the most economical way. The general importance of model and analogue studies for any type of long line stabilisation is emphasised.