Methods of voltage control of long highvoltage lines by the use of synchronous condensers

A.W. Copley: In amplification Mr. Koontz's paper and xcarrying out the thought a little farther, it may be pointed out that there is a very definite power limit on a transmission line on which the values of generator and receiver voltage are fixed. The addition of synchronous condenser capacity beyond a certain limit does no good as far as increasing the capacity of the line is concerned. For instance, on a 200-mile line with 200 kv. maintained at both ends, the addition of synchronous condenser capacity beyond the point which allows a load of about 220,000 kw. at the receiver end, does not increase the capacity for transmitting power. The power limit of such a line being in the neighborhood of 220,000 kw., it can be seen that, at least on projected lines, the limit is being approached. It is, however, possible to increase the power limit of the line by making, in effect, two lines in series. For instance, on a 400-mile line, with synchronous condenser capacity at the receiver end, the limit of capacity is around 120,000 or 125,000 kw. By breaking the line in two parts of 200 miles each, the power limit of the upper end of the line is about 220,000 kw. and with that power delivered to the middle of the line, the balance of it again has the oipacity of 220,000 kw. minus the losses, which bring the delivered power down to about 200,000 kw. That is, by the introduction of condenser capacity in the middle as well as at the receiver end, the line capacity is increased from 125,000 to 200,000 kw.