The Limitations of Output of a Power System Involving Long Transmission Lines

The conditions of stability of a system are discussed and it is pointed out that while the various transmission line diagrams as used at present implicitly assume the terminal voltage at the two ends to be constant the degree of voltage regulation as determined by load conditions is an important factor in the determination of the limit of output. A type of combined diagram is proposed whereby this factor and other characteristics of the load may be included. The effect of the inherent regulation of synchronous condensers is taken up particularly with respect to compound transmission lines. A numerical example of a 300-mile line is considered and various characteristic curvesaredrawn. The relation between the maximum output and the capacity of condensers installed at the mid-point shows the benefit obtained by increasing the condenser capacity-within certain economic limits. Mathematical analyses are presented to cover a number of different conditions.