Stability Limitations of Long-Distance A-C Power-Transmission Systems

Conventional methods of transmission are analyzed and discussed both for existing transmission distances up to about 300 miles and for greater distances up to a full wave length; also eight different methods that have been proposed for increasing the loading per circuit or distance to which a-c power can be transmitted are discussed. Of these methods, series compensation of the line reactance appears to be the most favorable for straightaway distances up to about 600 to 700 miles at 60 cycles. The problem is analyzed mathematically and with the aid of an a-c network analyzer. Curves are included which give the power limits and reactive kilovoltampere requirements for a large number of parameters, including the effect of distance, voltage, conductor size, series and shunt compensation, terminal impedances, and stability margin. This analysis indicates that the limitation of the transmission of a-c power greater straightaway distances than has been accomplished heretofore is primarily that of the cost of the line, the stability limitation can be overcome by a comparatively small increase in cost.