A semi-graphical method of determining the power limits of an interconnector

The practice of power system interconnection which to-day, after more than a quarter of a century´s gradual development, has become characteristic of the large-scale generation, transmission and distribution of electrical energy, is one which is based on a technique closely bound up with problems of system stability and power limitation. The starting point in the solution of such problems is, generally speaking, a determination of the power limit of an interconnector under a variety of operating conditions. By the term ¿interconnector¿ is here understood a compound power-transmitting circuit acting as a synchronous tie between two otherwise independent a.c. systems. The paper investigates the manner in which the electrical characteristics of a typical interconnector, comprising a transmission line and terminal transformers, limit the interchange of power between its terminal systems. A new method of evaluating the limiting transmitted power, based on the theory of the power circle-diagram, is described. This method employs a rapid geometrical construction for the appropriate charts which is based on the analysis established in the paper. The use of this new method of determining the power limit is illustrated by application to a specific example of interconnection.