Abridgment of automatic voltage regulators: Application to power transmission systems

Within a relatively short time conditions in transmission systems as regards continuity of service and maximum power have radically changed. A few years ago, the amount of power transmitted over important lines was relatively small compared with their ultimate transmitting capacity. In such cases, the systems were inherently stable, and there was a reasonable margin of power with respect to load swings and short circuits. Automatic voltage regulators were used at that time chiefly for maintaining more uniform voltage conditions than could be obtained by intermittent adjustment by hand control. Different types of regulators for this purpose have given satisfactory service for a number of years. However, conditions have gradually changed. Within the last few years the power to be transmitted has increased to such an extent that it has now become necessary to consider means seriously for increasing the maximum power and for insuring continuity of service during transient disturbances, such as load swings and short circuits. The object of this paper is to present the results of an extended investigation along these lines. A new regulator is described which will accomplish the above purposes, and the theoretical analysis is confirmed by test results.