Phase-Angle Control of System Interconnections

This paper describes an application of a new method of automatic control between two interconnected power systems, whereby greater utilization of the interconnection capacity is secured. As the stable limit of the interchange between systems is affected by variations in the magnitude and location of intermediate loads on the respective systems, direct control of the phase angle between systems recognizes such variations and permits a flexible and more stable type of operation including, when desired, maximum transfers of energy. An indication of the 60-cycle voltage from a desired point on one system is continuously transmitted by means of carrier current, to a point on the second system where its phase position is compared with that of 60-cycle voltage at the receiving point. The output of generating units at the control station is automatically regulated to maintain the phase angle between systems at desired values or within predetermined limits.