Tap Changing Under Load for Voltage and Phase-Angle Control

One of the most important, and sometimes most involved, problems brought about by the many interconnections of electrical systems, is a means of accurate and flexible regulation of power flow. The adjustment of voltage and the control of wattless current by means of tap-changing-under-load equipment has become quite extensive. The regulation of power flow by means of phase-angle control has been put into practise on a limited scale. One means of accomplishing this, which has been used in a few cases and which is being considered on a larger scale, is the adaptation of tap-changing-under-load equipment with properly connected static transformers. The purpose of this paper is to discuss briefly the connections employed and the equipment used in connection with static transformers for the purpose of voltage and phase-angle control.