A Study on the Condition of Reverse Control Action of Tap Changer in A Single OLTC Power System

Abstract

This paper investigates the voltage stability in a single OLTC (On-load Tap Changer) system, which consists of a single OLTC and multiple generators as well as loads. It is shown that the sensitibity of load voltage to tap position, dV/dn=(I₁=exact value), plays an important roll, independent of the existense of the equilibrium of the tap position. That is, when the equilibrium exists, the region where I₁>0 is in the stabity region; if the equilibrium disappears, the stability region aslo disappears but the voltage is still recovering in the region where the I₁>0. Based on these results, the region of reverse control action of OLTC is defined as the region where I₁<0. It is proved that another sensitibity, I₂, which is defined as dV/dn when constant power characteristics are assumed for loads, can be used to estimate the region of reverse control action when the exact load charecteristics are not available.