Load tap changers in emergency and preventive voltage stability control

This paper discusses the effect of load tap changers on the voltage stability of a power system and, in particular, under emergency conditions. This discussion covers two types of load tap changers (LTCs): on bulk power delivery transformers, which are controlled automatically and for which emergency tap-reversing is considered; and on transformers between higher voltage levels, typically extra high voltage/high voltage (EHV/HV) autotransformers, that in many cases are controlled manually. An algorithm to determine taps for the latter that will maximize loadability is presented.