Abstract
Voltage stability and voltage regulation are commonly confused concepts, particularly in the context of customer voltage complaints and power quality investigations. These two phenomena differ significantly in both cause and method of analysis. Voltage regulation is a steady-state, localized condition that can be directly observed using power quality measurements. In contrast, voltage stability is a system-wide dynamic issue strongly influenced by reactive-power availability, load behavior, transfer limits, and system controls and is not diagnosable from standard PQ measurements alone. This paper defines and compares both concepts, discusses practical causes of voltage variation, and outlines how voltage regulation can be evaluated using Power Monitors Inc. (PMI) PQ Canvass tools.