Voltage sags and Total Harmonic Distortion monitoring in power systems. A case study

The purpose of Power Quality measurements can be either continuous “surveillance” as a task performed by the Distribution System Operator or specific parameter “evaluation” for limit violation. Individual strategies can be applied for each goal but a combined approach is preferred. This paper presents a comparison between results obtained using an electricity meter with Power Quality capabilities (surveillance task) and a Class A Power Quality monitoring equipment (used to evaluate limit violation determination). Measurement uncertainty was calculated for each device and measurand and the result was compared with CEI 61000-4-30 requirements.