Uncertainty Evaluation for the Impact of Measurement Accuracy on Power Quality Parameters

2017 IEEE International Workshop on Applied Measurements for Power Systems (AMPS)

Location

Liverpool, United Kingdom

Links

DOI

Keywords

Harmonics, Unbalance, Measurement accuracy, Uncertainty Propagation, Monte Carlo Simulation

Abstract

Power quality (PQ) analysis requires to calculate a lot of different parameters (e.g. unbalance, THD, harmonic powers, harmonic impedances, …) based on measured voltages and currents (fundamental and harmonics). Respective standards and data sheets of measurement equipment define the measurement accuracies only for these measured quantities. The resulting uncertainty of parameters derived from these measurement quantities are usually not available, but are crucial for a wide variety of applications, like the assessment of prevailing harmonic phasor or the fundamental negative sequence unbalance. This paper studies the influence of the accuracy of voltage and current measurements (fundamental and harmonics) on a set of PQ parameters that are derived from them. The analysis is performed in two ways: analytical (if possible) and probabilistic based on Monte Carlo simulations. Even if the different aspects of uncertainty propagation are known and has already been studied for several of the mentioned parameters, this paper is intended to provide a summary for a as complete as possible set of PQ-parameters taking also practical accuracy characteristics of today’s PQ instruments into account. The paper finishes with a classification of the impact of the measurement accuracy on the resulting uncertainty of the discussed PQ parameters and indicates conditions where the calculated PQ parameters may suffer from insufficient accuracy.