An innovative technique for power quality assessment in electric utility networks

Abstract

The development of modern Electricity markets has bestowed the status of “commodity” on Electric Power which, in consequence, must be subjected to some specifications of quality to worth its price. Power Quality (PQ) is characterized by such distortion elements as harmonics, flicker, voltage and current imbalance etc. Of all these, the most prominent is harmonics. The major challenge facing power system market operators is how to identify harmonic sources and quantify their individual contributions at a Point of Common Coupling (PCC). In a typical Distribution Network, this is necessary so that appropriate penalties can be imposed on the real culprits. Earlier approaches to the solution of the problem relied on the flow of Active power and later Reactive power flow was used. In both cases, the results become ambiguous when certain circumstances exist. Instances arose where a consumer was wrongly penalized for harmonics he did not cause. Therefore, in this paper novel techniques for identifying harmonic sources and quantifying the harmonic contributions from individual sources at a measurement point is developed, for a network with multiple nonlinear loads. The concept is derived from some salient characteristics of harmonic apparent power flow. A comparative analysis is carried out on the suitability of the use of active, reactive and apparent power flows for each of the harmonic components. Results obtained from the analysis show that the flow of apparent power proved to be the most promising in predicting the source of harmonics in a network. The results also show that harmonic apparent power gives the best representation of harmonic contribution, while the usual ambiguity in the commonly used indices derived from harmonic voltage or current is eliminated. A tool for determining penalty charges is also developed.