Definition of Apparent Power in Three-Phase, Four-Wire Non-Sinusoidal Power Systems

In the below linked research paper published on the website OpenUCT, a researcher from Cape Town University uses a Yokogawa Test&Measurement High-Performance Power Analyzer to record instantaneous voltage and current of a three-phase, four-wire system.

• Title: Definition of Apparent Power in 3-Phase 4-Wire Non-Sinusoidal Power Systems
• Author: Michel Malengret
• Abstract: Concepts of apparent, active and reactive power, developed early in the 20th century, are widely applied in electrical power engineering. However, the distortions caused by large non-linear loads are increasingly significant. Conventional power theories are sometimes inadequate, or even incorrect, when dealing with unbalanced or non-sinusoidal systems. New power theories have been proposed and standard definitions revised, but inconsistencies are still reported, having technical and financial implications in power systems design, metering, reliability and quality of supply. The thesis starts by collating and comparing most power theories in the instantaneous and average power domain. The instantaneous theories are reformulated and classified into three groups, which can be linked with one equation. Introducing a new instantaneous theory based on vector space allows the fundamental properties of the groups to be examined and provides the means to extend instantaneous power into the rms domain and calculate the compensating currents required. The approach results in power components that can be attributed a real physical interpretation. The new approach to three phase power theory has significant potential for education, the practical design of active compensators, and the revision of international standard definitions of power.

To access the full research paper, click here: Definition of Apparent Power in 3-Phase 4-Wire Non-Sinusoidal Power Systems