Effects of the Selected Point of Voltage Reference on the Apparent Power Measurement in Three-Phase Star Systems

Abstract

The phenomenon responsible for the different apparent powers measured in a subsystem of a three-phase star-configured system, based on the voltage reference point, was identified in this paper using specific components of the instantaneous powers, as a result of applying the conservation of energy principle to the entire system. The effects of the phenomenon were determined using a proposed apparent power component referred to as the neutral-displacement power, whose square is the quadratic difference between the apparent powers of a subsystem, measured using two voltage reference points. The neutral-displacement power is a component of the apparent power, which is determined using the values of the zero-sequence voltages and the line currents in that subsystem. Expressions of the proposed power were derived using the Buchholz apparent power formulations. The validation of the derived expressions was checked in the laboratory and in a real-world electrical network, using a well-known commercial analyzer and a prototype developed by the authors.