Pointer Image Theory Usage for Common Mode Current Prediction at Power Lines

Abstract

This paper aims to explain the pointer image theory as a solution used to predict the common mode (CM) current at power lines, which is strongly related to radiated electromagnetic emissions. Techniques to measure the CM current at power lines in huge installations such as wind turbines (WT) are needed and novel methods are emerging. The WT tower may become an unintentional antenna due to the CM current flowing at its body through stray capacitances. The easiest way to measure the total CM current flow on a three-phase system is by measuring it using a device such as a current clamp or a Rogowski coil. This clamp must cover the whole 3-phase-cable bundle, however, the problem is that such a huge clamp or coil does not exist on the market, besides customized parts. The proposed method in this paper is to implement the pointer image theory to predict the CM current from a WT power plant. Laboratory measurements and SPICE simulations are used to show that the proposed method works well for CM current prediction.