Elevated NEV due to Triplen Harmonics: Modeling and Results

Modern single-phase loads contain significant harmonic components, particularly triplen harmonics. These harmonics are generated by the proliferation of electronic devices as well as electromagnetic devices (e.g., single-phase induction motors) that operate somewhat saturated. The growth of these non-linear loads has caused an increase of neutral current in the utility system at harmonic frequencies. Since the neutral conductor is grounded to the earth at multiple points, neutral currents flow in the power system neutral, the earth, and other parallel utilities. In a simple system with no parallel utilities, the return currents flow in both the neutral and the earth. Any disparity in the voltage drops caused by these currents results in a voltage difference between the neutral conductor and earth. Attempts to predict the NEV through modeling have proven difficult due to lack of parallel earth and neutral conductor models and representative interconnection between the two circuits. This paper has presented a model of a feeder that incorporates both return paths as well as a more accurate representation of the interconnection between the two systems