Ferroresonance is a nonlinear electrical phenomenon that can damage transformers, surge arresters, cable insulation, and switchgear — and create dangerous backfeed voltages on conductors that should be de-energized. Although relatively…
Harmonics
Recognizing Transformer Energization in Power Quality Data
Transformer energization events occur frequently in electrical distribution systems and often appear in power quality recordings. These events can produce large transient currents and waveform distortions that may initially resemble…
Power Theory in Multiphase Distorted Systems
Introduction “Geometric Foundations of Power Theory for Multiphase AC systems in the Frequency Domain” is a great research article written by Francisco Montoya and others and it clearly explains a…
Even vs. Odd Harmonics
Engineered Asymmetry Audiophiles routinely spend thousands of dollars on vintage vacuum tube amplifiers to deliberately inject their music with what power engineers spend millions trying to eliminate: harmonic distortion. Vacuum…
Residential Interharmonics
Interharmonics are produced when loads draw currentasynchronously to the utility voltage. Traditional loads include arc furnaces, welders, and AC-DC converter systems where the loads are fed from DC supplies. Historically…
Variable Frequency Drives and Harmonics
Abstract A VFD, or Variable Frequency Drive, is a device which takes in a 3 phase AC signal and outputs a somewhat arbitrary waveform using pulse width modulation. This is…
Harmonic Calculations
In a normal distribution network, the fundamental frequency is that of the voltage driving source, nominally 60Hz. Steady state deviations from the ideal 60 Hz sine wave shape are “periodic,”…
