With today's modern electronic, electrical components and circuitry constantly changing, the demand is forced upon the electrical power industry to produce and supply a clean source of electrical energy.
The Problem
The extensive utilization of solid state power conversion technologies has created new problems for the power industry and power engineer designer. This technology, called Switch Mode Power Systems (SMPS), consists of various types of solid state switching elements. These switching elements are solid state devices such as: SCR's, DIAC's, transistors and capacitors. These switching devices are in computers, copy machines, fax machines, telecommunications equipment, solid-state drives and controls, energy-efficient lighting ballasts, and numerous types of DC-Power Loads. These solid state elements continuously switch on and off producing non-linear or non-sinusoidal wave shapes in the current supplied from the energy source.

While a linear load uses current from the AC source continuously over the sinusoidal cycle, a non-linear load (such as the SMPS) uses current in large pulses from the AC source which creates harmonic distortion. These non-linear current pulses may exceed the nameplate ampere rating of the power source and may cause transformers to run hotter than expected, even when these transformers are supplying less than 50% of their rated nameplate capacity.

With non-linear loads, overloaded neutrals are also showing up in three-phase panel boards serving single-phase loads. In some cases the neutral conductor carries 180 Hertz currents, rather than 60 Hertz currents. This phenomenon is called triplen harmonics. Triplens are multiples of three, which do not cancel but are additive in the neutral conductor.
As defined by ANSI/IEEE Std. 519-1981

Harmonic
Harmonic components are represented by a periodic wave having a frequency that is an integral multiple of the fundamental frequency.

In other words, harmonics are voltages or currents at frequencies that are integer multiples of the fundamental (60 Hz) frequency, e.g. 120 Hz, 180 Hz, 240 Hz, 300 Hz, etc. Harmonics are designated by their harmonic number, or multiple of the fundamental frequency. Thus, a harmonic with a frequency of 180 Hz (three times the 60 Hz fundamental Frequency) is called the 3rd harmonic.

Harmonics superimpose themselves on the fundamental waveform, distorting it and changing its magnitude. For instance, when a sine wave voltage source is applied to a non-linear load connected from phase-to-neutral on a 3-phase, 4-wire wye circuit,
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