Harmonic Distortion

Tuesday, 17 April 2012 05:36

Are you constantly replacing lamps, ballasts, contactors, motor starter or motors?

You may very well have a power quality issue that is not only effecting your equipment but also costing you money on your electric bill. Capital City Electric can help solve your power quality and or grounding issues. Give us a call for a no cost consult. To learn more about power quality issues, see below for how to determine if your equipment and electrical are being affected by harmonic distortion.

Harmonics are caused by and are the by-product of modern electronic equipment. These non-linear power supplies draw current in high amplitude short pulses. These current pulses create significant distortion in the electrical current and voltage wave shape. The distortion travels back into the power source and can affect other equipment connected to the same source. Current distortion affects the power system and distribution equipment. It may directly or indirectly cause the destruction of loads or loss of product.


Problems Created by Harmonic Distortion

  • Voltage distortion and voltage drop cause the equipment connected to the branch circuit to draw more current to maintain the power rating (watts) of the unit. The bigger the current draw from the unit, the more it produces excess heat within the unit that was not factored for by its original design. In turn, the excessive heat causes premature component level failures within the unit. Additionally, you will experience computers locking up and other operational malfunctions that are unexplainable. Think about how many times we may have all experienced the "no problem found" syndrome with our computers. The excessive heat produced can directly contribute to downtime, thus contributing to lost productivity, lost revenues, lost savings, and more importantly lost time.
  • In special facilities such as call centers or data centers, the excessive heat produced due to the large concentration of monitors and PCs will also cost you money in energy dollars. The air computer room (CRAC) or building air conditioning system will run longer or harder, therefore requiring more energy to maintain the desired temperature.


  • While motor drives and commercial power supplies are most often blamed for harmonics, the most likely culprits in the typical commercial power system is "switched-mode-power-supplies" such as those seen in personal computers and other electronically driven devices.
  • Internal fluxuation or pulses in the electrical system, i.e. harmonic distortion, cause the branch circuit to draw more current into your lighting and electrical equipment and traveling back into the power source. This then spreads to other equipment connected to the same source.
  • The typical office can have as much as 50% of its load being determined by devices of this type, circulating throughout an entire electrical system.


  • If damage occurs due to current distortion, except for high neutral current, then one solution is to reduce the distortion. There are three methods for this. First, a passive filter can be used to reduce the current from one or two specific harmonics.
  • In the second method, an active filter reduces all the harmonic currents. It is more costly and complex to use, but it works better than passive filters.
  • The third method involves the use of transformers. Delta-wye transformers reduce certain harmonics, particularly what are called zero sequence harmonics. Zig-zag transformers can also be used to reduce zero sequence harmonics, but without changing the system type between delta and wye. In addition, they can help reduce high neutral currents.

Capital City Electrical works with multiple vendors to maintain excellent pricing that we can pass on to our customers and we currently are equipped with power quality analyzer machinery specialized to diagnose problems caused by harmonics.

Contact your account manager or ask your service tech about the availability of a no cost consult to help solve your power quality issues and help you save on your electrical bill.