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- What are Voltage Transients?
Sudden, short-duration, high-amplitude disturbances in the normal voltage levels across power lines are called voltage transients. Although lightning causes some of these voltage transients, most are caused by the switching on and off of internal and external loads, and occur regularly on any power system.
The typical transient produces an oscillatory event that continues for a period of approximately 6.5 microseconds, becoming damped out after about three cycles. These voltage transients occur whenever inductive loads such as transformers and motors are switched on and off, and result from sudden dissipation of instantaneous stored magnetic energy in the rest of the system.
The rate at which voltage transients occur is as many as 0 to 900 transients per hour for residential, 900 to 9,000 transients per hour for a busy office, 9,000 to 60,000 transients per hour for a small factory, 60,000 to 181,000 transients per hour for a processing plant.
Energy User News October 31, 2002, page 1 discussed a test developed by Dr. Walton N. Hershfield that Hershfield said, demonstrated that transient voltage activity can cause an increase in electrical; energy losses. Hershfield’s test demonstrated that transients could cause an increase in losses in iron-core devices such as transformers or electric motors, resulting in increased energy use.
Hershfield said “the worse case of transient activity that he has encountered and measured as 648,000 transients per hour.” This occurred in a dimmer switch for a lecture hall at UCLA University.
The possibility that transient voltage activity may cause increases in electricity use has been acknowledged for the first time by several utilities in a survey conducted by the Edison Electric Institute, a trade association for Investor Owned Utilities (I.O.U.s).
Edison Electric Institute asked its members for comments on the Hershfield findings. The responses did not dispute that transients could cause an increase in losses in iron-core devices such as transformers or electric motors, said Thomas Kinney, Edison Institute staff engineer.
These transients, being high frequency in nature, partially immobilize the magnetic systems of common devices such as transformers and motors causing them to operate with excessive hysteresis and eddycurrent losses. This reduces their normal efficiency and results in wasted energy and a higher power bill.
Transient Voltage is transmitted to all parts of the building via the electrical wiring. Transients (surges or spikes) can be generated any time you have changes in current flow demand or a load shift. The random cycling of motors, energizing and de-energizing of transformers and motor circuits, and power source faults create havoc with your electrical system. Even such routine things as turning on and off a light switch can cause large amounts of voltage transients.
Leo L. Holzenthal, P.E., author of white papers (available upon request) that examined the impact of harmonics on electrical motors describes the theory of operation as follows:
The device is installed as a system thru out the entire electrical service; the device eliminates all surge activities over one hundred thirty (130) volts. The device creates a surge free environment for all your equipment to operate in. The end result is all of your electrical equipment operates much more efficiently and uses less energy, “you use less so you pay less.”
Finally, as early as 1940, the impact of surges on the meter wheel was well known. In an article by Faucett, M.A., and Heim, M.A., (available upon request) The Accuracy of Watt-hour meters on intermittent loses, pointed out that surges could impact the meter by as much as thirty (30%) percent. Digital meters are much more sensitive, and the impact likely to be greater than the older disk meters.