Voltage Distortion

When the source voltage into a business is no longer sinusoidal, we say that it is distorted. Harmonic distortion implies that there are higher frequencies than just the 60 Hz involved in the power flow. These higher frequencies can disrupt, degrade, and damage equipment. Voltage distortion not only affects computer equipment, but even motors and lights, loads commonly thought to be rather immune to power disturbances.

If a customer's neighbor draws a large amount of distorted current, then this current distorts the utility's source voltage. This source voltage, which is now distorted, is then fed to the customer. This could cause problems for loads within the customer's business. These cases are rare. Most utilities have a low source impedance to prevent voltage distortion from customer loads.

Solutions to a voltage distortion problem like this are a little complicated. If Customer A is adversely affected by distortion generated due to Customer B, the utility must be brought in to the picture. In general, the utility is responsible for providing Customer A with appropriate power. Even though Customer B is distorting the voltage, the utility may deal with it in one of two ways.

The utility may be able to work with the offending customer to resolve the problem. Preferably, the level of voltage distortion should be significantly reduced at this customer's site, thus reducing it on the utility's bus. This can be achieved through reducing the amount of total current or reducing the amount of distorted current.

There are products which will clean up harmonically distorted voltages. They are large, costly, and a challenge to install and maintain. They are also new, with little history behind them to document their effectiveness.

Regenerating the voltage is also costly, but there are more choices with longer track records. Motor-generator sets and appropriate UPS will both provide low distortion.