Harmonic Distortion - Neighbors

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. But not just computer-based equipment. Voltage distortion affects even motors and lights, loads commonly thought to be rather immune to power disturbances.

If a 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. Loads within the customer's business are now subjected to possible problems.

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 messing up 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.

In lieu of this, the utility may have to resolve the problem on their own. They can either increase the distribution cable size in hopes that reducing the impedance will be sufficient, or else they may have to provide harmonic current filters at their expense to reduce the level of distorted current.

If there is no other recourse, the customer may have to deal with the distorted voltage. Unfortunately there are no cheap, easy answers to this one. The voltage must either be cleaned up or regenerated.

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 as to 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.

One final comment. It is also very likely that the level of voltage distortion delivered to a customer from the neighbors is not detrimental. But due to the customer's own non-linear loads, the voltage distortion worsens to a point of causing problems. In these cases, reducing the current distortion internally will reduce the added voltage distortion.