Sags and Swells - Neighbors

Voltage sags are a very normal occurrence on the power lines. Swells are not so common, though they do happen also. The closer a neighbor is to the customer, the more likely sags or swells caused by the neighbor may disrupt or damage equipment in the facility.

Sags or swells occur when there are changing currents interacting with system impedance. Loads in the neighbor's facility or office must be large enough and changing enough to affect the voltage feeding the customer's facility or office. Quite often this occurs when a panel, office, or whole building trips a breaker. A swell may happen at turn off. Then, when someone throws the breaker back on, a sag results.

If shared wiring is present, then simple devices like copy machines and printers may cause similar concerns.

Most of the time neighbor-induced sags or swells are difficult to identify. If they can be determined, then one solution may be a simple procedural change to prevent the radical load changes or breaker trippage.

Once again, if neighbors are creating these disturbances, it is a good idea to request the utility's input on how to resolve it.

If the voltage instability cannot be stopped at the source, then voltage regulators must be used to prevent the problems.