Momentary Interruptions - Utility

In order to maintain overall performance of the utility's system, large grid switching is periodically done. When this switching occurs it is possible to introduce momentary interruptions in the voltage. In a sense, these are very, very brief outages, typically less than a cycle in duration.

Most of these disturbances are overshadowed by the utility's distribution system. By the time the interruption gets to any customers, it hardly exists anymore.

But, for those customers close to substations, momentary interruptions are alive and well and living in the power lines.

Depending on the duration of the interruption, the electronic devices in a customer's business will probably withstand, or ride-through, the change. But if it is long enough, then the equipment will respond to it just like it would with a sag. The power supplies may not be able to keep the DC voltage perfectly stable, contributing to computer lock-ups and restarts.

If these anomalies are causing problems, then there are two alternatives. First, power supplies designed with longer ride-through times are available. Replacing the victim's power supply with one of these may resolve the problem.

Second, install an energy storage device such as a stand-by power system, called an SPS, or an uninterruptible power system, called a UPS. These devices, if properly specified and installed, will provide the needed ride-through time.