Transients - Effect on Equipment

Transients generated inside a building or office are very common. They come from three sources - electrostatic discharge (ESD), device switching, and arcing.

ESD is like a very small lightning strike. Static electricity builds up between two dissimilar materials. The resulting attraction force is what we commonly call static cling. If the electric field becomes large enough, an arc occurs, discharging the buildup. Humans usually don't feel a static "zap" unless the voltage is above about 1500 volts. But voltage levels as low as 500 volts can disrupt and damage electronic components.

Reactive loads turning on and off generate spikes whether these loads are heavy motors or copy machines. The term "reactive load" is generic. Basically, any piece of equipment can cause impulses. The compressor motor in a soda vending machine is one example. Computers and their peripherals is another. HVAC and refrigeration equipment can also be culprits.

Another source of transients is arcing. Arcing occurs when there are poor or degraded connections in the wiring system. A loose phase conductor in a panel is a good example. When the loose wire moves, arcs result which creates spikes.

Arcing is almost always associated with other disturbances. Momentary interruptions, higher voltage distortion, and sags are likely companions to arcing.

Most of the time it is difficult to determine where transients come from. Wherever they originate, most of the solutions are similar. TVSS systems and power conditioners, when properly specified and installed, can reduce transients to non-damaging levels. These devices are usually plugged into a standard outlet, and sensitive devices plugged into them.

By troubleshooting and diagnosing the transient activity, it is possible that the source of the spike can be located. If it is, then three more options exist.

  • First, if the offending device is failing or there is a bad connection somewhere, get it fixed. Eliminate the source rather than attempt to protect everything else.
  • Second, try stopping the transient at the source if it cannot be eliminated. Place a power conditioner on the vending machine, for example. This will prevent the normal spike of the compressor motor from traveling to other loads.
  • Third, relocate the offending device or the sensitive device. The normal wiring system is a great transient reducer. Rather than plug the computer into an outlet that is on the same circuit as the transient generator, find another. It is far cheaper to address these problems at the source, or side-step them altogether, than to invest time and money into device-based solutions.