Transients - Disruptions

Transients generated inside a facility are very common. They come from three sources -- electrostatic discharge, or ESD; device switching; and arcing.

ESD is like a very small lightning strike. Static electricity builds up between two dissimilar materials. The attraction force that results between them is what we commonly call static cling. If the electric field between these materials 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 equipment.

Reactive loads turning on and off generate spikes whether these loads are heavy motors or copy machines. The term "reactive load" is generic. 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, refrigeration equipment, and other large motors 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. As the loose wire moves, arcing is generated which creates spikes.

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

There is another problem from transients known as "back door hits." This refers to when a transient enters a device through the I/O ports rather than through the power lines. This happens whenever a distributed system, such as a computer with several monitors in different parts of the facility or a LAN, has components that are connected to each other via data cables.

If a spike hits one component, say an external monitor, then some of the energy gets on the data lines. This energy travels to another system component, say the main computer, and enters through the I/O port. Data disruption and lock-ups may occur, even though the disturbance did not impact the main computer's power.

Most of the time it is difficult to determine where transients are coming from. Yet 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. This device is usually installed in a standard outlet, and the sensitive device plugged into it.

Data line protectors may also be used to prevent back-door hits. This is a small device that connects directly to the output port, and the data cable connects to it.

It is possible to locate the source of the spike by actively troubleshooting and diagnosing the transient. If this is done, then three more options exist.

  • First, if the offending device is failing or there is a bad connection, get it fixed. Eliminate the source rather than 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 the time and money on device-based solutions.