Transients - Sources

Internally generated transients have three sources -- static discharge (or ESD), device switching, and arcing. The energy from these spikes ends up affecting digital chips inside the computers. What should be a digital "0" winds up like a digital "1", causing an error in the data.

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 or damage electronic components. A common example is when a different character than the one you typed is displayed on the computer screen.

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.

Arcing is another source of transients. 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 a problem from transients known as "back door hits." This refers to the issue when a transient enters an electronic device through the I/O ports rather than from the power lines. This occurs whenever a distributed system has components connected to each other via data cables.

If a spike hits one component, say a monitor, then some of the energy gets on the data lines. This energy travels to another system component and enters through the I/O port. Data flow can be disrupted, even though the disturbance did not affect the main computer's power.