Facility Optimization

What Causes "Dirty" Power?

Whether it's called a surge, a sag, a spike, a transient, a fluctuation, an interruption, or noise, "dirty power" is some type of abnormality in the electricity that runs your facility.

Dirty power originates outside of and within your facility. Sources like lightning, utility switching, capacitor switching, and faults on the utility's distribution system can all affect the quality of your power before they even reach your facility.

And daily fluctuations from internal electrical equipment—like devices that run in cycles or get turned on and off frequently—can cause cumulative and equally damaging power hazards. Even a small appliance can cause problems in sensitive equipment that share the same line. And the more electrical equipment a company uses, the more transients accumulate.

Here are some common power disturbances and how to detect them:


Power Disturbances  Definitions  Causes Possible Computer Symptoms
Normal Mode Noise(Amplitude 0.5V to 25V) Low-level signals, superimposed on the power sine wave Computers, switching power supplies, power line modulation equipment Processing errors, incorrect data transfer, terminal or printer errors
Normal Mode Impulses and Ringing Transients
(Amplitude 50V to 6kV)(Duration: 5 µsec to 2000 µsec)
A narrow, fast-rise voltage variation. Followed by a damped oscillation decaying to nominal in less than one cycle Switching loads on or off, computers, utility switching, lightning Incorrect data, processing errors, printer or terminal errors, hardware damage
Common Mode Disturbances(Amplitude: millivolts - hundreds of volts) Impulses and EMI/RFI noise superimposed on the power conductors Radios, computers, arcing contacts, lightning Incorrect data transfer, terminal or printer errors, I/O hardware damage
(Duration: Greater than one cycle)
A low-voltage condition on one or more phases Ground faults, starting large loads, low-power system capacity, lightning System crashes, hardware damage
(Duration: Less than one cycle)
Quick voltage variations, harmonics occur at the natural multiple of the standard power wave Switching nearby loads off/on, computer networks, utilities Data corruption, processing errors, incorrect data transfers, lock-ups, hardware damage
(Duration: Greater than one cycle)
A high-voltage condition on one or more phases Rapid load reduction, utility switching Hardware damage
(Duration: Greater than half a cycle)
A zero-volt condition Ground faults equipment failure, accidents, lightning, acts of nature System crashes, hardware damage