What causes dirty power?

Whether it is 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 fluctuation 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 Disturbance: Normal Mode Noise (Amplitude 0.5V to 25V)

Definition: Low-level signals, superimposed on the power sine wave

Causes: Computers, switching power supplies, power line modulation equipment

Possible Computer Symptoms: Processing errors, incorrect data transfer, terminal or printer errors

Power Disturbance: Normal Mode Impulses and Ringing Transients (Amplitude 50V to 6kV)(Duration: 5 µsec to 2000 µsec)

Definition: A narrow, fast-rise voltage variation. Followed by a damped oscillation decaying to nominal in less than one cycle

Causes: Switching loads on or off, computers, utility switching, lightning

Possible Computer Symptoms: Incorrect data, processing errors, printer or terminal errors, hardware damage

Power Disturbance: Common Mode Disturbances (Amplitude: millivolts - hundreds of volts)

Definition: Impulses and EMI/RFI noise superimposed on the power conductors

Causes: Radios, computers, arcing contacts, lightning

Possible Computer Symptoms: Incorrect data transfer, terminal or printer errors, I/O hardware damage

Power Disturbance: Sags (Duration: Greater than one cycle)

Definition: A low-voltage condition on one or more phases

Causes: Ground faults, starting large loads, low-power system capacity, lightning

Possible Computer Symptoms: System crashes, hardware damage

Power Disturbance: Harmonics (Duration: Less than one cycle)

Definition: Quick voltage variations, harmonics occur at the natural multiple of the standard power wave

Causes: Switching nearby loads off/on, computer networks, utilities

Possible Computer Symptoms: Data corruption, processing errors, incorrect data transfers, lock-ups, hardware damage

Power Disturbance: Overvoltage's (Duration: Greater than one cycle)

Definition: A high-voltage condition on one or more phases

Causes: Rapid load reduction, utility switching

Possible Computer Symptoms: Hardware damage

Power Disturbance: Outage (Duration: Greater than half a cycle)

Definition: A zero-volt condition

Causes: Ground faults equipment failure, accidents, lightning, acts of nature

Possible Computer Symptoms: System crashes, hardware damage