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Power Quality Events

There are no PQ Events.

Types of Power Quality Events 

Power Quality Event Description Possible Causes Effects
Sustained Interruption

A planned or accidental total loss of power that lasts more than two minutes.

 Equipment failure, weather, animals on power lines, auto accidents, mylar balloons, etc. The electrical system shuts down in the affected area.
Temporary Interruption

A planned or accidental total loss of power that lasts between two seconds and two minutes.

 Equipment failure, weather, animals on power lines, auto accidents, mylar balloons, etc. The electrical system temporarily shuts down in the affected area.
Momentary Interruption

A planned or accidental loss of power that lasts up to two seconds.

 Utility switching operations. Equipment trips off, programming is lost, disk drives crash, etc.
Sag or Undervoltage

A sag is a decrease in voltage below the prescribed input voltage range that lasts up to three seconds. An undervoltage is a sag that lasts between three seconds and two minutes.

 Start-up or shut-down of major equipment, short circuits or fault clearing, overloading the distribution system or customer wiring. Data errors, dim lights, equipment shutdown or reset, errors in sensitive equipment, low efficiency, reduced life of equipment.
Swell or Overvoltage
  A swell is an increase in voltage above the prescribed input voltage range that lasts up to three seconds. Overvoltages are swells that last between three seconds and two minutes.
 Incorrect transformer tap settings, improper application of power factor correction capacitors. Overheating and reduced life of electrical equipment such as motors, heaters, etc.
Transient or Spike
 A sudden change in voltage up to several hundred or thousand volts that lasts from a fraction of a microsecond to several milliseconds.
 Lightning, static discharges, utility switching operations, starting or stopping major equipment or machinery. Burned circuit boards, processing errors, or data errors.
Notch A disturbance of opposite polarity from the waveform that lasts milliseconds.
 Lightning, static discharges, utility switching operations, starting or stopping major equipment or machinery. Burned circuit boards, processing errors, or data errors.
Noise A sporadic, unwanted electrical signal of high frequency from other equipment.
 Electromagnetic interference from appliances, microwave and radar transmissions, radio/TV broadcasts, laser printers, heaters, thermostats, loose wiring, improper grounding, etc. Processing errors or data loss.
Harmonic Distortion
 Voltages or currents at frequencies that are integer multiples of 60Hz frequencies (i.e. 120Hz, 180Hz, 240Hz, etc.)
 Non-linear loads. Overheating of motors, transformers, and wiring.