| Power Outage |
Total interruption of electrical supply:
Momentary outages last 0.5 cycles – 3 seconds.
Temporary outages last from 3 seconds to 1 minute.
Long-term outages last longer than 1 minute. |
Accidents, acts of nature, etc. which require the proper operation of utility equipment (fuses, reclosers, etc.).
Internal short circuits requiring the proper operation of a customer's breakers and fuses. |
System shutdown
Loss of computer/ controller memory
Hardware damage
Product loss or damage |
Uninterruptible Power Supply (UPS) |
| Transient (Surge) |
A subcycle disturbance in the AC waveform, evidenced by a sharp, brief discontinuity of the waveform. |
Surges are caused by storms (lightning), operation of utility fuses, reclosers and breakers, turning on or off large equipment and capacitor switching (customer and utility). |
Computer lock-up, processing errors and data loss.
Burned circuit boards, electrical insulation damage and equipment damage. |
Surge protectors
Uninterruptible Power Supplies with built in surge suppression
Isolation transformers
Constant voltage transformer
Line reactors |
| Sag / Swell |
Any short-term (0.5 cycles – 1 minute) decrease (sag) or increase (swell) in voltage. Sags account for up to 87% of all power disturbances (according to a Bell Labs study). |
Major equipment shut-down and/or restart.
Short circuits
Utility equipment failure or utility switching. |
Memory loss and data errors.
Equipment shutdown
Flickering lights
Motors stalling or stopping and decreased motor life. |
Uninterruptible Power Supply
Constant voltage transformers
Voltage regulators
Power electronic sag correctors |
| Noise |
An unwanted high-frequency electrical signal that alters the normal voltage pattern (sine wave). |
Interference from radio or TV transmission.
Operation of electronic equipment. |
Lock-up of sensitive equipment.
Data loss and processing errors.
Distorted audio and video reception. |
Uninterruptible Power Supply
Isolation transformers
Power line filters |
| Harmonic Distortion |
The alteration of the normal voltage pattern (sine wave) due to equipment generating frequencies other than the standard 60 cycles per second. |
Electronic ballasts and other non-linear loads like switch-mode power supplies and variable frequency drives. |
Overheating of electrical equipment and wiring.
Decreased motor performance.
Improper operation of breakers, relays or fuses. |
Harmonic filters
Isolation transformers
Improved wiring and grounding
Isolated loads
Line reactors |
| Undervoltage/ Overvoltage |
Any long-term change lasting more than a minute, below or above normal voltage. |
Overloaded wiring or equipment.
Large load swings or improper transformer settings.
Undersized wiring and faulty or poor electrical connections. |
Dim or bright lights
Equipment shutdown
Overheating of motors or lights
Reduced efficiency or life of electrical equipment. |
Uninterruptible Power Supply
Constant voltage transformers
Verify electrical connections and wiring
Relocate equipment
Reduced voltage motor starters and voltage ride-through equipment |
