What is a voltage dip

  • According to internationally-adopted definitions (under European standard EN 50160), a voltage dip occurs when the power voltage drops to a level below 90% of standard voltage for no longer than a minute. However, most voltage dips last for less than one-tenth of a second before the standard voltage of the power supply is restored.
  • A voltage dip is not a power interruption. During the occurrence of a voltage dip, the power supply is not interrupted.
  • Voltage dips are usually caused by weather conditions or third party damage (see illustration). For these reasons, occasional voltage dips are unavoidable. Power companies all over the world have not been able to eliminate the occurrence of momentary voltage dips caused by the above-mentioned reasons.
  • Usually, users’ power supply will not be affected by a voltage dip. However, individual users may experience a momentary dimming or flickering of their lights.
  • Most of the users’ power equipment will not be affected by a voltage dip. However, for the more sensitive individual equipment, the protection device may be triggered during a voltage dip, which will result in tripping. If no irregularity is detected in an inspection, the equipment can be switched back on.
  • Most elevators are equipped to automatically switch themselves back on, and people will not be trapped in lifts during momentary voltage dips. For individual elevators that are affected, users may contact the suppliers of the elevators for measures to ensure normal operations during voltage dips.
  • CLP encourages users to install equipment with “ride-through” capabilities, e.g. install an Uninterruptible Power Supply (UPS), a voltage stabiliser and an appropriate protection device. CLP’s Power Quality Team is happy to offer professional advice to our users.
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