Risk of fire in old power factor correction assemblies

The purpose of this Safety Alert is to highlight the risk of fire in old power factor correction assemblies. Power factor correction assemblies are used by large business and factories to mitigate the electrical network effects of inductive machines, such as electric motors, refrigeration systems and air-conditioning.


A recent fire at a factory in Darwin revealed a number of old power factor correction assemblies installed in 1999. The capacitors contained within the assemblies have a rated life of 130,000 hours. Investigation of a fire in one such assembly found the capacitors had been in constant use for 150,000 hours, and had exceeded their design life.

Multiple protective devices were installed within the assembly to guard against catastrophic failure, however these were unable to prevent an explosion in a capacitor resulting in a cascade failure and conflagration causing massive damage to factory infrastructure.

Contributing factors

  • Capacitors have a limited life expectancy.
  • Heat may accelerate aging effects on capacitors.
  • Fire may result in old capacitors without warning.

Action required

  • Audit power factor correction assemblies to ensure operation only within designed life expectancy.
  • Arrange for an electrician to inspect capacitors annually for signs of bulging or leakage.
  • Replace capacitors which appear to be failing or have reached their life expectancy.
  • If possible locate power factor correction assemblies away from critical infrastructure.
  • Disconnect the power factor correction assemblies from supply if urgent repairs may be delayed.

Further information


Guidance publications


This Safety Alert contains safety information following inquires made by NT WorkSafe about an incident or unsafe practice. The information contained in this Alert does not necessarily include the outcome of NT WorkSafe’s action with respect to an incident. NT WorkSafe does not warrant the information in this Alert is complete or up-to-date and does not accept any liability for the information in this report or as to its use.