Electrical power systems

The topic of Electrical power systems is concerned with risks arising from electrical distribution systems and equipment at major accident hazard sites. Specifically, it is concerned with:

  • the management, design, installation, operation and maintenance of electrical power systems so that they provide the necessary reliability, availability and survivability and so that they prevent danger to personnel;
  • the initiation of major accidents by electrical equipment through fire and explosion.

Electrically powered hazardous installations such as large-scale chemical manufacturing processes should be designed to fail to a safe state on loss of electrical power, however, in certain circumstances it may be necessary to maintain electrical power to ensure safety. In some situations partial failure of the electrical distribution network may lead to more severe consequences than complete failure.

Electrical distribution systems generate, store and transmit extremely large amounts of energy. Uncontrolled releases of electrical energy, for example from catastrophic failure of equipment or poorly designed or maintained equipment, have been seen to result in electrical fires and explosions that are dangerous in themselves but can also initiate major accidents at major hazard sites.

The risks arising from the reliability, availability and survivability of electrical supplies and from catastrophic failure of electrical equipment should be managed by:

  • identifying the consequence of complete and partial failure of electrical supplies
  • identifying the consequence of catastrophic failure of electrical equipment
  • ensuring the electrical power system integrity is consistent with any risk reduction claimed
  • installing electrical equipment remote from major hazard installations or in protected locations
  • designing electrical distribution systems to discriminate faults to prevent cascading a failure across the site
  • selecting electrical equipment that is capable of withstanding anticipated fault currents
  • maintaining electrical equipment and protection devices
  • having robust safe systems of work and competency assurance to ensure electrical systems are only operated and maintained by competent persons

Guidance on risks arising directly from electricity is provided on the electrical safety at work pages of this website.

Technical Standards and Guidance

COMAH Competent Authority E, C&I Operational Delivery Guide


Technical Standards

Refer to the COMAH Competent Authority E, C&I Operational Delivery Guide.

Industry Publications

HSE Guidance

Other information

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Updated: 2021-08-26