SAFETY BULLETIN: Arc Flash Fatality

Arc Flash Fatality

In November 2018 a fatal accident [caused by an Arc Flash burns]. occurred to an technician whilst conducting ‘Return to Service’ checks on a previously decommissioned measuring system.

What Happened?

The decommissioned measuring system that was to be ‘Returned to Service’ feeds into a 20 kV customer’s supply.

  • Work was being carried out in a de-energised meter cabinet that was opposite to a 20 kV switchgear system, fitted with circuit breaker draw-out component trolleys. The cells were locked, disconnected and earthed on the outgoing side.
  • Approximately three hours after the technician had started, the smoke detector in his work area was triggered.
  • The emergency services found the technician lying on the ground in front of an open 20kV system switchgear cell. He showed signs of severe burns, presumed to have been caused by an electric arc.
  • Ten days later, the injured person succumbed to his injuries in a specialist hospital burns unit

 

 

 

 

 

Why did it happen?

  • It is unclear why the technician ventured into the 20kV area but the door to the switchgear cell was opened and the switchgear [circuit breaker] trolley removed.
  • The injured person was alone in the electrical control centre at the time and interface with other third parties is not thought to been involved.

 

Key Learnings communicated to date:

For all work in /on electrical systems, the type of task within the required work areas must be clearly defined and communicated [including de-energising and locking off all of equipment].

  1. The person responsible for organising the task had not conducted a written induction to the working area.
    • “safety check” a ‘PoWRA’ must always be completed before technical commercial activities are carried out.
  2. The person responsible did not approve any work on the instrument transformer in the 20 kV switchgear cell.
    • Work on electrical systems or equipment [even if they are supposedly disconnected] must only be carried out with authorisation by the person responsible for the system.
  1. The asset owners documented process must establish the permission to carry out work which must be given in writing i.e. ‘Permit To Work’.
    • If the plant operator [asset owner] does not provide a written certificate i.e. PTW, then work MUST not proceed until one is established.

Further Information

  • The Electricity at Work Regulations 1989 [HSR25];
  • Electricity at work – Safe working practices [HSG85];
  • Electrical switchgear safety – A guide for owners and users [INDG372];
  • OM 2009/003 – Standards and Markings for Personal Protective Equipment