Care & use of short circuiting devices

by | Jun 21, 2017 | Electrical Safety Info

ENSURE EQUIPMENT IS CERTIFIED FIT FOR PURPOSE

Earthing and short-circuiting has two distinct and separate functions:

  1. To limit current flow in the human body to a level that will not cause death or serious injury.
  2. To operate tripping devices at supply source.

 

The resistance value and condition of a short-circuiting device is fundamental and critical to both functions

THRESHOLD LIMITS

Resistance threshold limits are based on Internationally recognised safety standards which take into account the following:

  1. The level of operator protection to be provided.
  2. Amount of time the fault current can flow (tripping times)
  3. The prevailing fault level current.

 

Short-circuiting devices, which exceed their upper resistance threshold limits may be capable of disrupting supply but will not limit current flow in the human body sufficiently to prevent death or serious injury.  

IN A FAULT SITUATION A LOT CAN HAPPEN IN A FRACTION OF A SECOND

 

  • The device can fragment in 1/100th of a second if peak forces are not addressed
  • The device can melt in less than 1/10th of a second if thermal stress is not addressed
  • Electrocution resulting in death or serious injury can occur in less than 3/100th of a second if resistance values are not correct

 

INSPECT

Short-circuiting equipment must be checked and inspected before each use by a competent person to ensure that it is fit for purpose.  Any interference in the current path by way of contamination or joint function may dramatically increase resistance values and render the short-circuit jumper ineffective as a protection from death or serious injury. 

Areas for attention include but are not limited to the following:

Moving parts not working properly: Broken strands on conductor: Unclean or contaminated contact areas: Arcing or burn marks on contact areas: Annealed copper strands, moisture ingress, discoloration of cable sheath etc. If any defects are found the equipment is not fit for purpose and must not be used. Clean contact surfaces and lubricate moving parts regularly. To ensure integrity of earthing devices great care should be taken in storage and transportation

Short-circuiting equipment may be loaded only once with the permitted short-circuit current.

NOT TO STANDARD = NOT FIT FOR PURPOSE = UNNECESSARY DANGER

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