In order to ensure that those working on or near live electrical systems are not exposed to danger, having a safe isolation procedure in place is essential. Failure to do so can result in serious injury or even the needless loss of life.
So, to prevent this worst-case scenario from occurring, Electrical Safety First in association with other industry bodies has produced a document entitled “Guidance on the management of electrical safety and safe isolation procedures for low voltage installations (Best Practice Guide 2 Issue 2).”
Instrotech, a leading supplier of environmental and electrical test equipment, has produced a summary of this guidance on safe isolation procedures below.
Using the Right Equipment
When using a main switch or distribution board switch disconnector for isolation purposes, the best practice guide recommends that:
“The point of isolation should be locked off using a unique key or combination retained by the person carrying out the work or the appointed person, and a caution notice attached to the point of isolation.
“Where more than one operative is working on circuits supplied from an isolated distribution board, a multi-lock hasp can be used to prevent operation.”
All of the equipment required to isolate a circuit like this should be included within a standard locking off kit.
Using a Locking Off Kit
Although a number of different locking off kits are currently available, you should look for one that contains the following
A selection of MCB (Mini Circuit Breaker) and breaker locks
A padlock with a unique key or combination
A hasp for when more than one person is working on the system
Lock out tags and warning labels
The person carrying out the work must keep hold of the padlock’s unique key or combination, so as to prevent anyone else from removing the lock and accidentally activating the circuit. Padlocks with a key are considered to be the safest option, as combination locks often feature a default setting of zeros, which don’t always get changed.
After locking off the breaker, a warning tag should also be attached to clearly show that this is the case.
Verifying the Circuit is Dead
In addition to locking off the circuit, the person carrying out the work must also verify that the circuit is definitely dead before going any further. Because circuits are frequently mislabelled, you can never be certain that the correct circuit has been locked off.
Thankfully, the best practice guide also has advice in regards to using a dedicated voltage indicator and proving unit. “Following isolation of equipment or circuits and before starting work it should be proved that the parts to work on, and those nearby, are dead.
“It should never be assumed that equipment is dead because a particular isolation device has been placed in the OFF position.”
Therefore, you cannot just lock off the breaker and assume the circuit is dead. It is possible for the neutral conductor of a locked off circuit to become live if an energised load on another circuit is connected to it.
So there you have it, useful advice that will hopefully allow any qualified electrician to safely isolate an electrical system prior to carrying out any necessary work.
If you need any further advice regarding safe electrical isolation procedures then Instrotech are well placed to provide assistance and have the right equipment available to help you to get the job done safely.