Electrical Isolation in Distribution Board Safework Procedure

The purpose of this method is to highlight safe working practices for electrical isolation which is similar as lock out tag out.

Operators must wear necessary PPE as required by local conditions and task specific risk assessment.

Before start of the electrical isolation work:

Ensure that you are qualified to carry out this task. No one must carry out electrical isolation unless they are qualified, or are a competent / skilled person as defined in the current IEEE regulations.

Fully brief the client / main contractor on the work you are about to do before you begin.

Ensure that you have all of the tools and equipment required to carry out the electrical isolation work.

Steps for Electrical Isolation – lock out tag out

Establish which circuit/distribution board is to be isolated.

Understand and establish which distribution board / main supply it is fed from.

At the main supply find the main switch that controls the supply to that DB.

Isolate the supply to the DB by means of the switch. Where the switch has an internal fuse remove it and take it with you.

Place a padlock through the switch where possible, to lock it in the off position. Take the key away with you.

Place a sign on the switch and the DB saying “Electrician working do not switch on”.

Return to the circuit you wish to isolate and carry out a test to see if it is now dead.

A Martindale type tester can be used for a socket; other types of equipment can be tested with a Stienel type tester.

If it is still live you must establish where it is fed from, and repeat the above steps.

If it is dead, return to the DB and switch it off at the main switch.

Remove the cover, then before you go any further test the incoming cable at the incomer side of the main switch to establish that it is dead.

If you are simply working on a single circuit from a local DB, you may isolate the DB from the incoming supply using the DB Main switch only. However you must test to ensure that the board is dead before doing any work within it, and you must never leave the board with the cover removed for any reason.

Once you have established that the DB and circuit are dead you may carry out the work required.

When the work is complete, test the installation as required in current regulations.

Before you re-energize the circuit double-check that all covers / conduit box lids / trunking lids etc. have been replaced, and that all fittings are correctly fitted.

Re-energize the circuit only when you are sure that all tests have been carried out and passed and all labelling is complete and correct.

Carry out the re-energizing process by reversing the order above, starting with making the Main switch / DB live, then activating the MCB / fuse, then testing the circuit now that it is live.

Lastly remove all signs barriers etc. from the work area.

When the circuit has been re-energized, and you have checked that all of the labelling is fitted and correct, carefully remove all of the debris and surplus materials from the work areas.

Inform the client / main contractor that you are finished, and the circuit is live again.

Complete all relevant paperwork and return it to the project or building office.

HSE Control Measures to Avoid the Risk of Electric Shock

Activity: Temporary isolation of a circuit from a local distribution board

Electricians are trained in safe isolation practices. Only qualified electricians carry out this work.

The distribution board is always isolated from it’s supply point prior to any works taking place.

The supply point is locked off / signed as isolated whilst work takes place.

The circuit is fully tested to current regulations prior to being re-energized.

Activity: Temporary isolation of a local distribution board

Electricians are trained in safe isolation practices.

Only qualified electricians carry out this work.

The distribution board is always isolated from it’s supply point prior to any works taking place.

Supply point is locked off / signed as isolated whilst work takes place.

The distribution board and it’s circuits are fully tested to current regulations prior to being re-energized.

Activity: Permanent isolation of a redundant circuit / board / chamber

Electricians are trained to, where possible, fully remove redundant cabling from an installation.

Where cabling is left in place it is fully removed from the distribution board, and any fittings are removed from the circuit.

Cable ends are isolated and labelled as out of use in line with current regulations.

Activity: Temporary isolation of a main distribution chamber

Electricians are trained in safe isolation practices.

Only qualified electricians carry out this work.

The distribution chamber is always isolated from the main supply point prior to any works taking place.

The supply point is locked off / signed as isolated whilst work takes place.

This may include isolation from the supply authority incomer.

Electricians are trained in contacting the supply authority in sufficient time to get the main supply isolated.

The distribution chamber and all relevant distribution boards and circuits are fully tested as required by current regulations prior to being re-energized.