Page 401 - IGC BOOK

Isolation

The electrical work must be carried by proving the system is dead, this is done by isolating the
supply of power to the equipment. Isolation is done to:

• Break the circuit
• Physically securing the isolation.
• Using label or tag.

For example, switching off the power supply to an equipment, then using a Lock out system –
pad lock to secure the isolation, and displaying a tag with details of the worker and the nature of
work.

Locating Buried Services

Striking buried services can be avoided with the use of SSoW, in addition with cable avoidance
tool.

• Obtain necessary information about the underground services, arrange copies of plan,
however plans alone are not sufficient to identify and locate
services before starting work, it gives basic information about
the presence of underground services.
• Prior to start the work the position of buried services should
be pinpointed using locating device – Cable Avoidance Tool e.g.
Hum detectors detects the electromagnetic field radiated by
live electricity cables.
• Once detected the work should be carried out carefully digging
by hand tools. (spades & shovels).

• The located underground services should be clearly labelled
for easy visibility, consideration must be given to supporting
the cables beneath.

Work Near Overhead Power Line

Overhead power lines are bare and uninsulated which has potential to arc if any conductor is
found close to the proximity. Prevention can be achieved by:

• Isolate power supply when working near overhead
power lines, if practically not then sleeve low voltage
power lines.
• Use SSoW and PTW to control access to the proximity.

• Use sign boards, barriers, and goal posts to ensure
plant and vehicles maintain a safe distance.

• Use banksmen to control manoeuvring.
• Use non-conducting work equipment – wooden ladder
or fibre ladders.

ENSIGN | Unit IG2 – Element 11 – Electricity 12