18. ELECTRICAL EQUIPMENT 88
Protective Grounding
The conductive parts of a piece of equipment that are not part of circuit are grounded
on equipment that has protective grounding. In this case, e.g., if the conductive casing
becomes charged, the equipment’s own fuse will blow and discharge the equipment
to make it safe.
Fault Current Protection Switch
Fault current protection switches must be installed in all power outlets
in the distribution boxes (< 32 A) at the construction site, if they are used for handheld
electrical devices.
A fault current protection switch is a sensitive protective device that complements
the protection provided by fuses. The release of the switch makes the electrical circuit
dead in case of an insulation fault.
Use of Electrical Equipment in Confined Conductive Spaces
A confined conductive space can be defined as:
A corridor that is less than 1.25 meters wide or any other similar space
with conductive walls
A confined space with conductive walls, which is less than 1.25 meters
by 1,25 meters, or if one of these measurements is less than 1.25 m and
height less than 1.80 m
A conductive mast and any other similar conductive frame structure
In such case the equipment must meet one of the following requirements:
It runs on protective extra low voltage
A protective separating transformer is being used and only one device
can be plugged into it
It is pneumatic
It runs on batteries that suit the space.
These conditions must also be met in other similar situations where a major part of
the worker’s body touches conductive parts around him and where there are limited
possibilities to be released from this type of contact. Such a situation could take place
when holding a hand-held electrical device on a conductive floor when kneeling, sitting
or laying on the floor.