Work on Electrical Installations and in premises presenting a fire or explosion hazard
Definitions and concepts:
20. Technical instructions
20.3. Carrying out of live work on low voltage using the “in Contact” method
Basic Operations
Approaching the point of intervention
This operation precedes the work itself and is to be carried out once the Work Area has been signposted. The aim of this operation is to start insulating the Area and to establish a safety distance to any energized point greater than 40 cm.
At a height:
- Use gaffs (on wooden posts), an insulating ladder or insulating basket (in the remaining cases), wearing a safety belt, hook or strap, an insulating pulley and service rope.
- Attach the pulley at the safety limit distance and place the service rope in working order.
At the same level:
- Place the necessary insulating mats to allow comfortable access to and permanence in the Work Area of the person doing the job and his assistant.
In trenches or manholes:
- Cover the walls and floors of the areas near to the point of action where the electrician and his assistant may accede to with insulating mats or vinyl sheets.
Insulating the Work Area
The aim is to obtain a fully insulated Work Area where the electrician can move around freely only having to pay attention to the work point.
- Work is always to commence with the closest points, so that the worker always advances on an insulated area.
- All elements that present a possible current output (the input is covered by the insulating gloves) must be insulated:
- Conductores.
- Preformed fittings and accessories.
- Stays and props with which the worker might come into Contact.
- Earths of fittings or of the neutral conductor of the network.
- Walls and other elements of buildings.
- Walls and floors of trenches and utility shafts.
- Concrete or metal posts.
- The elements to employ when carrying out this insulation are:
- Insulating profiles for bare wires. To place one of these, start with one end and slide it on. Check that it cannot fall off easily if turned upside down. Otherwise, secure it with tape. It must be placed in such a way that it does not slide easily once in position, by means of a peg or insulating tape.
- Vinyl sheeting.Take every precaution when applying to places where there are sharp points or edges, as it can be relatively easily perforated. It must not be used over hot points if there is not sufficient space between the two to avoid its deterioration. Take every precaution when applying to places where there are sharp points or edges, as it can be relatively easily perforated. It must not be used over hot points if there is not sufficient space between the two to avoid its deterioration.
- Polyethylene plaques. To be applied as a covering for sections of facades and masses in general. Depending on their shape, these may be hung, fastened with adhesive tape or also nailed. They are very useful in LV distribution boards, general enclosures, brackets, frames, bars, etc., as they may be permanently shaped by applying a small amount of heat, thus obtaining general purpose preformed protections that can be very quickly placed and removed. Adhesive tape, vinyl sheeting or polythene plaques should not be used over hot points that easily deteriorate the insulation.
Identifying conductors
- The aim of this operation is to distinguish which is the neutral and which are the phases and, if applicable, the rotation of these.
- To be carried out after insulating the Work Area (WA).
- A voltmeter or discriminator and phase sequence meter is to be used, but in no case whatsoever is a lamp or neon pen to be used.
- On a bare line, it is sufficient to remove, connect and re-cover with provisional insulation at each point where measurement is carried out.
- In insulated conductors, a nick should be made in the insulation to allow testing. It is to be re-covered provisionally if this point is used for the definitive connection that is to be made or, otherwise, the insulation is to be restored.
