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
Operaciones Elementales
Intervening at the work point
Due to the diversity of possible interventions, this operation in itself is not described. The General Conditions for acting are:
- The work point is the only one that is bare.
- When a situation with voltage and charge is registered, other means will have to be used (bridges or by-passes) to reroute the charge and act only under voltage.
- Avoid using excessively long conductor elements: clamps, connection leads, etc. Start out from a spiral roll to facilitate their handling and, in some cases, insulate before handling them.
- The electrician doing the job must not carry out any additional tasks: hold the tool bag, pull ties, etc.
- The installations must not be electrically or mechanically overloaded.
Installing bridges and by-passes
Due to the large number of possible installations, the General Conditions give a summary of how to install these elements, which are needed to re-route the load and provide continuity to the circuit, either by rigid means (a bridge) or via a manoeuvre or protection element (by-pass).
- To previously identify the conductors, verifying the rotation if applicable. Marking them with coloured tape is advisable so as to avoid subsequent confusion should they not have differentiating elements.
- Check the mechanical reliability of the line for new openings at the time of manipulation.
- The length and flexibility must be appropriate to allow working comfortably.
- Choose the most appropriate points to make the connections on the main line, avoiding the destruction and subsequent restoration of insulation, whenever possible.
Bridges:
- Commence installing with one end covered or protected.
- Connect and protect one end and then the other.
- Once the two points have been connected and protected, act on the line.
- To dismantle it, proceed in the inverse order, protecting each end point and restoring the main insulation.
By - pass:
- Check using a multimeter that the manoeuvre element of the by-pass is open.
- If the by-pass is unipolar, it is installed as a bridge, subsequently closing the manoeuvre or protection element.
- In the case of multipolar by-passes, all the conductors must be protected.
- Successively connect and protect all the conductors on one side of the device starting with neutral. Repeat these operations for the conductors on the other side.
- Before closing a manoeuvre element, check phase concordance. Close the manoeuvre element.
- Before acting on the line, check that the manoeuvre or protection element of the by-pass is still closed.
- Once the work has been completed and continuity has been restored to the line, open the manoeuvre element of the by-pass and proceed to disconnect in the inverse order, disconnecting, restoring insulation and successively protecting the points at the two ends of the device.
Preparing the ends of wires
The aim of this operation is to prepare the ends of conductors so as to simplify connection operations as far as possible and to minimize the time that live bare parts are exposed.
- If the ends are taped, no other protection will be needed. Otherwise, insulating caps are to be placed on the ends to be prepared.
- Work is to be carried out on only one bare point, so the protection of only one end is to be removed.
- A sufficient length of insulation is to be removed from the first conductor so as to suitably carry out the subsequent work (connector, crimpit, terminal, ferrule).
- Once this operation has been completed, cover the bare part of this first conductor with an insulating cap or tape and repeat the same process for the remaining conductors.
Fitting terminals to a wire
The aim of this operation is to prepare the tip of the wire with connection terminals.
- Prior to the fitting of terminals, the ends of the conductors are to be prepared in accordance with the previous section.
- The insulating cap is to be removed, the terminal is to put in place and, using the crimping tool and corresponding dies, give the necessary crimps. Start pressing on the closest part to the terminal blade and finish at the other end to enable the terminal to stretch as it is compressed.
- The covering of the wire is to be restored with self-vulcanizing tape and vinyl tape. The terminal is to be covered up to its blade.
- Once this operation has been carried out, the terminal is to be insulated with an insulating cap or, if one is not available, with vinyl material or insulating tape.
- The same sequence is to be repeated for the remaining conductors.
