ELECTRICAL PANEL WIRING AND TERMINAL BOARDS CONNECTION PROCEDURE

Guide to Electrical Control Panel Wiring and Terminal Board Connection Procedure

This document provides a guide for the service provider on a high voltage and medium voltage transmission line power project from the employer site to ensure that all electrical equipment mounted in switch-gear, panels, kiosks, and desks, etc. must have readily accessible connections and be wired to terminal blocks for the reception of external cabling.

Of course, all wiring be situated of adequate cross-sectional area to carry prospective short-circuit currents without any risk of damage to conductors, insulation or joints.

Important to consider that selecting the wrong wire types may cause operational problems and could render the unsafe for human and equipment. Some of the important factor of such as:

·        Size of the conductor;

·        Insulation of material;

·        Made of;

·        Whether Solid, standard or flexible etc.

Panel Wiring Cable Selection Guide

All cable for panel wiring should be of type CR or CK to BS 6231 unless the design of the plant requires the cabling to withstand more onerous operating conditions in which case cabling should be suitable for these conditions.

The minimum cross-section of panel wiring cable or wire should be 2.5mm² for all secondary wiring associated with current transformers of the nominal secondary rating of 0.5A or higher.

The size of wiring cable for circuits other than CT (Current Transformer) secondary wiring should not be less than 1.5mm² cross-section.

The minimum strand diameter of copper or tinned copper flexible conductors should be 0.20 mm for flexible cable, the minimum cross-sectional area should ensure 0.5mm² for all control cables.

 The wiring within panels on circuits not directly associated with circuit breaker protection and control, having a continuous or intermittent load current less than 1 amp, the use of smaller line down to 0.25mm² may be permitted subject to Engineer’s Approval.

Where an overall screen is used, this should be a metallic screen or low resistance tape with drain wire as above.

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Control Panel Wiring Procedure

Wiring should be supported using an insulated system which allows easy access for fault finding and facilitates the rapid installation of additional cables.

Small wiring passing between compartments which may be separated for transport should be taken in terminal blocks mounted near the top of each compartment, separately from those for external cable connections.

Terminal Board Connection Procedure

Both ends of every wire should be fitted with ferrules of insulating material complying with BS 3858 or equivalent National Standard and engraved in black. The identification numbering system used for the ferrules should be to the approval of the Engineer.

Where new equipment must interface with existing equipment double ferrule should be employed if the two numbering system is not compatible.

Connections to apparatus mounted on doors, or between points subject to relative movement, should be made in cable type CK to BS 6231, arranged so that they are subjected to torsion rather than bending.