Cable Accessories & Earthing

A cable tray is an open support that carries many cables with good heat dissipation and easy additions, and is used in plants and substations. Conduit is a closed pipe that protects a few cables from damage and is common for final runs to equipment. Large power installations usually use trays for the main routes and conduits for drops.

Match the gland to the cable's outer diameter, armour type, the thread size and type on the enclosure, the required IP rating and, for hazardous areas, the Ex certification. Armoured cables need a gland that grips the armour for earth continuity, usually a double-compression type. Measure the cable over its outer sheath before selecting.

Common causes are the wrong lug size, the wrong die or too little crimp pressure, a damaged conductor, and mixing aluminium and copper without a bimetallic lug. A loose joint heats up, oxidises and heats further. Use the correct tool, check the crimp by pull and visual inspection, and torque bolted joints to specification.

The required value comes from the project specification and the type of installation. Substations and large power systems normally target a very low value, often 1 ohm or below, while smaller installations accept a few ohms. Soil resistivity, fault current and touch voltage limits decide the design. Follow IS 3043 and the advice of a qualified engineer.

Pipe earthing uses a galvanised iron or copper-bonded pipe driven or buried in a pit, with salts or backfill compound to hold moisture. Plate earthing uses a buried copper or GI plate. Pipe electrodes are the more common choice because they reach deeper, moister soil layers. The choice depends on soil and space.