Electrical Wires & Cables

Electrical wires are designed to bear consistent electric current which should not lead to a fire in case of accidents/short circuit. Most of the electrical failures in India are caused due to failure of electrical wires. People often ignore the significance of this major material.

Cabling is an expensive business and must be treated carefully. The expenditure of substitution once the routes are all concealed is bigger. The fault is not always visible like crushing, bending or kinking. Make sure that your cabling installer have made provision to protect installed cabling from other worker’s actions. This is substantially less costly than changing cabling in the future. If cable routes are guarded with no way of opening them between termination and installation, it is ideal to terminate the cables for the time being, so they can be tested before the routes are protected.

What is Cable Testing?

Given below are the tests and inspections that must be done before energizing low voltage cable rated 600V or below.

Compare cable data with drawings and specifications. Pay attention to the number of sets, the cable size, routing, and insulation ratings. Note these items on the test sheet.

Check uncovered parts of cable for material damage. Look at the condition of the cable jacket and insulation of exposed sections. Verify that the connection points match what is shown on the project single-line diagram. Check bolted electrical connections for high resistance with the use of a calibrated torque-wrench, low-resistance ohmmeter or thermographic survey.

When using a calibrated torque wrench, reference ANSI/NETA Table 100.12 US Standard Fasteners, Bolt Torque Values for Electrical Connections.

The values of similar bolted connections must be compared and check which value shift by more than fifty percent of the smallest value in the case where a low resistance ohmmeter is utilized.

Look at the condition of the exposed cable jacket and insulation when performing a visual inspection on low voltage wire and cable.

• Inspect compression-applied connections by verifying that the connector is properly rated for the installed cable size and has the proper indentations.
• Perform an insulation-resistance test on each conductor with respect to ground and adjacent conductors. Test period must be for 1 minute using a voltage according to manufacturer’s published data.

If no literature from the manufacturer is available, apply 500 volts dc for 300-volt rated cable and 1000 volts dc for 600-volt rated cable. Insulation-resistance values must be according to the manufacturer’s published data. If no data from the manufacturer exists, the values should be no less than 100 megohms. Perform continuity tests to ensure correct cable connection and phasing.

Verify uniform resistance of parallel conductors using a low-resistance ohmmeter. Measure the resistance of each cable individually and investigate deviations in resistance between parallel conductors.

Physical tests for Insulation

Tensile strength and elongation at break

Ageing in air oven

Ageing in air bomb

Ageing in oxygen bomb

Hot set

Oil resistance

Tear resistance

Insulation resistance

High voltage (water immersion) test

Flammability test (only for SE-3, SE-4)

Water abortion test (for insulation)