Wiring continuity tests should be conducted, as well as insulation resistance tests, Earth continuity tests, Earth resistivity tests, and any other tests that the Supervising Engineer specifies. Here we will look at these tests, as well as high voltage tests and commissioning.
1. Evaluating the continuity of electrical wiring
A continuity test, a short circuit test, and an earthing test should be performed after all wiring is completed and before the system is powered.
2. A Resistance test for electrical insulation
All fuses must be installed and all switches closed, as well as all lamps, except for concentric wiring, installed in the positions of both poles of the installation otherwise electrically connected together, along with the earth.
For medium voltage circuits, the direct current pressure should be at least twice the working pressure while not exceeding 660 volts. When the supply comes from a three-phase AC system, the neutral pole of which is connected to earth, either directly or indirectly, the pressure between the phase conductor and neutral shall be considered to be the pressure between the two.
When the insulation resistance measured as above is divided by the number of points on the circuit, it shall not be less than 50 mega ohms, providing that the whole installation does not exceed one mega ohm.
Insulation resistance must also be measured between every conductor connected to the phase conductor, neutral conductor, or to another phase conductor of supply. An insulation test, in this case, can only be performed after all metallic connections between the two poles have been removed. Under these circumstances, the insulation should not be less than that specified above.
In the installation of housing and power appliances, the insulation resistance should not be less than the value specified in the relevant British standard specification or, when there is no such specification, it should not be less than one mega ohm.
3. Testing Of Electric Earth Continuity Paths
Metallic earth continuity conductor envelops for cables, along with their earthing wires, shall be tested for continuity and electrical resistance, with the exception of earth leakage circuit breakers, in which case the earth continuity conductor shall not exceed one ohm at any point in the completed installation.
4. Test of single-pole switches that are not linked
A test shall be performed in a two wire installation to verify that all single pole switches have not been connected in parallel, each conductor shall be labeled or marked for connection, and it shall be marked to be connected to an outer conductor or phase conductor. All non-linked single pole switches must be fitted in a conductor connected to one of the outer or phase conductors of the supply. The Supervising engineer as well as the local authorities need to approve the entire electrical installation.
5. A Testing Of The Electrical Earth’s Resistance
Tests of earth resistivity must be performed according to the British Standard Code of Practice of Earthing. The Supervising Engineer must be present at all tests.
6. Testing Electrical Performance
Complete electrical installations and equipment shall be subjected to the final performance test as intended for each and every piece of equipment shall be tested according to the manufacturer’s instructions.