The UK was the first and is now probably the only country in the world that still uses the 30 amp ring system to connect outlets in electrical installations. The main circuit of the ring has long been the subject of many heated discussions between electro technical experts, but as an electrician you will undoubtedly have to test them in the course of your duties. Here is an overview of the inspection and testing procedures of Ring Main.
Warning- Please note that this is a & # 39; dead & # 39; test, so that the distribution board, the consumer unit or the circuit must be isolated from the electrical supply. To begin with, you must perform a safe isolation procedure and be allowed to disable the delivery.
Here is the test procedure:
Disconnect all devices and accessories from the ring circuit and carry out isolation tests between the line, neutral and ground CPC.
end-to-end ring continuity test
Set your test meter to a low resistance range and & # 39; zero & # 39; the test leads. Measure the resistance of the ring continuity of each of the active, neutral and earth conductor ring loops. Record these end-to-end measurements for future reference and entering a test sheet. Note that where the earth conductors are smaller, the resistance will naturally be higher. For example, for twin and ground cables, 1.5 mm will be 1.66 times higher than 2.5 mm.
Super lustest L & N
Cross connects the current carrying and neutral conductors of opposite ends of the ring and forms a super loop. If this sounds confusing at first, try to draw the live and neutral loops of a ring circuit on a piece of paper with the other ends connected. You will see that it is one big super loop.
Test the resistance between the ends that you just connected. The measured value between the ends of the super loop must be about half that of your previous continuity measurement. You can then verify the main wiring and connections of the ring by going to each outlet and testing it between live and neutral. If the connection is on the ring and the connections are good & # 39; your measurements must be within 0.05 of your original superloop reading on the distribution card.
These measurements are normally not recorded but form the basis for your assessment of the connections of the main loop circuit.
High readings may indicate that the socket is on a protrusion of the ring, that connections must be tightened or the socket is defective, resulting in poor connection to the plug and replacement. Where the measured values are not consistent, this may indicate that there are cross connections and the ring circuit is bridged.
Superloop test L & E
Cross the line and ground conductors from opposite ends of the ring and form a super loop. Test between the two sets of ends you just connected. The resistance value must be about half that of your previous continuity measurement. You can then check the main wiring and connections of the ring by measuring the resistance at each socket as described earlier for Live and Neutral. Testing between live and earth on the sockets also checks for correct polarity.