Earth Leakage Faults and Information.
Earth Leakage Protection Devices are the core balance type which monitor the difference in the current flowing in the live and neutral conductors.This imbalance is used to open the circuit and thereby stopping the current flow.
Under healthy conditions the vectoral sum of the currents in the live and neutral conductor will equal zero and no operation is necessary. If an earth fault occurs the live and neutral currents will not balance and the difference will be detected by the Earth Leakage Circuit Breaker or Earth Leakage Switch. This imbalance is used to open the circuit and thereby stopping the current flow. This is also true for three or four wire circuits, whether or not the load is balanced or unbalanced, the vector sum equals zero.
Earth Leakage Tripping Current (Sensitivity)
This is measured in milliamps (mA) and is referred to as the degree of protection in an accidental shock hazard situation.
Low voltage follow the IEC Standard 1008/1009 of 30 mA sensitivity for domestic and personal protection with the tolerance of 30 mA plus zero and minus 50%, that is, a range from 15 mA to 30 mA. CBI-electric: low voltage earth leakage units are manufactured to operate in the tolerance band of 19 to 26 mA.
For personal protection 30 mA offers a high degree of protection and will operate by cutting off the earth fault current well within the time specified in the IEC Publication 1008/1009.
Lower sensitivities above 30 mA are sometimes used for individual circuits where there is less chance of direct contact such as in hot water tanks in a roof or underfloor heating. These earth leakage units from 100 to 375 mA provide reasonable protection from the risk of electrical fires, but it should be noted that under certain circumstances a current of less than 500 mA flowing in a high resistance path is sufficient to bring metallic parts to incandescence and start a fire.
All earth leakage units are provided with a test button. When pressed, the test button causes an imbalance to simulate an earth fault operation. The test button should be pressed often to prove the unit is in working order. If the unit does not trip instantly, expert advice should be sought to check the electrical installation.
1. Faulty Earth Leakage Unit (Old Unit). There are two designs of Earth Leakage Units. The South African Design, which is the CBI design, sometimes called the Samite design. Recently legal copies of this design have been sold, and illegal copies which are difficult to spot.
2. The Second design is the international design which the trade refers to the DIN type. This design is going more popular, especially when new Distribution Boards are to be installed, as the DIN Earth Leakage Unit and DIN Breakers are cheaper.
Earth Leakage Faults could be to a number of various reasons, and sometimes can take awhile to determine the fault.
A few examples for Earth Leakage Unit Faults.
Old Earth Leakage Units. There is a button on the Earth Leakage Units that should be pressed once a month, which is a test button.
RSA Electrical are qualified to test single and three phase installations, and with our many years of experience and test equipment we will identify the fault