Step 1 : Switch off the main switch, earth leakage unit and all the circuit breakers, unplug everything and switch off isolators (stoves, pool, geyser, etc)
Step 2 : Switch on the earth leakage unit first then switch on the main switch, if the earth leakage trips chances are you have a neutral fault, you need to call an electrician. If the earth leakage unit stays up/on go to step 3
Step 3 : Switch on one circuit breaker at a time and wait a second or 2 as you switch them on, if the earth leakage trips as you switch on a circuit breaker, leave the circuit breaker down/off and move to the next circuit breaker, if the rest of the circuit breakers are reset without tripping the earth leakage unit then you have identified the circuit then you can start plugging appliance back in and switching on isolators, you will find some appliance don't work, you will need to get an electrician to trace the fault. If all the circuit breakers reset without tripping the earth leakage unit, then go to step 4
Step 4 : Start plugging in appliances and switch on isolators one at a time until the cable/ appliance trips the earth leakage, unplug the appliance which trips the earth leakage and leave it unplugged, you have identified the problem, you don't need to call an electrician, just replace the appliance, if you switch on the pool isolator and it trips the earth leakage you know it is the pool causing the problem.
Note!!!! This is a very basic explanation of what might be causing the earth leakage unit trip and if in doubt call your local electrician. Finding an "electrician" capable of tracing faults could be just as tricky as the fault itself.
Earth leakage unit : device that is capable of detecting the flow of a specified or predetermined current from a circuit to earth, and of disconnecting, automatically and reliably, the affected circuit within a specified time when such current exceeds the specified or per-determined value.
An extremely important device. One that can save lives and property!
A few points to consider:Firstly, the Earth Leakage Unit, must conform to Compulsory Safety Standards VC 8035. All Circuit Breakers that are manufactured and imported must conform to this standard. One of the requirements that VC 8035 states that VC 8035 be indicated on the Earth Leakage Unit; this being a quick way to identify if the Earth Leakage Unit is compliant.
Secondly, the following must reflect on the front of the Earth Leakage Unit: IΔn ≤ 30 mA. The rated earth leakage tripping current (rated residual current) IΔn required to activate an earth leakage protection device shall not exceed 30 mA. When a qualified (Single Phase Tester), Installation Electrician, or Master Electrician tests a facility one of the test instruments used is called an Earth Leakage Tester.
With power on the circuit, the tester is plugged into one of the switch sockets and leakage current is slowly increased in the circuit. Earth Leakage Current shall not exceed 30mA. Most Earth Leakage Units on the market trip at exactly 30mA. If the unit trips before 30mA the ELU could be to sensitive and become a nuisance factor.