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.
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