How do I get my De Dietrich oven to switch on without tripping the mains?

I have a De Dietrich FA5347E1 fan oven. We did a pyrolytic clean followed by wiping out with a damp cloth. When we tried to start the oven the mains were tripped. We asked a local electrician to assist and were advised that it was probably the main element that was malfunctioning - we purchased a new element but the problem persisted. We have tried to operate the oven without the fan and also with only the grill element switched on but the problem persists. When we switched on the 'defrost' programme it works at 40 degrees. When we tried the fan oven at 40 degrees it tripped the mains. Is there anything else can we do? The main switch that is being tripped is labelled 'current operated earth leakage circuit breaker'.