have an electric cooker to repair but the fault i believe is the house rather than the cooker.
The cooker is wired to a b40 40a circuit breaker.There is a 30a double socket near the cooker which is wired to a b32 circuit breaker.The house has overhead supply down through a big breaker to the distribution panel.When the cooker is on if you switch the kettle or toaster on the big breaker goes out.How can this be the socket and cooker are different circuits..Needless to say the kettle,toaster andcooker work fine individually.Its some kind collective thing.Any ideas welcome.

By big breaker,do you mean RCD?

You really need a tester. I'll assume it must be an rcd tripping, because afaik normal main switches are just switches and don't measure current flow. The rcd could trip either due to a slight short between live and earth in the appliance, or a similar small leak between neutral and earth anywhere in the house - either another appliance that is plugged in, or on your fixed wiring. This would be difficult to locate via trial and error.

You have an overhead supply called TT you will have an Earth leakage circuit breaker on the mains.

Anything with a heating element has a very small leakage current to earth quite normal and not dangerous as things get older the leak gets bigger.

If you have a few leaky appliances all on at the same time the ELCB will trip.

Yes its culumative.

Due to the earth leakage current and not an overload.

[Edited on 17/6/14 by big-vee-twin]