I think this is a similar problem with double pole switching as in this thread
http://talk.electricianforum.co.uk/topic/29057-odd-fault-tripping-rcd/
But instead of an RCD read "sensitive electronic equipment"
When I posted on that thread I had found by googling a post on the IET website which quoted from the BEAMA RCD handbook;
"
9.3 Double-Pole Switching
Double-pole switching within the fixed wiring is known to produce a strange phenomenon whereby switching OFF a double-pole switch supplied through an RCD can cause the RCD to trip. Single-pole switching does not produce this effect, and it is known that changing over from double-pole to single-pole switching can overcome the problem, where such
replacement is permissible and safe. The phenomenon is explained by the fact that while capacitance between neutral and earth will exist in all installations, the earth leakage through this capacitance will be negligible due to the low (almost zero) potential between neutral and earth. When the neutral pole of a double-pole switch is opened, the voltage across this capacitance will suddenly increase, with a subsequent increase in neutral-to-earth capacitive earth leakage currents. This increase will be at a maximum if the neutral opens first and will be aggravated by arcing at both switch contacts which will cause high frequency voltage spikes to cause even higher
neutral-to-earth leakage currents.The effect may be aggravated further by the slow-break feature of the switch often found in domestic a.c. switchgear. Closing a double-pole switch may also trip an RCD (as may closing a single-pole switch), but in this case any tripping is unlikely to be caused by neutral-to-earth capacitance since the fast-make characteristic of the switch reduces both arcing and the time that any significant voltage might exist between the load-side neutral and earth. Any circuit, which
incorporates only single-pole switching, will never experience this type of problem since (under normal operating conditions) the neutral-to-earth voltage is so low that the neutral- to-earth capacitive earth leakage is negligible.
The problem appears to occur most frequently in installations where a separate consumer unit and RCD are installed. The opening of the consumer unit switch will allow a higher voltage (possibly 230V) to appear suddenly across the neutral-to-earth capacitance of the whole installation. This can result in sufficient earth fault current to trip the RCD. "
So it seems that if the cooker switch was just used as a single pole switch, with the neutrals permanently connected, it would have been fine. The individual switches on the socket outlets are single pole.
Do you know if the circuit is a radial or a ring circuit? Just interested to know if the ring was joined at the cooker switch to make a figure-of-eight circuit.
