Why do we have 2 different pin configurations for the plug in octal relays 2 pole double throw c/o contacts and what problems have these caused by plugging in and forgotten to check.

We use them a lot in our 33/11 kV substations for alarms and the like.

here in NZ Email relays have 3 - 6 to the coil.
European relays 2 - 7 to the coil.

The product of rotation, excitation and flux produces electricty.