The key components used for the protection of motors are described in the section 02.09.16.00 entitled motor and starter protection.
Any motor protection device that detects a fault must de-energise the starter’s contactor(s) and the circuit must be so arranged that the starter’s contactor(s) cannot be re-energised until the fault detecting device has been manually reset and then the fault circuit manually reset.
Fault detecting devices must not automatically reset or be capable of being remotely reset, the reason for this is that plant operators tend to be motivated by production targets and will quite happily restart a motor if its trip system resets automatically or where they have access to a reset button, without any consideration being given to the reason for the trip, maintenance engineers adopt a more measured and sensible approach and always look for the reason for the trip and will correct the fault as necessary before resetting the trip device and control system.