There are several types of electrical protection systems, including but not limited to:
Overcurrent protection - detects and trips when the current exceeds a certain level.
Earth fault protection - detects and trips when a fault to earth occurs.
Distance protection - measures the impedance to earth of the power system and trips when the impedance exceeds a certain level.
Differential protection - compares the current flowing in and out of a protected zone and trips when the difference exceeds a certain level.
Voltage protection - detects and trips when the voltage exceeds a certain level.
Under/over frequency protection - detects and trips when the frequency deviates from the normal range.
Motor protection - detects and trips when the current or temperature of a motor exceeds a certain level.
Generator protection - detect and trips when the current, voltage or temperature of a generator exceeds a certain level.
Transformer protection - detect and trips when the temperature, current or voltage of a transformer exceeds a certain level.
Circuit breaker failure protection - detect and trips when a breaker fails to open or close when commanded.