Protection schemes currently in use are:
1). Direct acting overload protection (being an integral part of a DC switchgear)
2). Timed over current relays
3). Inverse time over current relays
4). rate of rise relay (with or without delta I)
5). Thermal modelling relay
5). Under-voltage relay
6). Inter-tripping between adjacent substations (via either electric cable or fiber optic cable)
7). Load measurement relay
8). Reclosing relay
These schemes will need to be coordinated so that maximum protection can be achieved - hence the term of protection coordination.
