Definition of the protection system
This step includes a selection of the protection components and a consistent, overall structure suited to the power system. The protection system is made up of a string of devices including the following:
1. Measurement sensors (current and voltage) supplying the data required to detect faults,
2. Protection relays in charge of continuously monitoring the electrical status of the power system up to and including the formulation and emission of orders to the trip circuit to clear the faulty parts,
3. Switchgear in charge of clearing faults, such as circuit breakers or combinations of switches or contactors and fuses.
The protection-system study determines the devices to be used to protect against the main faults affecting the power system and the machines:
1. Phase-to-phase and phase-to-earth short-circuits,
3. Faults specific to rotating-machines.
The protection-system study must take the following parameters into account:
1. Power system architecture and size, as well as the various operating modes,
2. The neutral-earthing systems,
3. The characteristics of current sources and their contributions in the event of a fault,
4. The types of loads,
5. The need for continuity of service