Pilot Protection Relaying uses a communications channel (pilot channel) to provide coordination between the line protection relays. The relaying system is an advanced alternative to Step Distance Relaying which requires no communication and therefore manual coordination between relays.
So why should utilities use Pilot Protection Relaying? The relaying system trips only the faulted line section, allowing other sections to continue operating. It provides high speed simultaneous clearing for all internal lines faults and it prevents overtripping on external line faults. The relaying system also reduces transmission line damage.
Pilot Protection Relaying operates using teleprotection channels to send and receive pilot signals between line protection relays. It’s responsible for the communications of the pilot signals and the key fundamentals of pilot protection. The teleprotection system may be incorporated into microprocessor based relays which include communications and it can include a wide range of communication mediums and methods.
The Pilot Protection Relaying system operates through various communication methods including: pilot wire, powerline carrier (PLC), audio tone circuits (phone line), digital networks (T1, SONET, etc.), fiber optic, microwave and wireless radio.
There are three fundamental elements of pilot protection:
- Security – the ability to NOT false operate, in the presence of noise or bit errors
- Dependability – the ability to operate when a valid command exists, in the presence of noise or bit errors
- Operate Time (Latency) – the amount of time it takes for the system to operate, measured in milliseconds or cycles, from the keying of the local input to the closing of the remote output.