Pilot relaying schemes are used for the protection of

The correct answer is 'option 4'

Concept:

• Pilot relaying refers to any relaying scheme employing a communication network between relays, at different substations, to transmit a “trip or don’t trip” signal. The intent here is to trip the circuit breakers as fast as possible.
• Pilot protection schemes use communication channels to send information from the local relay terminal to the remote relay terminal, thereby allowing high-speed tripping for faults occurring within 100% of the protected line.

 Additional InformationWhy pilot relay is used?

• Faster fault clearing time
• When compared to no pilot channel, the protection scheme exhibits increased security and dependability
• Enables high speed reclosing
• Simplifies relay coordination