A pilot protection scheme uses a set of forward-looking protection elements to detect line faults. For dependability, these elements must overreach the remote line terminal(s). Typical applications use overreaching phase and ground distance elements and zero- and negative-sequence directional overcurrent elements.
What is meant by pilot protection scheme?
Abstract: 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.
What are different types of pilot schemes?
There are four common pilot protection schemes for line protection used today: (1) Direct Underreaching Transfer Trip, (2) Permissive Overreaching Transfer Trip, (3) Direct Comparison Unblocking, and (4) Direct Comparison Blocking.
How does a pilot circuit work?
Theory is that when the pilot circuit is complete, an operating coil is energized, which closes the main contactor automatically and thus put ‘ON’ the motor driving the equipment. … A transformer in the gate end box gives supply to the pilot circuit. Typical values for pilot circuit voltage are 7.5 volts and 12 volts.
What is wire Pilot?
A pilot wire is a communication cable between the two relays located at diﬀerent. ends. Whenever a transmission line or equipment is to be protected by using a. diﬀerential relay, a wire is connected between the CTs (current transformer)
What is a pilot duty relay?
Resolution. A “Pilot Duty” rating means that this relay is made for a specific highly inductive load, such as controlling the coil of another relay or contactor. Contacts with a “Pilot Duty” rating have passed standardized testing to prove they can reliably control a “Pilot Duty” load.
What is the drawback of protection system?
Disadvantages: The downside was the challenge of installing and testing such a complicated scheme with the potential for mis-operation. I don’t recall any mis-operations occurring, but it was still a bit “dicey”.
What are the requirements of protection of lines?
The protection scheme must satisfy the following requirements: a) Under normal conditions the breakers are not tripped. b) Under fault conditions only the breakers closest to the fault on the source side are tripped. c) If the closest breaker fails to operate, the next breaker closer to the source should trip.
Why is carrier current protection?
Carrier current over the power line provides simultaneous tripping of circuit breakers at both ends of the line in one to three cycles. Thereby high speed fault clearing is obtained, which improves the power system stability. Besides, there are several other advantages of carrier-current protection.
Why is carrier current protection used?
Carrier-current protection is the most widely used scheme for the protection of Extra High Voltage (EHV) and Ultra High Voltage (UHV) power lines. The carrier signal is directly coupled to the power line itself which is to be protected.