0
Still curious? Ask our experts.
Chat with our AI personalities
Coach
Professor
JudyAdd your answer:
Earn +20 pts
Why current transformers are required in protective relaying scheme?
Current transformers (CTs) are used to monitor the current (or lack of) in high-voltage systems, and their secondary outputs controls the behaviour of protection-system relays. The CTs (1) reduce the current to values that match the current ratings of the protective relays, and (2) electrically-isolate the relays from the high-voltage system.
What is an impedance relay?
Impedance relays are used whenever over-current relays do not provide adequate protection. They function even if the short circuit current is relatively low. The speed of operation is independent of current magnitude. Impedance relays monitor the impedance between the relay location and the fault. If the impedance falls within the relay setting, the relay will operate. The basic construction for impedance relays on which the principle of operation is easily explained is the balanced beam.
How does a transformer protect an appliance?
Normally current transformers are used for two things . For measuring and protection. Whenever the CT is a protection CT it will be connected with the protection relays and there will be setting in the relays based on our requirement. when the current pass through the relays are more than the setting range then relay will send the tripping signal to the breaker available in the system to isolate the fault section. Finally the CT is not protecting the system. it will transfer the high primary current from the system to relay as small secondary current.
What is a holding relay?
Latching relays have no default position and remain in their last position when the drive current stops.
What is the difference between diffrencial relay and a distance relay?
They're completely different, used for different applications (usually). A distance relay uses both current and voltage. A differential relay uses only current. A differential relay usually has harmonic restraint capability, while distance relays ideally track system frequency. Differential relays require fast operation, while distance relays may not be required to operate as quickly. Distance relays have more issues with operating for out of zone problems than differential relays. There are many more, but this gives an idea.
