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A high impedance bus bar relay uses summed CTs from multiple breakers into a high resistance to determine a fault condition. Since all CTs connect to a single input on the relay, the relay cannot determine if a valid fault condition has occured, or one of the CTs is disconnected (open circuited). External CT supervision must be supplied to confirm.
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What is function of mho relay?
OFFSET IMPEDANCE RELAYOffset impedance relay is also known under names ADMITTANCE RELAY or MHO RELAY
What is difference between high impedance busbar protection scheme and low impedance busbar protection scheme?
high impedance circit provides a varistor unit which has stabilising resistor which ll protect the relay from being operating for maloperations like through fault, CT faults whereas this varistor unit is provided internally in an numerical relay where the CT of class 5P can be used.
What is instantaneous over current relay?
Instantaneous over current relay, which operates very fast with no intentional time delay and the operating time of these relay can be as low as 0.01sec . These relay operates only when the impedance between the relay and the source zsis very small compared to the impedance to the impedance of the protected section zl .
How relay used for protection purpose?
Relay are operated by small current /voltage connected to Secondary side of Current Transformer and /or Voltage Transformer. The signal stimulates the magnetic substance nearby with the attracting force. This closes or opens the circuit being used in protection purpose.
What is difference between reverse power relay and directional relay in electrical protection?
A reverse power relay is a directional overcurrent relay. Directional relays are relays that sense power flow in one direction, and include (directional) overcurrent relays, reverse power, and impedance based relays. So a reverse power relay is a directional relay, but a directional relay is not necessarily a reverse power relay.
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 distance protection Relay work?
Well any type of relay protection is extremely complicated any many people will spend their whole career learning about protection and control. But a distance relay essentialy looks at the impedance of the circuit to be protected. When a fault occurs the impedance of the circuit will change. It then calculates this new impedance to determine where the fault has occurred. By knowing where the fault is it can trip appropriate CB's to isolate the faulted section.
What is function of mho relay?
OFFSET IMPEDANCE RELAYOffset impedance relay is also known under names ADMITTANCE RELAY or MHO RELAY
What is difference between high impedance busbar protection scheme and low impedance busbar protection scheme?
high impedance circit provides a varistor unit which has stabilising resistor which ll protect the relay from being operating for maloperations like through fault, CT faults whereas this varistor unit is provided internally in an numerical relay where the CT of class 5P can be used.
What is Trip circuit supervision?
Trip circuit supervision is defined as the protection equipment which monitors the continuity of the trip circuits of a circuit-breaker. The trip circuit supervision relay will monitor the proper functioning of trip circuits.
Why impedance relay is called as distance relay?
because the distance is propotional to the impedance of the line ,so the operation of the impedance relay comes into picture when the impedance seen by the relay is less than the pre-setting value.When a fault occurs ,the current increases to a high value and so the Impedence decreases and the relay actuates
What is instantaneous over current relay?
Instantaneous over current relay, which operates very fast with no intentional time delay and the operating time of these relay can be as low as 0.01sec . These relay operates only when the impedance between the relay and the source zsis very small compared to the impedance to the impedance of the protected section zl .
How relay used for protection purpose?
Relay are operated by small current /voltage connected to Secondary side of Current Transformer and /or Voltage Transformer. The signal stimulates the magnetic substance nearby with the attracting force. This closes or opens the circuit being used in protection purpose.
What is distance really?
The most common form of protection on high voltage transmission systems is distance relay protection. Power lines have set impedance per kilometre and using this value and comparing voltage and current the distance to a fault can be determined. The ANSI standard device number for a distance relay is 21
What is difference between reverse power relay and directional relay in electrical protection?
A reverse power relay is a directional overcurrent relay. Directional relays are relays that sense power flow in one direction, and include (directional) overcurrent relays, reverse power, and impedance based relays. So a reverse power relay is a directional relay, but a directional relay is not necessarily a reverse power relay.
What is pilot wire supervision relay?
11
Is feeder protection relay and ring main unit protection relay same?
No there not same
