14-08-2012, 02:56 PM
Relays Of Modern Power Plant
[attachment=31505]
What is Relay ?
A relay is automatic device which senses as abnormal condition in an electric condition in an electric circuit and close its contacts. These contacts in turn close the circuit breaker trip coil circuit, thereby it opens the circuit breaker and the faulty part of the electric circuit is disconnected from the rest of the healthy circuit.
Why relay is important ?
The capital investment involved in a power system for the generation, transmission and distribution of electrical power is so great that proper precautions must be taken to ensure that the equipment not only operates as nearly as possible to peak efficiency, but also that it is protected from accidents.
TRANSFORMER PROTECTION:
Transformers are a critical and expensive component of the power system. Due to the long lead time for repair of and replacement of transformers, a major goal of transformer protection is limiting the damage to a faulted transformer.
BUSBAR FAULTS:
The majority of bus faults involve one phase and earth , but faults arise from many causes and a significant number are interphase clear of earth. In fact, a large proportion of bus-bar faults result from human error
rather than the failure of switchgear components.
With fully phase-segregated metalclad gear, only earth faults are possible, and a protection scheme need have earth fault sensitivity only. In other cases, an ability to respond to phase faults clear of earth is an advantage, although the phase fault sensitivity need not be very high.
[attachment=31505]
What is Relay ?
A relay is automatic device which senses as abnormal condition in an electric condition in an electric circuit and close its contacts. These contacts in turn close the circuit breaker trip coil circuit, thereby it opens the circuit breaker and the faulty part of the electric circuit is disconnected from the rest of the healthy circuit.
Why relay is important ?
The capital investment involved in a power system for the generation, transmission and distribution of electrical power is so great that proper precautions must be taken to ensure that the equipment not only operates as nearly as possible to peak efficiency, but also that it is protected from accidents.
TRANSFORMER PROTECTION:
Transformers are a critical and expensive component of the power system. Due to the long lead time for repair of and replacement of transformers, a major goal of transformer protection is limiting the damage to a faulted transformer.
BUSBAR FAULTS:
The majority of bus faults involve one phase and earth , but faults arise from many causes and a significant number are interphase clear of earth. In fact, a large proportion of bus-bar faults result from human error
rather than the failure of switchgear components.
With fully phase-segregated metalclad gear, only earth faults are possible, and a protection scheme need have earth fault sensitivity only. In other cases, an ability to respond to phase faults clear of earth is an advantage, although the phase fault sensitivity need not be very high.