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7EE3 SWITCHGEAR
& PROTECTION
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INTRODUCTION:
Causes and consequences of dangerous currents; fault over
loads and switching over currents. Basic idea of an over current relay as a
level detector selectivity, discrimination sensitivity reliability of relay
fastness of operation. Upper and lower limits for the time of relay operation
current grading Time grading and inverse time operation. Primary and backup
protection. Pickup and reset values.
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CONSTRUCTION AND OPERATION OF
RELAY: construction and operation of
electromagnetic over current and directional relays. Directional element to be
realized from rectifier bridge circuits. Connection of directional element and
their operating characteristics. Directional relay connections 30 deg,60 deg
and 90 deg. connections Directional Earth fault relay. Directional Relay
connections 30 deg, 60 deg and 90 deg connections. Directional earth fault
relay.
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DISTANCE PROTECTION OF TRANSMISSION LINES:
Construction and characteristics
of impedance relay, C.T. and P.T. connection for performance Reactance and mho
relay characteristics Transmission line protection.
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CARRIER CURRENT PROTECTION OF TRANSMISSION LINES: Basic apparatus used for
power line carrier system. Principle of operation of directional comparison
and phase comparison carrier protection, carrier assisted distance protection.
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PROTECTION OF SYNCHRONOUS GENERATORS AND TRANSFORMERS: faults in stator
winding of alternators, differential protection Effect of resistance in the
star point earthling single and multiple ground faults on the rotor. Protection
against excitation failure and prime mover failure. Negative sequence
protection. Differential protection of generator transformer unit.
Differential protection of 3-phase transformers; effect of magnetizing inrush
currents, methods for minimizing the effects. Beholds protection. CT
connections.
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BUS BAR PROTECTION:
Frame leakage and circulating current protection.
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CIRCUIT BREAKERS: Electric are, are characteristics, theories of current
interruption, energy balance and recovery rate theory, transient recovery voltage
in simple three phase circuits, rate of rise of restricting voltage, resistance
switching, current chopping, interruption of capacitive currents circuit breaker
ratings, practical systems of are quenching in air and oil. Construction and
operation of bulk oil, minimum oil and air blast circuit breakers. Recent
trends in HV circuit breakers, sulpher hexa fluoride,vacuum circuit
breakers, principle of DC circuit breaking, testing of circuit breakers.
RECOMMENDED BOOKS:
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M Chander: Switchgear protection 2. S S Rao:Switchgear & protection
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T M S Rao: Static Relays
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