Consider the following statements: In the case of suspension-type insulators, the string efficiency can be improved by
1. Using a longer cross-arm
2. Using a guard ring.
3. Grading the insulator discs
4. Reducing the cross-arm length
Of these statements
Match List-I (Type of relay) with List-II (For the protection of) and select the correct answer using the given below the lists:
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In connection with arc the extinction in circuit breaker, resistance switching is employed where in a resistance is placed in parallel with the poles of the circuit breaker as shown in the figure. This process introduces damping in the LC circuit. For critical damping, the value of 'R' should be equal to
Consider the following moderators used in nuclear reactors:
1. Graphite 2. Beryllium
3. Heavy water
Their correct sequence in increasing order of their neutron absorption cross sections is
Match List-I with List-II and select the correct answer using the given below the lists:
lighting arrestor connected between the line and earth in a power system
Corona loss can be reduced by the use of follow conductors, because
While using air-blast circuit beaker, current chopping is a phenomenon often observed when
In a power station the cost of generation of power reduces most effectively when
Consider the following statement: Distance relays used for protection of transmission line might operate undesirable due to
1. magnetizing-current in rush
2. Power swings
3. Series compensating capacitors
4. Switching over voltage
Of these statements
The number of discs in a string of insulators for 400 kV ac overhead transmission line lies in the range of
The insulation resistance of a single -core cable is 200 MW/ km.The insulation resistance for 5 km length is
Consider the following statements:
1. By using bundle conductors is an overhead line, the corona loss is reduced
2. By using bundle conductors, the inductance of transmission line increase and capacitance reduces.
3. Corona loss causes interference in adjoining communication lines.
What of these statement are correct ?
Which one of the following sequences of operation represents the rated operating duty cycle of a circuit breaker? (O-open; C-close; t= 3 sec; T=3min)
A2-phase circuit breaker is rated at 2000 MVA. 33kV; its making current will be
The most accurate and versatile method of achieving reactive power compensation is by using
If the positive, negative and zero-sequence reactance's of an element of a power system are 0.3, 0.3 and 0.8 respectively, then the element would be a
Disruptive corona begins in smooth cylindrical conductors in air at NTP if the electric field intensity at the conductor surface goes up to
If the inductance and capacitance of power system are respectively 1 H and 0.01mF and the instantaneous value of interrupted current is 10 A, then the voltage across the breaker contact will be
For successful parallel operation of two singlephase transformers, the most essential condition is that their
Arrange the following in the correct sequence in which the flue gas passes through them after coming out of the boiler in thermal power station:
1. I.D. Fan.
2. Air Preheater
3. Economizer
4. Electrostatic precipitator
Select the correct answer using the codes given below:Codes: