Transmission and Distribution

By which of the following methods string efficiency can be improved?

A. Using a guard ring
B. Grading the insulator
C. Using long cross arm
D. Any of the above
E. None of the above

Owing to skin effect:

A. current flows through the half cross-section of the conductor
B. portion of the conductor near the surface carries more current and core of the conductor carries less current
C. portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent
D. any of the above
E. none of the above

Which of the following bus-bar schemes has the lowest cost?

A. Ring bus-bar scheme
B. Single bus-bar scheme
C. Breaker and a half scheme
D. Main and transfer scheme

In AC.S.R. conductors, the insulation between aluminium and steel conductors is_________?

A. insulin
B. bitumen
C. varnish
D. no insulation is required

A conductor, due to sag between two supports, takes the form of____________?

A. semi-circle
B. triangle
C. ellipse
D. catenary

Transmission voltage of 11 kV is normally used for distances up to_____km?

A. 20—25 km
B. 40—50 km
C. 60—70 km
D. 80—100 km

Short transmission line: 0-20 kv, 0-50 km.
Medium transmission line: 20-100 kv, 50-150 km.
Long transmission line: above 100 kv and 150 km

Which of the following characteristics should the line supports for transmission lines possess?

A. Low cost
B. High mechanical strength
C. Longer life
D. All of the above

Which of the following distribution systems is more reliable?

A. Radial system
B. Tree system
C. Ring main system
D. All are equally reliable

The steel used in steel cored conductors is usually__________?

A. alloy steel
B. stainless steel
C. mild steel
D. high speed steel
E. all of the above

Which of the following relays is used on long transmission lines?

A. Impedance relay
B. Mho’s relay
C. Reactance relay
D. None of the above