Question: jCorona usually occurs when the electrostatic stress in air around the conductor exceeds?

• 1. 6.6 kV (r.m.s. value)/cm
• 2. 11 kV (r.m.s. value)/cm
• 3. 22 kV (maximum value)/cm
• 4. 30 kV (maximum value)/cm

Question: In a substation the following equipment is not installed?

• 1. exciters
• 2. series capacitors
• 3. shunt reactors
• 4. voltatre transformers

Question: For which of the following equipment current rating is not necessary?

• 1. Circuit breakers
• 2. Isolators
• 3. Load break switch
• 4. Circuit breakers and load break switches

Question: A circuit is disconnected by isolators when____________?

• 1. line is energized
• 2. there is no current in the line
• 3. line is on full load
• 4. circuit breaker is not open

Question: By which of the following a bus-bar is rated?

• 1. Current only
• 2. Current and voltage
• 3. Current, voltage and frequency
• 4. Current, voltage, frequency and short time current

Question: In aluminium conductors, steel core is provided to____________?

• 1. compensate for skin effect
• 2. neutralise proximity effect
• 3. reduce line inductance
• 4. increase the tensile strength

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

• 1. Using a guard ring
• 2. Grading the insulator
• 3. Using long cross arm
• 4. Any of the above

Question: Owing to skin effect:

• 1. current flows through the half cross-section of the conductor
• 2. portion of the conductor near the surface carries more current and core of the conductor carries less current
• 3. portion of the conductor near the surface carries less current and core of the conductor carries more cur¬rent
• 4. any of the above

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

• 1. Ring bus-bar scheme
• 2. Single bus-bar scheme
• 3. Breaker and a half scheme
• 4. Main and transfer scheme

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

• 1. insulin
• 2. bitumen
• 3. varnish
• 4. no insulation is required