An alternator is said to be overexcited when it is operating at
Unity power factor
Leading power factor *
Lagging power factor
Either lagging or leading power factor
In an actual transformer the iron loss remains practically constant from no load to full load because
Value of transformation ratio remains constant
Permeability of transformer core remains constant
Core flux remains practically constant *
Primary voltage remains constant
When a blackout occurs what should be your first reaction ?
Inform the chief engineer *
Inform the bridge about the reason for blackout and expected time
Investigate the cause of black out
Cancel audible alarms
What safeties to be followed while working on high voltage ships ?
The clearance distances and the corresponding voltage to which the qualified person will work
Proper precautionary work techniques
Proper use of PPE
All of the above *
Power loss due to corona is directly proportional to
Radius of conductor
Supply frequency *
Spacing between conductors
None of these
Lower voltage systems supplied through transformers from high voltage systems are to be protected against over voltages. This means
Direct earthing of lower voltage system
Appropriate neutral voltage limiters
Both A and B *
None of the above
Lower voltage systems supplied through transformers from high voltage systems are protected against over voltages. This means
Direct earthing of lower voltage system
Appropriate neutral voltage limiters
Both A and B *
None of the above
When two diesels generator stes are running in parallel during your engine room watch, what does it simply ?
That both diesels have the same voltage and the same frequency *
That both diesels have the same load in KW same reactive load in KVAR same amperage
That both diesels are running the speed
That both diesels have exactly a 506 share of the active load in KW
In an induction motor, motor runs at a speed
Equal to the speed of stator field
Lower than the speed of stator field *
Higher than the speed of stator field
Having no relation with the speed of stator field
For liquid-cooled static converters, the following monitoring arrangements shall be provided in addition
Stand-by alarm of coolant pumps
Coolant conductivity
Coolant temperature
All of the above *
Which of the following is the best conductor ?
Copper
Aluminium
Silver *
Iron
Alternating current power is transmitted at high voltage
To safeguard against pilferage
To minimise transmission losses *
To reduce cost of generation
To make system more reliable
Fully partitioned switchboards all selections of a fully partitioned, air insulated high voltage switchboard shall be partitioned with respect to each other and the surrounding so that they are arc-resistant
True *
False
HV shore supply plug is inter locked with equipotential bonding of ship and shore
True *
False
Where the procedures involve the removal of circuit main earths, that is testing under sanction for the test the earths will be secured with working locks. The keys to these locks will be
Retained by the duty authorized person (HV) who will remove and replace the earth as requested gap *
Retained by the chief engineer
Retained by electro technical officer
Kept in safety locker
What are the hazards of Arc Flash ?
During an arc flash, sudden release of large amounts of heat and light energy takes place at he point of arc
Exposure frequently results in a variety of serious injuries and may even be fatal, even when the worker is ten feet or more from the arc cent
Equipment can suffer permanent damage
All of the above *
Incorporated in HV switch gear low-voltage compartments for control and monitoring systems shall be separated from the high voltage compartments in such a way as to render impossible any contact with parts having a rated supply voltage of more than 1000 V
True *
False
Addition earth on HV system is defined as an earth connection applied to apparatus after the application of a circuit main earth, normally applied at the point of work if not already fitted with circuit main earth
True *
False
Lower voltage systems supplied through transformers from high voltage systems are to be protected against over voltages. Thus may be achieved by
Direct earthing of lower voltage systems
Appropriate neutral voltage limiters
Both A and B *
None of the above
What happens in the arc extinction using high resistance method
Arc resistance is decreased with time
Arc resistance is increased with time *
No change it remains same
Arc resistance is kept zero
For the high voltage conductors at high pressures, if the voltage is positive then corona appears as a
Uniform bluish white sheath *
Reddish glowing spots
Uniform greenish spots
None of these
SF6 also has a high thermal heat capacity that can absorb the energy of the arc without much of a temperature rise
True *
False
The heat produced at the contact point owing to flow of electric current is least affected by _______
Temperature of the surrounding medium *
Contact resistance
Magnitude of electric current flowing
Duration of flow of current
In a circuit breaker, ionisation is facilitated by _____
Increase in field strength
Increase in mean free length
High temperature of the surrounding medium
All of the above *
If two alternators are running in proper synchronism and the voltage of one machine is suddenly increased
Both machine will stop
One machine will stop
Synchronising torque will be produced to restore further synchronism *
None of the above
In an alternator, when the load power factor is unity
The armature flux will be demagnetising
The armature flux will be cross magnetising *
The armature flux will reduce to zero
The armature flux will have square wave from
The most commonly used insulating materials for low and medium voltage cables is
Polyethylene
Porcelain
PVC *
Vulcanized rubber
For voltage measurements, the gap which gives highest accuracy is
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