Surge voltage originate in power systems due to
A. lightning
B. switching operations
C. faults
D. any of the above
Ans d
Impulse testing of transformers is done to determine the ability of
A. bushings to withstand vibration
B. insulation to withstand transient voltages
C. windings to withstand voltage fluctuations
D. all of the above
Answer: Option B
Insulators for high voltage applications are tested for
A. power frequency tests
B. impulse tests
C. both (A) and (B) above
D. none of the above
Answer: Option C
Switching surge is
A. high voltage dc
B. high voltage ac
C. short duration transient voltage
D. hyperbolically dying voltage
Answer: Option C
surge diverters are
(A) non-linear resistors in series with spark gaps which act as fast switches
(B) arc quenching devices
(C) shunt reactors to limit the voltage rise due to Ferranti effect
(D) over-voltages of power frequency harmonics.
Answer: Option A
Impulse testing of transformers is done to determine the ability of
(A) bushings to withstand vibrations
(B) insulation to withstand transient voltages
(C) windings to withstand voltage fluctuations
(D) all of the above.
Answer: Option B
Surge voltage originate in power systems due to
(A) lightning
(B) switching operations
(C) faults
(D) any of the above.
Answer: Option D
Surge diverters are
(A) non-linear resistors in series with spark gaps which act as fast switches
(B) arc quenching devices
(C) shunt reactors to limit the voltage rise due to Ferranti effect
(D) over-voltages of power frequency harmonics.
Answer: Option A
Impulse testing of transformers is done using
a. Full wave standard impulse
b. Chopped wave standard impulse
c. Half wave standard impulse
d. Only (a) and (b)
Answer: Option D
The commonly used materials for HV insulation is
a. Paper-oil insulation
b. Polyester resin
c. Ceramic
d. PVC
Answer: Option a
The resin bonded paper bushings are designed to operate at a maximum radial stress of
a. 5 kV/cm
b. 10 kV/cm
c. 15 kV/cm
d. 20 kV/cm
Answer: Option D
Treeing phenomenon is observed in
a. Capacitors
b. Cables
c. Insulators
d. Only (a) and (b)
Answer: Option D
In Breakdown tests, the tests voltages required for these tests are usually of the order of
a. 0 10 kV
b. 20 50 kV
c. 50 100 kV
d. 100 200 kV
Answer: Option C
In routine tests, the cable is tested by applying an ac voltage of
a. 2 times the rated value
b. 2.5 times the rated value
c. 3 times the rated value
d. 3.5 times the rated value
Answer: Option B
At the instant of contact separation in asymmetrical tests, the dc component is
a. Equal to the ac component
b. Equal to the 50% of ac component
c. Greater than 50% of the ac component
d. Less than the 50% of the ac component
Answer: Option C
The voltage which produces the loss of dielectric strength of insulation is known as
a. Withstand voltage
b. Disruptive discharge voltage
c. Flashover voltage
d. Impulse voltage
Answer: Option B
For insulators and bushings of power transformers, circuit breakers and instrument transformers, the suitable materials is
a. Epoxy resin
b. Polyesters resins
c. Porcelain
d. Silicon rubber
Answer: Option C
The temperature limit for class F insulation is
a. 105°C
b. 120°C
c. 130°C
d. 155°C
Answer: Option D
The thermal breakdown stresses are
a. Lower under ac conditions than under dc condition
b. Greater under ac condition than dc condition
c. Equal in both condition
d. None of these
Answer: Option a
Most important tests conducted on isolators and circuit breakers are
a. voltage withstand test
b. short-circuit test
c. high voltage test
d. temperature rise test
Answer: Option b
Loss of charge method is used to determine
Insulation resistance
Dielectric constant
Loss factor-(tanδ)
Rate of charging of capacitor
Answer: Option a
Power supply used in resistivity measurements is
110 V
250 V
500 V
500 V to 2000 V
Answer: Option d
The peak value of lightning stoke current are of order
100 A
1000 A
10 to 100 KA
106 A
Answer: Option c
In order to limit the overvoltage developed on ground wires due to lightning strokes, tower footing resistance should be less than
25 Ω
1000 Ω
100 Ω
1 Ω
Answer: Option a
C-tan δ test on electric bushing is done using is done using
Impulse generator
High voltage Schering bridge
Power frequency cascade transformer unit
Resonant transformer
Answer: Option b
Fault location in an HV cable is done by
Voltage withstand test
Life test
Partial discharge scanning tests
Impulse test
Answer: Option c
Corona discharge is
An internal discharge
Surface discharge
A spark between conductors
Partial discharge around a high voltage conductor
Answer: Option d
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