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Transformer Internal Faults Transformer External Faults Transformer Cable Faults Transformer Bus Faults

The document discusses various topics related to electrical equipment protection devices including transformers, circuit breakers, relays, fuses, and earth electrodes. It covers the functions of Buchholz relays, insulation classes, vacuum pressure in vacuum circuit breakers, effects of open circuiting CTs, restriking and recovery voltages, uses of ELCBs, types of fuse wires, operation of IDMT relays, applications of vacuum circuit breakers, definitions of terms like PSM, characteristics of HRC fuses, optimum earth electrode resistance, devices for human electric shock protection, disadvantages of star-delta starters, components of numerical relays, protective devices in distribution transformers, uses of resistance switching in circuit breakers, ways to

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Nmg Kumar
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52 views4 pages

Transformer Internal Faults Transformer External Faults Transformer Cable Faults Transformer Bus Faults

The document discusses various topics related to electrical equipment protection devices including transformers, circuit breakers, relays, fuses, and earth electrodes. It covers the functions of Buchholz relays, insulation classes, vacuum pressure in vacuum circuit breakers, effects of open circuiting CTs, restriking and recovery voltages, uses of ELCBs, types of fuse wires, operation of IDMT relays, applications of vacuum circuit breakers, definitions of terms like PSM, characteristics of HRC fuses, optimum earth electrode resistance, devices for human electric shock protection, disadvantages of star-delta starters, components of numerical relays, protective devices in distribution transformers, uses of resistance switching in circuit breakers, ways to

Uploaded by

Nmg Kumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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1.

Buchholz Relay is used for sensing *


Transformer internal faults
Transformer external faults
Transformer cable faults
transformer bus faults

2. Insulation class F means the maximum temperature withstanding


capability of insulation confines to *
155 deg C
90 deg C
180 deg C
greater than 180 deg C

3. The vacuum pressure inside vacuum interrupter of a Vacuum Circuit


Breaker (VCB) would be *
100 mm of water column
76 cm of mercury
10-7 torr
1 bar

4. CT should never be open circuited because of *


high current in the primary
high voltage in the secondary
high current in secondary
none of these

5. Restriking voltage appearing across circuit breaker contacts during fault


current interruption will be of *
stable nature
transient nature
steady state RMS value
none of these

6. Recovery voltage appearing across circuit breaker contacts after fault


interruption will be *
RMS system voltage
transient voltage
high frequency voltage
50Hz high voltage

7. ELCBs are used to protect *


from heavy short circuits
from low earth fault currents
from electromagnetic interference
from over voltages

8. Rewirable fuse wires are also known as *


HBC fuse
HRC fuse
Kit Kat fuse
drop out fuse

9. The IDMTL relay plug setting is 5A, its TMS setting is 0.7. When a current
of 5A is passed through the electromagnet of the IDMTL relay, the relay
operating time would be *
3 sec
1 sec
will not operate
instantaneous

10. Vacuum circuit breakers are used up to *


33kV rating
above 66kV rating
above 110kV rating
above 220kV rating

11. PSM in an IDMTL relay means *


Fault current in relay coil / pick up value
pick up value / fault current in relay coil
rated current / fault current
fault current / rated current

12. HRC fuse has *


cut off characteristics
inverse characteristics
Reliability and discrimination
all of these

13.The best earth electrode resistance will be *


0.5 to 2 ohms
10 0hms
100 meg ohms
infinite value

14. The type of device used to protect human beings from electric shock *
MCB
MCCB
RCCB
MPCB

15. Disadvantages of star delta starter *


low starting torque
break in supply
six terminals in motor are required
all of these

16. The numerical relay requires *


hardware architecture
relay operating system software
all of these
none of these

17. Type of protective devices in a distribution transformer *


winding temperature gauge
oil temperature gauge
Buchholz relay
pressure vent
all of these

18. Resistance switching in circuit breakers are used to *


damp out restriking voltage
damp out recovery voltage
to improve power factor
to reduce arc impact

19. Arc in a circuit breaker can be quenched by *


lengthening the arc
splitting the arc
constraining the arc
all of these

20. Space heaters inside circuit breaker cubicle are used to *
avoid moisture condensation inside
heat up breaker contact assembly
quench arc during contact separation
to maintain vacuum pressure inside

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