Interview Questions Answers in Electrical Engineering

Questions / { ram niveth }

Questions Answers Category Views Company eMail

in trains i have seen the terminal which is connected at the top of the train is positive .where is negative ? track? i dont think so

9 Electrical Engineering 8383

In 110V DC supply,if a closed circuit gets open, How can we identify the voltage which is measured after the resistor(4KOhm) which is open with negative.it shows 55V +ve when measured, also the actual positive source is 55V +ve .Because there is no voltage drop in open circuit. How can we identify whether this is the voltage which is series with the resistor or the DC source direct +ve.

GE,

1 Electrical Engineering 3626

Answers / { ram niveth }

Question { ABC, 9453 }

What is mean by CT Saturate? how do we calculate?

Answer

when we apply voltage between the secondary upto certain
limit it draws some mA exactly at the knee point the mA
will be double and if we cross the knee point then the CT
gets Saturated.
any of these effects are possible:
1.angle error
2.ratio error
3.secondary gets open
4.secondary simply acts as a conductor showing no ratio

Is This Answer Correct ?

1 Yes

5 No

Question { 15716 }

what happen "when Dyn11 is parallel operation with Dyn1"?

Answer

dear Murali
my reference is from oxford university from book
name "Automated Technology for verification and analysis"
"http://books.google.co.in/books?
id=LbfOjdII174C&pg=PA111&dq=transformers+oxford+university#P
PA111,M1"

Is This Answer Correct ?

1 Yes

1 No

Question { 6215 }

how dc ct works?

Answer

there is no CT to sense DC current

but it can be sensed by using two sets of rectifier units
placing one input to primary side of transformer and the
other in secondary side of the transformer.

but this is too expensive

Is This Answer Correct ?

1 Yes

5 No

Question { KSK Energy, 69046 }

what is the diff. b/w restricted earth fault relay &
standby earthfault relay and where they are used?

Answer

i agrre with this answer with little correction
Standby Earth Fault relay is also connected to star side

the difference between SEF and REF is REF operates in
InZone only
SEF operates in In and Out Zones. If there is an earth
fault in outgoing feeders and the feeder protection is not
operated then SEF operates .
Tripping time for SEF will be more than REF and Earth fault
protection in O/G feeders.

Is This Answer Correct ?

112 Yes

11 No

Question { 6528 }

What is the secondry voltage of 420kV Current Transformer ,
the rated current is 2600A

Answer

There is no Current Transformer 420kV

Is This Answer Correct ?

1 Yes

3 No

Question { BSNL, 144499 }

how to check the earth resistance value& what is the
minimum earth resistance for good earthing sysytem.

Answer

as per the IEEE standards it should be less than 1 Ohms

Is This Answer Correct ?

186 Yes

37 No

Question { 24961 }

why the power cut problems occur in tamil nadu?
may i know the exact reason.plz

Answer

hello Mr.sennapparajan are you sure that our TNEB dont have
talented engineers . have you ever read the book issued by
TNEB engineers for "testing ,commissioning and maintanance
of electrical equpments" which is used all over the India.

coming to the question we require more power but we are not
generating as much power we consume .as the generation is
low they are making backups by powercut.
but the places for frequent powercut is not an electrical
related issue

Is This Answer Correct ?

71 Yes

19 No

Question { 6244 }

what is the fuction of electrical transducer in control
pannel?

Answer

transducer is a device which gives initially 4mA when
auxiliary supply is given and depending upon the input it
varies from 4mA to 20mA. usually this will be sent to
remote like DCS .
i have seen voltage transducer and current transducers
practically with this design

Is This Answer Correct ?

4 Yes

2 No

Question { 9720 }

Which transformer is suitable for 220/11 kV, 60 MVA,
distribution , Y-Y or D-Y or Y-D, give comparison for the
same.

Answer

if you are transmitting 11KV use (220KV)D-Y(11KV)
if you are transmitting 220KV use(220KV)Y-D(11KV)
because we have to provide return path to sense earth fault

Is This Answer Correct ?

2 Yes

1 No

Question { 39661 }

what is the diff between earth leakage relay and earth
fault relay?

Answer

both are same

Is This Answer Correct ?

8 Yes

21 No

Question { Essar, 29949 }

Shall we get electrical shock if we touch the positive
terminal of a 230 volt dc supply?

Answer

in DC voltage there are two types of distribution negative
earthed and negative unearthed
in negative earthed system you will get shock and if
neutral is unearthed you will never get shock unless you
touch the negative at the same time

you can easily idetify whether the distribution is earthed
or unearthed by measuring voltage the positive with respect
to earth. if it shows some voltage it is negative earthed
system

Is This Answer Correct ?

1 Yes

2 No

Question { 4348 }

what happen to the voltage and current in all phases when an
earth fault occur in a phase in three phase three wire
system(delta connected)...

Answer

the usual procedure for transmission is star to delta

for ex: 220KV/33KV
if they transmit 33KV then 33KV will be in star side and
vice versa

in this case say a delta is transmitted and gets an earth
fault .Zero sequence current will be flowing only in the
transformer .
fault current of phase which gets earthed with earth will
be almost zero .because no return path .
voltage becomes zero for the fault phase and the other two
healthy phases voltage gets root three times incresed which
may affect the whole system

Is This Answer Correct ?

3 Yes

0 No

Question { 7597 }

what is H.T?specify the range?

Answer

Low Tension L.T-415V
Medium Tension M.T-3.3KV
High Tension H.T-6.6KV
Extra High Tension E.H.T-11KV and above

Is This Answer Correct ?

5 Yes

10 No

Question { Gold Fields, 7204 }

how to check dc current,how to fix ammeter in dc line

Answer

no other way other than putting meter in series

Is This Answer Correct ?

4 Yes

0 No

Question { 16912 }

How do you think they do earthing or grounding in ships and
aeroplanes?

Answer

neutral is connected to the body of aircraft/ship.so body
is considered as earth for sensing earth fault

Is This Answer Correct ?

14 Yes

13 No