mohammad farman


{ City } delhi
< Country > india
* Profession * sr.electrical engineer
User No # 45702
Total Questions Posted # 3
Total Answers Posted # 21

Total Answers Posted for My Questions # 3
Total Views for My Questions # 9607

Users Marked my Answers as Correct # 159
Users Marked my Answers as Wrong # 112
Questions / { mohammad farman }
Questions Answers Category Views Company eMail

How do i calculate sizing of transformer on didstrubution load for high rise building.What should be MVA Rating of MV Panel feding by 122 kv.

 2 Electrical Engineering 5017

(1)For 3 No 1500 KVA transformer require on one single bus bar or need to be section through bus coupler means upto 3MVA.(2) 22KV Net work system as ring, How maney I/C required or 0ne I/C and one O/G.(3) What should be rating of VCB for 22 KV line.(4)Electrical/mechanical inter lock, why we need.

 Electrical Engineering 1621

Off-circuit Tap changers in distribution transformer required

 1 Electrical Engineering 2969



Answers / { mohammad farman }

Question { Assam Electricals, 99181 }

what is the purpose of NGR?


Answer

NGR; means Neutral Grounding Resistor, it used to limit the
fault current where rotating parts directly connected.

Is This Answer Correct ?    5 Yes 21 No

Question { Siemens, 168111 }

how to choose the cable rating for load (KW)? EXAMPLE.50KW load


Answer

Fisrt calcultate Load in Ampere as basic formula below

I (Amp ) = P ( KW) / 1.732*Voltage (400 or 415 or 380 )*
p.f

Voltage depend on frequency rating (50 Hz or 60 Hz)
then check where you have to laid in AIR or Ground
you have to consider so many factor.
suppose you laid in Ground then factor to be consider as
below
(1) Soil Thermal Rseistivity
(2) Group factor
(3)Rating factor of ground temprature
(4)Rating Factor depth of laying

then calculte Voltage drop on behalf of amper rating by
load.
once you calculate then check length

V.D = mv x I X L/1000 OR mv =V.D X 1000/IXL

VD= Maximum acceptable volt drop (in volt)
mv =appropriate volt drop (in mv /amp /metre
I = Current per phase (in ampere)
L= Length ( in meter)

Is This Answer Correct ?    50 Yes 15 No


Question { Suzlon, 65316 }

what do you mean by leading power factor & lagging power
factor


Answer

Leading power factor means current can lead by voltage and
always use for induction motor.

lagging power factor means caurrent lag by voltage and
alway use for improving power factor for office where we
need to improve power factor and get lost cost effect.

Is This Answer Correct ?    2 Yes 17 No

Question { 64369 }

Explain RYB?


Answer

R=RED PHASE
Y=YELLOW PHASE
B=BLUE PHASE

why this Configuration say in Electrical Distribution to
make easy under stand for phase in 3 line. other wise for
distribution in line from transformer always use

U= RED PHASE
V= YELLOW PHASE
W= BLUE PHASE

Is This Answer Correct ?    34 Yes 17 No

Question { 64369 }

Explain RYB?


Answer

RYB , Is absolutly three phase funtion in electrical system
to make from right to left as phase balance. RED ,YELLOW,
BLUE only can use for phase not for other . i know there is
confusion between "B" use for Black as neutral so, as per
IEC for neutral confusion using small "b". i hope you will
make sure about phase angle 120 anlge apart from each to
have balance phase.

Is This Answer Correct ?    25 Yes 2 No

Question { 7112 }

Why only mesh earthing is used in G.S.S.?


Answer

Because of reducing resistance , other touch and step
voltage to be reduce, once fault happens then get maximum
ways to go into ground

Is This Answer Correct ?    1 Yes 0 No

Question { Power Grid, 4599 }

what is the order of mgnetiation current in a current
transformer of 1000A/1A ratio?


Answer

same as per load ratio

Is This Answer Correct ?    0 Yes 4 No

Question { 6632 }

when a primary current injection test is required, it is
accomplished by what?


Answer

Primary current injection test require at time of
commissioning to distrubution switchgear.High pot theory.

Is This Answer Correct ?    3 Yes 0 No

Question { TATA, 4629 }

how to prepare PPM schudule


Answer

PPM Schedule prepare by project portfolio management and
check length of schedule of project.

Is This Answer Correct ?    0 Yes 5 No

Question { L&T, 12146 }

IF i have switchgear with busbar current rating of 1000Amp
35kA then is it necessary to have outgoing breaker kA rating
to be equal to busbar kA rating?


Answer

Not Necessary,depend upon your system means you are going
to use same KA rating for reactive power or normal power.if
you are using for reactive power then you hava to have same
KA rating of BB.however, you can check for normal load.

Is This Answer Correct ?    0 Yes 3 No

Question { Crompton Greaves, 22967 }

what is the purpose of battery tap voltage.


Answer

to boost up the power

Is This Answer Correct ?    4 Yes 2 No

Question { 8025 }

practically What is power factor



Answer

Power factor is ratio of KW/KVA.

POWER FACTOR IS LAWYAS LAGGING

Is This Answer Correct ?    6 Yes 1 No

Question { 5796 }

What is VCB'S @ ACB'S.Plz explain Briefly


Answer

While opening and closing the breaker the arc occures
between the contacts of the breaker. To resist the arc and
to protect contacts some arc quenching medium is used. In
ACB air and in VCB vaccume is used as arc quenching medium.

VCB= VACUUM CIRCUIT BREAKER and use for medium voltage
RATING 630A to 1250 A

ACB= Air circuit Breaker and use for LV side from 1600A to
3200A.

Is This Answer Correct ?    4 Yes 1 No

Question { 6121 }

MICOM P122 OC/EF RELAY HAVE HARMONIC RESTRAIN OR NOT?


Answer

MICOM P122 OC /EF relay have harmonic restrain because this
relay use in package unit for infrastructure use.

Is This Answer Correct ?    4 Yes 2 No

Question { 4853 }

do we need NGR panel when the output of the genset is LV
but after that it is step up to 22 kv. condition is 12
genset 400v are operating in parallel.


Answer

yes, this is required

Is This Answer Correct ?    0 Yes 1 No

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