Question { 30488 }

what is a relay?

Answer

Relay is a kind of Electromechanical object which sence the
perameter for which it is designed , compare with the
desired & act according to that

Question { ABB, 31400 }

What is the meaning of TRI Vector meter?

Answer

The meter which shows 1. Active power, 2. Reactive Power
3. Apprent power called a Tri vector meter.

Question { NTPC, 5767 }

wat are the transmission losses.... how can it be
compensated.......
wat s power system.......

Answer

The transmission losses is the diffrence between the Actual
load is transfered from Generating station & the quantum
of energy received at the receving sub station . this
losses is because of the I^2* R losses of the conductor for
transmission. & also the Copper & Iron Losses in the
transformer side. This losses can not be get down to zero
but can be reduce Eddy current losses in transfomer by
using thin lamination & at the transmission end by using a
High voltage transmission because as the voltage is high
the curret will be low & also the losses.

Question { 8101 }

What will happen if we parallel two transformer with
different %impedace?

Answer

While running parell both transformer will not share load
equally

Question { CA, 11100 }

HOW TO CALCULATE THE CABLE SIZE FOR POWER CABLE, CONTROL
CABLE AND INSTRUMENT CABLE

Answer

The size is based on the two factors the lengh ( as the
length will be high the voltage drop will increase )of the
two point & the load current to be flow from the cable .

Question { NTPC, 20355 }

what is pole slip ?

Answer

As the three phase power is givan to the motor the
mangnatic field is devloped in the winding & it starts
rotating at synchronus speed. the mangnatic field devloed
is cut by the rotor winding & force is applied on to the
winding & rotor srats rotating. generally rotor should run
with the speed of ,amgnatic field but due to load generally
it does not happen & rotor speed is just legs to the speed
of mangnatic field this diffrence is called a pole slip

Question { NTPC, 23513 }

what are the types of sus station ?

Answer

Here are the diffrent kind of substation.
1. Step up / step down substation
2. Power factor improvement substation
3. frequrecy changing sub-station
4. HVDC substation.
5. Outdoor substation
6. Indoor Substation
7. Grid Station ( Regional , National )

Question { 4061 }

Dear sir/mam
Iwant complete details of Naintenence of 33kv/433v
Transformer having 1250 KVa

Answer

Dear friend,

In routing maintenance you should take care of the
following .

Daily .

1. Percentage loading of a transfomer
2. Make sure the bucholze realy is full with oil no inert
gas is there if there then purge the same.
3. Check the record the Reading of OT & WT
4. Check manualy for any leakage from any part of the
transformer.
5. Check for any abnormal heating & noice in transformer.


Quarterly.

1. Check & change the silica gel of the breather .
2. Check teh Safety function tripping of HT breaker related
to transformer. ( tripping point of OT , WT & Tranfomer )

Annualy.

1. Check & fillter the Trasformer oil
2. with complete shut down take the reading of insulation
resistance of the transformer winding.
3. Open & check the condition of transformer HT & LT
bushing for any cracks or damage.
4. Chceck the condition of the earthing pit & take the
earthing resistance value for all the earthing pit (
Neutral & Body earth )

Do the same as directed & have a trouble free operation of
the transformer for a long period of time

Question { 10413 }

Hi,
We facing one similar problem in our computers i.e we are
newly constructed our design department after that shifted
our computers but our computer desktop screen is vibrating.
we are conducted our electrical maintainance person he told
that is UPS problem, then we changed the UPS also again we
are facing that problem in that room only. then we put lcd
monitors that problem is solved. But in other monitors why
the computer desktop screen is vibrating please give a
suggestion to me.

Regards,

Raju.N.G

Answer

As mr zakir & mohit said this problem is due to magnatic
field as in monitor CRT tube is there so it distrubs with
the magnatic field . please check if any havy cables are
passing nearby.

Question { ABB, 11289 }

if we convert kva into Ampers,which one formula use by
us,pls tell me?

Answer

KW = KVA*Pf

W = KW / 1000

W = 1.73 x VL x IL x PF

I = w / 1.73 x VL x PF

Question { Suzlon, 14748 }

why nearly all the voltage levels are in the multiples of 11
like 3.3 ,6.6 ,33 ,11 kv.....

Answer

correct is just because of form factor ,

Form factor = Rms value / Average value

Question { MAHINDRA, 17558 }

If connected load of Asphalt plant is 375Kw. What suitable
KVA DG set is required. What is calculation formula. what
extra load have to consider. in what efficiency it will
work.

Answer

Dear friends,


Total Connected Load = 375 KW
KVA required @0.8 PF = 375 /0.8 = 468
Taking a 0.8 as a Demand Factor = 468 *0.8=375 KVA
Considering running of D.G set on 80% load = 3750.8=468 KVA
Considering 20% load for future expansion = 468 + 20%(93KVA)
Total KVA of D.G set = 561 KVA

you can go with 600 KVA D.G set .

Question { Areva, 114715 }

what is the function of breather in a transformer

Answer

If anybody have seen the transformer carefully then you
must notice that breather is installed at the vent pipe
connected to the Oil tank & the open end of the vent pipe
in tank is on top.
In any kind of fault condition , if the heat is produced &
Oil gets expand then it will increase the volume of oil in
tank & excessive oil will be get drain through the way of
vent pipe , but in the healthy condition only are passed
through the vent pipe & obvisiosy air definately contain
the part of Moisture & as the moisuture is the one of the
enimy of electrical sustem , it needs to be prevent while
enrering in to the transformer . for that breather is
arranged the dry silica gel is put in to breather & once
the air passes thorogh breather as per silica property it
will absorb the moisture & change its own colour to the
pink,. once it shows the pink colour immediately open the
breather . remove the silica & apply heat for some period
of time & again you can re use it.

result shows that moisure can reduce the dielectrica
strengh of oil.
the good quality oil can sustain its property up to 50 KV &
the oil with some oil gave away at 18 kv.

Question { Engineers India Limited, 30009 }

what is buchholz relay?what is it used for?

Answer

Buchholz relay is the Gas operated relay in which there are
two contact & contacts are installaed in such a way where
they can be get short by mercury when gas lift one portion.

If any fault take place in the transformer winding then it
will put a nagative impect & the insulation between two
winding start burning & due to this some gases starts
forming this gas go up & lift the moving side of Bucholz &
through the mercury tripping signal is givan to the relay
installed at HT breaker side & hence the Brekaer gets
tripped & Transformer gets isolated. Means Bucholz relay is
spically installed for protecion of transformer winding
which is physically invisible & for otherfault there is a
OT & WT is provide.

Question { 7892 }

I have 500A load (WHICH IS SEPARATE MDP PANEL),an MCC panel
with 4000A Breaker.Already I have 2500A load.Can I connect
this load directly to the Busbar since I have PROTECTION IN
MY MDP Panel ?

Answer

Dear friend.

Mathamatically it looks possible but bofore making this
arrangment the other factor which you need to consider.

1. The Rating of a transformer.
2. the Ir seeting of a Breaker.
3. Total contract demand if you are using local electricity
board power.
4. change in OT & WT setting.


by checking all the above peramiters you can go ahead.