Question { IAF, 108395 }

Which of the following is the best conductor of electricity ?

(a) Copper

(b) Aluminium

(c) Gold

(d) Silver

Answer

Silver is a best conductor.. because i show some differences
are below:

Conductors Thermal Conductivity @25degree

Silver --- 429
Copper --- 401
Gold --- 310
Aluminium --- 250

Question { Schwing Stetter, 91764 }

what is different the DOL Starter and Star Delta STARTER

Answer

DOL Starter :
This starter is costwise cheap. it doesnot reduce the
starting current of the motor. The starting current of the
DOL starter is 6 to 7 times of the full load current. We can
use this starter for any higher kW range motors also even
6400kW motor.(In my working place using this DOL starter for
this 6400kW motor.

Note: for any standard cannot mentioned this much of the kW
motors only use in this type of starter nu..

Star/Delta Starter :
This starter is costwise higher. It can reduce the
starting current of the motor. The starter current of the
star/delta starter is 3 to 5 times of the full load current.
Generally in my working place this starter can be use above
75kW motors.

Question { 12238 }

Can I use measuring current transformers in protection
purposes?

Answer

Mr.Ramesh kumar said answer is very correct..

We cannot use the Measuring C.T. for the protection
purpose.and we also cannot use the protection C.T. for
Measuring purpose.

Protection C.T Classes are:
CL 5P20
CL 5P10
CL PS

Measuring C.T Classes are:
CL 0.2
CL 0.5
CL 1.0

Generally the Measuring C.T's and Protection C.T's are
differentiate by using the C.T Classes..

Question { APGenco, 114665 }

What is the major difference between P.T. & C.V.T ? Why CVT
is used in HT Transmission line in place of P.T.?

Answer

Hi Engr.L.O.Osuji,

You are said 132kV and above rating switchyard used CVT
but in my project we used 132kV PT ( Potential Transformer )
not used CVT..
So,can you reply me???

Question { Areva, 12389 }

What is Generator Protection & Transformer Protection?

Answer

Generator Protections are:

1. over current protection
2. Earth Fault protection
3. under voltage protection
4. pole slipping protection
5. under frequency protection
6. Impedence protection
7. df/dt protection

Transformer Protections are:

1. Differential protection
2. winding temperature protection
3. Oil temperature protection
4. overcurrent protection
5. Earth fault protection
6. undercurrent protection

Note:

The protection relays are increases deponds on the ratings
of the Transformer and Generator...

Question { 59292 }

one kva is equal to how much amps?

Answer

KVA = (1.732(VOLTAGE*CURRENT))/(1000)

If we assume the voltage as 415Volt then the KVA is has:

(1.732*1000)/415 = 1.391Amps...

Question { 6957 }

Whag is the PS class of accuracy of CT?

Answer

The PS class is protection class CT. This PS class C.T is
mostly used for the differential protection for
transformers,motors etc...

Question { 6226 }

What are the factors to be considered during the
Synchronization?

Answer

1.voltage
2.Phase sequence
3.Frequency
these three things are should be same for both the
alternator.

Question { 53689 }

how much current does 3ph. 10 hp ac motor draw.

Answer

10HP = 10*745watts = 7.45kW
I = 7.45/(1.732*415(volt)*0.8(power factor)*0.8(efficiency)
= 16.19Amps

Question { 5805 }

Why not instal the NGR in 11kv/433kv trasformer?

Answer

In my company we are generally using NGR for the secondary
side (433Voltage) of the Transformer....

Question { 11372 }

what is LT & HT?

Answer

Mr.k.Prakashchandra can you able send the IE Rules soft copy
for my mail i.d: karthikdote@rediffmail.com....

My Point of view the

LT Voltage ranges are -- 230volt , 433volt.(less than 433volt)
Medium Voltage(MV) ranges are -- 3.3kV,6.6kV
High Voltage(HT) ranges are -- 11kV,33kV

Question { 9929 }

IF THE OUTPUT OF A 100KVA, 415V GENERATOR IS STEPPED UP TO
11KV WITH A 500KVA TRANSFORMER,CAN THE TRANSFORMER BE
LOADED ABOVE THE SOURCE GENERATOR RATING?

Answer

No. Tranformer is for only stepping up the voltage, not the
power which should not be allowed to rise above the
capacity of the generator

Question { Adani, 10660 }

What is PIR (pre
inserting resistance)
in 400kv EHV SF6
BREAKER? Why it use?

Answer

PIR means Pre insertion resistor... This PIR is connects
parallel to the main interruptor..This is used to limit the
current to be interrupted.

Question { Alchemist, 9659 }

wich type of cable is selected for wiring of 20hp motor?

Answer

1.1kV XLPE insulated, 10sq.mm Aluminium power cable is
enough it.

Question { IGCAR, 18425 }

IS RTCC AND OLTC REQUIRED FOR 500 KVA 11KV/433V TRANSFORMER
FOR AN INDUSTRY?

Answer

The Transformers are haveing two types of tap changers are:
1. Onload Tap changing(OLTC)
2. Offload Tap Changing (OCTC)

OLTC:
If the industry needs to changes the Transformer
secondary voltage frequently then the OLTC is best choice..
Because in this OLTC Tap changer only to change the
Transformer output instantly without to Turn Off the
Transformer..
In this OLTC Transformer, to change the output voltage of
the transformer without turning off the Transformer.

OCTC:
If the industry need to change the voltage of the
transformer once the day or week means then the OCTC is best
choice...
In this OCTC Tap changer, to change the output voltage
of the transformer at only after turnoff the transformer.