Answer / hari

If u have the fault mva and the voltage level at which the
CB is to be installed then :
Normal current would be the continuous current flowing in
the line ( u can take the next higher value from standard
values to take care of over current)
Breaking capacity would be tha fault MVA.
Rated symmetrical breaking current in kA would be Fault
MVA*1000/(1.732x Voltage in kV)
Rated making ct would be peak value of symmetrical breaking
current i.e 2.55 times breaking current
Short time rating would be rated symm breaking ct for 3 secs

Answer / ravi kumar singh

Breaking capacity will be always iN MVA= 1.732*Voltage in KV * cerrent in KA

making capacity = 2.55 * symmetrical breaking capacity


note:-( 1.41*1.8=2.55)

full load current= 1.8 * KVA


ravi kumar singh

Answer / nighot jagdish

Rated symmetrical breaking current in kA would be Fault
MVA*1000/(1.732x Voltage in kV

Answer / karthik

BREAKING CAPACITY OF CIRCUIT BREAKER
=SQRT(3) x V x I x 10-6
V is supply voltage
I is circuit breaker capacity
answer appears in MVA.

Answer / usama badran ali

el salamo aleekom

to calculate circuit breaker breaker capacity...there are
four steps :
1-indicate all actual nominal voltages and MVA of your
system
2-indicate the location of circuit breaker.
3-calculate the actual impedance between the known supply
to the point of fault at which near to circuit breaker.
4-then calculate:
a- short circuit current =
voltage of supply/((3^0.5)actual impedance)
b-MVA short citcuit=
(3^0.5)*voltage of supply*short circuit current
c c-breaking capacity=
MVA short citcuit*assymetry factor.
or
short circuit current*assymetry factor
notes:
Assymetry factor:1.5~1.6 for midium voltage
1.25 for low voltage
MVAshort circuit= fault level
breaking capacity: it is the value of peak current where
the circuit breaker is breaking.

Answer / s.venkatesh

we can consider circuit breaker capacity for particular
feeder depend upon the 1.2 times of full load current for
receiving end equipments

how the speed decreases of a generator in power station if load increases

1 Answers   Tata Power,

explain me how a power factor is improved by adding a capacitor?what capacitor do to improve it?in simple words and in detail?thx

7 Answers  

What is CRT (Contact Resistance Test) for Isolators or Dis- connector Switches? Why we performed it & whats the Testing procedure.

1 Answers   Siemens,

Which motor will you choose which can operate in both lagging as well as leading power factors?

0 Answers   HPCL,

As per BIS, Earth pit resistence value?

4 Answers  

What is called grain-oriented laminations?

0 Answers  

what is the roll of power factor in induction motor.

3 Answers   Hindalco,

define regulation

3 Answers  

Is there any difference between circuit breakers and isolators

7 Answers  

HOW CAN YOU CALCULATE PRACTICAL EFFICIENCY OF A ASYNCHRONOUS INDUCTIONMOTOR OF 7.5KW,& MOTOR IS RUNNING WITH AVOLTAGE OF 410 VOLTS,& TAKING CURENT OF 13 AMPS

0 Answers  

what are advantage and disadvantage of zener diode?

2 Answers   Infosys,

For a CT the number of turns in the primary winding is.........

5 Answers