Answer / ariel

- Draw the per phase diagram of the system
- Express all impedance in per unit values
- Choose a common MVA base and express all Zpu on the
selected common MVA base

Znew= Zpu(MVA base/ MVA)
-Calculate the total per unit impedance of the system
using circuit principle
- Calculate the fault power
MVA fault= MVA base/ Z total per unit

I fault = MVA fault/ 1.73* V

Answer / mak

The fault current of a power transformer will depend on the following;
Transformer Rating (in KVA/MVA)
per unit impedence of the transformer (%p.u.)
line/phase Voltage (VL/VP)
the following formula can be used to find the fault current on the secondary side of a transformer
Fault Current = Transformer Rating /(per unit impedance x phase voltage)

The Values of Transformer Rating, per unit impedance & phase/line voltage will usually be mentioned on the transformer rating plate / data sheet
As an example a 500kVA, 11kV/400V/3-Phase/50Hz transformer with 5% p.u impendence will have the following fault levels on the secondary side

Fault level = 500/(5%)=10000kVA


Fault current = 500/(5% x 400 x 1.732) = 14.4 kA

Remember to use 3phase voltage!

is there any role of power factor with frequency variation? and how we can manage the frequency variation?

0 Answers   Wipro,

---

what are the different methods for the starting of a synchronous motor.

0 Answers  

---

i need to now what will be the cable size to the following load, transformer to distribution panel distance 110m, load 1000kw, voltage 400v, pf 0.85, permissible voltage drop 2.0%, overhead line, atmospheric temperature 35 degree c.

0 Answers   Bay Fishing Corporation,

---

If we are given a 10 amp cable type and asked to calculate the number of cores used and the thickness of the cable, how do we do it?? please help...urgent!! i hope the question is clear enough!!

0 Answers  

---

what is the difference between dropout fuse and horn gap fuse. how to choose between them

1 Answers  

---

---

what will happen if the input of a transformer is dc?

10 Answers   Hindalco,

---

What is difference between 3 point and 4 point starter

1 Answers   Genco, Kaltec, TATA,

---

0.5,1,1.5,2.5,4.0.6.0,10,16 square mm electrical wires how much take maximum current in 50htz

0 Answers   SoftLogic,

---

transform oil how going to act like ainsulation purpose

1 Answers   Siemens,

---

In ups static switch if i gives the supply at output end it will open the circuit in stactic switch or not if it will open then how it operates.

0 Answers  

---

why transformer tank is in rectangular shape what happen when it is in step shape

0 Answers  

---

hi frnz,can somebody give me any project work? i am a 2nd year student & interested in practical works...plz give me some projects

0 Answers  

---