Answer / kaustubh

if we known the pesentage of impedance then by using this
formula we can calculate the fault Lavel.

fault lavel in MVA= Rated KVa/% of Impedence

OR

Fault Lavel= 1.732xFault Currentx Rated Voltage

Answer / gopal

fault lavel in MVA= Rated power/% of impedence


or

Fault Lavel= 1.732xFault currentxRated Secondry Voltage

Answer / mukul

Dear friends above answer is wrong when you are using
transformer KVA in you calculations then pf is not required
the above answer can be corrected by omitting pf from this calcs

Answer / amar singh.

fault level depend on system impedance
full load current*100
Trasformer fault level= ----------------------------
%impedance of the transformer

Answer / pankaj

THERE IS A SIMPLE CALCULATION IF ASSUMING INFINITE SOURCE
BUS THE MAX LEVEL OF FAULT AT LT SIDE OF A 11/0.433 5%
1000KVA TRANSFORMER CAN BE CALCULATED AS:

KVA*100/SQRT3*433*Z% kAMPS

1000*100/1.732*433*5 = 26.7kAMS

Answer / k n naidu

hi,
Calculation of fault level of a distribution net work of
complex in nature manually is laborious. Use network
analyser for simulating the network and fault at the
required bus to get the fault current.
for manual calculation use the MVA method which is
simple and gives fairly acurate results

Answer / leonard

Fault level = Rated Voltage / system impedence (up to that
point)

transformer impedance can be calculated using the
following formula:

Z(transformer)=(Vsq*Z%)/(P*100)

where
Ztransformer is the source transformer impedance, in ohms;
P is the power of the transformer, in volt amperes;
Z% is the rated short-circuit impedance voltage of the
transformer, expressed as a percentage.

Answer / abhi

Fault level = (Rated power of transformer*100)/(percentage
impedance of transformer + imp of subsequent equipments)

Answer / jojo

rated capacity of transformer divide by its transformer
impedance.

Answer / avatar

When deciding the fault levels, isnt there a time component
as well? I have seen the fault levels being designated
as "350 MVA @ 1 sec". What does this mean? Please help.

why transformer ratings in kva?

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