How to calculate the breaking capacity(like 15ka,20ka) of
Circuit breaker (MCB,MCCB,ACB)

Answer Posted / t s gupta

Breaking Capacity of MCCB is pre-calculated permissible amount of fault current (value of current can flow from contacts before opening/tripping the MCCB without damaging) which may facilitate the safe operation of MCCB and distribution transformer both.
It shall be calculated/derived from the distribution Transformer MVA rating and %impedance = kVA*100/ system voltage of load side * % Impedance rating
e.g. 20 kVA transformer with 5% Impedance, secondary voltage 440V i.e. 0.440 kV
Fault current Isc = 20*100/.440*5 = 10kA approx.

Is This Answer Correct ?    0 Yes 1 No



Post New Answer       View All Answers


Please Help Members By Posting Answers For Below Questions

can a 150 kva 3 phase 440v/230V delta-wye step down transformer can be use as step up transfoermer with connected loads at 440v side?

1269


If we need 4c× 50mm sq cable but it's not available so we can pull 4c×25mm sq two cables?

939


what is the maximum permissible limit value of leakage current and leakage counter reading to replace lightining arrester?

4634


what is DRP panels?

1686


pls,send the previous year written test questions.

1453






full form of electrical?

2298


how to compute kvar in substation feeder to improve power factor and sending voltage

1649


how to define tell me about self

1524


At what factor resistance r of a conductor depends?

646


what is meant by tranformer impedance?

2163


What is installed in PAC that is control the humidity

1059


transformer phasor diagram under load explain it?

1673


Which motor is 3.3 or 11kV more reliable, in terms of efficeancy,maintenance, reliability.

1618


I am EEE student i want to improve my core side skills.how cn i approach it?

1992


I want to merge a cable..in between two metering Cubicals which contains CT's and PT's and Energy meter..before taking merger..what are the common things required?

1138