3-Phase High KA Reading

what do you mean by kA reading on three phase. I could not understand well but I will tell that breaker has normal operation ampere capacity like your main breaker 100 ampere and the other is kA capacity which is for fault. We only take consideration of kA for shortcircuit calculation.

see also these about breaker ampere.

http://cr4.globalspec.com/thread/51322#comment536297

http://cr4.globalspec.com/thread/54902#comment570191

How are you getting 11ka (11,000 amps) downstream of a 100a MCCB? What are NIC and EIC?

Are you talking about 11KA short circuit breaking capability??

if it is so, yes, 11KA BC is common for a 100A MCCB for the charts, check the breaker catalogue, you should find them there!!

1- KA kiloAmps is a capacity of the electrical componants to withstand first spikes of current in the event of a short circuit for a period of 1 sec to 3 sec.

2- The value of KA depends upon the location of the componants either installed directly after the transformer or downstream for final circuits.

3- You have to include in ordering data the KA rating required for your componants according to thier location in the network. For example for a final Distribution Board at 3 phase, 415 volts the outgoing MCCBs will be acceptable if the rated for 9KA short circuit withstand for 1 sec.

>For example for a final Distribution Board at 3 phase, 415 volts the outgoing MCCBs will be acceptable if the rated for 9KA short circuit withstand for 1 sec.<

Excuse me, but in the final distribution, one needs instant cut-off of short-circuit. Not wait for 1 sec (this 1s rating is usually required by upstream ACBs for discrimination). MCCBs are usually current-limiting, and do not have 1s rating. Final distribution is usually MCBs.

Excuse me, but in the final distribution, one needs instant cut-off of short-circuit. Not wait for 1 sec (this 1s rating is usually required by upstream ACBs for discrimination). MCCBs are usually current-limiting, and do not have 1s rating. Final distribution is usually MCBs

Neither 9 KA is a tripping current nor 1 Sec is tripping time. Tripping characteristics are different to short time withstand. Final circuits are MCBs and not MCCBs as it is a typing mistake.

i am not sure what you are trying to say here...

MCBs and MCCBs DO NOT have 1sec ratings. They are current-limiting by design. The trip time at full SC is less than 10ms. Only ACBs upstream of the whole distribution board will have a 1s rating, with an appropriately delayed trip to allow the downstream MCB/MCCB to clear the fault.

The OP is saying 11kA. Which is also non-standard.

The 100 amp 3-phase mccb on the main board represents the maximum rated current of the board given the load from 'numerous other boards' - total load current should not exceed 100A. This is different from short circuit current (usually in Kilo Amperes) which represents fault current, that can flow through the circuit safely over a specified time (e.g 1 sec, etc), during which the protective device (mccb, mcb, fuse, etc) should trip and disconnect from supply.

Discrimination in selecting protective device means that a fault on downstream can be handled and trip by the downstream protective device while the upstream device is still up feeding other healthy circuits. However, if downstream device does not trip on a fault, the upstream device will then trip and cut off the supply - this could take slightly longer time e.g 1.5 secs.

Thus the 3-phase mccb's fault current rating is slightly higher than downstream mcb's.

Check time current characteristics of your selected device (mccb, mcb, fuse, etc) for charts.

<...Where..the charts to show the NICEIC Inspectors?...>

NICEIC is a trade body that assesses the competence of installation and maintenance contractors throughout the UK. It does not, routinely, assess individual installations as they are done, for that is the role of the NICEIC-accredited electrician that certifies them as safe. However, NICEIC accreditation is open to periodic review, and the assessor will want to look at a (small) number of recently-completed installations to ensure that the accreditation can remain current. A NICEIC-accredited individual or operation will issue documentation attesting that the installation was safe when they left it.

Charts may be found within British Standard 7671 and it is to the current edition of this Standard that the NICEIC-accreditation refers.