Feeder Calculation Help

No! No! No! No! No!

You are not capable of this work!

You are also irresponsible!

You are not qualified! You will surely fail and in the process may even kill people!

Quit! Go away!

HIRE A PROFESSIONAL ELECTRICIAN/TECH/ENGINEER!

This forum does not give advice to the unknowing so that they can injure others or burn buildings.

if you read my question carefully, i have done calculations, what i have asked is just verification.

what is this forum then for?

i have done some calculations, some are missing,

this behavior of yours shows you are also not capable about this calculation, so why bothering to reply?

your previous posts that i have gone through depicts your replies based totally on discrimination.

OK, that's fine with me.

I went through your previous posts and discovered that your posts all ask for help with rudimentary concepts of electricity. So, neither you, nor I, can do the calculations. I don't need to, you do.

Did you ever get that free copy of NFPA 70 2014 Electrical Standards you needed?

That might help you discover some of the questions you have previously asked the forum.

Good luck.

yes,

i bought it from local market.

i am just confused regarding setting of tripping time, what i know is that the tripping times are adjusted according to short circuit (KA) withstand time of cable and for the coordination of upstream and down stream circuit breakers. anything else to consider?

thanks for your humble reply by the way.

Look at this: Fundamental characteristics of a circuit-breaker - Electrical Installation ...

In it you will find these, and more that may help.

• 4- Overload relay trip-current setting (Irth or Ir)
• 5- Short-circuit relay trip-current setting (Im)
• 6- Isolating feature
• 7- Rated short-circuit breaking capacity (Icu or Icn)

nice drawing by the way....

Get some electrical consultants to do the calculation before you kill someone with your calculation. if you don't know how to do the calculation then don't do it.

you were born qualified??????

The Anonymouse roars.

Seriously, this 13.8 kV system is fed from a higher voltage system by a transformer. Supposing that voltage at HV of transfo is unchanged by any short on 13.8 kV side, I guess you have worked out the fault currents.

Any setting curves you decide need to be inside the operating curves of the transformer protection relays (or upstream protection if there are no relays for transfo) by a margin to cover relay and CT errors i.e. the tolerance bands of upstream and feeder protection must not overlap on the time versus current graph.

Your setting curves must also be inside the withstand curve of the feeder, so you need the feeder overcurrent withstand capacity. You did not define insulated cable type or open wire feeder. Saruman (in the "Lord of the Rings" used a "crystal ball" - and you know what it did for him!

You have not given us a system diagram with impedances, CT numbers, locations etc.

The meaning of Ip and Ie is not clear, maybe phase and earth fault - here the diagrams help.

You cannot expect folk to verify settings on an unknown system.