# How to calculate the short time current rating for current transformer?

Respected sir's,

how to calculate the "short time current rating"(i.e-primary short time current rating-like if you take 400-400/5-15va/class1,40ka/3sec).

40ka/3sec-how to calculate this rating from the substation?

I am waiting for your's reply...

Thanks&regards,
Pandees.b

 anasmemon Posts: 3, Reputation: 10 Junior Member #2 Mar 10, 2011, 12:43 AM
Short time rating is defined by your MVA rating. Suppose you are using 0.8MVA transformer at 33/11KV, so your STC will be 0.8*1000/(1.73*11)=42KA.

I hope this will help you. So to calculate STC the data you have given is not useful..but system parameters are required.
 kkspwr Posts: 1, Reputation: 1 New Member #3 Jul 16, 2012, 11:00 PM
how much will be 6.6 /.4 kv transformer be equivalent in KVA
 tkrussell Posts: 9,673, Reputation: 3698 Senior Electrical & Lighting Expert #4 Jul 17, 2012, 04:50 AM

Not enough information provided, assuming you mean the primary is 6.6kV and the secondaray is .4 kV.

Quote:
 Originally Posted by kkspwr how much will be 6.6 /.4 kv transformer be equivalent in KVA

## Check out some similar questions!

Transformer current [ 2 Answers ]

What is the current rating of 100 KVA distribution transformer with ratings as V = 11KV/0.4KV f = 50Hz

How to calculate the short circuit current flow in a three phase circut?

100/5 current rating on Current Transfomer [ 4 Answers ]

What is meaning of current rating 100/5 printed on CT?/

Current transformer - short time withstand current [ 4 Answers ]

Hi, For ring-type (window-type) CT, do we need to size the CT short time withstand current at the same or above the system short time withstand current (short circuit level)? Any reference/technical explanation? Thanks!