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# Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

## Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

(OP)
Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

From my understanding, the "Rated Interrupting" current is the current the breaker can safely interrupt based on the max kV rating. This is then used to compare against the interrupting currents calculated in an SC study.
However, I am not sure what the "Max Interrupting" rating represents and what it would be compared against when performing an SC analysis.

Shown below are the two ratings for a GE 15kV HVCB

### RE: Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

After interrupting Max current the breaker should be inspected, repaired or replaced.
It is a one time rating for the maximum current that may be interrupted with the breaker containing the arc and interrupting the arc.
The breaker may be damaged, but the current will be interrupted.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

### RE: Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

It is because of the K factor (Voltage Range Factor) of the bkr. This K factor is printed on the name plate of your bkr.
In fact for this breaker K=15/11.5 = 1.3. That means this bkr can operate in the voltage range of 15 to 11.5kV.
Therefore, a bkr having the maximum rated voltage =15kV, can operate down to 15/1.3=11.5kV but with a higher interrupting rating.
These K factor breakers are constant MVA type. Therefore,
1) Maximum rated voltage =15kV
2) Rated interruting capability = 18kA
3) Maximum interupting capability = 18kA x 1.30 = 23.4kA @ 11.5kV
(15kV x 18kA = 11.5kV x 23.4kA)
All these are for ANSI old breakers specifically for oil. No such thing for IEC bkrs.
But for new vacuum & SF6, K=1

### RE: Can someone explain what the difference is between the Rated Int. and Max Int. ratings for HVCBs?

(OP)
Kiribanda

In other words the interrupting rating is for the breaker when applied for a system which is equal to the max rated kV, in this case 15 kv.

The Maximum interrupting rating however is the rating of the breaker when applied for the lowest voltage it supports which in this case is 11.5 kV.

That makes sense now, thank you so much!

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