Breaker Interrupter rating

[KnicksJets]

We are planning to replace an old 138 kV OCB (Westinghouse) for a new one with higher rating. The available fault on the system is 73kA asymmetrical which corresponds to 51kA symmetrical (X/R =39.1). We are struggling with what interrupting capability does the present breaker have. The nameplate info is:
Type 1380GM13000
138 kV (operating voltage=115 kV)
2000 Continuous Amp
60 Hz cycle
650 kV impulse withstand
10kA rated interrupting MVA@ rated voltage

Can one calculate the sym/asym interrupting rating of the above breaker from the nameplate info alone? I guess the other option is to run fault current analysis on the breaker?

Appreciate you going over this thread.

 

[jghrist]

The 10kA rated interrupting would be the symmetrical interrupting rating, a lot less than the 51 kA available. The MVA@ rated voltage would mean that you can get the old style MVA interrupting rating by using the rated interrupting current and rated voltage (2390 MVA). I don't know what you mean by running a fault current analysis on the breaker.

 

[KnicksJets]

10KA sounds a lot less. One of the vendor calculated it to be around 33 kA and I couldn't get an answer on how this was calculated.
How do we really test a breaker's interrupting capability?

 

[pwrtran]

I am wondering what fault levels do you guys have on your transmission system? We have about 22kA on our 230 kV system and 11kA on our 115kV system (both are at the delivery points). 51kA on 138kV is a very high level...

 

[jghrist]

10KA sounds a lot less. One of the vendor calculated it to be around 33 kA and I couldn't get an answer on how this was calculated.
How do we really test a breaker's interrupting capability?

Maybe I'm misinterpreting your OP. I thought you meant that the nameplate said the rated interrupting was 10kA. If so, why would you suppose it was higher?


How do you calculate the interrupting rating? See ANSI/IEEE Std C37.081-1981, IEEE Guide for Synthetic Fault Testing of AC High-Voltage Circuit Breakers Rated on a Symmetrical Current Basis for testing, but I don't think you really want to subject an old breaker to a fault interrupting test. Where are you planning to use the old breaker?