MV Breaker MPU

[saifshanshal77]

Hi - On Medium Voltage breakers 13800V how do we determine the MPU and TCC? I searched for the curves online but I could not find one.
Do MV breaker manufacturers provide those curves in their datasheets as the 480V Breakers, or should we build them through software?

 

[D. Castor]

Medium (and high) voltage breakers do not come standard with any type of overcurrent protection. That is provided by separate protective relays that are generally connected to current transformers in the breaker compartment. The relays themselves are often specified with the switchgear and mounted in the breaker compartment, but can be remote. The TCC curves will be based on the relays provided and the settings used.

Not sure what "MPU" stands for.

 

[saifshanshal77]

Multiples of pick up (MPU)

 

[D. Castor]

That's a new one for this old guy. Doesn't change the answer. You have to have the appropriate protective relay data and settings (and the correct CT ratio)

 

[saifshanshal77]

That's a new one for this old guy. Doesn't change the answer. You have to have the appropriate protective relay data and settings (and the correct CT ratio)

Noted and thanks for your help, most appreciated