Upgrading 12kV indoor breaker STC rating from 16kA to 25kA

Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
3 replies · 8K views
kranth
Messages
1
Reaction score
0
I want clarity on STC rating that is 25kA or 16kA or 18.4 kA.
If I want to change my Specification of 12kV Indoor Breaker from 16kA to 25kA STC rating then how can I support my self.
What are advantageous points.

Please clarify me.
 
Engineering news on Phys.org

Discussion

kranth said:
I want clarity on STC rating that is 25kA or 16kA or 18.4 kA.
If I want to change my Specification of 12kV Indoor Breaker from 16kA to 25kA STC rating then how can I support my self.
What are advantageous points.

Please clarify me.

Welcome to the PF.

What country are you in? Are you a licensed electrician in that country? What's an STC rating?
 
Welcome to PF.
Circuit breaker STC = Short Time Current = Short-circuit current.
Once a circuit breaker operates, due to a short circuit of the load, the CB must turn off the flowing high current quickly. The CB contacts open but draw an arc that will continue until the next change in AC load current polarity.

The STC is the extreme current that can flow in the arc while waiting for the current to reverse and the arc to extinguish. If the current is greater than the STC rating then the contact material may be sputtered against the insulator, creating a permanent conductor and an arc that reignites every cycle and destroys the CB.

http://ewh.ieee.org/r6/san_francisc...g_Capacity_and_Short_Time_Current_Ratings.pdf
http://en.wikipedia.org/wiki/Circuit_breaker#Short-circuit_current