STC Rating: 25kA, 16kA, or 18.4 kA - Advantages & Clarification

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SUMMARY

The discussion focuses on the Short Time Current (STC) ratings of circuit breakers, specifically comparing 25kA, 16kA, and 18.4kA ratings for a 12kV Indoor Breaker. It emphasizes that the STC rating indicates the maximum short-circuit current a breaker can handle before failure. Transitioning from a 16kA to a 25kA rating provides enhanced protection against potential damage from higher fault currents, ensuring the breaker can operate effectively without sustaining damage during short-circuit conditions.

PREREQUISITES
  • Understanding of Short Time Current (STC) ratings in circuit breakers
  • Knowledge of 12kV Indoor Breaker specifications
  • Familiarity with circuit breaker operation and arc extinction
  • Basic electrical engineering principles related to short-circuit protection
NEXT STEPS
  • Research the implications of changing STC ratings on circuit breaker performance
  • Learn about the design and testing standards for 12kV Indoor Breakers
  • Investigate the impact of arc behavior on circuit breaker longevity
  • Explore IEEE standards related to circuit breaker interrupting capacity
USEFUL FOR

Electrical engineers, licensed electricians, and professionals involved in the specification and maintenance of circuit protection devices will benefit from this discussion.

kranth
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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.
 
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I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?
 
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
 

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