Fault Current Capabilities of Circuit Breakers: Time Curve (IEEE Standard) 1

[111R]

I'm looking for the IEEE standard which discusses the allowable interrupting times for medium/high voltage circuit breakers at a given level of fault current. For example, a breaker may be able to interrupt a maximum fault current of 25kA, 40kA, or 63kA, but what is the maximum allowable clearing time at this level and, more specifically, at lower magnitude faults.

I'm going through the C37 standards, but I haven't come across the right one yet.

Thank you.

 

[iceworm]

I guessing you are not interested in the IEEE TCC for the protective relays. Rather you are looking for specs on the mechanical operating time for the contacts.
You have likely already looked at:
C37.20.2
C37.04
C37.05 (Table 1)

Disclaimer: 13.8KV and below, air-break and SF6.
My experience is the opening time specs are set by the MFG. IEE tells you how close the their spec each CB has to be. Additionally IEEE gives a list of preferred specs.. Doesn't say anybody has to meet these specs.

Item 2 Clearing Time Lower Magnitude Faults:
This one has me baffled. I have not seen any data/documents suggesting the mechanical operating time changes with current level. Once the current is out of the instantaneous range, the operating time is dependent on the relay settings. I'm pretty sure you already knew that. So, I am at a loss on what you are looking for.

iceworm

Harmless flakes working together can unleash an avalanche of destruction

 

[111R]

Thank you. I'm actually looking for the maximum time that the breaker can withstand current above the nameplate rating.

For example, a fault occurs and the relay takes 2 seconds to operate. During those 2 seconds, current exceeding the continuous current rating of the breaker will be flowing through the breaker. Is this acceptable? It seems like there would be a curve available. Such as, a 40 kAIC breaker can withstand 40 kA for 20 cycles, 20 kA for 60 cycles, etc without damage.

 

[iceworm]

Interestingly, A 2sec rating is one of the specs. Same references.

No, I have never seen a curve, say like a transformer damage curve.

Just guessing, by the time 2 seconds has elapsed, the protective relay has kicked in and the CB trips according to its curve, well below damage point

Which doesn't answer your question, but may explain why damage curves are not common.

Have you sent a note to any of the mfg engineering departments?

ice

Harmless flakes working together can unleash an avalanche of destruction

 

[ScottyUK]

The fault withstand current of a breaker is typically determined by its capability to withstand the first assymetric peak of the fault current where the electro-dynamic forces are at their maximum, and not by the (virtually) adiabatic temperature rise of the contacts and conductors. This failure mode doesn't have an inverse-time characteristic - the breaker is either able to withstand the forces involved, or it isn't.

The adiabatic rise during through-fault conditions is relatively simple to control by ensuring sufficient mass of metal (energy input and specific heat capacity), where by contrast interrupter design is far more complex.