Ground fault protection for > 1000A protective device

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anbm

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Another dump question: NEC article 517 application, if our main service protective device > 1,000A, code requires to have (2) levels of ground fault protection. So, if our main switchboard has a main 2,000A fused disconnect and all its first level downstream protective devices are also fused switches.

How are we going to provide ground fault protection for fused switches?

I always deal with Circuit breakers in main service entrance Switchboard but never think about fuses, (it's easy to specify electronic CB with L.S.I.G. features and comply with code), in case the client wants to use fuses instead of CB? Thanks!
 
anbm said:
Another dump question: NEC article 517 application, if our main service protective device > 1,000A, code requires to have (2) levels of ground fault protection. So, if our main switchboard has a main 2,000A fused disconnect and all its first level downstream protective devices are also fused switches.

How are we going to provide ground fault protection for fused switches?

I always deal with Circuit breakers in main service entrance Switchboard but never think about fuses, (it's easy to specify electronic CB with L.S.I.G. features and comply with code), in case the client wants to use fuses instead of CB? Thanks!
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You must replace the fuse switches with shunt trip capable devices (historically only found on the 800A and larger Class L style although there are some hybrid smaller devices) or circuit breakers.

FWIW, it is possible to meet the requirements for selective coordination using only circuit breakers. Yes it is more expensive, it takes pre-planning for each manufacturer, and may require some "oversized" breakers but it is possible.
 
Bolted pressure switches with GFP relays and shunt trips, Cutler Hamer and maybe Siemens make a Fused Safety Switches with spring charged shunt opening.
 
anbm said:
Another dump question: NEC article 517 application, if our main service protective device > 1,000A, code requires to have (2) levels of ground fault protection. So, if our main switchboard has a main 2,000A fused disconnect and all its first level downstream protective devices are also fused switches.

How are we going to provide ground fault protection for fused switches?

I always deal with Circuit breakers in main service entrance Switchboard but never think about fuses, (it's easy to specify electronic CB with L.S.I.G. features and comply with code), in case the client wants to use fuses instead of CB? Thanks!
Click to expand...

Device selection and selective coordination is an engineering task.It is an engineering issue, so refer the problem to one.
 
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