What is Maintenance Mode? (MMS, ERMS, ARMS, RELT, DAS)
EDIT:
I made a mistake in the script. There is nothing inherently different between "commercial" and "industrial" according to NEC so 240.87 technically would apply to industrial facilities with equipment over 1200A. In speaking generally, a facility with a medium voltage service will (typically) have a relay and fast enough breaker or some other means to limit the arcing current, meaning maintenance mode isn't (typically) relevant for heavy industry. There are many, many times where a maintenance mode switch is the appropriate choice for an industrial customer to limit fault current about on a breaker at or above 1200A.
Here's a quick discussion about the benefits, implementation, and limitations of the "maintenance mode" systems found on electrical switchgear!
Eaton's ARMS mode
Square D's MMS and ERMS mode
GE/ABB's RELT system
Siemens' Smart DAS system
0:00 - What is Maintenance Mode?
2:20 - Why does it exist?
5:38 - What does it do?
8:15 - Limitations & Drawbacks
11:06 - ABB & GE RELT
12:41 - Square D MMS and ERMS
14:02 - Siemens DAS
14:36 - Testing Procedure
19:03 - Conclusion
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