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 Post subject: Changing Breaker Settings on the fly.
PostPosted: Wed Nov 05, 2014 11:17 am 

Joined: Sat Nov 01, 2014 7:19 am
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Does anyone have their electricians lower the settings on an energized main circuit breaker to lower the I.E. and then return them back after work is done? In other words, manually do what the new remote switches are intended to do.


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 Post subject: Re: Changing Breaker Settings on the fly.
PostPosted: Wed Nov 05, 2014 2:04 pm 
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Location: Rutland, VT
This has been discussed previously on this forum. See link below.



viewtopic.php?f=2&t=3265

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 Post subject: Re: Changing Breaker Settings on the fly.
PostPosted: Thu Nov 06, 2014 9:33 am 
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NNASAM wrote:
Does anyone have their electricians lower the settings on an energized main circuit breaker to lower the I.E. and then return them back after work is done? In other words, manually do what the new remote switches are intended to do.


Not sure what you mean by "remote switches intended to do".

Yes, it can be done. It has been done here many times and is a way to address arc flash with older electro-mechanical relays. However there are problems:
1. You don't know (without testing) whether or not the lower setting still works correctly. This might be just a nerdy relay engineer drumming up business but it's a real concern.
2. We found out the hard way but I forgot which manufacturer that when you do this, the "no pin" or "dial in between clicks" settings are the same as "minimum" which can induce an unintentional trip.
3. How you insure that it gets adjusted properly not only down but also going back up.
4. It gets guys used to making changes to settings, something that you may not want as a routine habit.
5. Every relay manual out there has weasel clauses in it that say something to the effect of not changing settings on the fly because there can be unintentional consequences, failures, etc. Yes, and every time we do anything to electrical equipment, or NOT do something, there is risk involved. Unfortunately the manufacturer lawyers insert ridiculous anti-lawsuit clauses like this that tend to either just create paranoia or get ignored. There are real concerns here like item #2, but inserting statements like this is anything but beneficial and causes nothing but problems in today's paranoid world.

The big advantage of a "maintenance switch" is that essentially we are selecting between just two sets of settings and there is not as much risk involved. We can take care of all 4 issues possibly excepting #3 with a "maintenance switch". The function of this switch is usually one of three things:
A. Turn on instantaneous. Since "maintenance switches" are almost always an "upstream" function protecting a "downstream" operation, typically the "upstream" relay would not have instantaneous trip settings in the first place (feeder breakers).
B. Switch between sets of settings. For instance most electronic relays come with between 2 and up to about 8 sets of settings.
C. Modify just one setting. For instance in one implementation we manipulate the "torque" setting in an SEL relay which effectively toggles a particular trip curve on and off without affecting any other settings.


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