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Have you ever racked in/out a MEDIUM VOLTAGE (above 1 kV) circuit breaker?
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 Post subject: Have you ever racked in/out a MEDIUM VOLTAGE circuit breaker
PostPosted: Sun Apr 24, 2016 3:25 pm 
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This week's question of the week is part 2 regarding racking in/out a circuit breaker.

Have you ever racked in/out a Medium Voltage (above 1 kV) circuit breaker?
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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Apr 25, 2016 5:28 am 

Joined: Mon Dec 15, 2014 8:44 am
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In fact Jim,

I work for a small G&T Coop, that has several gas powered steam turbines. One location, due to the nature of the customer, racks out old 13.8 kV breakers often. And the bus is hot when they do this. They are 60's vintage breakers, and incident energy level is just a little under 100 calories. We have a 100 Cal suit that they wear when conducting this work, with a fan vented hood for a tiny bit of comfort.


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Apr 25, 2016 7:00 am 

Joined: Fri Apr 22, 2011 1:51 pm
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When performing breaker racking technique, this is accomplished using a "remote" racking mechanism, such that the mechanism is securely placed on the cubicle door, then the operator using an remote control box racks out the breaker while at a "safe" distance.


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Fri Jun 03, 2016 10:48 am 
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cromig wrote:
In fact Jim,

I work for a small G&T Coop, that has several gas powered steam turbines. One location, due to the nature of the customer, racks out old 13.8 kV breakers often. And the bus is hot when they do this. They are 60's vintage breakers, and incident energy level is just a little under 100 calories. We have a 100 Cal suit that they wear when conducting this work, with a fan vented hood for a tiny bit of comfort.


Sir,
You know that's not allowed per 70E, right? 40 is the limit. Does the NESC allow interaction at 100 calories?


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Sat Jun 04, 2016 7:39 pm 
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mayanees wrote:
cromig wrote:

Sir,
You know that's not allowed per 70E, right? 40 is the limit. Does the NESC allow interaction at 100 calories?


The only thing in 70E that has a "40 cal/cm2" limit is two things. First, the table-based incident energy method stops at 40 cal/cm2. Second there is an informational note (information only, NOT a part of the Code) that states that there should be an increased concern for anything over 40 cal/cm2 but gives nada, zip, zero, zilch, as far as guidance at that point. Historically this "cutoff" existed simply because the original "pickle suits" were limited to 40 cal/cm2. Since that time you should hear some of the ridiculous explanations. The most ridiculous is that somehow you will be liquified on the spot inside an arc flash suit starting at 40 cal/cm2 due to a billion PSI pressure wave or some such silliness. It is even to the point that a number of software packages print out labels in total violation of ANSI Z10 that say something like "Danger! No PPE available" which is utter, blatant, total garbage.

Fortunately this will all be resolved in the 2018 version. The ridiculous informational note that has caused so much silliness is deleted.

NESC is different. Just as OSHA, it starts out with the "minimum" incident energy without PPE at 2.0 cal/cm2 rather than 1.2 cal/cm2. It contains a table that is quite a bit different than 70E (more equipment oriented) and basically provides not risk assessment whatsoever. OSHA wasn't that stupid...they specify risk assessments and even give an example table that is far more lucid than 70E.


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Wed Jul 20, 2016 12:06 pm 
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SPC300 wrote:
When performing breaker racking technique, this is accomplished using a "remote" racking mechanism, such that the mechanism is securely placed on the cubicle door, then the operator using an remote control box racks out the breaker while at a "safe" distance.


Yep. We have this device at a couple of our substation switchgear houses. A lot safer and easier than standing in front of the gear and manually "screwing" them in. We have remote open/close push button switches too in our newer gear.

_________________
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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Jul 25, 2016 8:45 am 

Joined: Mon Oct 19, 2009 7:42 am
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[quote="PaulEngr"][quote="mayanees"][quote="cromig"]
It is even to the point that a number of software packages print out labels in total violation of ANSI Z10 that say something like "Danger! No PPE available" which is utter, blatant, total garbage.

Fortunately this will all be resolved in the 2018 version. The ridiculous informational note that has caused so much silliness is deleted.
quote]

Paul,

Can you explain this? I didn't see where ANSI Z10 addressed this. I'm thinking that ANSI Z535.4 may be the applicable std. Do you know how NFPA 70E 2018 will address the prohibition on using Danger on arc flash labels?


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Jul 25, 2016 9:09 am 
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jtinge wrote:
Paul,

Can you explain this? I didn't see where ANSI Z10 addressed this. I'm thinking that ANSI Z535.4 may be the applicable std. Do you know how NFPA 70E 2018 will address the prohibition on using Danger on arc flash labels?
[/quote][/quote]

70E is not going to per se address use of the word "Danger". In fact it really doesn't have to. This whole concept is promoted by others. What 70E is "guilty" of is the note that greater caution (without defining it) has to be used above 40 cal/cm2. Removal of this artificial and somewhat nebulous "limit" removes the stigma of the magic 40 cal/cm2 "threshold".

Going by ANSI Z10 is another matter. This invokes the hierarchy of controls. There have already been a couple IEEE publications outlining methods to get incident energy down to 8 cal/cm2 for large petrochemical facilities. The next challenge would be to successfully design equipment to get down to 1.2 cal/cm2. I believe this can be done but it cannot be done with circuit breakers and fuses in the main lineups. We need to place such protection within the secondary compartment of the transformer.


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Jul 25, 2016 9:41 am 

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PaulEngr wrote:
jtinge wrote:
70E is not going to per se address use of the word "Danger". In fact it really doesn't have to. This whole concept is promoted by others. What 70E is "guilty" of is the note that greater caution (without defining it) has to be used above 40 cal/cm2. Removal of this artificial and somewhat nebulous "limit" removes the stigma of the magic 40 cal/cm2 "threshold".


I see in Annex E of ANSI 535.4, a matrix that explains the rationale for selecting signal words and colors based on accident probability, severity, and probability of worse credible severity. Only when the probability that an accident will occur of hazardous situiation is not avoided and when death or serious injury will result if the accident occurs is the use of "Danger" as a signal work recommended. For all other situations when one or both of the conditions is could, "Warning" is the recommended trigger word.


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 Post subject: Re: Have you ever racked in/out a MEDIUM VOLTAGE circuit bre
PostPosted: Mon Jul 25, 2016 1:41 pm 
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jtinge wrote:
PaulEngr wrote:
jtinge wrote:
70E is not going to per se address use of the word "Danger". In fact it really doesn't have to. This whole concept is promoted by others. What 70E is "guilty" of is the note that greater caution (without defining it) has to be used above 40 cal/cm2. Removal of this artificial and somewhat nebulous "limit" removes the stigma of the magic 40 cal/cm2 "threshold".


I see in Annex E of ANSI 535.4, a matrix that explains the rationale for selecting signal words and colors based on accident probability, severity, and probability of worse credible severity. Only when the probability that an accident will occur of hazardous situiation is not avoided and when death or serious injury will result if the accident occurs is the use of "Danger" as a signal work recommended. For all other situations when one or both of the conditions is could, "Warning" is the recommended trigger word.


The key difference here is the word "will" compared with "could". Exposing energized bus, especially when direct contact is not a requirement (1 kV or higher) presents a hazard that cannot be avoided except through the use of shock protection techniques and PPE. In most instances when working with electrical equipment though, arcing faults are not that common. We are placing labels on ALL equipment. Normal operation of equipment that is in good condition has an extremely remote probability of resulting in an arc flash injury. Unless someone takes a set of specific actions that are likely to result in an arc flash injury (and even then, almost all tasks normally performed have a very low risk), an arc flash is definitely in the category of "could". This is vastly different for instance compared to opening an access panel covering bare bus bars where a severe injury or fatality WILL occur without taking proper precautions (energized work techniques and tools). There is no playing around here...no "probability". If someone gets near enough, it will happen every time. So "Danger" applies to shcok hazards. "Warning" applies to arc flash hazards. And there is no elevated risk when it comes to the incident energy level...either there is a risk or there isn't. This is like the old H/RC tables where one was required to wear 40 cal/cm2 suits while performing one task and only 8 cal/cm2 PPE while performing another task, and nothing at all (H/RC 0) while performing yet another task, on the exact same piece of equipment. This is very different from the current (2015) requirement where either adequate PPE is required, or it's not. There is no kind/sorta/wishy-washy in between category.


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