Arc Flash

[zog]

"An older, high end, metal clad compared with a current production molded case."

I never said anything about MCCB's, the new high end draw out breaker are cheap plastic junk and we do more field repirs on those than the older stuff. As the saying goes, they dont build them like they used to.

"Also interesting you apparently like the older mechanical protective relays installed on 35 year old metal clad. Can't say I do"

No, those mech relays rarely pass a primary injection test, I agree with you on that one, I should have said a retrofitted 35 year old breaker with a solid state trip unit.

Just curious coulter, how many of these have you tested, rebuilt, or repaired?

 

[coulter]

Metal clad? A few dozen since the early 80s.

I don't think I have ever tested a molded case - maybe checked a contact resistance or two (or 20)

carl

 

[ItsHot]

life of equipment

life of equipment

I was in a continuing ed. class a few months ago and the instructor started out about safety, working space etc. He was talking about arc flash and the "life" of equipment. He pointed out that an electrical system begins to breakdown the moment that it is installed! What do you think?

 

[Pierre C Belarge]

I have also heard that we start to die the day we are born. Sounds very similar, but different.

 

[coulter]

...He pointed out that an electrical system begins to breakdown the moment that it is installed! What do you think?

I'll try and keep it clean.
Let's see ... how about: Insane, unknowledgable, scare speak by a poor instructor. He's right up there with TV news casters, "If the news doesn't fit our agenda, we'll make some up." This is right up there with wiggys are unsafe cause someone might stick one in 4160V. Or ungrounded systems are unsafe cause someone will get in the habit of it's okay to put your hands on the bare terminals.

(How come we don't have a barf icon)

Clean as I could get it.

carl

 

[coulter]

.... He pointed out that an electrical system begins to breakdown the moment that it is installed! What do you think?

I would tend not to agree. I likely would say (in a gentle voice), "Electrical systems start to break down when the maintenance starts to break down."

 

[zog]

Wiggys are unsafe because they are not CAT III rated and cant handle the available fault currents found in CAT III systems (I know, there are some new wiggys out there with CAT III ratings, but most are not)

 

[weressl]

Wiggys are unsafe because they are not CAT III rated and cant handle the available fault currents found in CAT III systems (I know, there are some new wiggys out there with CAT III ratings, but most are not)

I think that the "unsafe" world is inappropriate to use here. Even though it is propagated by the meter industry as the categorization has to do with safety, it really is a market ploy to protect themselves from cheap competition.

I believe that it is inaccurate and highly misleading to state that the meters can not withstand the "fault level" as the categorization has nothing to do with that. It has to with expected surge voltage withstandibility on specific areas of the electrical system.

I think that tha categorization is a technological over-reach. There was no statistical data available, nor was a study done on the surge incidences - if any - on meters. It only has to do with voltage measurements.

Reflect back on your usage. Out of ~8700hours in a year we are at work ~2000 hours, we are on the job 75% of the time, so it is 1500 hours. The majority of that time is taken up with the actual construction of the job. So how much time you estimate you are actually measuring voltage in total? An hour would be generous, and that is not a continuous time, you are actually spending 5-10 seconds to take the measurement, so the premise of the categorization is that you are going to experience the simultaneous occurence a major 1/2 second voltage surge occuring simultaneously with the one of the 0.00000951293759512938 segment of the year, is probably equivalent of trying to hit an ICBM with a slingshot. Will you ever hit it? Of course, but people also have died while their airbags properly deployed.

 

[coulter]

Wiggys are unsafe because they are not CAT III rated and cant handle the available fault currents found in CAT III systems ...

Category ratings defined. Test instruments are rated on their ability to withstand a voltage spike, which is applied through a specified level of resistance (Table). The ratings are broken down by categories ? CAT I, II, III, and IV.

...I believe that it is inaccurate and highly misleading to state that the meters can not withstand the "fault level" as the categorization has nothing to do with that. It has to with expected surge voltage withstandibility on specific areas of the electrical system....

Zog -
I don't know what you had in mind with your comment. You are extremely knowledgable and have excellent understanding of this subject. Perhaps we did not translate correctly.

All the evidence I have (after discarding special interest hype) leads me to believe wiggy type instruments are only unsafe for unqualified people to use.

Which is also true for most everything else in the earth.

carl

 

[weressl]

All the evidence I have (after discarding special interest hype) leads me to believe wiggy type instruments are only unsafe for unqualified people to use.

Which is also true for most everything else in the earth.

carl

Hear, hear!!!!!!

 

[zog]

I was under the impression the the location catagories were based on typical Is/c values of those type of systems and the meter cat ratings were based on the voltage spike that could initiate (sp?) a fault through the meter. Maybe I am wrong, which I dont mind admitting (thats how you learn more right?). I will have to look into this a little deeper.

 

[ItsHot]

instructor update

instructor update

I'll try and keep it clean.
Let's see ... how about: Insane, unknowledgable, scare speak by a poor instructor. He's right up there with TV news casters, "If the news doesn't fit our agenda, we'll make some up." This is right up there with wiggys are unsafe cause someone might stick one in 4160V. Or ungrounded systems are unsafe cause someone will get in the habit of it's okay to put your hands on the bare terminals.

(How come we don't have a barf icon)

Clean as I could get it.

carl

Just to inform you this instructor is also a highly qualified electrician with over 40 years of experience and training. He is employed with an outfit that is in the top 5 largest contactors in the country!

 

[ItsHot]

good point

good point

I would tend not to agree. I likely would say (in a gentle voice), "Electrical systems start to break down when the maintenance starts to break down."

That is a good point about maintenance, but as far as the "breakdown" of equipment/systems how do you explain all the inground feeders that have to constantlly be changed. Or all the ocpd's that fail and have to be replaced etc.,etc.?

 

[coulter]

Just to inform you this instructor is also a highly qualified electrician with over 40 years of experience and training. ...

Humm ... Somehow that makes the offense even worse.

Sorry George - again I edited out about 100 words of relatively truthful opinion:grin:

carl

 

[coulter]

...how do you explain all the inground feeders that have to constantlly be changed. Or all the ocpd's that fail and have to be replaced etc.,etc.?

First, I didn't know I needed to.

But, if I had to guess:
Inground feeders fail mostly from poor installation

OCPDs mostly fail from improper operation and improper specification.

There are 70 year old generating stations, complete with open switchboards out there that are doing fine. Maintenance on them is impecible.

But even so, you and the instructor are correct - even the pyramids (sp?) will eventually return to sand.

carl

 

[petersonra]

Just to inform you this instructor is also a highly qualified electrician with over 40 years of experience and training. He is employed with an outfit that is in the top 5 largest contactors in the country!

that doesn't mean that the criticism doesn't have any validity.

i think there is a certain scare factor being put into the whole arc flash thing, and mostly to benefit people financially.

reading the rules literally would require you to don PPE to operate a light switch.

 

[brian john]

Just curious, how many of these have you tested, rebuilt, or repaired?

Over 30 years, too many to count.

As for the Wiggy stuff...I still stand by my statement I made in another post.

I know of no one that was ever hurt from proper use of a Wiggy*, I know a few that were shocked and/or moderately to severely hurt from not using a Wiggy.

*Had one case were an electrician used his wiggy on 4160.....

 

[weressl]

First, I didn't know I needed to.

But, if I had to guess:
Inground feeders fail mostly from poor installation

OCPDs mostly fail from improper operation and improper specification.

There are 70 year old generating stations, complete with open switchboards out there that are doing fine. Maintenance on them is impecible.

But even so, you and the instructor are correct - even the pyramids (sp?) will eventually return to sand.

carl

Installation is of course a factor as with everything else, but even without installation error your cable will eventually fail.

Buried (inground) feeeders are constructed with polymer jacketing such as PVC, Neoprene and other synthetic material. Polymers are artificial constructs through chemical process. The chemical bonds that are forced to from via chemical reaction will eventually reverse themselves or subject to further chemical reaction that changes their properties into something different.

Reason number two is that no chemical reaction is ever 100% comeplete, eg. not all molecules have taken part of the reaction. These are the measure of purity of the compound that is very important in MV dielectric formulation. (Kerite had championed a high purity compund and that is why their cables were/are the longest lasting.)

Thirdly, no polymers are completely imprevious to moisture. With time they become saturated that will lead to the breakdown of the dielectric properties. Continous metal jacketing systems, such as lead sheeting or CLX type continously welded metallic jackets are far superior, but of course much more difficult to install, more expensive and lead is pretty much outlawed everywhere.

 

[davidr43229]

believe THIS to be the core issue and that OSHA needs to step up in enforcing the short circuit and protection coordination requirements and compliance with those

OSHA 1910.334 Reclosing circuits after protective device operation." After a circuit is deenergized by a circuit protective device, the circuit protective device, the circuit may not be manually reenergized until it has been determined that the equipment and circuit can be safely energized. The repetitive manual reclosing of circuit breakers or reenergizing circuits through replaced fuses is prohibited.

Note: When it can be determined from the design of the circuit and the overcurrent devices involved that the automatic operation of a device was caused by an overload rather than a fault condition, no examination of the circuit or connected equipment is needed before the circuit is reenergized
Just my $.02
edited because I couldn't spell OSHA correctly....

 

[andinator]

Just to inform you this instructor is also a highly qualified electrician with over 40 years of experience and training. He is employed with an outfit that is in the top 5 largest contactors in the country!

In several years of resi work, and now 11 1/2 mos. commercial work, I've come to the realization that in some cases that resume means nothing. Idiocy is everywhere.