Science of Arc Flash & Engineering

[tersh]

I'd wager a bet its open delta for two reasons:

1) A closed delta secondary - wye grounded primary turns the bank into a "grounding transformer", meaning faults on the primary line will cause nuisance fuse blowing on the bank. The solution to that is a delta or ungrounded wye primary (which is great) but susceptible to ferroresonance during single pole switching at voltages over 12kv.

Which leads me to ask, how many volts is your primary system? 34.5kv by chance?

2) Being that in your area everything is connected phase-phase on the LV, you would need a 138 volt transformer to get 240 volts on a wye secondary. This is the ideal solution- but such are rare in the US and really unheard of in many places. Thus the only way to get 240 volts from standard US pole pigs is to connected the secondary in delta.



Anyway- This is a good read:






https://myelectrical.com/notes/entryid/254/what-is-an-open-delta-transformer





at voltages above 12kv can produce ferroresonance

I'll ask the power company what is the exact primary voltage. I forgot. My concern about all this is because the panel in the office building can't be considered Arc Flash Category 0. It is Category 1. So I'm contemplating what kind of PPE to buy to let the electrician wear next time he would open it because I'm nervous already due to the experience in 2015. Also I read:

https://www.ecmweb.com/content/keys-understanding-nfpa-standard-70e

"The key numbers to remember are 1.2 and 40. Incident energy levels greater than 1.2 calories per centimeter-squared can produce second-degree burns. Flame-resistant garments are necessary for protecting yourself against possible burns caused by energy levels above 1.2. Arc-flash energy levels above 40 can be fatal because they're accompanied by a massive pressure blast and sound pressure waves, which produce projectiles. Clothing is available for arc-flash exposures all the way up to 100 calories per centimeter-squared, but it's useless against the force of the pressure blast."

I'm reading this paper too:
https://ep-ca.mersen.com/fileadmin/...fecting-Sustainability-of-Arcs-Below-250V.pdf

"Investigation Of Factors Affecting The Sustainability Of Arcs Below 250V"

However if mwired or other arc flash experts can convinced me there is no way carbon deposit itself can initiate arc flash between phase to phase terminals of breakers. Then I can forgot all of the above, lol.


​

 

[romex jockey]

at voltages above 12kv can produce ferroresonance

my attempt to keep up....>>>

https://www.hdelectriccompany.com/a...lained_Incident Prevention Article_100212.pdf

Ferroresonance is a rare condition most likely to occur with three-phase pad-mount deltaconnected transformers. Not nearly as often, ferroresonance has also been documented in wyewye transformers and in aerial three-pot banks served by long-dedicated aerial circuits.

When ferroresonance does occur in a transformer,
high voltages three to five times the rated primary can
appear on the primary, in the core and on the
secondary.

~RJ~

 

[kwired]

I was not asking if the arc would sustain (for long period), I was only asking if such an arc would at all formed when there were carbon between the phase to phase terminals of breakers for example. The following as I explained was an actual case that occurred in 2015. The electrician simply connected the live wire to the right terminal, and there was a flash. Not only was the chassis torched. He suffered 2nd degree burn to a large rat size area in the arms. Imagine a rat size part bubble over. Not just blister.

There was a first short before the incident above between live wire and chassis which may have caused carbonization in the breaker casing. Many hours later, the above occurred. I was just asking if the carbon deposited was enough to initiate an arc flash. The key word is "initiate", not "sustain". I know when it sustained, it can cause a classic switch gear level arc flash that can throw the electrician to the floor. But it didn't happen or I could be injured too. So what I wanted to know whether it can "initiate" it just by carbon deposition between the 2nd and 3rd terminals of the breakers. Then I can imagine the arc flash forming higher up explaining why the plastic in between them is not scorched.

The supply is 3 phase open delta composed of two 75kVA tranformers. The CoPo even let me paid the two transformers because it was to serve only my office building and a one-storey office beside it. So the incident energy was large considering we didn't have much load that day and there were no breakers upstream of it. So the terminals were exposed to the full blunt of the energy. So could it "initiate" arc flash due only to the carbon deposit? If you or others will say the electrician short the two phases. I was sure it didn't happen that way because of the earlier short and hence we were very careful the second time with 3 or 4 people double checking everything like the breaker in off position and all the chassis were covered, etc. and of course he wouldn't connect the last remaining live terminal to the 2nd filled up terminal but the last empty one (as we clearly saw with our own eyes).

It certainly can, but is difficult to say exactly what will happen. Some cases might not flash at all, Sometimes you might be lucky enough to land your conductor and then later conditions are finally right for it to flash.

 

[tersh]

It certainly can, but is difficult to say exactly what will happen. Some cases might not flash at all, Sometimes you might be lucky enough to land your conductor and then later conditions are finally right for it to flash.

It has happened in the office building with ordinary 240v 3 phase. So next time when I'd send an electrician or the contractor (it was the contractor electrican who got injured) to fix something. What PPE is standard for Arc Flash Category 1? I only have the following. I guess the polyurethane face mask would suffice? But how about whole arms gloves and body shield. In year 2015. The arc flashed injured the electrician hands (rat size bubble blister) and even his chests got some fragments from the vaporizing cooper or exploding mcro plasma burst. What is NEC standard for PPE Cat 2?

Also can you estimate the heat (in Fahrenheit) that can melt the aluminum terminal in the arc flash? I don't think it is 6 times the temperature of the sun. Maybe 1/2 or just a fraction? How do you compute for the heat and melting temperature of it?

Also please share video as I couldn't find in youtube about how normal short circuit damage from 120v in the US look like versus one with arc flash.

One may say all short circuit has arc flash. But I think arc flash (tm) is defined as plasma explosion. Whereas normal short circuit just heat the conductor enough to melt it. I'd like to know the differences in their damages. Of course I and no one would try it. That's why I wanna see video of it. Like how the conductor in 120v short circuit gets damaged if there is no overcurrent device to stop it. In the 2015 incident. There was no overcurrent device to stop it. So how could I tell if the damage above was caused by ordinary short circuit or plasma explosion (micro explosion) damage? Can someone explain in gory details or give references about the exact details. Thank you.

 

[mbrooke]

my attempt to keep up....>>>

https://www.hdelectriccompany.com/a...lained_Incident Prevention Article_100212.pdf




~RJ~

Rare at 12kv, probable at 25kv, common enough at 34.5kv to warrant utilities avoiding ungrounded primaries above 15kv. As such Ungrounded standard product offerings typically stop at 13.8 or 14.4kv:


https://www.powerpartners-usa.com/w...three-phase_t-t_product_spec_sheet.pdf?x57229


Further restrictions are also placed on the tools used to open transformer cut outs:


https://www.sandc.com/globalassets/...all-documents/descriptive-bulletin-811-30.pdf


From page 5:

A Note on Single-Pole Switching

In single-pole switching of ungrounded-primary
three-phase transformers or banks (or singlephase
transformers connected line-to-line), circuit
connections or parameters may, in some cases,
produce excessive overvoltages. In particular, for
the following applications above 22 kV, single-pole
switching by any means—including the Loadbuster
tool—should be performed only under the conditions
stated in italics:


⬥⬥ For unloaded or lightly loaded delta-connected
or ungrounded-primary wye-wye connected
three-phase transformers or banks (or line-toline
connected single-phase transformers), rated
150 kVA or less three-phase, or 50 kVA or less
single-phase—or of any kVA rating when combined
with unloaded cables or lines—where maximum
system operating voltage exceeds 22 kV. Single-pole
switching should be performed only if each phase
is carrying 5% load or more, or if the transformer
or bank is temporarily grounded at the primary
neutral during switching.


⬥⬥ For loaded or unloaded ungrounded-primary
wye-delta connected three-phase transformers or
banks—alone or combined with unloaded cables or
lines—where maximum system operating voltage
exceeds 22 kV. Single-pole switching should be
performed only if each phase is carrying 5% load
or more and if the lighting-load phase is always
switched open first (or switched closed last); or if
the transformer or bank is temporarily grounded
at the primary neutral during switching.

In other words switching can only be performed with the bank grounded or well loaded to dampen out the ferroresonant oscillations. When feeding a few or one customer like in most North American applications, the odds of having an unloaded or lightly loaded bank skyrocket.

 

[tersh]

It has happened in the office building with ordinary 240v 3 phase. So next time when I'd send an electrician or the contractor (it was the contractor electrican who got injured) to fix something. What PPE is standard for Arc Flash Category 1? I only have the following. I guess the polyurethane face mask would suffice? But how about whole arms gloves and body shield. In year 2015. The arc flashed injured the electrician hands (rat size bubble blister) and even his chests got some fragments from the vaporizing cooper or exploding mcro plasma burst. What is NEC standard for PPE Cat 2?

Also can you estimate the heat (in Fahrenheit) that can melt the aluminum terminal in the arc flash? I don't think it is 6 times the temperature of the sun. Maybe 1/2 or just a fraction? How do you compute for the heat and melting temperature of it?

Also please share video as I couldn't find in youtube about how normal short circuit damage from 120v in the US look like versus one with arc flash.

One may say all short circuit has arc flash. But I think arc flash (tm) is defined as plasma explosion. Whereas normal short circuit just heat the conductor enough to melt it. I'd like to know the differences in their damages. Of course I and no one would try it. That's why I wanna see video of it. Like how the conductor in 120v short circuit gets damaged if there is no overcurrent device to stop it. In the 2015 incident. There was no overcurrent device to stop it. So how could I tell if the damage above was caused by ordinary short circuit or plasma explosion (micro explosion) damage? Can someone explain in gory details or give references about the exact details. Thank you.

[above is message #104]

By the way. I want to know something. In the US. Is it a requirement that there must always be main breaker in the service entrance before the gutter box and meters and breakers. In my office building original electrical plans. There was a main breaker. But the electrical contractor didn't put one because he was into cost cutting and told me the budget for it was used up in other area of the building. That was the reason there was no overcurrent breaker upstream of the breakers below the meters.

So without the main breaker and it is very difficult to add one because of long process and permit from city hall. Any future electrician who wants to work with the breakers below the meters need to call the PoCo to shut down the power to entire building. However, my concern now is just any electrician turning off any individual breaker which required putting the hands inside the panel to reach the breaker levers. That's why I'm asking what kind of PPE for Arc Flash Category One (1) Hazard. What guys do you use? And also please share the video commented above as I wanted to see it very much. Thanks a lot.

 

[kwired]

[above is message #104]

By the way. I want to know something. In the US. Is it a requirement that there must always be main breaker in the service entrance before the gutter box and meters and breakers. In my office building original electrical plans. There was a main breaker. But the electrical contractor didn't put one because he was into cost cutting and told me the budget for it was used up in other area of the building. That was the reason there was no overcurrent breaker upstream of the breakers below the meters.

So without the main breaker and it is very difficult to add one because of long process and permit from city hall. Any future electrician who wants to work with the breakers below the meters need to call the PoCo to shut down the power to entire building. However, my concern now is just any electrician turning off any individual breaker which required putting the hands inside the panel to reach the breaker levers. That's why I'm asking what kind of PPE for Arc Flash Category One (1) Hazard. What guys do you use? And also please share the video commented above as I wanted to see it very much. Thanks a lot.

Not an NEC issue, some POCO's will have different rules than others though - they are usually concerned about how easy it may be to tap onto unmetered conductors when deciding what their rules may be. This often results in no enclosures ahead of meters unless they are capable of POCO somehow locking them. Multi-meter centers get POCO approval, often based on how easily one may be able to tap into unmetered conductors also, though a majority of them are designed that it is difficult to access anything not metered without breaking locks or seals of some sort.

 

[tersh]

My house is served by a 10kVA pole transformer, assumed 2% impedance. 10,000VA / 240V / 0.02 = 2,083A short circuit current available.

While that's a lot of current, compared to some industrial installations that have 50kA available, I'd say 2kA is not substantial as far as arc fault risk is concerned. I'm still not going to put myself in a situation where I could come in contact with live busbars or drop tools or hardware on them.

I just talked to the PoCo. The voltage of the primary is 34.5kV for the 75kVA transformers (they said the 115kV is only from substation to other facilities). I'm computing for the exact short circuit current from source. In the computation above. Why was 240V used? It's the secondary voltage. Aren't you supposed to use the primary voltage? For my 34.5kV primary, then should the short circuit current be:

75,000/34,500V/ 0.02 = 108.69A or is it

75,000/240v/0.02 = 15,625A?

I'm concerned with all this because I thought I witnessed an arc flash. When you see one, you will never feel the same again. You will never want to see someone work live and want to be sure you are far away from it. And you want to be sure the electrician will always wear some kind of PPE.

 

[mbrooke]

For incident energy and interrupting you assume an infinite primary source on the transformer.

 

[tersh]

I'd wager a bet its open delta for two reasons:

1) A closed delta secondary - wye grounded primary turns the bank into a "grounding transformer", meaning faults on the primary line will cause nuisance fuse blowing on the bank. The solution to that is a delta or ungrounded wye primary (which is great) but susceptible to ferroresonance during single pole switching at voltages over 12kv.

Which leads me to ask, how many volts is your primary system? 34.5kv by chance?

2) Being that in your area everything is connected phase-phase on the LV, you would need a 138 volt transformer to get 240 volts on a wye secondary. This is the ideal solution- but such are rare in the US and really unheard of in many places. Thus the only way to get 240 volts from standard US pole pigs is to connected the secondary in delta.

Yes, it's 34.5kv as the PoCo told me today. What were you describing above? Please relate it to arc flash possibility.

I'd make it a closed chapter if the electrician just accidentally connected phase to phase and it was a phase to phase dead short back in 2015. But it really wasn't. He just connected the live wire to the terminal lugs and it arc flashed to the middle terminal by perhaps just carbon deposits?? What kind of scenario or ferroresonance coincidence can create such an arc flash provoked by the carbon and not dead short at all?

Anyway- This is a good read:






https://myelectrical.com/notes/entryid/254/what-is-an-open-delta-transformer





at voltages above 12kv can produce ferroresonance

 

[kwired]

I just talked to the PoCo. The voltage of the primary is 34.5kV for the 75kVA transformers (they said the 115kV is only from substation to other facilities). I'm computing for the exact short circuit current from source. In the computation above. Why was 240V used? It's the secondary voltage. Aren't you supposed to use the primary voltage? For my 34.5kV primary, then should the short circuit current be:

75,000/34,500V/ 0.02 = 108.69A or is it

75,000/240v/0.02 = 15,625A?

I'm concerned with all this because I thought I witnessed an arc flash. When you see one, you will never feel the same again. You will never want to see someone work live and want to be sure you are far away from it. And you want to be sure the electrician will always wear some kind of PPE.

You did witness an arc flash, but it was at the lower end of scale when it comes to severity, still an eye opening experience for most though. Again amount of available fault current is only one piece of the puzzle. The more available fault current there is the higher the severity possibly can be with arc flash incidents though.

Commonly used methods to calculate available fault current assume infinite capacity of the primary, that does give you basically worst case possible with your result, which is better than underestimating in most situations. Also understand that a 75 kVA transformer is a relatively small load on many distribution systems and the difference between infinite primary ability and actual primary side impedance may not be all that significant to to the point being determined as most of the impedance is going to be in the transformer and not the distribution system.

 

[jeremy.zinkofsky]

Yes, exactly. How high incident energy before it is considered a safety hazard to be around without any kind of PPE.

When you have a small transformer, like 500vA, the overcurrent can still reach 20 times or much higher than it before the winding heats up enough to be destroyed. So in a 100kVA utility pole transformer. Overcurrent can go much higher. Let's say its connected to a 12kV lines. And we eliminate all conductor impedance. And supposed the lineman (for sake of discussion) just shorted the secondary of the transformer. Would there be arc flash meters wide?

Or let's take the case of utility pole transformers where simply the terminals got shorted by accidents. Are there videos of these showing how big is the arc flash?
​

Tersh, buddy, you are making my head spin. Can't imagine how fast yours is.

You need to take a step back and think a bit more simplistic about arc flash. You are expecting to see a correlation between all of the physics going on in an arc flash with available short circuit current and you are over-complicating the theory.

Short circuit current is a function of impedance. An Arc flash blast is basically a function of expanding and collapsing electrical fields. It is true that fault current and arc flash are co-related, however they are not this complicated physics puzzle that you are making them out to be.

No one can answer your questions regarding how much energy in an arc flash, particle destruction, etc. because you are not considering that incident energy is a function of time. The length of time that a fault is in a system before being cleared is what determines the available incident energy. So what you should be including in your hypotheticals are the clearing times of the upstream protective device. It's not any more complicated than that. Also, much of what you are asking has little to do with electricity and more to do with material physics.

The electrical industry did not create Arc Flash guidelines solely based on the complicated physics of material science and electromagnetism. Engineers like simple methods for calculation and thus certain assumptions are built into the calcs. That being said, have a look at IEEE 1584 Guide for Arc Flash. This guideline will show you the equations used when determining incident energy. I believe this will give you the mathematical explanation you are looking for.

When i calculate arc flash energy in a system, I use a program like SKM or ETAP which basically uses the newton-raphson method for approximating an answer. Notice i used the word approximate because that is how arc flash is calculated.

Your kind of unnecessarily spinning your wheels.

 

[kwired]

Tersh, buddy, you are making my head spin. Can't imagine how fast yours is.

You need to take a step back and think a bit more simplistic about arc flash. You are expecting to see a correlation between all of the physics going on in an arc flash with available short circuit current and you are over-complicating the theory.

Short circuit current is a function of impedance. An Arc flash blast is basically a function of expanding and collapsing electrical fields. It is true that fault current and arc flash are co-related, however they are not this complicated physics puzzle that you are making them out to be.

No one can answer your questions regarding how much energy in an arc flash, particle destruction, etc. because you are not considering that incident energy is a function of time. The length of time that a fault is in a system before being cleared is what determines the available incident energy. So what you should be including in your hypotheticals are the clearing times of the upstream protective device. It's not any more complicated than that. Also, much of what you are asking has little to do with electricity and more to do with material physics.

The electrical industry did not create Arc Flash guidelines solely based on the complicated physics of material science and electromagnetism. Engineers like simple methods for calculation and thus certain assumptions are built into the calcs. That being said, have a look at IEEE 1584 Guide for Arc Flash. This guideline will show you the equations used when determining incident energy. I believe this will give you the mathematical explanation you are looking for.

When i calculate arc flash energy in a system, I use a program like SKM or ETAP which basically uses the newton-raphson method for approximating an answer. Notice i used the word approximate because that is how arc flash is calculated.

Your kind of unnecessarily spinning your wheels.

You summed up what I have kept trying to tell him pretty well. He keeps overthinking it for the most part, and at same time kind of ignoring the time factor. Every arc flash incident will have it's own set of variables making nearly every incident a little different.

Just because you have a high level of fault current available doesn't automatically mean you will have a high energy arc flash event. Lower fault current but for longer time can have higher arc flash energy level.

Just because there is carbon deposits between live terminals doesn't mean you will automatically have an arc flash incident, but does increase the chance of triggering some sort of flash event.

 

[mbrooke]

Yes, it's 34.5kv as the PoCo told me today. What were you describing above? Please relate it to arc flash possibility.

I was basically describing why your secondary is open delta instead of Wye grounded.

I'd make it a closed chapter if the electrician just accidentally connected phase to phase and it was a phase to phase dead short back in 2015. But it really wasn't. He just connected the live wire to the terminal lugs and it arc flashed to the middle terminal by perhaps just carbon deposits?? What kind of scenario or ferroresonance coincidence can create such an arc flash provoked by the carbon and not dead short at all?

Ferroresonance can create over voltages which break down insulation, but that is not what happened in your scenario.

 

[tersh]

Tersh, buddy, you are making my head spin. Can't imagine how fast yours is.

You need to take a step back and think a bit more simplistic about arc flash. You are expecting to see a correlation between all of the physics going on in an arc flash with available short circuit current and you are over-complicating the theory.

Short circuit current is a function of impedance. An Arc flash blast is basically a function of expanding and collapsing electrical fields. It is true that fault current and arc flash are co-related, however they are not this complicated physics puzzle that you are making them out to be.

No one can answer your questions regarding how much energy in an arc flash, particle destruction, etc. because you are not considering that incident energy is a function of time. The length of time that a fault is in a system before being cleared is what determines the available incident energy. So what you should be including in your hypotheticals are the clearing times of the upstream protective device. It's not any more complicated than that. Also, much of what you are asking has little to do with electricity and more to do with material physics.

In the incident in 2015. There is no upstream protective device. The contractor was saving money and didn't put any main breaker upstream of it. So the contractor was to blame for what happened to their own electrician, that was the reason the electrician didn't come after me (it's their fault).

Anyway. About the material physics and electromagnetism of it. Presently I'm discussing with an arc flash expert who think of arc flash all day because that's his line of expertise and work. See PaulEngr detailed replies and messages at:

https://brainfiller.com/arcflashforum/viewtopic.php?f=2&t=4873&p=22370

Do you know of other exclusive arc flash forums? I want to understand if the following is really caused arc flash damage:

This is what I want to understand. It is possible for the arc to take the middle screw path then go up by curving outside enough not to damage the plastic enclosure between them then go up and hit the right terminal and melt one third of it? Can arc flash do this? Remember what happened was the electrician simply lowered the live wire to the right terminal without touching the middle and it suddenly flashed damaging the terminals and his hands. It's not dead short. Is the above consistent with arc flash jumping between the two terminals with only carbon as the triggering factor?

I want to ask other arc flash experts in USA what are their experiences regarding the above. 120/240v arc flash is rare so there is few resources about it.

Also does anyone know what happened in 2009 in Georgia when one of two electricians died when removing temporary 120/240v panel from a construction site? ​

The electrical industry did not create Arc Flash guidelines solely based on the complicated physics of material science and electromagnetism. Engineers like simple methods for calculation and thus certain assumptions are built into the calcs. That being said, have a look at IEEE 1584 Guide for Arc Flash. This guideline will show you the equations used when determining incident energy. I believe this will give you the mathematical explanation you are looking for.

When i calculate arc flash energy in a system, I use a program like SKM or ETAP which basically uses the newton-raphson method for approximating an answer. Notice i used the word approximate because that is how arc flash is calculated.

Your kind of unnecessarily spinning your wheels.

 

[tersh]

In addition to the above. I just wanted to know how the arc flash damaged the breakers. I just think now there may be two separate arc flashes in the terminals. See:

The first arc flash occured between the terminal screws where it curved outside enough not to damage the plastic enclosure between them. Then the second arc flashed occured between the right terminal and live wire (from above (not shown). We can say the separate arc flashes occured at same time.. just separate areas. Was this possible?

Before today I was thinking there was just one big arc flash that took the path of 2nd terminal screws to the right lugs. But why does the right terminal suffered so much damage versus the middle terminal? A two stage or separate arc flash can explain them right?

Which of the above scenario is more likely and matched experimental setup? I was sure the electrician didn't connect the two live wires together so it wasn't just a normal dead short.

My concern about all this is what if the panel full of dust would be opened just to turn off the breakers (in case the rooms need service). Would it just spontaneously arc flashed if the dusts happen to have a lot of carbon content. So I was thinking what is the best PPE for Arc Flash Category 2 Hazard I can buy and be ready to give to electrician.

 

[kwired]

In addition to the above. I just wanted to know how the arc flash damaged the breakers. I just think now there may be two separate arc flashes in the terminals. See:

The first arc flash occured between the terminal screws where it curved outside enough not to damage the plastic enclosure between them. Then the second arc flashed occured between the right terminal and live wire (from above (not shown). We can say the separate arc flashes occured at same time.. just separate areas. Was this possible?

Before today I was thinking there was just one big arc flash that took the path of 2nd terminal screws to the right lugs. But why does the right terminal suffered so much damage versus the middle terminal? A two stage or separate arc flash can explain them right?

Which of the above scenario is more likely and matched experimental setup? I was sure the electrician didn't connect the two live wires together so it wasn't just a normal dead short.

My concern about all this is what if the panel full of dust would be opened just to turn off the breakers (in case the rooms need service). Would it just spontaneously arc flashed if the dusts happen to have a lot of carbon content. So I was thinking what is the best PPE for Arc Flash Category 2 Hazard I can buy and be ready to give to electrician.

Those dusts wouldn't even need to have carbon content, just need to be conductive and reach high enough level of conductivity between terminals to start some current flow. That dust alone probably isn't resulting in severe arc flash, but once conductor/terminal metals start vaporizing you have higher conductivity to support even more current flow through the vapor cloud and that ends up being what turns it into a more severe arc flash incident, the continued arcing resulting from conductive gases being present.

 

[tersh]

I was basically describing why your secondary is open delta instead of Wye grounded.




Ferroresonance can create over voltages which break down insulation, but that is not what happened in your scenario.

After the arc flash occured that day in 2015. We were thinking how to disable the power since there was no main breaker. The contractor engineer talked with the power utility company. The solution was simply to remove the meter from the power socket and the PoCo engineers gave us permission. So the electrician removed it but he had hard time unplugging it. Do you know the proper way to remove meter so it won't get damaged in case we need to service one of the breakers underneath the meters in future?

But the electricians were so ignorant about meter sockets they didn't know how the bypass lever worked. One of them pulled it up to disconnect the power with the upper wires live. They actually were able to remove and replaced the two arc flashed wires and added/connect it the wires to new 3-pole breaker. Days later I realized bypass lever up means it was connected to the bottom wires! Very stupid mistakes. It was good they still followed proper procedure by taping the wires ends before replacing them or it could cause another arc flash or short. You can see the contractor electricians are good in connecting it and there was no short to either phase to phase or phase to chassis. Therefore in the arc flash incident earlier, they really just lowered the live wire to the right terminal and didn't short it to the left wire or terminals. Hence it's the carbon that really did that.

In USA. Can any electrician cut the seal, remove the meter from socket even if they were given permission by the PoCo? I assumed all electricians in US know how the bypass lever works. In the Phils. Most electricians don't know how it works.

Also even if we put a main breaker before gutter. PoCo told us it had to be sealed too. Therefore to fix any breakers, we need to ask them permission to open the main breaker box with the switch inside or we ask them permission or let them temporary remove the meter from socket themselves. This was one reason I didn't insist they added main breaker after contractor cheated because it would take very long city hall process just to add a main breaker (even now, there are many red tapes). And the PoCo could just remove the meter from socket in case service is needed in future to replace the breakers. Actually btw.. the PoCo told me why didn't I get it replaced live as that's what electricians are good at.

For US buildings with 5 disconnects/breakers. How do you replace any breaker when there is no main breaker. Do you remove the meter from socket (with permission from PoCo) or do you let them cut the power to the entire building by removing all the service entrance wires temporarily?

 

[kwired]

After the arc flash occured that day in 2015. We were thinking how to disable the power since there was no main breaker. The contractor engineer talked with the power utility company. The solution was simply to remove the meter from the power socket and the PoCo engineers gave us permission. So the electrician removed it but he had hard time unplugging it. Do you know the proper way to remove meter so it won't get damaged in case we need to service one of the breakers underneath the meters in future?

But the electricians were so ignorant about meter sockets they didn't know how the bypass lever worked. One of them pulled it up to disconnect the power with the upper wires live. They actually were able to remove and replaced the two arc flashed wires and added/connect it the wires to new 3-pole breaker. Days later I realized bypass lever up means it was connected to the bottom wires! Very stupid mistakes. It was good they still followed proper procedure by taping the wires ends before replacing them or it could cause another arc flash or short. You can see the contractor electricians are good in connecting it and there was no short to either phase to phase or phase to chassis. Therefore in the arc flash incident earlier, they really just lowered the live wire to the right terminal and didn't short it to the left wire or terminals. Hence it's the carbon that really did that.

In USA. Can any electrician cut the seal, remove the meter from socket even if they were given permission by the PoCo? I assumed all electricians in US know how the bypass lever works. In the Phils. Most electricians don't know how it works.

Also even if we put a main breaker before gutter. PoCo told us it had to be sealed too. Therefore to fix any breakers, we need to ask them permission to open the main breaker box with the switch inside or we ask them permission or let them temporary remove the meter from socket themselves. This was one reason I didn't insist they added main breaker after contractor cheated because it would take very long city hall process just to add a main breaker (even now, there are many red tapes). And the PoCo could just remove the meter from socket in case service is needed in future to replace the breakers. Actually btw.. the PoCo told me why didn't I get it replaced live as that's what electricians are good at.

For US buildings with 5 disconnects/breakers. How do you replace any breaker when there is no main breaker. Do you remove the meter from socket (with permission from PoCo) or do you let them cut the power to the entire building by removing all the service entrance wires temporarily?

A good safety procedures policy will say after opening the circuit somewhere upstream that you still test for voltage before you perform your work, if that would have been something those workers were in the practice of doing they would have figured out the lines they were working on were still energized even if they didn't fully understand that bypass handle in the meter socket.

But keep in mind even that that still leads to potential arc flash event when it comes time to close the bypass handle and install the meter - if there is a fault when you close the circuit.

 

[tersh]

A good safety procedures policy will say after opening the circuit somewhere upstream that you still test for voltage before you perform your work, if that would have been something those workers were in the practice of doing they would have figured out the lines they were working on were still energized even if they didn't fully understand that bypass handle in the meter socket.

But keep in mind even that that still leads to potential arc flash event when it comes time to close the bypass handle and install the meter - if there is a fault when you close the circuit.

The 3rd technican was able to test that there was voltage between the phase and the chassis. He told the other electricians it had strong grounds, that's why the others got careful. He didn't test phase to phase because he thought pulling the bypass lever up would disconnect the top and bottom anyway. I remembered him shaking his head wondering why phase to voltage had 120v. They are not familiar with the PoCo transformer centertapped neutral thing and all this split phase detail which is basic to most americans.