Arc Flash Documentation

[Beuwolf_1 0]

I know this is a bit out of the rhelm of the normal control type topic, but it seems that I have been awarded the new title of "Arc Flash Guru Guy" for our facility. I was wondering if anyone else out there has been awarded this title, and if so, have they found any good modeling and analysis software? Also, has anyone found any good websites regarding the arc flash topic? Any information on this subject would be fantastic. Thanks in advance, Beuwolf

[TimWilborne 108]

I have just recently been apointed that position. Reading the NFPA 70E is a must to start with. Have you got it yet?

[Beuwolf_1 0]

I am waiting for my copy to come thru the mail. I am also investigating different modeling software too, just not sure what to look for besides the typical price justification. Also has anyone had any formal arc flash training that they would be willing to recommend?

[TimWilborne 108]

Also there is a some NFPA 70E Blue Book that might explain things a little better. I'm going to get one this weekend. Will let you know if it helps Depending on the complexity of your power distribution system, you may not need modeling software. The calculations are not that hard. I'm writing some code to do it. Don't know how much modeling software is but you may be able to do it with your own software (even excel could make the calculations) or do it on paper. Talked to another guy and he said if you do it yourself, just document how you did it and OSHA will be fine with it.

[benbrad 0]

Found this http://www.bussmann.com/apen/arcflash/ May be worth a look, once you've registered.

[Wordman 0]

We have SKM Systems's ArcCalc software. It has specific device trip curves for many brands of protective devices, and documents everything including the boundry, incident energy and PPE level required. It even can print 70E compliant labels to put on your panels. In the past we had just used the 4ft default for 50-600V as allowed for panels where you haven't done the calculation, but for most of the panels, 4ft was absurd once you calculated it.

[TimWilborne 108]

How did you calculate you energy for PPE? Or did you just go by the chart in the book. Both the 48" and chart are definately absurd after viewing the results of the calculations. Did you look at changing you fuse types to reduce you Arc Flash? The type of fuse can really reduce it. I'm debating whether it would be cost effective or not to reduce the PPE that is necessary Edited 23 Feb 2006 by TWControls

[Wordman 0]

"in lieu of the flash hazard analysis of 130.3(A), Table 130.7©(9)(a) shall be used to determine the hazard/risk category for a task" For instance, if you were voltage testing 480V, and you obviously are standing within 48", so you have to have PPE Level 2*

[TimWilborne 108]

Did you just impement the Arc Flash labeling of the panels or are employees required to use the proper PPE? We are wondering how much resistance we will get from having to wear the PPE. Do you have any suggestions or are some PPEs for Arc Flash more comfortable than others?

[gravitar 3]

Was the pun intended? :)

[Wordman 0]

The employees are required. If they were caught without it, they woulld be written up. It's just the rules. We provide them with the FR pants and shirts. There is no excuse. Usually during the hot summer months, they just wear the pants and have the shirt ready in case they need to perform a task that requires it. They go through Electrical Safety training so they understand it's an OSHA requirement.

[TimWilborne 108]

So did most of your panels require class 2 protection? One other thing I haven't found in the book is when we are working above 6' from the ground, we are also required to wear fall protection. They are not allowed to wear rings but our harnesses have metal buckles. How are we suppose to protect them from the metal buckles on the harness?

[Wordman 0]

We have fall protection requirements here too. We had to select a harness that didn't flash or melt and affect the FR rating. I don't remember ever discussing the metal ring. But I think at the end of the day, we decided that here people probally wouldn't be working around exposed live conductors in a harness anyway. It seems to me you can read it two ways. You could say that it is a conductive article being worn, and not allow it period. Or a conductive material being handled: 130.6(E) "Conductive materials, tools, and equipment that are in contact with any part of an employee's body shall be handled in a matter that prevents accidental contact with live parts..." It also says that "means shall be employed to ensure that conductive materials approach exposed live parts no closer than that permitted by (restricted approach boundry)" So for 50 to 300V, it would be avoiding contact. For 301-750V it would mean ensuring it was 1ft away from any exposed part. What 'means to ensure' would be I do not know. It's a very good question.

[GerryM 2]

I also have done the arc flash for my plant. I started by hiring a PE to do a full Short circuit, coordination, and arc flash study of the plant distribution down to the panelboard and distribution bus level. The short circuit study uncovered many instances of circuit breakers not rated high enough. I just finished correcting all of that with replacements and series ratings. The PE used SKM software. The IEEE calculation is supposed to be better than the NFPA calculation but I am not sure why. The full SKM software to do the short circuit, etc. is about $10,000 for a decent sized facility. The PE I hired was a little cheaper. Then I bought the SKM Arc Calc program for $995. And I am now calculating arc flash down to each individual machine's disconnect, based on the short circuit values from the study. The bussmann short circuit guides are great for calculating short circuit currents, they match the SKM software pretty well. Don't forget the 4X FLA Motor Load contribution. For PPE we have been going by the chart in the NFPA 70E, until now. We changed alot of fuses feeding our bus duct distribution system and we now have almost all Class 0 or 1 throughout the entire plant. We use the bussmann low peak fuses, class RK1. If you have a small plant you can calculate everything just fine. If you have a large plant, especially an old plant with alot of revisions over the years, I reccommend hiring a PE to get you started. This whole issue is over safety and I would think when dealing with OSHA a PE's stamp is alot more convincing than a staff engineer's or tech's work. Especially if they visit after an accident. The PPE our guys wear is all Class 2, or if they wear long sleeves there own clothes are Class 0. They have a couple of Class 4 suits for the high voltage rooms, but there may be only one place where they are required, since the study was done. We have one spot on out 480V substations where the incident energy is over Class 4. So basically you can't work on the substation without completely deenergizing it. You wouldn't want to work on it hot anyway. We are still labeling everything. The label is necessary to tell the employees what level of PPE is required. You will get alot of resistance from all employees. I even gave it some resistance. Our PPE requirement came from our safety department. I got involved with the calculations later on. Our PPE kickoff started with two days of electrical hazard training. It was all those videos of guys dying of electrical shock and stuff. It was taught by a guy who worked the Utility business his whole life, so no one could win an argument with him. It set the tone very well. I believe the training on how and when to use PPE is required by OSHA as well. Edited 24 Feb 2006 by GerryM

[TimWilborne 108]

Just finished writing software to calculate the values using the IEEE method. Hadn't thought about hiring a outside guy who was experienced in this to introduce the arc flash training. This could give it much more weight than than our safety director doing the class. Are there any faster acting circuit breakers that could replace some of our existing circuit breakers? The fault clearing times on these are killing us. With the fuses we are at class 1 on most of our machines.

[TimWilborne 108]

One of the guys just asked me if prescription safety glasses would meet arc flash specs since they have metal frames that could absorb heat. Any ideas?

[GerryM 2]

In our last training session we were informed that plastic frames are now required for electrical work. I don't know what code book calls for it though, probably OSHA. The glasses are supposed to meet an ANSI spec., i believe it is Z87.1 I have a sefety manager that handles all of that. So i'm not completely familiar with all the glasses requirements.

[DanW 41]

A little off-topic, but there's a couple great video clips of some serious arcing at http://205.243.100.155/frames/longarc.htm see: - 230 kV (1.2 MB mpeg) and 115 kV image of three-phase air break switches opening "hot" - 500 kV switch creates a 100+ foot arc when one phase opens "hot" (1.5 MB mpeg) - Arcing fault causes a substation transformer to explode (5.1 MB mpeg) New - Another arcing fault in a substation - HV fuse fails to open properly (10 MB avi) Dan

[Kirby K. 0]

This 70E thing has almost turned into a joke. I work in the Auto manufacturing industry (UAW), and now when I open a panel to look at the status of a PLC, I must wear my "face shield (special UL appr.), HV gloves (rubber/ under leather), special clothing and no synthetics'. The company had to pay out big bucks for a survey on 'calory' exposure, training, etc etc. Now, per law, when your working with a 24 volt signal and a 22 ga. wire in a enclosure that has 480v in it......you gotta wear all that. Unless you lock out/ tag out. So I really love these guys out there making all the rules for us. If your a real sparky, you know the one hand rule, dont touch the hot wire, and dont carry on a conversation when you got your hand in the box. Oh, did I mention how comforably WARM these Bullwark shirt and pants are. Cant wait for summer.

[GerryM 2]

It is extreme sometimes. We used to cheat all the time, until we got caught and some of the electricians were written up. Now we try to design for it, and alot of our panels are at Class 0 or 1, so the need for the heavy gear is minimized to almost never now. The fact most of our equipment is fed from fuses saved us in the long run. Unfortunately, sometimes the only way people will take it seriously is to have an accident happen. That is what pushed the whole thing at my place. Fortunately the guy recovered almost all the way. Edited 1 Mar 2006 by GerryM

[TimWilborne 108]

Ok, got most of my calculations done and have designed my labels, now I am a little confused about where to put them. Do they need to go on the front of the panel or can they go on the side of the panel? Most of our labels are on the side of the panel. The reason I do not really want them on the front of the panel is it is subject to more abuse and dirt than the side of the panel.

[TimWilborne 108]

One of our welder technicins asked another question. When working on a wire feeder (which is less than 50 volts), do you need arc flash protection since it is feed from a 480 Volt power unit. My initial answer is no since the power unit is pretty much the same as a transformer but was wondering what others thought

[GerryM 2]

My take on it is: If you work in a hot panel with a voltage >50 volts then you need the arc flash stuff, unless the >50 volts stuff is segragated and covered from the under 50 volts stuff. Most of our panels have a main CB, 480V. If the three wires at the top of the CB are hot but the main is off, the panel is still considered hot. Unless the CB is covered. Which was tuff for all of else to swallow initially. Now we mount disconnects on the outside of the panel, and lock that out. Edited 1 Mar 2006 by GerryM

[Beuwolf_1 0]

Now how important is it to "REDO" all the calculations if motors are added or transformers changed and all that good stuff? In some plants I have been in, this could be almost impossible since machinery is moved in and out of production areas all the time. Would calculations just be done on the buss drops, or per machine? We typically move some kind of large current type device here at least once a week if not more. According to what I have read, that would require a new set of calculations, and it would mean a full time job for some one. Or am I making a mountain out of a mole hill.

[GerryM 2]

I think you summed it up the best here. Just use your best judgement when you move something.