The most frequently asked question that I receive regarding the 2018 edition of IEEE 1584 is:
“How do I determine the electrode configuration?”
The 2002 edition was based on arc flash tests with the electrodes oriented in a vertical configuration. When performing an arc flash study based on the 2002 edition, there were only two options available – an arc flash in an enclosure and an arc flash in open air – both based on a vertical electrode configuration.
Since the original 2002 edition was published, additional research has shown that incident energy can be influenced by the electrode configuration. As a result, many new tests were conducted using additional new electrode configurations including vertical electrodes that terminate into an insulating barrier as well as horizontal electrodes in an enclosure/box and in air. This is in addition to the original vertical configurations in an enclosure and in air. The additional configurations and the resulting Continue reading
Yes, you read the title correctly – Second degree burns, my wife and a chili cookoff! And it all took place at home. But, before I get into that story, let me back up a bit.
Standards such as NFPA 70E, IEEE 1584 and several others address the arc flash hazard in terms of incident energy with the severity quantified in terms of calories per square centimeter (cal/cm2). The generally accepted value for “the onset of a second degree burn” is 1.2 cal/cm2 as shown in the following examples.
The NFPA 70E definition of the Arc Flash Boundary contains an Informational Note that references the “the onset of a second degree burn on unprotected skin is likely to occur at an exposure of 1.2 cal/cm2 “
“The onset of a second-degree skin burn injury based on the Stoll curve.” is also found in Informational Note 3 of the definition of Arc Rating. Continue reading
125 kVA – Going, going, gone!
After much speculation about the fate of the 125 kVA transformer “exception”, the 2018 Edition of IEEE 1584 – IEEE Guide for Performing Arc-Flash Hazard Calculations has finally been published and made it official. The 125 kVA transformer exception has been deleted!
In its place is the new language:
“Sustainable arcs are possible but are less likely in three-phase systems operating at 240 V nominal or less with an available short circuit current below 2000A” Continue reading
As the International Chair of IEC TC78 Live Working Committee, I am excited to announce the recent publication of the second edition of IEC Standard 61482-2 Live working – Protective clothing against the thermal hazards of an electric arc – Part 2: Requirements.
This revised standard is applicable to protective clothing used in work where there is the risk of exposure to an electric arc hazard. The document specifies requirements and test methods applicable to materials and garments for protective clothing for electrical workers against the thermal hazards of an electric arc. Continue reading
The 65th Annual IEEE-PCIC Conference will be held this year in Cincinnati, Ohio on September 24-26.
This year I will have both my “IEEE hat” and “IEC hat” on and join a couple of colleagues in presenting a technical paper comparing the use of ANSI vs. IEC short circuit calculations as part of an arc flash study. The official title is: “Comprehensive Overview and Comparison of ANSI vs. IEC Short Circuit Calculations: Using IEC Short Circuit Results in IEEE 1584 Arc Flash Calculations” Continue reading
I have been receiving many questions lately about the status of the next edition of the standard: IEEE 1584 – IEEE Guide for Arc-Flash Hazard Calculations. As Vice-Chair of the IEEE 1584 working group, I would like to provide an update about the progress and current status.
The formal voting process (known as a Sponsor Ballot) for the next edition of IEEE 1584 was actually completed during August of 2017. However, that was only the beginning of a very long process. As part of the first round of balloting, many comments were submitted by the voters which needed to be formally addressed. There are over 160 people in the ballot pool that represent a wide cross section of the industry.
The IEEE 1584 Working Group voted to establish a Ballot Resolution Committee (BRC) which includes the Chair, Secretary and me along with a few others that represent various sectors of the industry. Continue reading
When the topic of incident energy above 40 calories per square centimeter (cal/cm^2) comes up, the discussion can be quite interesting. People will sometimes refer to the high values in terms of a bomb or some other sensationalized description. Although a higher calculated incident energy can be more hazardous, all is not as it appears to be. Is the large value due to a very strong source or is it simply due to a protective device possibly taking a long time to clear? Each will behave differently.
When performing an arc flash study, if the calculated incident energy exceeds cal/cm^2 at any locations. people often just shake their head and ask, “Now what do we do?”
We need to place the equipment into an electrically safe work condition but that in itself poses some risk.
When the 40 cal/cm^2 value is exceeded, it is often treated like an absolute go/no-go threshold and can trigger many different responses and comments that are not always correct. Above 40 cal/cm^2, arc flash labels may have the statement “No PPE Available.” This value also frequently triggers using the signal word “DANGER” on the label. There may be comments made such as, “Above that value, the blast pressure will kill you.” My favorite sensationalized comment that I have heard is, “Above that level, PPE just Continue reading
Published: May 2017
Part 2 of 2 Part Series
There is an endless list of reasons for keeping your skills and knowledge up-to-date in the electrical industry. These days many electrical industry-licensing boards require a contractor to attend a minimum number of hours of training each year, often referred to as continuing education. However, the best reason is simply to stay current with the latest technology in the electrical industry.
One of the biggest attractions to any program is the word “FREE.” It will draw attention to anything, and there are a lot of FREE resources out there. The following are some examples of FREE electrical industry training options and resources.
Webinars: Free webinars, and the invitations to them, are everywhere. Although some webinars may be a bit commercial, a growing number are jam-packed with the latest information about industry trends, products, methods and ideas.
Published: May 2017
Part #1 of a 2 Part Series:
What if you had been stranded on a deserted island for the past five years? By the time you were rescued, you would have missed the explosion of real-time social media, including Facebook, YouTube and Twitter, mobile marketing trends, as well as advancements in smart grids and wind and solar energy—it would be more than you could imagine. You may think, “I was only lost for a few years, how could industry and technology change so rapidly?”
What if you were stranded for just one year? You would have missed the latest Internet-of-Things (IoT) smart home technology, Augmented Reality (AR) and Virtual Reality (VR) technology movies, toys and games. You even would have missed the latest edition of the National Electrical Code (NEC) and the 2015 soon to be 2018 edition of NFPA 70E.
Get the idea? Just as the world continues to turn, with or without us, technology continues to change at a very fast pace. If you pause for too long, it will pass you by, and catching up could become quite a challenge. If you’re leaning against the ropes, you might as well learn them, so you can rebound faster and better.
There is an endless list of reasons for keeping your skills and knowledge up-to-date in the electrical industry. One reason is that many licensing boards require a contractor to attend a minimum number of hours of training each year, often referred to as continuing education. A participant receives credit known as professional development hours (PDHs) or continuing education units (CEUs). However, one of the best reasons is simply to stay current with the latest technology in the electrical industry.
What do competitive companies recognize that others do not?
How Does Everyone Else Do This?
By Jim Phillips
ARC FLASH LABELS
- What do you list on an arc flash label when
the prospective incident energy is greater
than 40 cal/cm2?
How Does Everyone Else Do This?
There are many frequently asked questions about performing an arc flash study (risk assessment) and understanding electrical safety requirements. A careful read of standards such as NPFA 70E or IEEE 1584 can answer some questions. Yet, other questions can be more complex, gray areas can lead to confusion, second-guessing and wondering how everyone else does it. Continue reading
With the awareness of arc flash, many giant manufacturers do not manufacture the Service Disconnect and the Automatic Transfer Switch located in the same section or enclosure. However, this practice can be seen in the field for switchboards rated as high as 600 Amps.
The dangerous part is the upstream of service disconnect is like a blind spot as the only protective device is the utility’s fuse on the primary side of the transformer and often result in high incident energy (greater than 40 Cal/cm2 in most of the cases) at the service disconnect. But because of service disconnect as protective device, in the downstream the incident energy on the ATS(normal-utility side) gets reduced to for instance less than 4 cal/cm2. The problem is although ATS has lower incident energy, it is located right below the Service Disconnect in the same section (enclosure). This is a arc flash hazard and I affix the conservative label (service disconnect) on the section that has service disconnect on the top and ATS at the bottom. So please share your thoughts on how you affix labels:
1. When the Service Disconnect & ATS is located in the same section (enclosure)
2. When there is a barrier between Service Disconnect and ATS located in the same section (enclosure).
Personal protective equipment (PPE) recommended for arc flash is not always designed for arc flash exposure. The purpose of this paper is to warn of the dangers posed by using the improper materials in arc flash exposures until standards have caught up on this issue.
The table below shows a representative range of everyday textiles along with some of the measurements of importance in establishing their response towards convective and radiant heating:
Times to ignition or melting of the 20 fabrics in Table above were reported by Wulff,  for different incident heat fluxes. The Wulff’s data have been used to develop a methodology by which ignition and melting times may be forecast. A semi-empirical relationship between ignition/melting time and radiative heat flux has been derived:
[NF0] = -1 / NBi * ln(1 – NBi / [qxrad]) + a * [qxrad]^b * (1 – NBi / [qxrad])^-1, Equation 1
where [NF0] is the non-dimensional destruction time of the fabric (that is, time to ignition or melting) and is given by:
[NF0] = (k/l) * t / (pl * c), Equation 2
(k/l) – average thermal conductance, W / (m^2 * C);
t – ignition/melting time, sec;
pl – mass/unit area, kg / m^2;
c – average specific heat, W * sec / (kg * C).
NBi is the Biot number which is defined as the ratio of the average convective heat transfer coefficient of the fabric to the average thermal conductance of the fabric. It is obtained experimentally for each fabric.
The non-dimensional radiative heat flux [qxrad] is given by:
[qxrad] = ads * W0 / (k/l) / (Tim – T0), Equation 3 READ MORE
Question of the Week
Some equipment may have multiple arc flash labels for a variety of reasons.
- Different operating configurations
- Equipment is long/large – including busway
- Equipment has different incident energy for main/feeders such as some switchgear.
There may be other reasons as well.
This week’s question:
What is the greatest number of arc flash labels you have seen/used on electrical equipment?
More than 3 (how many?) ANSWER
In the NFPA 70E-2015 Handbook, page 122, 130.5(D) states incident energy or PPE category shall be on the equipment arc flash label, but not both. Yet when reviewing Annex H in the NFPA 70E-2015 handbook, on page 279 it states “Arcflash PPE categories may be applicable when using incident energy method to perform an arc flash risk assessment. When performing an incident energy analysis, the arc flash labels created may include an arc flash category”. Am I missing something or is this a mis-print?? READ MORE.
Question: What are you guys recommending to reduce incident energy levels on fire pump controllers fed directly from the secondary side of utility transformers?
Answer: Can’t be done. This is a common practice but is very illegal in most cases. NEC is very specific in that overload protection (ie, overload relay) is eliminated and short circuit protection only remains. I have no idea why and I’ve had multiple fire marshals actually try to tell me that fire pumps get ZERO protection which is utterly false. In most cases the short circuit protection on the primary side is NOT sufficient to protect the branch circuit on the secondary side. And that’s the answer to your problem…short circuit protection (e.g. a MCP aka magnetic-only circuit breaker or simply a fuse) with the instantaneous trip point set below the arcing current fixes the problem and is 100% legal, and in most cases such as what you describe where it’s a huge Code violation, it also fixes that issue. READ MORE.
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I believe it to physically impossible to sustain an arc flash at 120 V but can someone point me to the proof? Can someone indicate where a code specifically states no arc flash PPE is required at 120 VAC? READ MORE.
About Jim Phillips, P.E.: Electrical Power and Arc Flash Training Programs – For over 30 years, Jim Phillips has been helping tens of thousands of people around the world, understand electrical power system design, analysis, arc flash and electrical safety. Jim is Vice Chair of IEEE 1584 and International Chairman of IEC TC78 Live Working. He has developed a reputation for being one of the best trainers in the electric power industry, Learn More.
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NFPA 70E requires that an Arc Flash Risk Assessment be updated when a major modification or renovation takes place. It shall be reviewed periodically, at intervals not to exceed 5 years, to account for changes in the electrical distribution system that could affect the results of the arc flash risk assessment. Countries outside of the US that do not use NFPA 70E may have a similar label review/updating requirement.
NFPA 70E further states that where the review of the arc flash hazard risk assessment identifies a change that renders the label inaccurate, the label shall be updated.
What is the maximum number of times you have updated any arc flash label since first applied?
-Still have original labels
-Updated more than twice
-No labels yet
-I don’t do labeling
The intensity of an arc flash is dependent on the magnitude of short circuit current. Lower voltage systems (less than 600 volts) tend to have the highest short circuit currents. Here is this weeks question:
What is the maximum short circuit current that you have seen?
less than 50 kA
greater than 50 kA
greater than 100 kA
greater than 150 kA
1910.269 requires arc flash protection for hands with exceptions when wearing leather protectors over rubber gloves, and when wearing heavy duty work gloves. The workers state that sticks should be used bare handed, and that work gloves will contaminate the stick. Any advice on this topic?
Leather gloves aren’t going to contaminate a hot stick unless for instance they get saturated in creosote or other materials. Granted there are tons of nasty, sticky materials in the utility work site and if the gloves get soaked with the more flammable ones, their “fire retardant” properties disappear.
It has been shown that up to 12 cal/cm2, leather gloves are sufficient.
You can’t use gloves realistically at high voltage and above (as per IEEE 516) because the voltage across the gloves might exceed their ratings. Since it is so hard to find class 3 or 4 gloves I kind of disagree with the current version of IEEE 516 cutting off the “no gloves” limit at 40 kV and I think it is more realistic to do this above 15 kV.
Finally with the hot stick method the intent is that some current flows through the worker’s body. Wearing gloves with hot sticks interferes with this. You are basically mixing work methods, the insulated tool method and the rubber glove method. READ MORE
Could i use the (DB) empirically derived model equation of IEEE Std 1584-2002 to calculate the Flash-protection boundary (for box configurations) and the Lee (DB) equation (for open air configurations)?
I can´t find a equation for DC Arc flash boundary. READ MORE.
It always seems as if we are kicking the dead horse on arc flash labels but I was just interested in your opinion of how to label a piece of equipment which is fed from a circuit breaker with an Arc Flash Reduction Switch (ARMS) or Reduced Energy Let-thru (RELT) switch.
We are currently performing a project with several new circuit breakers using the RELT switch.
Install two labels on the equipment? One with ARMS and one without?
To avoid confusion, how to distinguish between the two.
Wording on the label?
Any opinions welcome. READ MORE.
As a electrical engineer who performs arc flash studies and investigates electrical accidents I have come across a company who is faking their arc flash studies. They go into companies and collect a little data such as the number of electrical panels then go back and print labels with made up numbers. I have proven that this particular study was totally fabricated. This false study resulted in three maintenance personnel being burned with two having very serious injuries. There is presently a civil case against the company who performed the study and additional action is anticipated such as criminal action.
MY question is how do we prevent such these bogus studies? I will be publishing information of the accident and the arc flash company as soon as I can but that is not enough. There could be many companies with arc flash studies out there where the information on the labels that are wrong. READ MORE.
What is the practice for the use of arc detection relay trip time in the arc incident energy calculations? NFPA-70E recognized arc detection relay but kept under “Other Methods” as opposed to “Incident Energy Reduction Method”. Does this means the arc flash relay tripping time should not be used for the arc incident energy calculations? READ MORE.
Hi. I currently work as an Engineer in the energy management field. I would like to branch off in to doing Arc Flash, Short Circuit and Coordination Studies. How would I go about doing this. I have been exposed to these reports but have never done them before. Would any of you happen to have any training material on how to get started? From what I’ve read I should learn how to do these reports manually then look in to getting software to aid with the reports. Not sure if it matters or not but I’m located in Canada. Thanks. READ MORE
I repair UL listed appliances that are sometimes directly wired into a fused or unfused disconnect box if they exceed 50A.
Sometimes I need to test the voltage on both sides of the knife switch. The new boxes seem to come with shields on the “hot” side, with little holes so that I don’t accidentally short things out with my probes. That would be okay except that my probes are not long enough to make contact with anything when I insert them in the holes.
So I have to remove the shield (usually very easy to thwart) and test as if it didn’t exist. I’m using a fluke meter with probes about 1.5″ long, so there is nothing wrong with my meter or probes. I was working with an electrician today and pointed this out and he said “Do not adjust your set. You are not doing anything wrong.”
And then he pointed out the obvious way to thwart the shielding.
So what gives? READ MORE
It has been a while since a question of the week was asked about the Arc Flash Boundary. This is the distance from a prospective arc flash where the incident energy is 1.2 cal/cm^2 which is the generally accepted value for the onset of a second degree burn. IEEE 1584 has a method for calculating this distance.
Since electrical safety practices continue to evolve, this week’s question is about the Arc Flash Boundary. Although the AFB is required to be on the warning label and is a calculated value, many are opting to keep unprotected/unqualified workers further away from a possible arc flash during live work (which should be kept to a minimum). This week’s question:
For your (client’s) electrical safety practices, do you use:
Select up to 2 answers
Something larger (please explain)
Keep unprotected people out of the electrical room
Please feel free to elaborate READ MORE
Would a Harmonic Correction Unit impact the incident energy during an arc flash in an MCC line-up? READ ANSWER
Finally! The 40 cal/cm2 threshold my finally be deleted.
The For many years, the 40 cal/cm2 threshold that is part of Informational Note 3 presently found in the 2015 Edition of NFPA 70E Section 130.7(A) has been the subject of constant debate. Continue reading
Webinar – Utility Short Circuit Current Data, Arc Flash Studies and Change
by Jim Phillips, P.E.
[See more about Jim Phillips]
It goes up, it goes down, sometimes it is thought to be infinite (although it really isn’t!) and other times it seems impossible to find. “It” refers to the available short circuit current from the electric utility which is one of the more important pieces of information for an arc flash hazard calculation study. Used to help define the severity of an arc flash hazard, it represents the magnitude of current that could f
low from the electric utility during a short circuit. Continue reading
An arc flash study can be a bit complicated if you are new to this field. Knowing where to begin, what to include, how far to go, how to use the software etc. can seem like an insurmountable undertaking. WORSE – you are going to contract the study and don’t know what to ask for. The good news, there are many well qualified consultants that can help guide you through the process. The bad news – there are plenty of people ready to take advantage of the situation once they realize this might be your first study. Continue reading
“Raise your right hand” Pretty intimidating words – especially if they are said in a court room and the trial is about an injury or death. – and you are on the wrong side of what happened. Let’s face it in the litigious society that we have in the United States, it seems anytime there is an accident where there is a significant economic loss, personal injury or worse – someone died, there will almost certainly be legal actions. Continue reading
NFPA 70E – Standard for Electrical Safety in the Workplace, was first published in 1979 and consisted of only one part, The 2015 Edition marks the tenth edition to NFPA 70E and with it, many sweeping changes. This article provides a review of the major changes to the latest edition of this important electrical safety standard. Continue reading
The surface area of the earth is approximately 197 million square miles, and IEEE 1584—IEEE Guide for Performing Arc-Flash Hazard Calculations has been covering more of it every day since it was first published almost 11 years ago. Although the IEEE 1584 standard has its roots in the United States, it has gained widespread international use as the most common method for performing arc flash calculation studies. Continue reading
IEEE 1584 – Where It All Began – 2002
A lot has happened since 2002 when IEEE 1584 – IEEE Guide for Arc-Flash Hazard Calculations was first published. The development of this land mark document included conducting over 300 arc flash tests which were used to create the empirically derived equations. Applicable for three phase calculations and voltages ranging from 208 volts to 15,000 volts, four main calculation Continue reading
Although beginning with an erratic schedule with revisions to NFPA 70E being spaced anywhere from 2 to 5 years apart, this very important electrical safety standard is now on a regular 3 year revision cycle. In early 2011, I wrote an article about the significant changes that were about to be part of the 9th Edition, the 2012 Edition of NFPA 70E Standard for Electrical Safety in the Workplace. This article will take us a little further into the standard and address some changes that I was not able to include in the previous article. Continue reading
In the earlier years of NFPA 70E and the emergence of arc flash protection requirements, many people would use the NFPA 70E Hazard/Risk Tables to determine what arc rated PPE to wear. This approach continues to shift towards the use of arc flash studies involving incident energy and arc flash boundary calculations based on IEEE 1584. Continue reading
Electrical Power Training and Arc Flash Training remain even more important in a down economy.
What if you had been stranded on a deserted island for the past five years? By the time you were rescued, you would have missed the explosion of social media usage, including Facebook, YouTube and Twitter, as well as advancements in smart grids and wind and solar energy—it would be more than you could imagine. You may think, “How could the industry have changed so much? I was only lost for a few years.”
What if you were stranded for just one year? You would have missed the latest tablet computer, the rapid development of smart phone apps and quick response (QR) codes (those odd looking bar codes for smart phone scanning). You even would have missed the latest edition of the National Electrical Code (NEC) and the 2012 edition of NFPA 70E. Continue reading
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One sentence in the IEEE 1584 Standard, IEEE Guide for Performing Arc-Flash Hazard Calculations, frequently has people scratching their heads: Equipment below 240V need not be considered unless it involves at least one 125 kVA or larger low-impedance transformer in its immediate power supply. What does this sentence mean? What is so significant about 240 volts and 125 kilovolt-amperes?
Download: 125 kVA / 240 Volt Exception
About Jim Phillips: Electrical Power and Arc Flash Training Programs – For over 30 years, Jim Phillips has been helping tens of thousands of people around the world, understand electrical power system design, analysis, arc flash and electrical safety.
Jim is Vice Chair of IEEE 1584, International Chairman of IEC TC78 Live Working and Steering Committee Member – IEEE/NFPA Arc Flash Collaborative Research Project. He has developed a reputation for being one of the best trainers in the electric power industry. Learn More
Arc Flash & Electrical Power Training Classes by Jim Phillips Click Here
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Sign-up for my monthly publication “Grey Matter” which contains news about new standards, conferences, technical articles, Electrical Engineering news and more! Click Here
Determining the arc flash duration is the most important piece of information in predicting its severity. The arc flash duration is usually dependent on how fast an upstream protective device will trip. The longer it takes, the greater the incident energy and resulting hazard.
Download: Arc Flash Duration
Begin at the End – What Answer Would You like to Have? Simplifying the arc flash study – Would you like to know a little secret about how to simplify an arc flash studies? Perform the study backward. Well, not actually backward, it just seems that way
Performing the study: Arc rating > incident energy. An arc flash study is one method that can be used to determine the level of arc-rated clothing and personal protective equipment that is appropriate for protection from the thermal energy of an arc flash. Continue reading
Arc Flash – The need for risk assessment is embodied in European Law through directive 89/391 and is transposed into UK Law through Management of Health and Safety at Work Regulations. Most people are familiar with the general principles of prevention as laid down in these documents and in other UK regulations. They say that “Where an employer implements any preventative measures, he shall do so on the basis of the principles of prevention” shown below. The authors discuss how these principles can be interpreted when it comes to arc flash prevention.
Jim Phillips, P.E. and Mike Frain, FIET – October 2009 – Electrical Review U.K.
Download: U.K. Article – Arc Flash – EAWR – Part 3 of 3
BUY NOW: 2018 NFPA 70E Changes Part 1
It seems like the more you attempt to learn about arc flash and electrical safety, the more confusing it becomes. A mixture of letters such as OSHA, NFPA 70E, NEC, IEEE 1584, ASTM F1506 seem to be the secret language used by the electrical safety industry. Who created this alphabet soup of standards, and how did we get here?
Arc Flash – Dynamite, gasoline, gunpowder and electricity: What do these have in common? Each one can explode. Something as simple as the slip of a screwdriver can cause the electric power system to act like a bomb. Technically known as an arc flash, this potentially devastating explosion can occur when accidental contact is made between energized conductors or between one conductor and a grounded surface, such as an equipment enclosure.
This article by Jim Phillips of the U.S. and Mike Frain of the U.K. elevated the awareness of the electrical flashover (arc flash) hazard in Europe to a new level. This ultimately lead to one of the very first public forums in which the authors and a member of the British Health Safety Executive (HSE) discussed their views on the subject of electrical flashover (arc flash in the U.S.)
PPE happens to be last resort in the UK risk control hierarchy behind removing and avoiding the hazard altogether. There is evidence that some UK companies adopt a comfort/protection balance argument such that it is better to allow a lower level of arc protection PPE rather than to insist on better protection that will be difficult to enforce because workers will not wear for comfort reasons.
Jim Phillips, P.E. and Mike Frain FIET – The IET – June 2007
Download Article: United Kingdom | Europe | Fear of Flashover