Electrode Configuration and 2018 IEEE 1584

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

Arc Flash, Second Degree Burns (My Wife and a Chili Cookoff)

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

IEEE 1584 – Changes to the Next Edition

It has been sixteen long years since IEEE 1584 – IEEE Guide for Performing Arc-Flash Hazard Calculations was first published in 2002.  This standard was highly celebrated back then because for the first time there was an internationally recognized standard that provided a method to calculate the arcing short circuit current, incident energy and arc flash boundary.  The results of these calculations are often listed on arc flash/equipment labels and have become an integral part of arc flash studies and risk assessments globally.

However, it did not take long before the focus began to shift towards what comes next. Continue reading

Don’t Automatically Reset a Circuit Breaker that Trips!

Circuit Breaker SettingsThe circuit breaker just tripped.  Production is down, alarms are sounding in the background.  Panic time.  For many, this scenario would mean quickly re-set the circuit breaker and “see what happens.”  Not the best idea – the question needs to be asked – why did the circuit breaker trip?  This situation can become an even larger problem if the circuit breaker has setting adjustments.  Before I go any further, let’s back up a few steps. Continue reading

Zero-Sequence Impedance and Incident Energy

A question that I am often asked either on-line or in one of my arc flash training classes is in regards to incident energy calculations and line-ground short circuit current:

“Since it is possible for the line-to-ground short circuit current to be greater than the three- phase current, could the line-to-ground condition be the worst case for incident energy calculations using IEEE 1584 equations?”

The short answer: No.

The longer answer: Let’s look at the equations for each short circuit calculation using symmetrical components.

The equation for calculating the three-phase fault current is: Continue reading

IEC 61482-2 Second Edition Just Released!

IEC 61482-2As 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

PCIC Conference – ANSI vs. IEC Short Calculations and Arc Flash Studies

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

IEEE 1584 Status Update

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

40 cal/cm^2 Deleted – But Some Confusion Remains.

140 cal/cm^2 Arc Flash Suit

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

IEEE and IEC Standards Update

By Jim Phillips

March has been a busy month for me with Standards Committee work.  I just returned home from three weeks of travel that included IEEE Standards meetings in Ft. Worth, Texas and various IEC meetings held at British Standards Institute (BSI) in London, U.K.

On the IEEE front, the IEEE 1584 Standard where I am Vice-Chair, has made significant progress over the past year and has completed the formal consensus ballot process, resolution of numerous comments from the balloters and has proceeded though another round of balloting. This new edition will provide more detailed equations for the calculation of incident energy from an arc flash as well as more detailed arcing current and arc flash boundary equations.  Although I can’t provide a date when it will finally be published, the draft has been clearing Continue reading

Global Use of IEEE 1584

IEEE 1584 – It’s a Small World
The world’s electrical systems do not discriminate when it comes to electrical safety.  Electric shock, electrocution and arc flash hazards can occur anywhere on the planet that has electricity.  An interesting side note is that according to an International Energy Agency Report, around 1.2 Billion people do not have electricity.  Hard to imagine as I type this on my laptop, with good lighting and the heat pump working away.

Earth at night

IEEE 1584 – IEEE Guide for Performing Arc-Flash Hazard Calculations has been gaining global traction every day since it was first published in 2002. Although the IEEE 1584 standard has its roots in the United States, it has gained widespread international use as the most common method for Continue reading

Arc Flash Labels – Information No Longer Required (maybe)

New Label ExceptionNew Exception 130.5(H) Exception No. 2 – Arc Flash Label Information May Not Be Required.
It is amazing how the requirements for arc flash labels have evolved with each new edition of NFPA 70E. Known as Arc Flash Warning Labels by the National Electrical Code and Equipment Labels according to NFPA 70E 130.5(H), most people simply refer to them as arc flash labels.

What first began as a simple requirement to warn people of the arc flash hazard, has morphed into a list of required information found in NFPA 70E 130.5(H).  As an example the evolution of label requirements was the information to aid in selecting Personal Protective Equipment and Arc Rated Clothing.  In the past, the requirements began with Hazard Risk Category Tables, then it became using the Hazard Risk Category Tables OR the calculated incident energy.  Today the Hazard Risk Category Table is now the PPE Category Table and there is an array of options listed in 130.5(H). Another evolution was with the term originally known as Flash Protection Boundary.  It was later changed to Arc Flash Protection Boundary and finally to Arc Flash Boundary.  It is interesting to look at labels today and see what term is being used.  You still see some of the earlier terms but regardless of terminology, the Arc Flash Boundary remains as the distance (approach limit) from an arc source where the incident energy is 1.2 calories/centimeter2  (cal/cm2).  This is boundary is for the case when an arc flash hazard exists.

Fast forward to the 2018 Edition of NFPA 70E and yet another change to the labeling requirements has been added.  130.5(H) Exception No. 2 now permits eliminating the detailed information from the arc flash label!

No Information on the Label??!!           What?  Huh?  Are you kidding me?

Continue reading

IEEE Opens Its European Technology Center in Vienna, Austria

IEEE continues to expand its global presence with the opening of the European Technology Center in Vienna. The ribbon-cutting ceremony and official opening were just recently held on September 22. The center will provide support and services to the European technical community, focusing specifically on the needs of academia, government, and industry. In addition, the center will contribute to IEEE’s programs globally. The new office is located in the Austrian Standards Institute building.

“Establishing the European Technology Center marks an important step in furthering IEEE’s global, strategic activities within Europe and beyond,” says Karen Bartleson, 2017 IEEE president and CEO. “We see a strong foundation Continue reading

IEC TC 78 Live Working Standards

By Jim Phillips, P.E.
International Chairman IEC TC 78

Jim at the IEC Central Office in Geneva

As the International Chairman of IEC TC 78, a frequent question that I receive is “What is IEC TC 78?”

IEC is the acronym for the International Electrotechnical Commission based in Geneva, Switzerland.  TC 78 standards for Technical Committee 78 which is the Live Working Committee.  This committee is responsible for over 40 different International Live Working standards and documents and is represented by 42 countries via National Committees which includes 136 individuals known as Experts. Before I go any further, let’s back up a few steps first. Continue reading

The 2017 NEC and Arc Flash

By Jim Phillips

The 2017 National Electrical Code (NEC) contains several changes regarding arc flash:

Download FREE Arc Flash Calculations

  • 110.16(B) Arc-Flash Hazard Warning of Service Equipment
  • 240.87 Arc Energy Reduction (Circuit Breakers)
  • 240.67 Arc Energy 
Reduction (Fuses)

The severity of an arc flash is largely dependent on two key variables which include the available short-circuit current and the duration of the arc flash. The short-circuit current is determined by performing a short circuit study involving extensive calculations. The duration is normally defined by determining how long it takes an upstream overcurrent device, such as a circuit Continue reading

2018 NFPA 70E Update – What’s New? What’s Changed?

Published: June 2017

By Jim Phillips 
Based on Jim’s article originally published in the
May 2017 Issue of Electrical Contractor Magazine.

It is hard to imagine that three years have passed since I wrote the 2015 NFPA 70E update article for Electrical Contractor Magazine ECMag.com. My latest article about the changes for the 2018 Edition was just published in last month’s May issue and is also printed here.

Once again there are many significant changes such as a major reorganization of Article 120, the introduction of many new definitions, an even greater emphasis on the Risk Assessment, moving the hierarchy of risk control methods to mandatory language and the deletion of the informational note containing the 40 cal/cm2 reference. So get a jump on bringing your electrical safety and arc flash training programs in line with the soon to be released 2018 Edition of NFPA 70E.

Around 2,500 years ago, the Greek philosopher Heraclitus is credited with the saying, “The only thing that is constant is change.” Who knew this ancient proverb would apply to NFPA 70E, Standard for Electrical Safety in the Workplace? The 2018 edition is right around the corner, and once again, change is a constant theme. From both minor and major revisions to new additions and major reorganizations, this 11th edition contains many changes.

This article does not contain every change, and some language is paraphrased due to space limitations. Since the final document has not yet been formally approved, additional changes are possible before publication. Therefore, refer to the final approved version once it is published.

Continue reading

Keeping Skills Current with FREE Training

Published: May 2017

By Jim Phillips

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.

Free Training

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.

Continue reading

Keeping Skills Current on a Limited Budget

2-Part Series

Published: May 2017
By Jim Phillips

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?

Continue reading

What Could Go Wrong?

Creating An Electrically Safe Work Condition

Published: April 2017

By: Jim Phillips


“Kill the Circuit.” This phrase is a colorful way of saying, “De-energize the Circuit.” Easy enough — just open a switch or other protective device and the circuit is “dead.” It should then be safe to work on right?

WRONG! Simply opening a switch does not guarantee the circuit is de-energized. Really? What could go wrong?

There are many who still consider this simple “kill the circuit” approach to be standard electrical safety practice. This is a very dangerous method, for example, instead of the circuit being dead, the worker could end up dead!

According to NFPA 70E, there are many additional steps necessary to ensure the circuit is truly safe to work on. This multi-step process is known as creating an “electrically safe work condition,” which requires the following steps:

  1. Determine all possible sources of electrical supply – check up-to-date drawings, diagrams, etc.
  2. Interrupt the load and open the disconnecting devices.
  3. Visually verify that all blades of the disconnecting means are open if possible – drawout devices must be withdrawn to the fully disconnected position.
  4. Apply lockout/tagout devices in accordance with established policy.
  5. Use an adequately rated test instrument to verify absence of voltage.
  6. Apply properly rated ground connecting devices if there is a possibility of induced voltage.

(These steps are paraphrased from NFPA 70E 120.1 Process of Achieving an Electrically Safe Work Condition, which should always be used to define the complete procedure).

Continue reading

Arc Flash Study Top 10 FAQs Part #2

How Does Everyone Else Do This?

By Jim Phillips

3-Part Series



  1. Does your company or client permit energized work where the incident energy is greater than 40 calories per centimeter squared (cal/cm2)?

Continue reading

Arc Flash Study Top 10 FAQs Part #1

How Does Everyone Else Do This?

By Jim Phillips

3-Part Series


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

Forensic Electrical Engineering Blog #3

Past – Present – Future

3-Blog Series

By Jim Phillips, P.E.


Blog #3: Evolution in Forensic Electrical Engineering

There has been much advancement in the field of forensic electrical engineering since the days of Morse, Latimer, Edison and others. A few of the more significant advancements include:

  • Better Understanding of Electric Shock and Arc Flash Hazards
  • Codes and Standards
  • Computer Simulations

Personal injury that is a result of contact or exposure to energized electrical conductors is usually due to electric shock/electrocution and/or burn injury from an arc flash. In the early years of electrical power systems little was known about these hazards other than they can occur. Today, research, testing and new and improved electrical standards have greatly expanded the knowledge of these hazards. Continue reading

Forensic Electrical Engineering Blog #2

Forensic Electrical Engineering

Past – Present – Future

3-Blog Series

By Jim Phillips, P.E.


History of Forensic Electrical Engineering

Some historical articles suggest the field of electrical investigations began hundreds of years ago when early attempts were made to provide a scientific understand lightning. Of course lightning has been around since the beginning of time and was usually explained using philosophical and religious views before scientific explanations were first made. Continue reading

Forensic Electrical Engineering Blog #1

Past – Present – Future

3-Blog Series

By Jim Phillips, P.E.


Blog #1: What is Forensic Electrical Engineering?

Welcome to my 3-part blog series about the Past, Present and Future of Forensic Electrical Engineering. In this blog series, you’ll get insights into what can be considered some of the first forensic investigations into electrical engineering. Beginning way back in the 1700s with the study of lighting and “bell ringers” up to today’s investigations using elaborate computer simulations to recreate events. Welcome back each week to digest the next bit of insight, data and information.
Continue reading

Electrical Safety Training: It Will Save Your Life!

By Jim Phillips

Performing electrical work without being properly trained can be deadly. I have seen this hold true during numerous investigations.

Many companies proactively provide employee training and refresher courses at least every 3-years. Some companies use shorter intervals for refresher training. However, for others, training is not thorough or a low priority. Some simply just want to check training off their to-do lists without much regard to safety for self or employees. In the end, does it matter? Continue reading

Utility Short Circuit Current Data, Arc Flash and Change

Webinar – Utility Short Circuit Current Data, Arc Flash Studies and Change
by Jim Phillips, P.E.

[See more about Jim Phillips]

Agua Caliente 1It 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

Specifying Arc Flash Studies and IEEE 1584.1

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

NFPA 70E – Qualified Workers

“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 – 2015 Edition – Update of Changes

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

Global Use of IEEE 1584

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 Revision Update – 201X Edition

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

Happy August 11! (and call before you dig)

Today is a special day.  August 11 – Also known as 8 11 (unless you use the format day/month) What is so special about 811?  8-1-1 is the telephone number that you use to find underground utilities before you dig.  Known as “Call Before You Dig” it is a nationwide network (in the U.S.) that is designed to assists in locating underground utilities. Continue reading

Arc Flash Labels – Simplified!

“What do you mean we need to relabel the electrical equipment? Didn’t we just do this a few years ago?”

This is a pretty common response when addressing the requirements of NFPA 70E 130.5(2), which necessitate that the arc-flash risk assessment shall, “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.” Continue reading

Electric Shock – It CAN Happen to Anyone – Like Me!

Electric shock happens to more people than they care to admit. In almost every NFPA 70E / electrical safety training class that I conduct, I ask the group “how many of you have NEVER experienced an electric shock.” I have yet to see a hand go up. In today’s “Modern World” electricity is part of daily life and as a consequence, an electric shock can happen to anyone – Including Me! Continue reading

Working Distance Mistakes in an Arc Flash Study

Download FREE Arc Flash Calculations

The term “working distance” appears 20 times in the 2012 Edition of NFPA 70E, the Standard for Electrical Safety in the Workplace. It appears 12 more times in the annexes. The working distance is an important component of the arc flash hazard analysis and is frequently listed on arc flash warning labels and in the arc flash report.

IEEE 1584—IEEE Guide for Performing Arc Flash Hazard Calculations 2002 defines the working distance as “the dimension between the possible arc point and the head and body of the worker positioned in place to perform the assigned task.” Continue reading

NFPA 70E Major Updates for the 2012 Edition – Part 2.

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

How to Perform an Arc Flash Study

Download FREE Arc Flash Calculations

What started as a slow drip a decade ago has turned into something more like a tidal wave. I’m not talking about a leaky faucet or a failing dam; I am referring to arc flash studies. Years ago, only a few mostly larger companies performed these complex studies. Then little by little, the “drip” of studies turned into a steady Continue reading

Arc Flash Hazard Calculation Studies

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

Arc Flash Training – Keeping Skills Current in a Down Economy

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

Using Correct Electric Utility Data for an Arc Flash Study

One of the first steps in performing an arc flash calculation study is to request short-circuit data from the electric utility company. This kind of request is pretty routine, and utilities have been providing this type of data for short-circuit studies for years. The problem is the data used for a short-circuit study may not be suitable for an arc flash study. Continue reading

Arc Blast and 40 calories/centimeter squared

You look at the arc flash warning label and scratch your head. Danger! No PPE Category Found. No personal protective equipment (PPE) category? Now what? This type of language is often on arc flash warning labels when the calculated incident energy exceeds 40 calories per centimeter squared (cal/cm2). What is so special about the number 40?  The fear of the Arc Blast is not always well founded. Continue reading

Coordination and NEC 240.87

NEC 240.87 has addressed a potentially hazardous situation beginning with the 2011 edition. When selective coordination is critical, e.g., minimizing the extent of an outage, a common design practice is to use a main circuit breaker without an instantaneous tripping function and feeder breakers with one. Without an instantaneous, the main can time delay up to 30 cycles or 0.5 seconds greatly increasing the arc flash hazard.   Continue reading

IEEE 1584 – 125 kVA Transformer / Less than 240 Volts Exception

Download FREE Arc Flash Calculations

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.

NFPA70E 2018 Update video by Jim PhillipsJim 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
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IEEE 1584 Two Second Rule

A lot can happen in two seconds. What may seem like the blink of an eye can feel like an eternity, especially during an arc flash. When calculating the incident energy as part of an arc flash study, sometimes the IEEE 1584 equations can produce unusually large values. Although many variables are included in these calculations, the two most significant are the magnitude of arcing short-circuit current and the duration of the arc flash.

Question 1: How long?
The duration is normally determined by the tripping and clearing time of the next protective device upstream from the equipment being studied. Time current curves, such as the one in the figure, define the device’s tripping characteristic. The horizontal axis represents the arcing short-circuit current, and the vertical band represents clearing time in seconds.

When using time current curves to determine the arc flash duration, the relationship between the arcing short-circuit current and the instantaneous trip band is very important. The instantaneous is shown as the vertical band on the graph. If the arcing current is to the left of this band, the device should operate in its time-delay region and may take many seconds to clear the arc flash. If the arcing current is to the right of the band, the device should trip instantaneously, and the arc flash will have the shortest possible duration. The precise value of the instantaneous trip is usually not known, but it will lie somewhere within the width of the vertical band, which includes a plus/minus tolerance. The actual value of current could be as low as the left side of the band or as high as the right side.

In this example, the arcing short-circuit current lies within the device’s instantaneous band. This means the device could trip in either the time-delay or instantaneous region, but it is unclear which way it would actually respond. The worst case would be to assume it operates in the time-delay region. The graph in the figure indicates the maximum clearing time for the arcing current is 23.6 seconds. This would result in a calculated incident energy of 170.0 calories per square centimeter (cal/cm2) which is well beyond the limits of personal protection. Although this value may appear to be unusually large, two very important questions need to be answered.
Question 1: Will it sustain?Is it realistic to expect that an arc flash could sustain for long periods of time—23.6 seconds, in this example? It is difficult to say. There are cases where the arc flash is capable of sustaining, but it depends on many factors, such as voltage, gap distance, enclosure size, the conductors melting and more.

How do you know how long the arc may sustain for a particular situation? You don’t. IEEE 1584 has one exception commonly referred to as the “less than 240V/125 kVA transformer rule” where it is believed the arc may not sustain (see Electrical Contractor, September 2010, page 52). However, with the rest of the cases, until more research is completed, it is always best to assume the worst based on the device’s time current curve.


Question 2: Will you remain?


Jim Phillips, P.E. – November 2010 – Electrical Contractor Magazine


How to Perform an Arc Flash Calculation Study

This article by Jim Phillips provides an overview of how to perform an arc flash study.  It was originally presented at the 2010 NETA Conference.  InterNational Electrical Testing Association.

Arc Flash Hazard Calculations Studies guide


Arc Flash Calculation Study
Many separate codes, standards and related documents are available regarding electrical safety and arc flash. However, a standardized recommended practice or guide that integrates all of the components into an Arc Flash Calculation Study does not presently exist. Continue reading

Predicting the Arc Flash Duration

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 


Get Ahead of It! – NESC Arc Flash Requirements

The NESC’s Arc Flash Requirements first appeared in the 2007 Edition. Determining how much incident energy could be available at a piece of equipment or location on a line is something you do not want to discover from a field test (accidental or intentional this means the only alternative is to predict it from calculations)

Beginning with the 2007 NESC, The Arc Flash Requirements are: Continue reading

Simplifying Arc Flash Studies – Select the Arc Rating First

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

Reduce Arc Flash Accidents Using Totally Integrated Automation

Several years ago Henry was the maintenance manager at a large manufacturing facility. He was married, had a very upbeat personality, a good position at the company, and was pleasant to be around. One day, Henry was trying to track down a low voltage problem and was conducting voltage measurements on a 4,160V to 480V dry type transformer on an upper level mezzanine. He Continue reading

U.K. Article – Arc Flash – Not Just an Electrocution Hazard – Part 3

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

U.K. Article – Arc Flash – Not Just an Electrocution Hazard – Part 2

Arc Flash – Working safely in accordance with the requirements of the Electricity at Work Regulations 1989 is about decision making. This includes the decision to work live in the first place through risk assessment. One of the factors that would need to be taken into account in deciding whether live proximity work could proceed is stated in the memorandum of guidance to the EAW Regulations “the level of risk involved in working live and the effectiveness of the precautions available set against economic need to perform that work”.
Jim Phillips, P.E. – September 2009 – Electrical Review – U.K.

Download:  UK Arc Flash – Not Just an Electrocution Hazard – EAWR – Part 2 of 3

U.K. Article – Arc Flash – Not Just an Electrocution Hazard – Part 1

Arc Flash Hazard – Working safely in accordance with the requirements of the Electricity at Work Regulations 1989 is about decision making. This includes the decision to work live in the first place through risk assessment. One of the factors that would need to be taken into account in deciding whether live proximity work could proceed is stated in the memorandum of guidance to the EAW Regulations “the level of risk involved in working live and the effectiveness of the precautions available set against economic need to perform that work”.
Jim Phillips, P.E. and Mike Frain, FIET – August 2009 – Electrical Review U.K.

Download:  Arc Flash – Not Just and Electrocution Hazard – Arc Flash – Part 1 of 3

How Did We Get Here? The History of Electrical Safety

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?

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Three – Two – One – Liftoff! Behind the Scenes at the Kennedy Space Center

Like many kids growing up in the 1960’s, I was obsessed with America’s space program. I would watch launches and ultimately the moon landing on television, build and fly model rockets and dream about what it would be like to be out in space. Earlier this year, I had the opportunity to go behind the scenes at the Kennedy Space Center (KSC) in Florida and actually see what it takes to make it all happen. I was given access to everything, from the launch pad and tower to the Orbiter Processing Facility, the solid rocket boosters, sections of the space station, and more.

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Behind the Scenes – Ethanol Production

Recently, I had the opportunity to go behind the scenes of an ethanol production facility and see that power distribution system as well as see how it all works.  Electricity requirements for ethanol production average 0.75 kWh per gallon.  Some facilities have production capacity over 100 million gallons per year and electricity is a major cost component.  Large facilities are served at medium voltage at 12.47 to 13.8 kV

Ethanol Production


Arc Flash – Unplugged

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.

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United Kingdom Article – Fear of Flashover

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

Surf’s Up – Broadband Over Power Lines

Are we on the edge of another technological tidal wave or will this just be a small ripple in the pond? Surfing the internet is once again beginning to move in a whole new direction. For the past several years there has been slow and steady growth towards using existing electric power lines for broadband. Known as “Broadband Over Power Line” or BPL, the concept is simple. In fact, electric utilities have been transmitting data on transmission lines to control substations for decades. Traditional pipelines for broadband have included cable and DSL but this new technology is often referred to as the “third pipeline.”
Jim Phillips, P.E. – August 2006 – NEC Digest
Download Article: Broadband over Power Lines

Electromagnetic Compatibility of Variable Frequency Drives

Every electrical component can produce EMI when energized. Electromagnetic compatibility issues in the form of Electromagnetic interference is caused by the voltage and current in the form of electric and magnetic fields. Depending on the strength of the fields, EMI can degrade or disrupt the performance of other devices. As power increases, the EMI can increase and if not considered in the design and installation of a device, significant problems can result. Some equipment intentionally produces emissions, such as cellular telephones and radio transmitters, while other equipment, such as computers, fluorescent lights, power lines and variable frequency drives produce unintentional emissions, so they’re referred to as incidental radiators.
Jim Phillips, P.E. – June 2006 – NEC Digest
Download Article: EMI Pass Interference

Snow Job! Behind the Scenes – Ski Resort Electrical System

Every November the snow making equipment at your favorite ski resort is expected to start up flawlessly. The pumps, compressors, mechanical and electrical systems are good to go. The lifts are ready for the tens of thousands of people heading to the slopes. But what does it take to make all of that happen? Earlier this year I made a trip to Mount Snow, located in the mountains of Vermont, to take a look behind the scenes of a ski resort electrical system.
Jim Phillips, P.E. – December 2005 – NEC Digest

Download Article: Snow job

NEC and Hazardous Locations

The NEC defines a “Hazardous Location” as a location “where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitable fibers or flyings.” There are 13 articles and 68 pages in the NEC regarding hazardous locations, installation practices and equipment requirements. Understanding what makes a location “hazardous” is the first step in providing a safer electrical system.

Materials that can cause a location to be classified as hazardous range from hydrogen, to grains, coal dust, petroleum products and many others.
Jim Phillips, P.E. – October 2005 – NEC Digest

Download Article: NEC Digest Hazardous Locations


Grounding Power Distribution Systems

The NEC contains specific articles that dictate when you shall ground, when you shall not ground, and when you are permitted – but not required – to ground. These code requirements are based on various factors such as whether or not there are connected phase to neutral loads, whether only qualified persons service the installation, and operating voltage levels.
Jim Phillips, P.E. – April 2005 – NECDigest

Download Article: Grounding Power

OSHA, NEC, NFPA – Pieces of the Puzzle

The next time you are near the bulletin board at work, look for the poster that has the words “It’s the Law” and “OSHA” on it. It has probably been hanging there for a very long time but most people never really notice it or seem to read it. Further down on the poster is the statement “each employer shall furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to employees. This statement is known as OSHA’s General Duty Clause and is at the heart of linking many of the other standards to OSHA.

Jim Phillips, P.E. – February 2005 – NEC Digest

Download Article: OSHA NEC NFPA

Testing for Improved Power Distribution Reliability

Those responsible for a facility’s operation hear the same thing over and over again – reduce costs and improve productivity. Much attention has been given to reducing raw material and labor costs, increasing production efficiency, automating processes, and other key areas, but what about the often overlooked cost of an electrical outage? Depending on the type of facility, one outage can paralyze building systems and cost thousands – or even millions – of dollars in lost production, downtime, damage to equipment and product, and possible injury or death to personnel.
Jim Phillips, P.E. – November 2004 – NECDigest

Download Article:  Testing for improved power