Arc Flash Duration Defined by Clearing Time of Upstream Protective Device
One of the main variables that is part of an arc flash study is the arcing short circuit current. However, going back through the evolution of arc flash calculations, consideration was not always given to this value. Due to the impedance of the arc, the arcing current will always be less than the bolted short circuit current and the lower value could lead to a greater incident energy. Why? Because the lower current could result in the upstream protective device taking longer to operate leading to a longer arc flash duration.
Let’s take a look at a few milestones regarding arcing current calculations up through the use of the Arcing Current Variation Factor found in the 2018 Edition of IEEE 1584. Continue reading →
I was at the IEEE PCIC Conference in Vancouver, British Columbia last week where I had the privilege of being part of the first presentation with three great colleagues (actually thee great friends) The topic was the new IEEE 1584 standard.
During the presentation while I was looking out into the 1000 plus faces, it occurred to me, “I wonder how many people know how IEEE began?” So, in case that very important question has been keeping you up at night, here is the short history from IEEE’s website. Continue reading →
One of the main variables used for incident energy and arc flash boundary calculations is the arcing short circuit current. How the arcing current is calculated has gone through an evolution beginning back in the 1980’s up through today.
The arcing current will always be less than the “bolted” short circuit determined by performing a “traditional” short circuit study that is used to evaluate the interrupting rating of protective devices. During an arc flash, the short circuit current flows across an air gap which introduces an arcing impedance. The result is that the arcing short circuit current Continue reading →
For the first time ever, Jim Phillips is bringing his Arc Flash Studies class based on the 2018 IEEE 1584 to Canada! This very intense 2 day course includes an in depth discussion of:
Five different electrode configurations to enable more detailed modeling More choices for enclosure types and sizes Enclosure correction factor calculation to adjust for specific enclosure size The effect of grounding has been eliminated An arcing current variation factor calculation replaces the 85% factor Calculations performed at 1 of 3 voltage levels with interpolation to actual voltage The 125 kVA transformer exception was eliminated
Each calculation is now performed in 2 steps which includes an initial calculation based on one of three voltage levels and a second calculation interpolating to the specific system voltage. The 125 kVA “exception” was replaced. Learn why and what has replaced it. What about the 2 second rule?
Loaded with Hands-On Calculation Problems
This class will be packed with many hands-on calculation examples using Jim’s worksheets. The calculations will illustrate the various changes with the new edition and provide comparisons between the results using the 2002 Edition of IEEE 1584 and the 2018 Edition.
Hands-On Calculation Examples include: • Arcing Short Circuit Current – Intermediate and Final • Necessary Extrapolation and Interpolation • Enclosure Size Correction Factor • Incident Energy – Intermediate and Final • Arc Flash Boundary – Intermediate and Final • Low Voltage and Medium Voltage Calculations • DC Arc Flash Calculations
Jim will be joined by special guests Len Cicero and Jim Pollard who will be discussing CSA Z462 requirements for arc flash studies and how the study results are used to select appropriate arc rated clothing and PPE.
By: Rebecca Frain – Managing Director, Electrical Safety UK, Rotherham, England – A Brainfiller, Inc. Strategic Partner.
Recently I had the opportunity to interview Jim Phillips regarding the new IEEE 1584 standard and what to expect with some of the new changes. In addition to being Associate Director for Electrical Safety UK and founder of Brainfiller.com, Jim is also Vice-Chair of IEEE 1584 and International Chair of IEC TC 78 – Live Working.
As an introduction, IEEE 1584 – IEEE Guide for Performing Arc Flash Hazard Calculations was first published in 2002 and is the standard that defines the equations and methods used in many of the arc flash software packages used for arc flash risk assessments. The second edition was published towards the end of 2018 and is a real game changer. Jim will be the Keynote Speaker at the upcoming International Arc Flash Conference on Tuesday September 24, 2019 in Manchester. Continue reading →
It is once again a privilege to announce the recent publication of IEC 61482-1-1:2019 Live working – Protective clothing against the thermal hazards of an electric arc – Part 1-1: Test methods – Method 1: Determination of the arc rating (ELIM, ATPV and/or EBT) of clothing materials and of protective clothing using an open arc. This standard is one of the dozens of standards that fall under IEC Technical Committee 78 that I have the privilege to Chair.
IEC 61482-1-1:2019 specifies test method procedures to determine the arc rating of flame resistant clothing materials and garments or assemblies of garments intended for use in clothing for workers if there is an electric arc hazard. An open arc under controlled laboratory conditions is used to determine the values of ELIM, ATPV or EBT of materials, garments or assemblies of garments. Continue reading →
One of my latest articles regarding the new 2018 IEEE 1584 Standard was recently published in the United Kingdom’s premier publication Electrical Review. In this article I take you through the major changes to new IEEE 1584 Standard – IEEE Guide for Performing Arc Flash Hazard Calculation Studies and what it means for arc flash studies and risk assessments.
I just returned from a CENELEC TC78 Live Working Standards meeting in Brussels, Belgium a few days ago and it occurred to me that many people may not know what CENELEC is – or does.
CENELEC is the European Committee for Electrotechnical Standardization and is responsible for standardization in the electrotechnical engineering field. CENELEC prepares voluntary standards, which help facilitate trade between countries, create new markets, cut compliance costs and support the development of a Single European Market.
Ever since the 2018 Edition of IEEE 1584 – IEEE Guide for Performing Arc-Flash Hazard Calculations was published a few months ago, people continue to sift through the many changes that have occurred. One of the more significant changes is the introduction of a correction factor to adjust the calculated incident energy and arc flash boundary to account for the effect of the enclosure size.
When an arc flash occurs, the size of the enclosure can influence the arc flash hazard. The smaller the enclosure, the more concentrated the energy is – focusing it more towards the worker resulting in greater incident energy exposure. The opposite is also true. Larger enclosures have Continue reading →
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 →
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 →
The 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 →
For many, it is nightmare scenario. Your department manager just came by and asked you to prepare and present a short training program for a client. It doesn’t matter if it is about Electrical Safety, Arc Flash, the latest National Electrical Code or any one of an infinite number of topics, your reaction could range anywhere from feeling faint to watching your life pass before your eyes or any number of other responses. Today, training has become more important than ever and there is an increasing likelihood that someday you may be called upon to put on the show – if you haven’t already.
I conducted my first training program “under duress” back in the very early 1980’s. It was exactly the scenario above – the department Continue reading →
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.
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 →
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 →
Short Circuit Calculations – Transformer and Source Impedance
An infinite bus short circuit calculation can be used to determine the maximum short circuit current on the secondary side of a transformer using only transformer nameplate data. This is a good (and simple) method for determining the worst case MAXIMUM short circuit current through the transformer since it ignores the source/utility impedance. Ignoring the source impedance means it is assumed to be zero and voltage divided by zero is infinite, hence the often-used term “infinite bus” or “infinite source”.
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.
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 →
New 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?
The 2018 Edition of NFPA 70 provides a new definition for the term “Condition of Maintenance” :
BUY NOW: 2018 NFPA 70E Changes Part 1
The state of the electrical equipment considering the manufacturers’ instructions, manufacturers’ recommendations, and applicable industry codes, standards and recommended practices.
Another term that is cited in NFPA 70E is “Properly Maintained” —these two words often will have people scratching their heads. And often, developing a legal disclaimer. The term is often a hot topic (pun intended) when discussing the arc flash hazard. Why? Because protective devices such as circuit breakers and relays that have not been properly maintained may not operate as quickly as they should. This means that during an arc flash, a longer duration will result in a greater total incident energy, creating an even greater arc flash hazard.
Calculating the prospective incident energy from an arc flash depends on many variables including the available short-circuit current and the time it takes an upstream protective device to clear the fault. IEEE 1584 – IEEE Guide for Performing Arc-Flash Hazard Calculations provides equations that can be used for Continue reading →
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 →
One word. Deadly! If someone performs energized electrical work without being properly trained, the results can be catastrophic – and deadly! I have seen this play out regularly during accident investigations and legal cases. The victim was either not properly trained, or perhaps ignored a few steps from the electrical safety training program.
Many companies are very pro-active and make sure their employees are not only trained, but that they receive refresher training at least every three years based on NFPA 70E requirements. Many even use shorter intervals for refresher training or updates. Either way, refresher training is important for staying up to date with current standards and it can be a reminder to those that pick up bad habits along the way.
Electrical Safety Training – More than “Checking the Box”
However, a looming problem is that for some companies, training is either way down the list for various reasons or was not very thorough. I have seen many companies that simply want to “check the box” i.e. state they had training without much regard to what the content was and check it off their to do list. after all, what could possibly go wrong?
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 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 →
National Electrical Code 110.9 Interrupting Ratings states that:
Equipment intended to interrupt current at fault levels shall have an interrupting rating at nominal circuit voltage at least equal to the current that is available at the line terminals of the equipment.
Download FREE Arc Flash Calculations
To comply with this requirement, a short circuit studies is typically performed to determine the available fault current for comparison to the protective devices interrupting rating. The results of a short circuit study are also a critical component for other studies such as an arc flash study. Requesting the available short-circuit data from the electric utility company should be one of the first tasks in performing the study. This information is very important because it defines the magnitude of current that could flow from the utility and is used as a starting point for arc flash calculations.
In addition to requesting this data for normal operating conditions, for an arc flash study the request should also include minimum short-circuit current conditions, if available. The minimum condition could be for a utility transformer or transmission line out of service or similar scenario. The minimum value can then be used to determine if the lower current could result in a protective device operating more slowly, which may increase the total incident energy during an arc flash.
Having been in charge of the Short Circuit Studies group for a very large electric utility company in a past life, the accuracy of the Continue reading →
ByJim 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.
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.
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?
“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:
Determine all possible sources of electrical supply – check up-to-date drawings, diagrams, etc.
Interrupt the load and open the disconnecting devices.
Visually verify that all blades of the disconnecting means are open if possible – drawout devices must be withdrawn to the fully disconnected position.
Apply lockout/tagout devices in accordance with established policy.
Use an adequately rated test instrument to verify absence of voltage.
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).
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 →
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
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 →
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 →
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 →
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 →
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 →
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 →
With the 2015 Edition of NFPA 70E being published and all of the changes that it brings, it is time to review your arc flash study, labels and overall practices. There are many key areas that should be evaluated. Here ten of the more important areas to look at to give your site a check up. 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 →
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 →
“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 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 →
Wind and Solar Electrical Safety – Rising to the Occasion – A few months ago I was driving home from the Los Angeles area and suddenly found myself surrounded by thousands of wind turbines lining both sides of Interstate 10. Even though I have made this trip many times before, I am still in awe at the scale of it all. Looking through my Continue reading →
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 →
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 →
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 →
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 →
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 →
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 →
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 →
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?
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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.
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 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 →
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.
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)
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 →
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 →
Read the label? Use as directed? It sounds like I’m reading a prescription bottle. However, the warning label produced from an arc flash calculation study contains more than just the words Warning! Arc Flash and Shock Hazard It actually holds a lot of very specific information that can be used when preparing for work where electrical hazards may exist.
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.
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.
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.
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?
This is the third article in a three part series about how to perform an arc flash study that was published in the December 2007 Edition of NFPA’s NEC Digest Magazine. The series breaks the arc flash study process down into individual steps.
Arc Flash – This is the second article in a three part series about how to perform an arc flash study that was published in the October 2007 Edition of NFPA’s NECDigest Magazine. The series breaks the arc flash study process down into individual steps.
This is the first article in a three part series about how to perform an arc flash study that was published in the August 2007 Edition of NFPA’s NEC Digest Magazine. The series breaks the arc flash study process down into individual steps.
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.
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
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
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
NFPA 70E has given a whole new meaning to the phrase “dress for success.” Correct PPE selection can make the difference if the very rare but potentially deadly arc-flash occurs. This article discusses PPE selection based on the 2004 Edition of NFPA 70E. Dress for Success – Oct 2006
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
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
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
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
Have you wondered is there a simpler way to calculate short circuit currents without a computer program? A very simplified method known by many as the “infinite bus” calculation method is a good way to approximate short circuit calculations. This article takes you thought the steps with an example of the infinite bus calculation process. If you would like to know how to perform more detailed short calculations which include the source impedance, conductor impedance and motor contribution in addition to the transformer impedance, Jim has a 4 DVD series that takes you through the entire short circuit calculation process complete with many examples and calculation worksheets. Now, on with the article…
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.
A power factor study is a key to properly determining a system’s power factor correction requirements. A study determines capacitor size and location as well as the number of steps and incremental sizes to be switched. A study also provides an economic analysis of the proposed installation based on the forecast reduction in electric utility bills. A power factor study can be divided into three major steps.
▪ Review of the electric utility company’s rate structure.
▪ Development of a graphical profile of the facilities kVA, kW and kvar.
▪ Determination of the required capacitor kvar additions for the desired power factor improvement level.
The power factor study begins with a utility rate structure review together with a historical sample (six to 24 months) of electric bills. This information is used to evaluate present use patterns and to determine the potential economic benefits of improving power factor. Utility rate structures usually provide significant economic incentives to reduce total kVA demand.
Typical demand charges can vary from minimal to $20 per demand kVA, so for reducing a demand by just 100 kVA with a demand charge of, let’s say, $10 per kVA could save $1,000 per month. It’s easy to see that larger demand reductions and higher demand charges could potentially large savings. After reviewing the rate structure and billing history, a detailed graphical profile of the facility’s use over typical 24 hour operating periods should be developed.
The profile could be created from recorded kW and kVA data and either calculated or recorded power factor and var data. This data is obtained from on –site monitoring over several 24 hour periods. Some utilities are prepared to provide this data. However, independent monitoring usually is necessary using a commercially available energy analyzer to record demand, power factor and total energy use. The data is used to develop the graphical profile which is plotted with respect to time to provide a representation of a complete operating cycle. This profile can then be used to determine the required kvar of capacitors necessary and the number of Switching steps to offset the inductive kvar.
The minimum reactive kvar determine the amount of capacitors that can be used without switching to provide close to 100 percent power factor during minimum load conditions. Additional capacitor requirements can be determined based on the profile and sized as needed. Capacitance is introduced into the facilities electrical distribution system to balance inductance due to equipment operation. When equipment load, and subsequently inductance decreases, capacitance also should be reduced. For more erratic demand patters, more switching steps may be required.
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.
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
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