Utility Short Circuit Data – Different Formats

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.

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

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

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

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

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

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

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