Dave is an electric power consulting engineer and president of Young Engineering, Inc. of Wilmington, Delaware. Dave has been working with and teaching all aspects of the NESC and electric power distribution for over 36 years. Dave teaches the electric power curriculum at the University of Delaware and is a member of the NESC Interpretations Subcommittee and the Overhead Line Clearances Subcommittee. Dave is also an inspector member of the IAEI.
Safety Signs, Part 3
This sign is yet another example of signs that does not effectively warn the public of the hazard. As discussed in detail in Part 2 of this series, this sign should be a WARNING sign. The reader of the sign is outside the fence and is not in immediate danger. The symbol has failed testing many times. It is not one that the general public understands. The sign does not explain the consequences of not avoiding the hazard and it would be more effective if the sign said "Keep Out!” instead of "No Trespassing.”
Wind Powered Electric Generation for Your Home or Business
A little before the ’70s energy crisis, Peter, Paul and Mary suggested in their famous song, "The answer, my friend, is blowing in the wind.” Today we realize that wind is a valuable resource we cannot ignore, but wind energy is just one piece in the pie. To fix this energy crisis, we are going to need a lot of conservation plus every alternative energy source we can find.
Safety Signs, Part 2
Whether the hazard is electrical, toxic chemical or a slippery sidewalk, the best way to prevent injury, death, property damage and litigation is to eliminate the hazard. Since eliminating the hazard is often not possible, the second best method is to place physical barriers between the public and the hazard and to install effective safety signs to alert the public of the hazard.
Whether the hazard is electrical, toxic chemical or a slippery sidewalk, placing physical barriers between the public and the hazard is not enough to prevent injury, death or litigation. I mention litigation because many companies only care about preventing litigation. The National Electrical Code (NEC) and the National Electrical Safety Code® (NESC®) both recognize...
Building Inspectors and Electric Power Lines
Was this done to encourage pole-ish jokes? Where was the building inspector? Where was the electrical inspector? I understand the contractor obtained a building permit and when the addition of the bar to the restaurant was complete, the owner received a certificate of occupancy.
If Electricity Is So Expensive, Why Don’t You Buy a Generator? Part 2, Parallel Systems
As we saw in part 1 of this series, it is tough to make alternative electric sources economical when you are trying to operate a completely independent system. Usually the only time people install such systems is when the normal electric service is not available.
If Electricity Is So Expensive, Why Don’t You Buy a Generator?
Alternative electric sources have been around for a long time. I have a sister-in-law who lives on the side of a mountain near Rutland, Vermont. She built her house about the time of the first energy crunch in the mid-seventies. She and her husband decided not to connect to the local electric utility. For over thirty years, they have generated all of their electricity for their house and businesses (production of maple syrup and engineering consulting) from solar panels on the roof of their house and a small windmill located several thousand feet from their house. So why don’t more people do it? When I ask people this question, they usually answer, "It’s not economical.”
What Are You Paying for Electricity? Part 4, Large Commercial and Industrial Electric Rates
To protect your and your company’s wallets, it is very important to understand the rates you are being charged for electricity. In this segment, I am going to share with you and discuss in detail the large commercial and industrial electric rates of a typical utility. The example I am using is a utility that publishes their rates on the Internet. The electric rates you are being billed may vary greatly from my example. I recommend that you contact your utility to get a copy of your rate and to find out what other rates are available to you. Some of the terms I am using in this article have been previously defined and discussed in parts 1, 2 and 3 of this series.
What are you paying for electricity? Part 3, Commercial Electric Rates
To protect your and your company’s wallets, it is very important to understand the rates for which you are being charged for electricity. In this segment, I am going to share with you and discuss in detail the small commercial electric rates of a typical utility. The example I am using is a utility that publishes their rates on the Internet. The electric rates for which you are being billed may vary greatly from my example. I recommend that you contact your utility to get a copy of your rate and find out what other rates are available to you. Some of the terms I am using in this article have been previously defined and discussed in parts 1 and 2 of this series.
What are you paying for electricity? Part 2, Residential Electric Rates
To protect your and your company’s wallets, it is very important to understand the rates for which you are being charged for electricity. To get your feet wet, I am going to share with you and discuss in detail the electric rates of a typical utility. The example I am using is a utility that publishes their rates on the Internet. The electric rates for which you are being billed may vary greatly from my example. I recommend that you contact your utility to get a copy of your rate and find out what other rates are available to you. In most states, if a residential, commercial or industrial establishment wants electric service, they do not have a choice as to the service utility.
What are you paying for electricity? Part I, Load Management and Demand Charges
Electric utility rates vary greatly from utility to utility and from state to state. To protect your and your company’s wallets, it is very important to understand the rates by which you are being charged for electricity. The cost of electricity is so high that some commercial and industrial companies have entire departments whose sole responsibility is to study the utility rates and make load management recommendations for saving money. The work of these departments pays for itself many times over.
Two readers have e-mailed me with the question, "Is there a test I can take to become a certified National Electrical Safety Code‚ (NESC‚) inspector?” The short answer is, no. There are no such tests for the NESC‚ because certification as a NESC inspector does not exist. That doesn’t mean there are no qualified NESC inspectors. Let me explain.
The 2007 NESC – Part 4
This article is a continuation of what I see as significant changes that are coming in the 2007 revision of the National Electrical Safety Code.
The 2007 NESC – Part 3
This article is a continuation of what I see as significant changes that are coming in the 2007 revision of the National Electrical Safety Code.
The 2007 NESC – Part 2
In the March/April issue of IAEI News, I discussed what I think is the most important change coming in the 2007 edition of the National Electrical Safety Code. That change is the addition of a third loading requirement, extreme ice and concurrent wind, to the strength and loading sections of the NESC. What is considered important to one utility may not be important to another. For example, utilities that do not have structures (poles) taller than 60 feet in height, will find the extreme ice and concurrent wind change to be of very little importance because it applies only to structures taller than 60 feet. In my effort to identify the significant changes, I have tried to look at the changes from an industry prospective.
The 2007 NESC – Part 1
The National Electrical Safety Code® (NESC®) is presently being revised on a five-year cycle. The 2007 edition will be published and available for purchase on August 1, 2006. The NESC is published by the Institute of Electrical and Electronics Engineers (IEEE). The 2007 edition shall become effective no later than 180 days following the publication date. For the 2007 cycle, 297 change proposals were submitted by the July 17, 2003, deadline. In October 2003, the seven NESC subcommittees met to consider the change proposals.
Basic Electricity – Part 10
In part nine of this series, I discussed the development of the phasor diagram, a graphical representation of voltage or current magnitude in ac circuits at any instant in time. To better understand the uses of a phasor diagram, let’s take a look at the phasor diagrams of typical utility supply voltages. Before doing so, it is important to define a few terms.
Basic Electricity, Part 9
It is time to bite the bullet. Before we can continue into three-phase electrical circuits and calculations, we have to have a solid understanding of voltage and current phase angles. To do this we turn to phasors. I’m not talking about Captain Kirk’s weapon of choice. I’m talking about a graphical representation of the voltage or current magnitude in ac electric circuits at any instant in time. To get into phasors, let’s first review a little from Part 5 of this series when I introduced the idea of alternating current (ac).
Basic Electricity, Part 8
Electrical resistance is not the only property of materials that resists the flow of current. Let us consider an experiment. Let’s purchase a 12,000-foot spool of insulated 20 AWG copper wire commonly used as communications wire and pull the wire off the spool and lay it out on the ground. If we take the two ends and connect them to a male electrical plug and plug it into a 120 V AC source, we would expect the current magnitude that would flow in the wire to be equal to the source voltage divided by the resistance of the wire.
Basic Electricity, Part 7
In Part 2, I discussed power. A light bulb rated at 100 watts and 120 volts will use 100 watts of power when operating at 120 volts. If I wanted to operate ten 100-watt light bulbs on a gasoline powered generator, the rated power output of the generator would have to be at least 1000 watts. The rated horsepower of the gasoline engine that runs the generator is related to the rated power output of the generator. Energy is power times time. Electrical energy is usually measured in watt hours abbreviated Wh, kilo-watt hours abbreviated kWh, and mega-watt hours abbreviated MWh. If we operate ten 100-watt light bulbs for 24 hours, we would have used 1000 watts X 24 hours = 24,000 Wh or 24 kWh of energy. The amount of gasoline consumed by the generator is related to the amount of energy delivered by the generator.
Basic Electricity, Part 6 – Large Conductors
Most of my training in college was in electronics. When I graduated in 1971, most of the electronics companies were not hiring so I took a job with the local electric utility until I could find a job in electronics. Thirty-three years later, I’m still with the utility. Over the years working for an electric utility, I have become accustomed to referring to bare wire as wire and insulated wire as cable. In general, most of our aerial or overhead construction involves wire and most of our underground construction involves cable.
Basic Electricity – Part 5
Up until now, I have been talking about dc, direct current, in which the current in the circuit travels in one direction. Batteries and other sources of dc are marked with what we call polarity marks, + and –. When a battery is connected in a circuit, the current comes out of the positive (+) end of the battery and returns to the battery at the negative (–) end. This is true for all sources of dc. If we connect the test leads of a volt ohm meter (VOM) to a battery with the red colored positive (+) lead connected to the positive end of the battery and the black negative (–) lead connected to the negative end of the battery, the voltage reading on the display will be positive.
Basic Electricity, Part 4
In Part 2 of this series in the September/October issue, I worked through two simple example voltage-drop calculations. In both examples, I calculated what voltage I would have to have at the house to insure the voltage of 120 V at the chicken coop. Let’s call this calculation method A. The reason I used method A was because I had limited information about the bulb and heater. In each case, the manufacturer’s information only gave me the power requirement of each load when operating at 120 V.
Basic Electricity, Part 3
In parts one and two of this series, I have only spoken about direct current (DC), were the source of voltage is trying to push the current in one direction. Another form of electricity is alternating current (AC) in which the voltage source alternates the current direction. Everything I have covered in parts one and two apply to both DC and AC. As I continue I will point out the differences.
Basic Electricity, Part 2
In part 1, I described current as being the motion of electrons from one atom to the next within a material. A material’s ability to conduct current is a function of its ability to pass on electrons. All materials conduct current to some degree. Materials that resist the passing on of electrons are called insulators. Materials that put up very little resistance to the passing on of electrons are called conductors.
Basic Electricity, Part 1
The more accident investigations I perform, the more I am convinced that a thorough understanding of basic electricity is critical in solving tough cases. In the past twenty years, I have taught basic electricity more than any other subject. A majority of my students are lawyers. In order for them to understand how an electrical accident happened, they must know the basics of electricity.
The Effects of Ruling Span on Sag and Tension
Since the National Electrical Safety Code (NESC) minimum vertical clearance between conductors at supports and between the conductors and ground are a function of the sag of the conductors, some utilities might choose to reduce the sag by installing their aerial conductors at the highest tension for which they are allowed without exceeding the NESC limits. By limiting the conductor sags, the structure heights can be reduced and/or the spans can be increased, both of which reduce the cost of construction. What is the maximum tension?
The National Electrical Safety Code (NESC) only addresses conductor ampacity directly relative to grounding conductors. Rule 93C, page 19, requires grounding conductors to have a short-time ampacity adequate to handle the available fault current magnitude for the time it takes the source protection device to operate without melting or otherwise affecting the design characteristics of the conductor. One source for calculation of short-time ampacity is Aluminum Electrical Conductor Handbook published by The Aluminum Association, Inc., chapter six under short-circuit performance.
The World of Industry Standards
The National Electrical Safety Code (NESC) and the National Electrical Code (NEC) are both examples of industry standards. These two standards are very important to most IAEI members because we use one or both of them every day. Though these two standards are prominent in our minds, there are thousands of other industry standards that have a significant effect on us each day. Did you know that there are industry standards that cover everything from toilet paper to topsoil? For those standards, see American Society for Testing and Materials, ASTM D3905 and D5268.
Delayed Accident Investigations
About twenty times each year, I am consulted on accidents involving our electric power delivery system. Most of them are accidents involving property damage. The following are some examples of this type of accident: a house fire that appears to be of electrical origin, a truck is damaged when hitting wires, a truck hits a anchor guy which results in two poles breaking and three spans of wire and equipment falling to the ground, appliances burning up when a high voltage line drops on to a lower voltage line. On the average about six times each year, I am asked to investigate electrical contact accidents involving injury or death.
Existing Facilities Must Comply With What Edition?
Lawyers often ask me if the particular electric supply conductors involved in an electric contact accident were in compliance with the National Electrical Safety Code (NESC) at the time of the accident. Since the code from 1990 to the present requires all existing facilities to comply with either the code in effect at the time of the original installation, a subsequent code, or the present code, I first ask when the accident occurred and if there have been any changes to the facilities since the accident. Barring any changes to the facilities since the accident, I then evaluate whether the conductors and the structures to which they are attached comply with the code in effect at the time of the accident.
Safety Sign Placement on Large Substations
The National Electrical Safety Code (NESC) in Rule 110A1 describes the type of enclosure necessary to surround an electric supply substation. "Rooms and spaces in which electric supply conductors or equipment are installed shall be so arranged with fences, screens, partitions, or walls to form an enclosure as to limit the likelihood of entrance by unauthorized persons or interference by them with equipment inside.” The rule also requires posting of a safety sign at each entrance and one on each side of fenced enclosures. A "NOTE” informs readers that American National Standards Institute (ANSI) standards Z-535.1, .2, .3, .4, and .5 contain information regarding safety signs.
Inspection of Lines and Equipment
To insure that electric supply facilities comply with the rules of the National Electrical Safety Code (NESC), Rule 214A 2 states, "Lines and equipment shall be inspected at such intervals as experience has shown to be necessary.” What does this mean? How frequent is "…intervals as experience has shown to be necessary”? To understand this rule, we need to talk about the limitations of inspection in identifying NESC violations and averting electrical contact accidents.
Sailboats in Peril Near Power Lines
About fifteen years ago, on a beautiful Saturday in September, my then nine-year-old son and I had just finished a wonderful day of sailing. Five hours earlier, when we put in at a new boat ramp, there were very few cars with trailers in the parking lot because the stiff wind was scaring the power boaters away. When we arrived back at the ramp, the parking lot was almost full. As I pulled my boat out of the water, I had to park on the far side of the parking lot well away from the water. As I pulled into the parking space to down rig the mast, I noticed a power line between the front of my car and the adjacent roadway. The high voltage conductors seemed too low for their location adjacent to an area that the National Electrical Safety Code (NESC) would clearly define as an established boat ramp and associated rigging area.
NESC Substation Grounding – Part 2
The almost two hundred pages and ninety five equations of IEEE Standard 80-2000 provide a well explained procedure for the design of safe and practical grounding systems for electric substations. There are two objectives of a safe grounding system as detailed in Clause 4.1: "To provide means to carry electric currents into the earth under normal and fault conditions without exceeding any operating and equipment limits or adversely affecting continuity of service,” and "To assure that a person in the vicinity of grounded facilities is not exposed to the danger of critical electric shock” under normal and fault conditions.
NESC Substation Grounding
I have written several times in the IAEI News about the hazards associated with substations and some of the easy ways to understand NESC requirements for substations. In my November/December 1997 article titled "A Substation is Not Just a Fence,” I discussed the fallacy of using a fence as a quick and inexpensive fix to electrical facilities with clearance problems.
In the article titled, "Overhead Line Design From Scratch — Part 1? in the March/April 1998 issue of IAEI News, I discussed aerial conductor choice based upon steady-state ampacity, maximum operating temperature, and the sag/tension characteristics of the conductor at the maximum operating temperature. During the operation of the line, if we allow the conductor temperature to exceed the maximum operating temperature used to design the line, the conductor clearances may violate the National Electrical Safety Code (NESC) minimums and the conductor can be permanently damaged. This damage is loss of strength due to annealing of the conductor. Depending upon how closely the line is designed to the NESC maximum conductor tensions, conductor loss of strength can also violate the strength requirements of the NESC. So, why would anyone intentionally exceed the design maximum operating temperature?
Math Behind Extreme Wind Loading
In the last IAEI News (March/April 2002), I shared with you the details of the new extreme wind loading requirements of the 2002 National Electrical Safety Code (NESC). For structures sixty feet tall and shorter, the extreme wind loading only applies to the structure. For structures taller than sixty feet, the extreme wind loading applies to the structure and all the supported facilities. To understand the impact of the 2002 revision, lets crank through an example calculation.
The 2002 NESC Strength and Loading $$
The most significant change to the 2002 National Electrical Safety Code (NESC) is in the strength and loading requirements for aerial electric distribution and transmission facilities. Supporting structures and their supported facilities shall be designed to withstand extreme wind loading and a combination of ice and wind loading.
High Voltage Electrical Facilities that are Completely Safe
There are hundreds of customers in my company’s service area who own their own high voltage transmission, distribution and/or substation electric supply facilities. The service voltages for these customers range from 4 kV to 138 kV.
What’s Coming in 2002? Part II
Rule 217A2 requires readily climbable supporting structures to be equipped with barriers to inhibit climbing by unqualified persons. The old rule had an exception that said that this rule does not apply when the right-of-way is fenced. Since there was no requirement for the fence, a split rail fence would satisfy the rule. The new exception says, "The rule does not apply where access to the supporting structure is limited by a fence meeting the height requirement of Rule 110A.” The fence must now be seven feet tall and limit access to the structure. If a seven-foot-tall fence does not limit access, then the fence doesn’t meet the requirements of the rule. A fence meeting all the requirements of Rule 110A will certainly limit access.
What’s Coming in 2002?
The National Electrical Safety Code (NESC) is now on a five- year revision cycle. The 2002 edition will be published on August 1, 2001, and "shall become effective no later than 180 days following its publication date” (Rule 016). There are a lot of changes. Over the next few IAEI News issues, I will try to share with you what I see as the significant changes.
NEC vs. NESC: Understanding the World of Code
Rob and I have been friends for many years even though we were brought up on different sides of the tracks. By different sides of the tracks I mean Rob is a National Electrical Code (NEC) inspector and I am a National Electrical Safety Code (NESC) inspector. Up until the time we met, I didn’t know much about the NEC and Rob didn’t know much about the NESC. This lack of knowledge of the other code is common. Ever since I joined the IAEI, I noticed that most of the NEC experts have very little knowledge of the NESC and that most of the NESC experts have very little knowledge of the NEC.
Who Really Knows What It Means?
I have been working with and searching all aspects of the National Electrical Safety Code (NESC®) for almost 30 years. I refer to the book at least twice a day. Engineering, construction, claims and legal personnel in my company call or e-mail me regularly to ask questions about the NESC. Five years ago, I thought I had a very good understanding of the NESC.
I Dare You to Climb That Tower
How do we stop people from killing themselves? In particular, how do we stop teenage boys from climbing high voltage transmission towers like this one? Whether they are located in a secluded forest area or in someone’s backyard, a high voltage transmission tower looks like a "jungle gym” as we used to call them in elementary school. Every year, hundreds are injured and dozens are killed trying to climb them. Most of them are teenage boys. Why do they do it? Is it a dare? Are they looking for attention? Do alcohol or drugs impair their judgment? A nationwide TV campaign to inform them of the hazards wouldn’t stop them. It didn’t stop smokers.
The Pole Just Jumped Out in Front of Me!
Every year, thousands of vehicles run into electric and communication utility poles. The consequences are obvious. There may be some things we can do to reduce the number of accidents or the severity of the accidents.
This Pole Is Not Big Enough for Both of Us
With the incentive of Internet access business, some telephone and cable TV companies are scrambling to add more communication cables to some already overcrowded utility poles. Each additional cable, whether installed as a separate attachment or installed by overlashing on an existing cable, adds mechanical load to the poles.
Just Don’t Bump Your Head On It
When we talk about mini- mum ground clearances of span conductors, we have to know the sag of the conductor because the minimum height of attachment on a structure to comply with the National Electrical Safety Code® (NESC®) is the minimum clearance plus the maximum sag of the conductor. The ground clearance for equipment cases and rigid live parts is very simple and yet often ignored. Too often someone says, "Mount it high enough so someone doesn’t bump his head on it.” This design "philosophy” is a gross violation of Rule 232B2 & 3 (page 72) of the 1997 NESC.
Working in Dangerous Proximity to Overhead High Voltage Lines – OSHA, NESC, and the Law
There are two sets of rules for work in proximity of overhead high voltage lines: The rules for qualified persons and the rules for unqualified persons. There is no gray area. Occupational Safety and Health Administration (OSHA) regulation 29CFR1910.269(x) defines a qualified person as "one knowledgeable in the construction and operation of the electric power generation, transmission, and distribution equipment involved, along with the associated hazards.”
The Storage of Hazards
The excess space inside electrical supply stations (substations) is often considered for storage of construction materials. The National Electrical Safety Code® (NESC®) in Rule 110B2 prohibits storage inside an electrical supply station even when stored well away from the energized conductors and equipment. The only exception is the storage of minor parts essential to the maintenance of the installed equipment, i.e., fuses, switch handles.
How Hot is That Wire?
The conductor temperature is a critical part of the design, construction, and checking clearances of aerial electric supply lines. Line Design In my article on "Overhead Line Design From Scratch – Part 1? in the March/April 1998 issue of IAEI News, I discussed conductor choice based upon steady-state ampacity, transient ampacity, short-time ampacity, voltage drop...
How Low is That Wire?
Electrical inspectors involved with aerial high voltage facilities frequently have to determine whether electrical conductors are in compliance with the National Electrical Safety Code (NESC).
An Inspector’s Most Common Hazardous Conditions
I spend a lot of time inspecting electric supply facilities for hazardous conditions and violations of the National Electrical Safety Code® (NESC®). Even when I’m on vacation, I don’t stop inspecting. I’ve shared the "problems” with my wife so often that now she points them out to me. I’ve driven all over the United States and find that no matter where I go, the hazards are out there, particularly in non-utility owned supply facilities.
The Cost of Losing an Arm
Tom had flash burns to his face. Fortunately, he had been wearing safety glasses. What was left of his right arm had to be amputated above the elbow. He was in the hospital for almost four months. The medical care and physical therapy would continue for years. Tom said that he and two experienced linemen were called out on trouble at two o’clock in the morning. A relatively new housing development was completely out of telephone service.
Safety Signs, Labels and Tags
The National Electrical Safety Code® (NESC®) occasionally references other standards. For example, ANSI Z535.1-1991 through ANSI Z535.5-1991 inclusive are referenced many times within the NESC. Most of these references are made in a NOTE: following a rule. Rule 015D explains that a NOTE: indicates material provided for information or illustrative purposes only. When a standard is referenced in a NOTE:, compliance with the standard is not mandatory.
Overhead Line Design from Scratch—Part 4
In Part 3 (July/August issue) we determined the height of our structures and the strength of our structures and foundations to comply with the National Electrical Safety Code® (NESC®). The last step in the design of a high-voltage overhead line up to 50 kV to comply with the NESC is to design the guying. Stringing conductors between poles puts tension on the poles. Though poles and foundations can be designed with enough strength to hold the tension, guying is much more economical.