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Upcoming Webinar, September
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FREE Wood Pole Structure Design Seminar
Location:
Courtyard by Marriott Denver Cherry Creek in Denver, CO
Dates:
September 24 - 26, 2013
Instructor:
Richard Lovelace
Hi-Line Engineering
18 Professional Development Hours will be earned by those completing the course.
Space is limited to 40 attendees so enroll NOW!
Click here to view the event flyer and registration form.
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WEI + NWPPA Utility Pole and Overhead Systems Conference and Trade Show
October 10 - 11, 2013
Join us for the WEI + NWPPA Utility Pole and Overhead Systems Conference and
Trade Show
Location:
Seattle Airport Marriott
Seattle, WA
Dates:
October 10 - 11, 2013
Highlights Include: ~ Emergency preparedness
~ Lessons learned from the Eastern Washington wildfires and Hurricane Sandy
~ Vegetation and woodpecker management ~ Pole replacement and mitigation
~ Best practices for recycling Poles
~ Pole supply
~ Preservative treatment changes
~ Lineman wood pole poll results
Visit here for more details and please join us in October.
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Wood Pole
Standards Course
The North American Wood Pole Council will also hold a Wood Pole Standards Course for a registration fee of $795 per attendee.
Location:
St. Louis Airport Marriott
10700 Pear Tree Lane
St. Louis, MO 63134
Dates:
November 19 - 20, 2013
Instructor:
Martin Rollins
H.M. Rollins Co.
14 Professional Development Hours will be earned by those completing the course.
Registration will include a copy of the latest Standards & Technical Report, a $700 value!
Space is limited to 30 attendees!
Click here to view the event Flyer, and here to view/print the Registration Form. |
Copyright © 2013 North American Wood Pole Council, All Rights Reserved.
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OVERVIEW
The National Electrical Safety Code requires initial inspection of lines for compliance of rules and inspections of power systems "at such intervals as experience has shown to be necessary." This vague requirement will be explained and the repercussions that system inspection has on system reliability and public safety. We will address the NESC record keeping requirement. Inspection intervals required by regulators will be presented along with pole inspection guidelines based on geographic location. Techniques will be presented for record keeping of joint-use inspections that identify numerous violations which are not compliant with NESC. Pole inspection also includes compliance with NESC strength and clearance rules. We will also discuss the NESC requirements for determining when a pole must be replaced. One of the challenges with pole inspection is to determine if and when a pole must be replaced and this will be discussed through different methods used to evaluate pole strength such as core drilling and other inspection techniques.
WHO SHOULD ATTEND
~ Engineers ~ Power line workers
~ Staking technicians ~ Contractors ~ Consultants
LEARNING OUTCOMES
~ Define the NESC requirements for system inspection
~ Define the NESC requirements for when a pole must be replaced
~ Describe types of pole decay
~ Evaluate different pole inspection methods
INSTRUCTOR
Kevin Mara, P.E., a Vice President of GDS Associates, and the Principal Engineer of Hi-Line Engineering
EUCI is authorized by IACET to offer 0.2 CEUs for the webinar.
For more information use this link:
NAWPC In-Service Inspections Flyer
To Register use this link:
NAWPC In-Service Inspections Webinar Registration
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Two NESC Change Proposals Will Increase Line Construction Cost
The National Electrical Safety Code (NESC) has entered the process of evaluating potential changes to the code in preparation for the next publication of the code in 2017. The deadline for submittal of change proposals was July 15, 2013. These change proposals will be evaluated and discussed at committee meetings in September of 2013.
There are two issues under consideration that have also been proposed in past code cycles. One of these is the elimination of the present exemption from the extreme wind design criteria for structures less than 60 feet in height. In other words, under the code today, distribution structures are not required to be designed to meet the extreme wind criteria. However, designing to the existing district load requirements provides for design loads on wood poles, that would be equivalent to wind speeds of 105 mph or higher. The 60-foot exemption exists for a combination of reasons. First, and primary, is the belief that most line failures during extreme wind events are caused by secondary damage effects such as wind blown debris and falling trees, not just the load from wind on the conductor, crossarm, and pole. This is supported by reports from the field after storm events. These secondary damage loads cannot be reliably calculated so it is not possible to design for them. The second reason for the 60-foot exemption may be that there is normally some reduction in actual wind close to the ground due to sheltering from structures, trees, and other vegetation. This issue is, in reality, essentially limited to coastal locations with hurricane winds, as the district loads provide higher design loads in most other areas of the country. The crux of the issue is that to require designs to 150 or 160 miles per hour will substantially increase the cost of construction and the storm performance many not be improved.
The second potential issue of import for the users of wood poles is the possible change to a probability-based load and resistance factor design (LRFD) basis in the NESC. This scenario would be an "extreme value" design scenario for both extreme wind alone and extreme ice and concurrent wind. This design scenario typically uses a statistically defined weather load at some return period, such as 50 years, with a load factor of 1.0, and a 5% lower exclusion limit (5% LEL) strength value with a strength factor of 1.0. If more than one grade of construction would be provided for, as with the current Grade B and Grade C in the NESC, the grades would be established by simply adjusting the predicted return period for the storm event. There are several issues with this approach. One is the fact that the present NESC essentially allows the design load on wood poles to double between Grade B and Grade C. This is difficult to accomplish by simply changing the storm return period. The second issue is that the strength distribution of wood poles is different from that of manufactured products such that if natural wood poles and engineered poles are both designed to the typical 5% LEL strength value used in LRFD designs, the wood poles will have a much higher capacity to withstand loads higher than the design load. So wood poles would be much more reliable in extreme weather events where the typical failure loads are associated with secondary damage, not the design wind load. The reliability-based LRFD design procedure will not result in equal reliabilities if the coefficient of variation of the different materials is markedly different and if the actual loads due to secondary damage effects are higher than the extreme value weather load. For this reason, any attempted change to a simple reliability-based LRFD format would in effect penalize wood poles and would change the long standing historic strength relationships between wood and other materials in the various grades of construction recognized in the NESC. The cost of overhead construction using wood poles would be unnecessarily increased.
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Call us at the North American Wood Pole Council 888-693-9958 (message line)
Or at the Western Wood Preservers Institute
360-693-9958 (M-F 8-5)
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