The Telecommunications Act of 1996 has caused a significant increase in pole-attachment permit applications. Gone are the days when the only requests for attachment permits were from the telephone company or the local cable television provider. As the act intended, the number of telecommunications providers has risen dramatically in the last five years.

Increased competition and the race for market share, coupled with investor demands to generate cash flow, have driven the telecom providers to plan and build their systems in the quickest and most cost-effective manner possible. They accomplish this by maximizing the construction of aerial facilities on existing utility poles. Therefore, pole owners must develop and implement processes to effectively handle the increase in attachment applications, which can be a challenging task given the complexities involved.

Federal and Utility Requirements

The U.S. Federal Communications Commission (FCC) has dictated that approval of permit applications cannot take an inordinate amount of time, and utility companies have a duty to insure that the safety and reliability of the existing system is not compromised. These two things are not necessarily compatible. Take, for instance, the requirement for a wind and ice-loading study to determine the structural capacity of each pole in an application. This is not something that is typically done quickly, especially if a large number of poles are involved.

This is the scenario currently taking place in the Kansas City metro area where Brungardt Honomichl & Co. (BHC; Overland Park, Kansas, U.S.), in alliance with Capital Electric Line Builders (CE; Kansas City, Missouri, U.S.), has been working on a project for Everest Connections. Since the summer of 2000, Everest has been building a hybrid fiber/coax network to provide bundled broadband services to residential and commercial customers.

A significant portion of Everest's project involves the construction of aerial plant on existing poles. Kansas City Power and Light (KCP&L; Kansas City, Missouri), which owns a large number of the poles in the Kansas City area, has implemented an attachment-approval process that requires the inventory and analysis of each pole in the application. The required analysis is to include a check of clearances per the National Electric Safety Code (NESC), as well as a wind and ice-loading analysis.

BHC and CE have been heavily involved with this aspect of the project since it began, and the pressure to deliver the required analyses quickly has been ever present. Because of this, BHC has focused on maximizing efficiency while maintaining a high level of quality.

System Evaluation

When work first began on the project, paper forms were used to record the data collected by pole inventory crews. The data collected for each pole included general pole information, span lengths, conductor and cable sizes, attachment heights, line angles, equipment and hardware information, guy information and service drop data. Office personnel used the paper forms to perform the required analyses. Ultimately, the data was entered by hand into a spreadsheet and used to calculate loads for the structural analysis.

As the project progressed, it became apparent that a better method for collecting and disseminating the data was needed. Despite efforts to minimize them, reoccurring errors were the result of inconsistent nomenclature between field crews, non-legible handwriting and data-entry mistakes made while transferring the data to the spreadsheet. In addition, the process was just not very efficient.

In the summer of 2001, BHC began investigating methods to make the inventory and analysis process more efficient. The most obvious place for improvement was in collecting inventory data. Our project team felt that if we could develop a system to collect the data electronically and in a format that was readily usable by office personnel, efficiency and quality would increase greatly.

The new system had to meet several objectives. First, to minimize retraining time and expense, the system had to mimic existing workflows. The workflow that had been developed over time was proven and project personnel were accustomed to it. The introduction of a completely new process was to be avoided if possible. Secondly, the hardware and software comprising the new system had to be reliable. Lastly, the new system had to be flexible so we could make modifications and improvements in the future.

After researching off-the-shelf data collection programs, BHC decided none of them were appropriate; they either did not integrate well with existing workflow or did not provide sufficient flexibility. Therefore, BHC decided to develop a custom solution using Microsoft Access and Visual Basic for Applications programming. Access was already in use within the companies, and the Access database format is widely used and compatible with most GIS systems.

The second piece of the system was the field hardware needed to run the application. BHC had several factors to consider, including cost, durability, processing speed, ease of use, battery life and screen readability under varying conditions. BHC eliminated the various Windows CE devices from the start, because they would not run Microsoft Access and screen size is typically limited. Ultimately, BHC decided to use the Fujitsu Stylistic 3500 pen tablet.

Application Development: Phase One

Once we selected the software platform, Mike Spickelmier of BHC and I [Matt Brungardt] began developing the application. While we both had some programming experience, we had never undertaken a project of this magnitude.

The main focus of the application early in its development was to automate the collection and storage of field data. Therefore, most of the initial work involved designing the database structure and developing the interface for field personnel. We developed the main field data collection screen to resemble the original paper forms as closely as possible. To increase efficiency and provide for more consistent data collection, we incorporated drop-down lists into the various fields for things like conductor sizes and equipment types.

As the application evolved, we incorporated additional features such as a sketch utility to allow personnel to clarify field conditions through a sketch. The sketch is stored in JPEG format and linked to the database for easy retrieval. The application also will draw a plan and elevation view of the pole using the stored data so the field crew can check it visually while standing at the pole.

After the application was in use for some time, we added two additional features that further enhanced the data collection effort. First was a utility that facilitated the collection of data for consecutive poles along a line. It reduces field time by automatically copying redundant data for adjacent poles. Another added feature addressed the problem of missing data. It was not uncommon for a pole to be missing a piece of data, such as a conductor attachment height, a service drop line angle or a guy lead distance. This necessitated another trip to the field to obtain the missing information, thus disrupting the workflow in the office because further processing stopped until the missing data was obtained. Despite efforts to be more careful, crews encountered missing data problems on about 15% of the poles inventoried. The solution was to add a pole check feature to the application. When the field crew finishes a pole, they press a button and the system checks for missing and inconsistent data. The addition of this feature has virtually eliminated missing data problems.

Application Development: Phase Two

The second phase of developing the application focused on making use of the data in the office. The first utility we developed was a cable clearance calculator. One of the focuses of the analysis is to check the clearance between the various equipment, conductors and cables attached to a pole. Using the attachment height data stored in the database, the utility calculates the clearances and compares them to acceptable values specified in the NESC. The clearance utility then allows the designer to make adjustments to any of the attachment heights to remedy code violations or create space for an additional cable. The adjustments can then be written back to the database.

The stored data is also used to facilitate the wind and ice-loading analysis for each pole inventoried. As stated earlier, personnel use a spreadsheet to calculate the loads imposed by the various conductors and equipment on the pole. Since this spreadsheet took considerable effort to develop, the project team did not want to duplicate the effort in the new application. Therefore, BHC developed an interface between the database application and the load calculation spreadsheet. The spreadsheet is now populated automatically with the appropriate data, thus eliminating data-entry errors that were a problem with our earlier process.

We've also added other various tools to make the application more useful and user friendly, such as tools that help users navigate the data more efficiently, custom reports for data output, and automated output of data into electronic form for transmittal to KCP&L.

Deployment and Implementation

The system was deployed in late January 2002, and as of mid-January of 2003, crews had processed approximately 14,000. As with any endeavor of this sort, there have been bugs and glitches to work through but most have been minor. The inventory crews have successfully used the pen tablet and software in a wide variety of conditions. Office personnel also have had ample opportunity to use the application, which has performed well. Having the flexibility to make updates and enhancements at the request of users or to address specific problems has proved to be invaluable.

Overall, the increase in efficiency realized through the implementation of this system has been significant. While field inventory times are not notably lower than before, the collected data has far fewer errors and the electronic format has greatly increased the efficiency of the rest of the process. For example, prior to implementing the new system, a technician could perform the structural analysis on approximately 15 poles per day. Currently, it is not uncommon for the same technician to analyze 40 poles in a day's time. The benefit of having the data stored in a database rather than on paper has proven to be greater than first envisioned. There have been several occasions in which required information was obtained via a database query where the previous method would have necessitated a hand search of paper records.

Another recently added feature automatically creates design information that can be imported into AutoCAD for inclusion on the construction drawings. As further experience is gained or as the needs arise, additional features will continue to be added. Some of the possibilities already under consideration are automatic capture of digital photographs and a GPS interface for collection and storage of positional data.

Matt Brungardt is director of Brungardt Honomichl & Co. P.A. He earned a BSCE degree from the University of Texas at Arlington in 1986. He has been involved with telecommunications projects for the past 15 years and has specialized in joint-use issues for the past five years. He is a registered professional engineer.

Analysis of a Pole

Collection and efficient use of inventory data is a significant part of the pole-analysis process. However, the project stakeholders ultimately are interested in the results of the analysis, which often determine the allocation of costs for make-ready work and pole replacements. For instance, if a pole is overloaded prior to placement of new cables on the pole, the utility company is typically responsible for upgrading the pole to meet code. If, however, the pole becomes overloaded due to the addition of new cables, the attaching company is responsible to remedy the over stress.

From a technical perspective, analyzing a utility pole is fairly straightforward. However, there are several factors to consider and assumptions to make, so good engineering judgment must be applied. The analysis process consists of a check of attachment clearances and a structural analysis. Section 23 of the National Electric Safety Code (NESC) contains the requirements for the minimum clearance between various attachments on a pole and surrounding objects. These requirements were incorporated into the original distribution system construction. However, over time, changes have occurred, such as the addition of communications cables, that necessitate another review of the system. In addition, we have to determine if the poles have space for an additional cable.

Rules 232, 235 and 238 contain provisions related to clearances that have the biggest impact on joint-use poles. Rule 232 of the code specifies the minimum vertical clearances between cables/conductors and the ground. It is important that cables are not placed too low in areas like road or railroad crossings or across navigable waters. Table 232-1 provides the clearance values required for these and other scenarios (Note that the values indicated in the table are for maximum sag conditions.). The engineer is responsible for determining what the maximum sag condition is in each case. Rule 235 specifies minimum clearances between conductors on the same structure. This rule establishes the worker safety zone between the supply space and the communications space. Table 235-5 shows the required clearances for various scenarios. Rule 238 establishes clearance requirements between cables and various equipment that may occupy a pole.

The clearance analysis typically has three outcomes:

• The pole has sufficient space for attachment of the new cable without any adjustment to existing attachments.

• The pole has sufficient space for the new cable if adjustments to existing attachments are made. (Relocating existing attachments is often referred to as make-ready construction.)

• There is insufficient space on the pole for the new attachment. This is remedied by replacing the pole with a taller one.

On our project, of all the poles analyzed approximately 60% have had sufficient room to attach a new cable, 35% have required make-ready adjustment, and 5% have required a taller pole.

Once clearance issues are resolved, the structural analysis can be performed. Structural analysis of an existing utility pole is more involved than checking clearances. The basic process is to determine the loads, apply them to the structure and calculate the resulting stresses. The stress level is then compared to the allowable level specified in the NESC. Sections 24, 25 and 26 of the NESC provide the requirements for structural analysis. In simple terms the NESC says the following: For the grade of construction specified in Section 24, a pole must be able to withstand the loads specified in Section 25 while meeting the strength requirements in Section 26.

Section 24 of the NESC specifies the relative strength required of a pole using a concept called Grade of Construction. The three grades of construction, in order of increasing strength, are N, C and B. Application of a specific grade is dictated by the level of risk associated with the installation. For instance, Grade B is required for installations over limited-access highways where a failure would have a high potential for injury and property damage. Conversely, Grade N may be used in exclusive private right of ways where the potential for injury or property loss due to a failure would be much less.

The loadings required for Grades B and C construction are specified in Section 25. Included in this section are the requirements for wind and ice loading for the three loading districts in the United States. Section 25 also specifies overload factors that are applied to the calculated loads. Loads carried by an electric distribution pole can be broken down into three categories, vertical, longitudinal and transverse.

Vertical loads are all loads acting in a vertical direction. They include the weights of all cables and equipment attached to a pole, including the appropriate thickness of ice, as well as the vertical component of guy wire forces.

Longitudinal loads are all loads acting on the pole in the direction of the pole line. These loads originate from wire tensions and guy wire forces. For tangent poles, the longitudinal loads originating from cables spanning in both directions are often balanced, thus having a net affect of zero on the pole.

Transverse loads are all loads acting on the pole in a direction perpendicular to the pole line. At angle poles, the transverse direction is assumed to be the bisector of the line angle. Transverse loads originate from wind, wire tensions and guy forces. Transverse loads are calculated based on wind loads as specified in NESC, and wire tension loads are calculated using various methods.

Of all the load types affecting a pole, wire tension loads are the most difficult to calculate. This is because of the variety of factors affecting wire tensions such as temperature and sag. This is especially true with an existing system. In order to accurately calculate the tension in a wire, the amount of sag in the wire, the span length, and the characteristics of the wire must be known. In addition, in order to predict the wire tension at a range of temperatures, the temperature corresponding to a known sag value must also be known. Collecting the data required to make these calculations for a pole with many cables attached would be expensive. An alternative is to make assumptions about the sag values based on experience and observation of existing field conditions. These assumptions then can be used to calculate anticipated tension values. This method saves time and expense, while providing a sound solution from an engineering standpoint.

Once the loads have been determined, they can be applied to the structure and the corresponding stress values calculated. This can be done manually, however it is more common to use structural analysis software for this task. PLS Pole from Powerline Systems is one such piece of software. It provides a straightforward interface for modeling and analyzing pole structures and outputs the results in a logical manner. Several load cases are input for each pole analyzed to account for the effects of wind blowing from different directions and to determine the effect of the new cable on the pole. In most cases, the maximum stress will occur at the ground line and will be the result of bending stress caused by transverse loads and axial stress caused by vertical loads. In our experience, on a typical tangent structure, bending stress accounts for 95% or more of the total.

Section 26 of the NESC specifies the allowable stress level for supporting structures. For wood poles, ANSI 05.1 is the referenced standard specifying the designated fiber stress for different wood species. These values are then reduced by the application of strength factors to determine the allowable value.

The results of the structural analysis will show if a pole is capable of carrying the imposed loads or not. In cases where the pole is over stressed several options exist. The first option is to attempt to remedy the over stress without replacing the pole. One method of accomplishing this is to add a guy. This option is usually best when the overstress is caused by an unbalanced wire tension. Even though adding a guy may fix a pole overstress problem, the lack of physical space or the lack of guying easements may make it impractical. Another option is to add some form of mechanical stiffener to the pole. This may take the form of metal plates bolted or strapped to the pole or possibly a stub pole installed adjacent to the existing one. If neither of these remedies work, the last option is to replace the pole with a larger one.

With so much riding on the results of the analysis, it is important that they be accurate. As with many engineering projects, engineers face a challenge in delivering results as quickly as possible without compromising the quality of the results. The use of technology can help but there is no substitute for good judgment.