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California Public Utilities Commission

Re-Evaluate & Update General Order 95 Standards for the Design of Wood Utility Poles

Ground fires that are caused by utilities’ poles failing in high wind conditions prompted the California Public Utilities Commission (CPUC) to convene a panel of experts from the major public utilities and telecommunication companies, in the State of California, to evaluate and update General Order 95 (GO95).  GO95 is the governing administrative law for the design of wood pole structures in the State of California.  Very similar to the National Electric Safety Code (NESC), GO95 was developed in response to more severe coastal wind conditions and funneling of strong winds in areas of high residential values within coastal and Malibu Canyon areas of California.

CAutilities

The scope of this project was to evaluate and update GO95 for best practices, design parameters, and modern materials.  In addition, the desire of the CPUC was for utilities and telecommunication companies to agree on common testing and analysis procedures that were prudent and fair to all parties, in order to determine cost sharing parameters for replacement of facilities.

Realtime Utility Engineers, Inc. (RUE) was engaged as one of the experts to provide input and evaluation for structural design of wood poles, and to evaluate current GO95 parameters against the NESC, and known recorded weather events that have occurred in recent years.  Additionally, the panel of experts worked together to understand and evaluate the practice of allowing pole attachments from telecommunication companies.  This was to ensure that wood structures were not overloaded at the time of attachment.

Additionally, new and updated weather loading parameters and wind maps were evaluated, and agreed to, with regard to more restrictive design parameters.  This analysis was evaluated for regions that regularly encountered Santa Ana winds and coastal winds, uncommon for inland areas.

Line design and structural engineers from RUE were heavily engaged in forensic analysis of actual pole attachment disputes, along with predictive structural analysis of actual measured and predicted extreme weather conditions, as dictated by the CPUC.  Sophisticated structural analysis programs such as PLSCADD, SPIDA Calc, STAAD, and RISA were used to check historic performance against current codes and other extreme loading cases, such as a broken conductor cases, or heavy ice and wind conditions.   This type of analysis provided information for structure loading under various conditions, and was used in defining risks of structure component failure and predictive maintenance for upgrade schedules, under the revised loading case conditions.

 

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