69kV Transmission Line Assessment

TRC assessed Unitil’s entire 69kV system (approximately 50 miles) located in and around the area of Fitchburg, Massachusetts.




Project Location

Fitchburg, Massachusetts

Unitil had experienced several static wire failures and needed an assessment of their transmission system to note any other potential problems that could occur.

A high-level review of the system was conducted based on both a technical and visual investigation.

From a technical approach, TRC looked at the most predominantly used structures and reviewed their structural capacities based on current NESC and Massachusetts’s codes as well as industry standards.

TRC used PLS-POLE, the leading software of wood pole analysis, to determine capacities of various configurations, span lengths and wire tensions. TRC also looked at static wire and conductor tensions to ensure they were within acceptable standards through the use of PLS-CADD. From this overview, TRC determined what areas of the design were at the highest risk of causing failures.

During this process, TRC also assessed the samples of the failed static wire to provide our opinion as to the probable cause of failure. Another important aspect was a visual inspection of the line to determine its general condition.

The project culminated with a report describing areas needing improvement for reliability with a plan created to prioritize the work. Priority was based on which lines were more at risk for future static wire failure.

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