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Inspection and Maintenance Standards

Decisions 96-11-021 and 97-03-070 establish inspection cycles and record-keeping requirements for utility distribution equipment, which are contained in General Order 165.  In general, utilities must patrol (walk, drive, or fly by) their systems once a year (in urban areas) or once every two years (in rural areas).  Utilities must conduct detailed inspections every 3-5 years, depending on the type of equipment.  For detailed inspections, utilities' records must specify the condition of inspected equipment, any problems found, and a scheduled date for corrective action.  The utility must submit an annual report summarizing inspections made, equipment condition observed, and repairs made.  Utilities are required to make intrusive inspections of power poles; no pole should go over 25 years before its first intrusive inspection, and once passed, every 20 years thereafter.   Currently GO 165 is being studied for revisions to optimize the Commission's ability to identify areas on noncompliance with its safety standards GO 95 Overhead and GO 128 Underground and its inspection, maintenance and repair standards GO 165.

Tree Trimming Standards

Decision 97-01-044 of Investigation 94-06-012 establishes standards for trimming trees near power lines, issued as a revision to Rule 35 of General Order 95-A.  For lines at voltages higher than 750 v, in general, trees must be trimmed so as to provide no less than 18 inches of clearance from lines under normal annual weather variations.  When trimmed, where practicable, trees must be 4 - 15 feet from power lines over 2,400 volts (clearances vary with voltage).  Detailed rules are contained in Appendix A of the decision.   Note that "service drops" (the lines that supply electricity to individual homes) are insulated and operate at 750 volts or less.  At these lower voltages, arcing (the creation of a spark between the electric wire and another object) is unlikely.  Contact is therefore allowed if there is no strain on the wire or abrasion of the insulator.   Decision 97-10-056 completed the Commission's Investigation.  General Order 95-A, Rule 35 was modified, adding an exemption for mature trees which are allowed to remain in place if they are more than six inches from power lines.  The decision clarifies that the utilities are responsible for appropriate trimming around a service drop when they know of strain or abrasion and addresses various smaller issues raised in this case.

Last Modified: 2/22/2008

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