Estimation of overhead line condition

The ranking of old overhead lines with respect to their refurbishment requirements, according to reliability-centered maintenance (RCM) methodology, is based on two values: condition index and importance index. This paper describes a proposed methodology for determining the overhead line condition index by applying fuzzy mathematics. A determination of the overhead line condition index is proposed based on: (1) building elements condition index, (2) condition index of conductors, (3) condition index of protection against lightning impulse, (4) conductor accessories condition index and (5) line route condition index. The value of the indicated indices is determined as a result of detailed inspection of the condition of overhead line components. The inspection is made for the purpose of observing the degree of aggravation of their instantaneous condition in relation to their designed condition. On the basis of the estimation of condition aggravation rate by using fuzzy rules and membership functions, we obtain values for each of the above listed partial condition indices. By combining all the listed partial indices into a uniform grading we get the overhead line condition index. It represents a basis for the objective determination of priorities for taking proactive maintenance actions for the purpose of diminishing the risk of old overhead line operation.