Life-Cycle-Cost Evaluation on Degradation Diagnosis for Cables

Abstract

Degradation diagnosis is aimed at preventing unexpected failure and extending the service life of electric power apparatuses. It is, however, necessary to investigate the economic feasibility of degradation diagnosis, because the life-cycle cost of cable maintenance changes with the diagnostic parameters such as diagnosis cost, diagnosis interval and replacement criterion. In this paper, based on the actual data of water-tree degradation, we proposed a method of life-cycle-cost evaluation and evaluated the economic effect of degradation diagnosis. We also discussed the economic feasibility of practical nondestructive diagnosis of 6.6 kV XLPE cable, i.e. DC leakage current measurement and residual charge measurement, and compared the economic effects of these methods. As a result, the residual charge measurement is economically feasible and has higher effectiveness than the DC leakage current measurement.

Robustness Assessment of Life-Cycle-Management of CV Cables based on Degradation Diagnosis

“…The annual density distribution of maximum water tree length I in the k-th year Nk(l) was expressed as the following logarithmic normal distribution. As for the typical cables, the number of remaining cables which have been in use for k years in the n-th calculation year g,1(k) is calculated by considering P(k) and R(k) [1,2]. Assuming failure loss cost Cf, replacement cost Cr and diagnosis cost Cd expressed as relative values, the total life-cycle cost LCC is expressed as follows.…”

“…The setting of adequate conditions, such as the periods of diagnosis and replacement of aged equipment, is important for minimizing LCC of the equipment operation taking diagnosis costs into account. In our previous study, therefore, we formulated a numerical model of life-cycle management based on conditionbased maintenance (CBM) [1,2]. Then, assuming that the maximum length of water tree as a replacement criterion can be measured nondestructively, we evaluated the economic effect of degradation diagnosis of power cables with water tree degradation as an example of power apparatuses, for which relatively rich data on degradation and remaining life are available.…”

Investigation on different maintenance rules in the case of load variation

“…the kth year), can be calculated. The calculation method of lifecycle cost is described in [2], with the assumption that the load of each apparatus in the reality is of the same value.…”

“…CALCULATION METHODS Generally, assuming a certain physical diagnosis parameter l of power apparatus in the kth year (real aging time) following logarithmic normal distribution as follows [2] :…”