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As the cities expand, the local government has provide to use the underground distribution cables considering the city image; the use of power cables under medium and high voltage will be on the rise, considering the reliability of urban power network. Since the power cables are more and more widely used in high voltage grid, the power cables’ reliability of operation has been more important than ever. But in recent years, all kinds of aging fault have already started to appear in some cables which have been running longer, so it is better to predict the aging failure rate of the power cables, and slow the growth trend of failure rate, by changing some cables which have been running longer, in order to improve the stability of cables.By dealing with the record provided by a power supply bureau of failures of power cables in the numbers of65,this paper has fitted the annual failure cumulative the number of power cables using empirical distribution, Weibull distribution of both two-parameters and three-parameter, Crow-AMSAA model, and come to the fitted values of the parameters of the distributions, discussed the pros and cons of these distribution models’ fitting results, the feasibility of using economic life as the indexes of the power cables in the regular preventive, discussed the replacement cost in two case that the power is with warranty or not, when the size relationships between the warranty period and the economic life is uncertain. Advices has been given separately to provide reasons to replace power cables with potential age failure ahead of time, In the meantime, considering the economy of the preventive maintenance of the power cables, this paper has brought in the preventive maintenance cost economic algorithm of power cables, calculated the preventive maintenance cost of power cables of15years designed life, the results showed that, in the given parameters, the cycle of2years is more economical than the cycle of1years as the cycle of power cables’ preventive maintenance. which will avoid major loss.
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