Aging of Cross-Linked Polyethylene Insulation Cable Lines

Abstract. Preference is given to cable lines with  cross-linked polyethylene insulation in electrical networks with a nominal voltage of 10 kV during reconstruction of existing and construction of new industrial enterprises. The standard service life of such cables is at least 30 years (subject to the conditions of storage, transportation, installation and operation), and the actual one   is determined by the technical condition of the cable. The service life of a cable line depends on the state of its insulation, the aging of which occurs under the influence of several factors. Conventionally, all factors influencing one or another degree on the cable insulation resource can be divided into thermal, electromagnetic, climatic, mechanical and operational. The most significant reason for the insulation aging  is high temperature, which accelerates the reaction of thermo-oxidative destruction, during which high-molecular polymer compounds decompose. In fact, cables are operated at temperatures below the long-term permissible values, and, therefore, the aging of the insulation is slower, and the actual service life will be longer than the standard. At present, condition of the insulation is monitored with the use of high voltage tests related to destructive testing methods. When designing and operating cable lines, it is necessary to estimate the duration of the actual service life under various operating conditions. In theory, there are several expressions for calculating the service life of a cable line when exposed to temperature, humidity, electric field and aggressive environments, but all of them are not applicable in practice due to the presence of a large number of coefficients whose values are unknown. The paper presents an analytical expression obtained for determining the service life of power electric cables, taking into account the aging of the insulation under the influence of temperature and electric field.