Features of thermal ageing of cables with different type of insulation

Abstract

Abstract A wide range of temperature and duration of cable routes operation requires the development of objective methods for assessing the properties of cable insulation. While working, preparing and repairing cable routes, it is important to use express methods to determine the technical condition of insulation, to search for diagnostic parameters indicating the process of crack formation. An ongoing monitoring of cable insulation with standard devices controlling electrical resistance and leakage currents is not sufficiently effective for evaluating the performance and predicting the properties of cable insulation. The study is aimed at further testing of the technique by analysing the properties of materials used in cable engineering, as well as comparing the results obtained by various devices manufactured by national and foreign companies. Tests were carried out to assess the quality of insulation based on the monitoring of hardness of the hose insulation and the conductor insulation of KNR and KNREk cables. In the KNREk type cables, the core insulation is also made of the RTI type rubber, but the hose insulation is created on the basis of a material from polyvinyl chloride compound. The method of assessing the quality of insulation and assessing the degree of ageing of cable material is implemented by measuring the hardness of insulation material using the Shore method using portable hardness testers of the following types: TH-200, NOVOTEST TS D-A (TS D-D) up to 100 HSА (HSD). It is shown that the proposed technique makes it possible to identify objective statistical parameters of the material hardness and to diagnose the quality of insulation in operation without dismantling cable routes. The hardness parameters of hose insulation from polyvinyl chloride compound can be controlled by TS D-D devices. The heat resistance of hose insulation of the KNREk type cables is higher than that of the cables of the KNR type, which creates opportunities for their longer operation at high temperatures.