The reaction mechanism function can effectively characterise the insulation ageing and deterioration process of GIS basin-insulators

which helps to reveal the failure mechanism of insulating materials and provides a new way to assess the insulation performance of basin-insulators. By resolving the differential equations of the reaction mechanism

an integral expression for the reaction mechanism function with four basic parameters is established

which can be modified for different reaction stages or paths and has a wider scope of application. On this basis

a structural form of this test function is derived based on the non-isothermal kinetic equations and the formulae for calculating the model are derived. Using this method it is also possible to calculate the finger front factor at the same time. The reaction mechanism functions for basin insulators and cross-linked polyethylene are further specified and the validity of the generic characterisation model and solution method for the reaction mechanism functions is verified based on the Coast-Redfern method and the modified Flynn-Wall-Ozawa method. The above work provides an effective method for analysing the reaction mechanism of the degradation process of insulator insulation materials.