The towing cable for coal cutters is always subjected to the joint effects of electric

thermal and mechanical stresses in actual operation

which severely deteriorates its insulation performance. In order to be able to master the insulation performance of ethylene propylene rubber (EPR) for the towing cable of coal cutter under simultaneous action of mechanical and thermal stress

the the dielectric spectroscopy of the EPR under the action of the extrusion force and temperature is measured in this paper

and the influence of temperature and extrusion force on the real part of complex permittivity and complex conductivity of EPR is studied. Then

the spectroscopy of imaginary part of complex permittivity is fitted by Havriliak-Negami function

the characteristic parameters of the Havriliak-Negami function are extracted and the relationship among the characteristic parameters

temperature and the extrusion force is analyzed. The result shows that the complex permittivity and the real part of complex conductivity of EPR are not only closely related to temperature and frequency

but the complex permittivity is also related to extrusion force and the real part of the complex conductivity is to negatively related to the extrusion force. The imaginary part of complex permittivity of EPR is in good agreement with the Havriliak-Negami function. It is concluded from the analysis of the characteristic parameters that the influence of temperature on DC conductivity and of the extrusion force on loss strength is the main cause leading to complex permittivity variation of EPR insulation.