The Study On Diagnosis And Testing Technology Of XLPE Cable Insulation By Dielectric Spectroscopy

This paper describes the dielectric properties and aging characteristics of XLPE insulation cables,summarizes the common diagnosis methods of domestic and the development of dielectric response measurement and prosents three common methods of dielectric response measurement.Extended Debye model which could reflect dielectric relaxation and lumped equivalent circuit are also given in this paper.XLPE cable insulation test system is designed and built,including cable accelerated aging part and measurement part.For different aging condition of XLPE cable insulation,frequency domain spectroscopy method is used to study the FDS curves under different aging time and different test temperature.Dielectric theory is used as a helpful tool to analyze the experimental data.It is concluded that FDS method can distinguish XLPE cable samples between different aging time.The dissipation loss factor increases obviously with the increase of aging time,but capacitance and permittivity almost changes nothing when frequency is higher than IHz.It is demonstrated from FDS curves under different test temperatures that FDS curves moves to the high frequency region with the temperature increase,for a sample at certain aging time,its minimum values of dissipation loss factor measured are close to each other at different test temperatures,it can be considered that the minimum value a helpful tool to estimate the aging condition of XLPE.Cascaded linear amplifier circuit based on the frequency domain spectroscopy testing purpose is designed in this paper.The circuit is capable of good linearity,AC-DC available,a wide frequency range of 10-3-104Hz,the amplified factor is 40 times and two-stage series amplified factor is 80 times.