The invention discloses an ultra-
low frequency dielectric loss-based DC cable
extrusion insulation aging state evaluation method, wherein the
extrusion type
solid insulation of a DC cable is adopted as a
research object. The method comprises the following steps of preparing an insulated inner-layer slice sample, an insulated intermediate-layer slice sample and an insulated outer-layer slice sample of a cable; according to the rated
operating voltage of the cable and the dimension parameters of the cable, determining a measurement
voltage; measuring the
dielectric loss of slice samples under different voltages at a frequency of 0.1 Hz;
processing measurement data and preparing a
dielectric loss-
voltage graph in a normalized coordinate
system; according to the
dielectric loss values of the inner and outer
layers of the
dielectric loss-
voltage graph and the varying trend thereof along with the application of an externally applied voltage, evaluating the
extrusion insulation aging state of the DC cable. According to the technical scheme of the invention, the extrusion insulation aging state of the DC cable can be accurately evaluated, so that the real-time state of the extrusion type DC cable can be effectively determined. Meanwhile, the method is small in
test sample size, and low in requirement on the voltage and the capacity of a test instrument. The influence of the test instrument on the
system error is reduced. The requirement on the accuracy of the test instrument is lowered. Meanwhile, the data of the method are free from being compared with historical data, so that the method can be used for evaluating the cable state, wherein
original data are missed.