Method for detecting and evaluating insulating property of power cable by utilizing ultralow-frequency dielectric loss

The invention relates to a method for detecting and evaluating the insulating property of a power cable by utilizing ultralow-frequency dielectric loss. The method comprises the following steps: testing wiring; respectively measuring dielectric loss factors of a tested phase cable under the voltage of 0.5 U0, U0 and 1.5 U0, increasing the voltage from 0.5 U0 to 1.5 U0 according to a stepping valueof 0.5 U0 during testing, completing dielectric loss factor measurement for at least five times under each stepping voltage, and keeping an interval of 10s between every two times of measurement; recording a dielectric loss factor value under each test voltage, carrying out data processing and storage, and calculating a dielectric loss factor average value, a dielectric loss factor change rate and dielectric loss factor stability of the test data; and taking the dielectric loss factor average value, the dielectric loss factor change rate and the absolute value of the dielectric loss factor stability as evaluation ind