optimizing validation of voltage and time for VLF (0.1 Hz) voltage testing on-site

Very Law Frequency (VLF) voltage test on-site has been applied widely for evaluating the status of installation and operation of medium voltage power cable lines. For optimiting and validating the test voltage and test time, the validity, equivalency and relationship of test voltage and test time of VLF voltage test is discussed and analyzed in this paper. The results of research and optimization in the paper have proved and verified that the VLF voltage test method of 3U
0
test voltage and 40 min test time is a better choice for checking and verifying the safe operational life of power cable lines, and 2.5 U
0
/25min or 3U
0
/25min is suggested for verifying the safe operational life of aged cable line that has been in service more than 7 years. VLF voltage test may establish the present status of dielectric quality of power cable lines.