Optimizing design of over voltage protector for HV power cable metallic shield grounding

Operation faults of HV power cable lines have been increasing because of multi-points grounding of cable sheath which caused by over voltage breakdown. Cable metallic shield grounding and over voltage protecting techniques have been noticeably along with more and more underground power cable lines applied in urban transmission and distribution system. It is the key for us to design and optimize the technical parameters of over voltage protector used for single-core power cable metallic shield grounding and over voltage protecting. But neither international nor national standards have defined the rules of how to choose the parameters until today. In this paper, the rules and methods of design and optimization of over voltage protector for cable metallic shield grounding and over voltage protecting were discussed based on national standards of China such as GB 50217 code for design of cables of electric work, DL/T401 guide to the selection of high voltage cables and DL/T5221 Technical Rule for Design of Urban Power Cables as well as practical experience of long-term operation of power cable lines. Furthermore, lightning impulse test and large impulse current test were used for validating reliability and preponderance of the protector design in the paper. The results of theory analysis and tests proved that the over voltage protector for cable metallic shield grounding and over voltage protecting designed by the rules can satisfy the technical requirements of the standards and meet the practical demands of power cable lines operating safely and reliably.