The Suitability Analyses of Sheath Voltage Limiters for HV Power Cable Transmission Lines

With the rapid development of urban power system, the proportion of high voltage (HV) power cable transmission lines used in urban power grid was increasing. Under the lightning striking, switching or fault conditions, a high induced voltage could generate on the insulated sheath of cable so it was necessary to protect and limit the sheath induced voltage of HV cable. The sheath voltage limiter (SVL) could be installed between the metal shield of cable and grounding. In order to clarify the temporary and transient characteristics of sheath induced voltage and its influences with the SVL, the models of simulating calculations were established based on a typical 220kV cable transmission line and with the PSCAD/EMTDC software in this paper. The transient characteristic of sheath induced voltage and its influence with the SVL were calculated under the conditions of different short-circuit currents and lightning strike currents, respectively, through the cable core. Two kinds of SVLs with two grounding manners, i.e. cross-bonding grounding and single-point grounding, were investigated respectively. According to the energy absorption capacity of each SVL, the suitability curves of SVL for different cable lengths and short-circuit currents were obtained, which would provide the basis and the improvement approaches for the engineering design of cable grounding. Furthermore, based on the different suitability curves of SVLs, the design principles and typical parameters of the improved SVLs were presented. The improvement effect of a newly improved SVL was analyzed also. The methods used in this research could also be extended to other voltage class cable transmission lines and/or other laying methods.