Analysis on single-phase short-circuit current in insulated ground wire during ice-melting of EHVAC transmission lines

For heavily ice-coated overhead transmission lines the full-length isolation design is applied to the ground wire for DC ice-melting, however the isolation design of the ice-melting ground wire impacts the distribution of short-circuit current between the tower and the ice-melting ground wire. Accurate computation of short-circuit current in the ice-melting ground wire is of significance to the analysis on both step voltage and safety of the grounding mesh. Taking actual full-length insulated ice-melting ground wire as research object, the erection mode of insulated ice-melting ground wire is expounded and using ATP-EMTP simulation software a transmission line model with full-length insulated ground wire is established. The distribution characteristics of short-circuit current in ice-melting insulated ground wire system for EHVAC transmission system under different single-phase short-circuit states are researched and the obtained results are compared with those of uninsulated ground wire system for EHVAC transmission lines. Research results show that the induced voltage due to single-phase short-circuit leads to the breakdown of clearance of ice-melting insulated ground wire and the erection of ice-melting insulated ground wire changes the channel of short-circuit current; after the erection of ice-melting insulated ground wire the short-circuit current flowing back to the grounding mesh changes slightly and does not impact on the safety of grounding mesh; the maximum rising of the current flowing into the ground via tower grounding appears at the position where the short-circuit occurs, therefore special consideration should paid to the step voltage at this position. ©, 2014, Power System Technology Press. All right reserved.