Study on Grounding Ways of Secondary Cable in UHVDC Converter Substation

The ground potential will rise abnormally when impulse current injects into grounding grid if a converter substation is struck by lightning or there exist short-circuit faults. Transient ground potential rise (TGPR) could couple to the cable core wire through conductive and near-field coupling ways and it will invade the secondary system eventually. Taking those two coupling ways into consideration, this paper builds a simulation model describing the technisim on how TGPR couples to the secondary cables in an UHVDC converter substation and searches for the best grounding way for suppressing disturbance voltage in secondary cables' cores caused by TGPR. Through simulation and test, for a single cable harness with armor double-ended grounded, we propose that cable's shielding sheath should be grounded only in protecting cabin. For a four-segment cable, we find the best grounding way is that for the harness segment between protecting cabin and terminal box, we should guarantee armor double-ended in both sides while shielding sheath be grounded only in protecting cabin, for the segment between terminal box and operating cabinet, we should guarantee armor double-ended in both ends while shielding sheath be grounded only in terminal box, what's more, the armor and sheath among operating cabinets should be grounded only in phase B's cabinet.