Research On Immunity Of Controlling And Protective Devices On The Basis Of Field-Coupling

The ground potential will rise abnormally because of impulsing current injecting into ground grid when a converter substation is struck by lightning or there exist short circuit fault.On one hand,transient ground potential rise(TGPR)may damage equipment insulation and bring a threat to the safety of operation staff;on the other hand,TGPR could couple to the core line through conducting and near-field coupling ways which invades the secondary system and influences the power system's operation stability.Taking those two coupling ways mentioned into consideration,this paper built a simulation model describing the technisim on how TGPR couples the secondary cables in a UHVDC converter substation's 500kV filtering yard and searched for better grounding ways for suppressing interference voltage in secondary cables' core wires caused by ground potential rise,which will improve the immunity of secondary devices.Through simulation of the real secondary cables' layout,we proposed that cable's shielding sheath should be grounded only in protecting cabin for a single secondary cable harness with armor double-ended grounded.Through simulation and test on a four-segment secondary cable applied in the spot,we found the most effective grounding way is that:for the harness segment between protecting cabin and terminal box,we should guarantee armor double-ended in both protecting cabin and terminal box 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 terminal box and operating cabinet while shielding sheath be grounded only in terminal box;The armor and sheath among operating cabinets should be grounded only in phase B's cabinet.