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SECTION 8 - WIND TURBINE GROUNDING SYSTEMS Until recently wind turbine grounding systems have incorporated design concepts developed from European standards with applicability to the Canadian market being advised by a simple statement ``The resistance to ground must be in accordance with the requirements of the local authorities. `` CEC requirements need to be reviewed to ensure that the local inspection authority will provide approval. Wind turbine systems are stand-alone, incorporating a perimeter ring of bare copper with driven copper-weld rods that serve as the grounding electrode. This system serves as an equipment-personnel safety ground, as well as lightning protection. If individual wind turbine grounding is determined to be inadequate due to high soil resistivity conditions at the site, individual grounds can be interconnected to “get more copper in the ground” - reducing the ohmic value of the system. WIND TURBINE COLLECTOR GROUNDING SYSTEMS. Medium voltage (23,000V to 46,000V) radial feeders are used to collect the power output of the individual wind turbine generators, routing it to the substation collection bus. These feeders can be underground cable, overhead conductor construction, or a combination of both. Underground designs employ standard URD cables with concentric copper neutrals. Overhead designs use construction that are typical with the local distribution utility, which will also dictate the type of connection that will be specified for the turbine step-up transformer (Delta, Wye or grounded Wye). Usual connection on the medium side of the transformer is Delta to prevent Zero Sequence current from a ground fault on the low voltage generator side from entering into the medium voltage collector system. However, this will provide an ungrounded system in the collection feeder should open and no other ground point on the feeder is provided, which can lead to possible damaging over voltages on the other two phases if a Single Line – to Ground fault occurs on any phase. At risk are surge arresters, the turbines and their electronic controls. Therefore, common practice on this design is to include grounding resistors or transformers to provide that ground point. Another method being used recently are switchgear that detect a fault, open the feeder and automatically grounds the feeder as well within one cycle. WIND PLLANT SUBSTATION GROUNDING SYSTEMS Wind farm substations employ practices defined in Section 3.

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