Design, commissioning and testing of IPP ground electrodes

The design, commissioning, and testing of ground electrodes for Intermountain Power Project (IPP) ±500 kV HVDC transmission systems are described. The results from subsurface geotechnical investigations, including the statistical analysis of different parameters, are presented. The ground electrode design was based on conservative bulk ground resistivity measurement results. The electrode resistance achieved suggests that the earth layer resistivity values developed during geotechnical information are more dependable and could be used for design purposes. The variation of different parameters and optimization of the electrode design are discussed. The selection of deepwell vertical electrodes is explained. Different approaches to ground electrode commissioning and testing and test results are presented. It has been demonstrated that using the low-current testing procedure presented, very small unit resistances of wells and groups of wells can be accurately measured, even during conditions of significant telluric activity and polarization potentials