CIGRE TB 852 – Offshore HVDC Substation Grounding Best Practices Checklist

CIGRE TB 852 establishes a systematic, lifecycle-oriented approach to offshore HVDC substation grounding, emphasizing integration with overall system design rather than treating grounding as an afterthought. It distinguishes between functional grounding (e.g., reference potential for control electronics), protective grounding (fault current path and touch/step voltage mitigation), and lightning protection grounding—each requiring tailored design criteria due to the conductive seawater medium and absence of conventional soil. The brochure advocates for multi-physics modeling—including electromagnetic transient (EMT) simulations, thermal analysis of conductor sizing under DC fault conditions, and corrosion-aware material selection—to quantify ground potential rise (GPR), mesh voltage gradients, and long-term integrity. Crucially, TB 852 introduces a staged verification framework: conceptual design review, detailed modeling validation (including seabed resistivity profiling and anisotropic soil–seawater interface modeling), factory acceptance testing (FAT) of grounding components, and site commissioning measurements (e.g., fall-of-potential and clamp-on resistance tests adapted for submerged structures). It also mandates documentation traceability, including grounding system as-built records, corrosion monitoring plans, and periodic integrity assessments aligned with IEC 62878 and ISO 15686 standards.