Project Overview
Gridserve delivered a comprehensive earthing system design for the Salisbury Bioenergy Plant, a utility-scale anaerobic digestion facility. The project focused on managing Earth Potential Rise (EPR) and ensuring personnel safety across a complex site featuring high-voltage infrastructure, large-scale concrete digestion tanks, and intricate gas processing skids.
Key Project Scope & Deliverables
- Infrastructure Hazard Analysis: Conducted BYDA searches to identify third-party assets and reviewed 11kV fault levels, clearing times, and soil resistivity surveys.
- HV Earth Grid Engineering: Designed a local earthing network for the site’s HV switchboard, transformers, and auxiliary equipment, optimizing conductor size and orientation for a low-impedance path.
- EPR & Safety Modelling: Calculated the Earth Potential Rise (EPR) and overall system impedance. Rigorous modelling evaluated step and touch voltage hazards within the plant and safe contour distances for nearby metallic infrastructure.
- Asset-Specific Earthing: Developed specialized earthing for core infrastructure, including the Anaerobic Digesters, Hydrolysis Tanks, and Gas Upgrading Skids.
- Compliance Documentation: Produced a detailed Earth Grid Design Report and technical drawings (General Arrangements/SLDs) to demonstrate full compliance with South Australian utility and national safety standards.
Key Challenges
- Complex Soil Resistivity: Navigating the specific soil profiles of the Edinburgh region to achieve target earth resistance and accurate EPR modelling.
- High-Density Infrastructure: Coordinating a buried earth grid within a footprint containing significant underground services, digestion tank foundations, and gas processing pipelines.
- Proximity to Third-Party Assets: Managing the zone of influence of the Earth Potential Rise to ensure no hazardous voltage transfer to neighbouring industrial metallic fences or telecommunications networks.
Technical Standards Followed
- AS 2067: Substations and high voltage installations exceeding 1kV AC.
- ENA EG0 / EG1: Power System Earthing Guides.
- AS/NZS 4853 / 3835: Low frequency interference and EPR hazard mitigation.
- IEEE 80: Guide for Safety in AC Substation Earthing.