ConsultJR provided a detailed earthing system design and electromagnetic field (EMF) study to allow a thirty-story building constructed over an existing Energex substation tunnel with live 2x110kV & 33x11kV feeders. For this challenging project, Energex has required the builder to complete an engineering study to ensure the construction of the building around the tunnel would be safe and not expose the public and workers to the risk of electric shock or unsafe EMF levels. A temporary metallic structure was to be used to support the tunnel during the construction/excavation phase and then converted to a permanent concrete structure at the end of the construction phase. CJR’s EMF and earthing design and assessment satisfied the Energex requirements.
Scope of Works included:
- Data collection, information review, and site visit
- Negotiation with Energex to allow non-standard earthing arrangement
- Earthing system assessment for the temporary works based on AS 2067 and ENA EG-0
- Deterministic earthing system design for the permanent installation according to IEEE Std 80
- EMF measurement and assessment based on IEEE Std C95.6 and ICNIRP guidelines
Project highlights:
- Detailed analysis of soil resistivity results measured at various locations close to the site
- Combined LV and HV earthing system
- Identifying the worst-case scenarios for single-phase to ground (SLG) faults at 11kV and 110kV feeders
- Safety assessment during temporary excavation works by considering:
- the probability of coincidence
- probability of SLG faults during excavation
- earth potential rise (EPR) limits
- risk control measures to reduce the probability of fatality during excavation
- Deterministic earth system design for the final structure by determining:
- the earth grid conductor size
- number of earth rods
- the acceptable levels for step and touch voltages and EPR levels
- Argon and Elek software used for the earth system design and the EMF assessment
- EMF measurements and EMF assessment based on the maximum demand
Project Details:
