HV Earthing Design and Testing Services Australia

HV earthing is the system of buried conductors, electrodes and bonding connections that ties a high-voltage installation to the general mass of earth. It has two main jobs. It gives earth fault current a low-impedance return path so protection operates quickly, and it limits the step, touch and transferred voltages that people and equipment are exposed to during a fault. In Australia, HV earthing systems for installations above 1 kV a.c. are generally designed to AS 2067:2016, with ENA EG-0 setting the risk-based safety criteria and ENA EG-1 giving the substation earthing detail.

Earthing design is the process of sizing and arranging an earthing system so it safely carries the prospective fault current for its full duration. It starts with a soil resistivity survey, builds a layered soil model, then designs the earth grid geometry, conductor size and electrode arrangement, and verifies the result against permissible step and touch voltage limits.

Soil resistivity testing measures how readily the ground at a site conducts current, usually using the Wenner four-pin method at a range of electrode spacings. The results are modelled as a layered soil profile, which is the starting point for every earth grid design because soil resistivity directly determines the earth grid resistance that can be achieved.

Earth resistance testing verifies that an installed earth grid achieves the resistance assumed in the design. The fall-of-potential method is the standard technique for measuring the resistance of a substation earth grid to remote earth, confirming the as-built system performs as designed before energisation.

An HV earthing design follows the same broad steps on every site:

1. Design inputs. Confirm the earth fault current and how it splits between the earth grid and other return paths, the primary and backup clearing times, the site layout and the metallic services nearby.
2. Soil resistivity survey. Measure the ground with the Wenner four-pin method and build a layered soil model.
3. Preliminary earth grid. Lay out the grid and size the conductors for the fault current and its duration.
4. Modelling. Model the grid in CDEGS to calculate the grid resistance, the earth potential rise and the surface potentials.
5. Step and touch voltages. Compare the calculated step and touch voltages with the safety criteria of AS 2067 and ENA EG-0, using IEEE 80 as a supporting reference, and refine the design with extra conductors, driven rods, gradient control conductors or a surface layer where needed.
6. Transfer potentials. Assess voltages transferred to fences, pipelines, telecommunications and neighbouring low-voltage systems, and design the mitigation.
7. Verification. Issue the earthing design report and drawings, then verify the installed grid by fall-of-potential or current injection testing before energisation.

Soil resistivity testing characterises the electrical resistivity of the ground at the project site using the Wenner four-pin method, taken along multiple traverses and at a range of electrode spacings. Megavar models the results as a layered soil profile, which sets the achievable earth grid resistance and underpins the entire earthing design. Soil resistivity surveys are carried out early so the earth grid can be sized correctly before construction.

Megavar designs high-voltage earth grids from first principles for substations, renewable energy connections and industrial installations. Earth grid design covers conductor sizing for the prospective fault current and clearing time, grid geometry optimisation, buried conductor and electrode layout (driven rods, deep-driven electrodes and ground enhancement material where soil resistivity is high), and above-ground bonding of plant and structures. Every earth grid design is verified against the permissible step and touch voltage limits in ENA EG-0 and IEEE 80 before it is issued.

Substation earthing controls the earth potential rise during a fault and keeps step and touch voltages across the switchyard within safe limits. Megavar designs and tests substation earthing for transmission and distribution substations, including the main earth grid, fence and gate bonding, gradient control conductors, and surface layer treatment to raise the tolerable touch voltage. Design and as-built testing follow ENA EG-0, ENA EG-1, AS 2067:2016 and IEEE 80.

A neutral earthing resistor limits the earth fault current in a generation or distribution system to a designed value, protecting plant and simplifying earth fault detection. Megavar tests NERs to verify the resistance value, continuity and connection integrity, and confirms the associated earth fault protection picks up and operates correctly. NER testing is carried out as part of substation commissioning and routine maintenance.

Step and touch potential testing measures the actual voltages a person could be exposed to within and around an energised installation. Megavar measures step and touch potentials during staged fault injection and compares them against the permissible limits derived from ENA EG-0 and IEEE 80, validating the earthing design under real fault conditions and identifying any locations that need mitigation.

Calculation of the maximum earth potential rise during fault conditions and assessment of hazardous voltage transfer to telecommunications, pipelines, fences, and other metallic infrastructure within the EPR zone of influence.

Detailed calculation of step and touch voltages at all accessible locations within and around the substation. Comparison against permissible limits derived from body impedance models per ENA EG-0 and IEEE 80. Identification of areas requiring mitigation (surface treatment, insulating mats, gradient control conductors).

Assessment of hazardous voltage transfer onto LV systems, telecommunications, water pipes, and other metallic services that enter the EPR zone. Design of isolation and mitigation measures including NERs, isolation transformers, and optical isolation.

Earth resistance testing confirms that an installed earth grid achieves the resistance assumed in the design. Megavar uses the fall-of-potential method, and staged fault current injection where a large grid requires it, to measure the grid resistance to remote earth. The result is compared against the design value to confirm the as-built earthing system performs correctly before the installation is energised. Our earth resistance testing guide explains the fall-of-potential method step by step.

Earth testers are available from our earth testing equipment hire range.

• Earth grid resistance: Fall-of-potential and staged fault testing methods to verify the earth grid resistance meets design requirements.
• Step and touch potential measurement: On-site measurement of actual step and touch voltages during staged fault injection to validate the design analysis.
• Soil resistivity measurement: Wenner four-pin surveys at multiple traverse directions and electrode spacings.
• Continuity testing: Verification of bonding connections, earthing conductor continuity, and equipotential zone integrity.
• Earth fault loop impedance: Measurement to verify fault current return path impedance for protection coordination.

Megavar uses CDEGS (Current Distribution, Electromagnetic Fields, Grounding and Soil Structure Analysis) by SES Technologies, the industry-standard earthing design and analysis platform. CDEGS enables detailed 3D modelling of complex earth grid geometries and accurate prediction of surface potentials.

Megavar designs and tests earthing systems for sites in Melbourne and across regional Victoria, including wind, solar and battery projects and industrial substations. Engineers and injection test equipment mobilise from our Tasmanian and Adelaide offices.

• Australia-Wide Expertise: Serving clients in all states and territories.
• Industry Compliance: Meeting AS/NZS and ENA standards.
• Custom Solutions: Tailored earthing designs for renewable energy, utilities, mining, and industrial applications.
• Minimised Risk & Optimised Performance: Reducing equipment failures and downtime.
• Ongoing Support: Providing maintenance, monitoring, and compliance updates.

Partner with Megavar for expert HV Earthing Design and Testing. Contact us today to discuss your project needs!