HV Earthing Assessments: More than a compliance exercise

High-voltage (HV) earthing is sometimes treated as a box-ticking exercise to satisfy standards. In reality, a well-designed and well-maintained earthing system is fundamental to substation safety, reliable network operation, and the ability to safely accommodate future modifications.

At existing substations, changes in network fault levels, incremental extensions, ageing infrastructure, and undocumented alterations can all impact the performance of the earthing system over time. Without a structured assessment, latent deficiencies may remain unidentified, potentially affecting fault current dissipation, system integrity, and compliance with applicable UK requirements.

What does an HV Earthing Assessment involve?

A comprehensive HV earthing assessment goes far beyond a single earth resistance test. It combines site investigation, measurement, and detailed analysis to evaluate how the earthing system behaves under credible fault conditions. This typically includes:

• Soil resistivity testing to establish representative ground models.
• Earth resistance and impedance measurements of the existing earthing system.
• Visual inspection of above-ground earthing conductors, terminations, and bonding.
• Continuity and joint resistance testing between key items of primary plant.
• Identification and verification of buried electrodes and conductors.
• Detailed earthing system modeling using CDEGS software.
• Assessment against UK legislation and network standards.

The outcome is a clear understanding of whether the existing earthing system remains compliant, effective, and suitable for current and future operating conditions.

Why is this Critical?

HV earthing assessments serve two key purposes:

• Demonstrating compliance with UK legislation and network standards, supporting safe operation during fault conditions.
• Enabling safe design for new plant, equipment upgrades, or substation extensions, reducing technical risk and avoiding late-stage redesign or mitigation.

By understanding the true performance of the earthing system early, potential issues can be identified and addressed in a controlled and cost-effective manner.

Getting it right first time

HV earthing assessments require a high level of technical judgement, practical site experience, and a clear understanding of how safety, compliance, and future development interact.

At PSC, we offer:

• An experienced specialist team with a strong track record in HV earthing assessments across UK substations and complex operational environments.
• A safety-led approach, ensuring earthing systems are assessed against credible fault conditions and real site constraints.
• Robust analytical capability, using advanced modeling to support clear, defensible conclusions.
• Proportionate, practical outputs, focused on identifying real risks and supporting informed design decisions rather than over-engineering.
• Responsive support, helping to identify and resolve issues early to reduce program and construction risk.

Our approach gives asset owners and developers confidence that existing earthing systems are safe, compliant, and suitable for both current operation and future modification.

Contact our specialist team to learn more about our services and how we can help.