Earthing Assessment for Major Network Upgrade

Project Overview

Existing Earthing Survey

DACI Utilities Engineering Consultancy delivered a comprehensive earthing assessment and design package to support a major SSEN network reinforcement programme involving an upgraded transformer and new Gas Insulated Switchgear.

The works required a detailed understanding of the existing earthing installation before new high-voltage assets could be safely integrated. DACI combined field survey, soil testing, fall-of-potential testing and detailed earthing design to support a compliant and construction-ready solution.

The first stage of the project focused on establishing the condition, extent and continuity of the existing earthing infrastructure. This included a structured survey of the operational compound, equipment bonds, accessible earth connections and perimeter interfaces.

Project Facts

Project Overview

Major SSEN network reinforcement programme involving an upgraded transformer and new Gas Insulated Switchgear

Delivered within an existing, live operational site

Combined field survey, soil testing, fall-of-potential testing and detailed earthing design

Survey evidence, testing results and design development aligned into a single engineering package

Our Scope

DACI Scope of Work

Existing substation earthing survey to verify installed bonds, connections and accessible earth grid interfaces.

Soil resistivity testing for the soil model.

Fall-of-potential testing to assess the performance of the existing earthing system.

Electrical continuity testing of the existing earthing system.

Earthing design for integration of an upgraded transformer.

Earthing design for Gas Insulated Switchgear and associated high-voltage plant interfaces.

Engineering Challenges

Designing Around Existing Infrastructure

The project required new high-voltage assets to be integrated into an established earthing network. This created several design challenges around verification, modelling confidence and physical connection points.

Existing asset uncertainty

A reliable understanding of installed earthing arrangements was needed before the upgrade design could progress. DACI completed a survey and continuity checks to confirm available earthing interfaces and identify areas requiring attention.

Ground model accuracy

Representative soil parameters were required for a meaningful earthing assessment. Soil resistivity testing was used to establish model inputs for fault current dissipation and voltage performance assessment.

System performance validation

The existing earthing system performance needed to be confirmed before reinforcement works were integrated. Fall-of-potential testing provided a practical benchmark for the operational earthing system.

Plant integration

The upgraded transformer and GIS required robust bonding and earthing coordination with the existing grid. DACI developed targeted earthing design measures for the new plant and interfaces.

Operational constraints

Survey and testing activities had to consider the constraints of an existing live infrastructure environment. The assessment approach prioritised safe access, practical verification and design decisions that could support construction delivery.

DACI Solution

Engineering Response

DACI combined site evidence and engineering analysis to develop an earthing design capable of supporting the upgraded network arrangement while making best use of the existing earthing system.

Key Deliverables

Existing earthing survey and condition assessment
Soil resistivity testing and interpretation
Fall-of-potential testing and performance assessment
Transformer earthing design
Gas Insulated Switchgear earthing design
Earthing model development and compliance review
Construction-ready earthing design outputs

Outcome

Technical Assurance for Network Reinforcement

The completed assessment provided a clear technical route for integrating the upgraded transformer and Gas Insulated Switchgear into the existing earthing system. The work helped reduce delivery risk by aligning survey evidence, testing results and design development into a single engineering package.

Benefits Delivered

Compliant design to the DNO spec and manufacturer preferences.
Improved confidence in the existing earthing system
Clear design basis for integrating new high-voltage assets
Reduced uncertainty for construction and commissioning teams
Practical compliance-focused approach to touch, step and EPR performance

Conclusion

This case study demonstrates DACI's capability to deliver complete earthing services from field investigation through to detailed design for high-voltage network reinforcement projects.

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Earthing Assessment for Major Network Upgrade

Project Overview

Existing Earthing Survey

Project Overview

Major SSEN network reinforcement programme involving an upgraded transformer and new Gas Insulated Switchgear

Delivered within an existing, live operational site

Combined field survey, soil testing, fall-of-potential testing and detailed earthing design

Survey evidence, testing results and design development aligned into a single engineering package

DACI Scope of Work

Designing Around Existing Infrastructure

Existing asset uncertainty

Ground model accuracy

System performance validation

Plant integration

Operational constraints

DACI Solution

Engineering Response

Key Deliverables

Outcome

Technical Assurance for Network Reinforcement

Benefits Delivered

Conclusion

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Integrated Earthing and Safety Studies for a PV Solar Farm

BESS – 400kV connection

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