Confidential UK DNO / ICP — UK Grid Substation
145kV Eco-Efficient Circuit Breaker Installation & Commissioning
Northern HV installed and commissioned a Hitachi Energy LTA 145D1 145kV circuit breaker using eco-efficient CO₂ gas technology. Full mechanical, electrical, and gas handling works delivered within a constrained outage window.
Client
Confidential UK DNO / ICP
Location
UK Grid Substation
Contractor
Northern HV Ltd
Project Overview
Northern HV was appointed to install and commission a Hitachi Energy LTA 145D1 145kV live tank circuit breaker at a UK grid substation. The project formed part of a primary plant replacement and network reinforcement programme.
What made this job different: the breaker uses Hitachi's eco-efficient CO₂-based gas mixture instead of conventional SF₆. It's part of the client's strategy to reduce environmental impact and move away from high-GWP gases — and it required our team to apply specialist gas handling techniques alongside standard HV installation practices.
We delivered the full scope within a constrained outage window in a live operational environment.
Scope of Works
Pre-Installation Engineering
- Review of OEM drawings, GA layouts, and schematics
- Interface checks with existing protection and control systems
- Outage planning and switching programme coordination
- Inspection and verification of civil foundations and anchor points
Mechanical Installation
- Offloading and inspection of breaker poles and operating mechanism
- Assembly of pole units and operating mechanism
- Installation onto prepared foundations with torque tightening to OEM specs
- Alignment, levelling, and installation of interconnecting pipework and control cabinets
Primary Connections
- Installation of palm connections and terminal pads
- HV conductor alignment and mechanical stress verification
- Contact surface preparation and joint compound application
- Final torque verification and QA recording
Secondary & Control Works
- Control cabling installation and termination
- Marshalling kiosk modifications
- Trip/close circuit integration
- Anti-pumping and interlocking verification
- SCADA interface checks and protection scheme validation
Eco-Efficient Gas Handling
- Pre-filling evacuation and vacuum/moisture verification
- Controlled filling using calibrated gas handling equipment
- Density monitoring system configuration
- Temperature-compensated pressure verification
- Leak detection and environmental documentation
Testing & Commissioning
- Timing tests (Open/Close, O-C, O-0.3s-CO sequences)
- Travel and velocity analysis
- Dynamic contact resistance measurement (DCRM)
- Insulation resistance and contact resistance testing
- Secondary injection and trip/close circuit supervision
- End-to-end protection verification and SCADA validation
Technical Challenges
Eco-Efficient Gas Technology
This wasn't a standard SF₆ installation. Hitachi's CO₂-based gas mixture has a fraction of the global warming potential of SF₆, but it requires different handling procedures and equipment.
Our engineers are trained in both conventional SF₆ and alternative gas technologies. We carried out pre-filling evacuation, moisture verification, controlled filling with calibrated equipment, and comprehensive leak detection — all in accordance with Hitachi technical manuals, IEC 62271 requirements, and environmental compliance standards.
Gas quantities were recorded and full environmental documentation provided to the client.
Constrained Outage Window
The breaker replacement had to happen within a tightly controlled outage. We coordinated closely with the client's control engineers to align switching programmes, complete pre-commissioning activities ahead of the outage, and deliver energisation within planned timescales.
No programme overruns. No network disruption beyond what was planned.
Protection & Control Integration
The new breaker needed to integrate seamlessly with existing protection schemes and SCADA systems. We carried out end-to-end trip circuit verification, remote operation validation, alarm and indication checks, and protection relay functional confirmation before handover.
Safety Performance
Works were delivered under Northern HV's ISO-accredited management systems — ISO 9001 (Quality), ISO 14001 (Environmental), and ISO 45001 (Health & Safety).
We implemented detailed RAMS and task briefings, Permit-to-Work compliance, environmental risk assessments for gas handling, lift plans for heavy components, and QA hold points throughout.
The project was completed with zero accidents and zero environmental incidents.
Project Outcome
The Hitachi LTA 145D1 circuit breaker was successfully installed, gas filled, tested, and energised in accordance with OEM and network operator requirements.
The client achieved enhanced system reliability, reduced environmental impact through eco-gas adoption, compliance with evolving SF₆ reduction strategies, and a fully documented and certified installation.
All milestones delivered within programme.
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