Project Scope

AC ROUTE – COMPLETE CIRCUIT REFURBISHMENT

The 132kV AC Line is a double circuit route that runs from Dolgarrog to Connahs Quay. The Northern Circuit comes through into Holywell, Kinmel Bay, and Colwyn Bay and connects to the AD (Pentir) Line just outside Dolgarrog at Tower AC192A.

The route has a circuit length of 97.29km and comprises 174 PL16 specification towers. Built-in 1952, it is over seventy years old, with only minor modifications in 1963 and 1969, with further modernisation taking place between Towers AC101B, AC121R, and AC124 in 2007. This latter modification was due to the connection of the offshore wind farm near Kinmel Bay, whereby the installation of poplar phase conductors and OPGW Earth wire took place. The recent refurbishment project saw the replacement of the Lynx 175mm² ACSR Phasewire with new Poplar 200mm² AAAC conductor and the Horse 70mm² ACSR earth wire with 36 fibre Horse equivalent OPGW.

AC ROUTE – SUBSTATION, STEELWORK AND CONDUCTOR REFURBISHMENT

Keltbray undertook tower steelwork condition assessments, with a corresponding detailed report, along with the replacement of:

• All identified corroded, damaged, or missing steel members that are NGC category five or above.
• All phase conductors and earth-wire between towers AC06 – AC54 – AC301 – AC302, including down-leads at tower AC302 on to ground anchors at Holywell substation on 1 circuit.
• All phase conductors and earth wire between Holywell Substation AC302 – AC101, including down leads on both circuits on AC101 at St Asaph Substation.
• All phase conductors and earth wire between towers AC124 – AC193, including downleads on AC193 on to the concrete gantries at Dolgarrog Substation.

AC ROUTE – FIBRE OPTICS, FOUNDATIONS AND LOGISTICS MAINTANENCE

Additional works included the Installation of ducted fibre optic system and associated fibre to ODF cabinets at Connahs Quay, St Asaph, Holywell and Dolgarrog substation ends. Restoration and reinstatement of foundations as necessary. Installation and removal of all necessary access/egress roads and work areas.

AC ROUTE – HIGH VOLTAGE EQUIPMENT INSTALLATION

The project saw the installation of various high voltage components including:

• 285.2 kilometres of conductor, including OPGW (Optical Ground Wire) installed on the AC Route during this outage period equated to 285.2 kilometres (177.2 miles). This is the equivalent of travelling in a straight line from the AC Route offices (Hendre Bach, Flintshire) to Keltbray offices (Esher, London)
• 32 Tension Towers (3,528 – 125KN Tension Glass Insulators and Fittings)
• 108 Suspension Towers (7,216 – 80KN Suspension Glass Insulators and Fittings)
• 8 Suspended Tension Towers (Bottom Phase on Suspension Towers re-designed to Tension Towers for archiving electrical ground clearance)

Key Challenges and Solutions

Third Party Assets

• Challenge: Pulling the conductor over third party assets and environmental spaces (Network Rail Infrastructure, A55 Dual Carriageway, Various Roads, Live 11kV and 33kV Distribution Circuits, Sites of Special Scientific Interest (SSSI) and Watercourses, Housing Estates, Golf Courses, and Caravan Park). Keltbray also had to pull the conductor under a 400kV National Grid Transmission Circuit.
• Solution: The planning, development, and approvement of a Safe System of work enabled works to be safe, efficient, and to a high standard. The use of our own Aerial Catenary Support System (ACSS) was critical in providing a temporary protection system while replacing the conductor over the highways, electrified railway lines, power lines, private houses, and waterways. It also assisted in meeting our outage deadlines.

Avoiding Disruption of Distribution

• Challenge: Twenty-seven 11kV and twelve 33kV Distribution outages were required for the AC Line installation. Among these, twenty 11kV outages were due to scaffolding nets, while the remaining seven were to deploy ACSS equipment, causing electrical infringements over live 11kV pole lines
• Solution: Efficient deployment and securing of ACSS on the 132kV line enabled re-energizing of 11kV lines within the same working day, minimizing customer disruption

COVID-19 Response

• Challenge: challenges posed by the COVID-19 pandemic, implementing strategies to protect staff health and safety, revising policies, including Risk Assessment and Method Statement (RAMS), travel, and accommodation, led to significant implications and changed working methods.
• Solution: Swift adaptation to pandemic challenges included revised policies and procedures, ensuring staff safety while maintaining project support away from home, demonstrating resilience and professionalism.

Environmental Challenges

• Challenge: Mitigate risks associated with habitats and SSSI and obtaining several licences from Natural Resource Wales (NRW), including Badger, Doormouse, Great Crested Newt (GCN), and breeding birds.
• Solution: A dedicated Ecological Clerk of Works (ECoW) was on site to supervise the works. The production of constraint maps following relevant stakeholders’ advice was distributed to each member of the working party, inclusive of designated access/egress, specific routes, and a ‘traffic light’ methodology highlighting constraints within the vicinity.

Archaeological Constraints

• Challenge: Archaeological constraints included three registered historic landscapes, which pass close to numerous heritage assets, including the remains of a Neolithic chambered tomb near Dolgarrog, along with bronze age burial mounds.
• Solution: Baseline assessment took into consideration all known archaeological assets, following a successful mitigation strategy involving careful planning, design, and demarcation of sensitive assets to prevent or minimise adverse impacts on the cultural heritage resource in the proposed scheme.

Navigating Terrains and Inclement Weather

• Challenge: Overcoming challenges posed by inclement weather and mountainous rural terrain
• Solution: Ensuring the provision of correct PPE and equipped welfare units to counter adverse weather conditions and rugged terrains, ensuring worker safety and comfort.

Negotiating Access Agreements

• Challenge: Passing through diverse landscapes including woodland, fields, equestrian centres, and residential areas necessitated extensive negotiations with landowners for access agreements, while managing landowner concerns and ensuring safety considerations.
• Solution: Advanced negotiations secured necessary access agreements and addressed landowner concerns, ensuring safety considerations throughout the project.

Infrastructure Access and Safety Measures

• Challenge: Ensuring access to infrastructure works on often challenging terrains, whilst maintaining stringent safety measures.
• Solution: Installation of temporary trackway panels, stone roads, and scaffold structures, particularly in environmentally challenging locations, while ensuring safety for operatives and equipment in Equipotential Zones (EPZ), and managing traffic diversions and closures in private residential areas.