Annex 4A.14: SP Manweb 132kV Plant and Circuits Strategy

Annex 4A.14:

SP Manweb 132kV Plant and Circuits Strategy

RIIO-ED2 Business Plan December 2021

RIIO-ED2 Business Plan

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Contents

1. AN INTRODUCTION TO THIS ANNEX ....................................................................................... 3

2. LIST OF FIGURES ....................................................................................................................... 8

3. LIST OF TABLES ........................................................................................................................ 8

4. LIST OF ENGINEERING JUSTIFICATION PAPERS ................................................................. 9

5. SP MANWEB 132KV NETWORK ............................................................................................. 10

132kV Network Geography and Topology ...................................................................................... 10

Deployed 132kV Asset Overview..................................................................................................... 11

5.2.1 Transformers and Reactors ........................................................................................................ 11

5.2.2 Circuit Breakers ........................................................................................................................... 11

5.2.3 Disconnectors and Earth Switches ........................................................................................... 11

5.2.4 Cables ........................................................................................................................................... 11

5.2.5 Overhead Lines ............................................................................................................................ 11

6. ASSET STEWARDSHIP THROUGHOUT RIIO-ED2 ................................................................ 12

Overarching Principles ..................................................................................................................... 12

132kV Plant ........................................................................................................................................ 12

6.2.1 Transformers and Reactors ........................................................................................................ 12

6.2.2 Circuit Breakers ........................................................................................................................... 15

6.2.3 Disconnectors and Earth Switches ........................................................................................... 17

6.2.4 Plant Expenditure Summary ....................................................................................................... 18

132kV Circuits ................................................................................................................................... 19

6.3.1 Cables ........................................................................................................................................... 19

6.3.2 Overhead Lines ............................................................................................................................ 20

6.3.3 Circuits Expenditure Summary .................................................................................................. 23

7. TRACK RECORD AND DELIVERABILITY ............................................................................... 24

Transformers ..................................................................................................................................... 24

Circuit Breakers ................................................................................................................................ 25

7.2.1 132kV CB (Air Insulated Busbars) (ID) (GM) ............................................................................. 25

7.2.2 132kV CB (Air Insulated Busbars) (OD) (GM) ........................................................................... 25

7.2.3 132kV CB (Gas Insulated Busbars) (ID) (GM) ........................................................................... 26

7.2.4 Circuit Breaker Modernisation Programme .............................................................................. 27

Disconnectors and Earth Switches (Switchgear – Other) ............................................................ 27

Cables ................................................................................................................................................ 28

7.4.1 Cable Replacement ...................................................................................................................... 28

7.4.2 Cable System Refurbishment ..................................................................................................... 28

Overhead Lines ................................................................................................................................. 30

7.5.1 Conductor Replacement ............................................................................................................. 30

7.5.2 Steel Tower Refurbishment ........................................................................................................ 31


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7.5.3 Wood Pole Replacement ............................................................................................................. 31

7.5.4 Insulators and Associated Fittings Replacement .................................................................... 32

8. CONCLUSION ........................................................................................................................... 34

9. BIBLIOGRAPHY ........................................................................................................................ 35


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1. An Introduction to This Annex

Scope

The RIIO-ED2 price review period aligns with wider societal changes. During this time, distribution networks will

be a key enabler of Net Zero and will stimulate the national Green Recovery.

Network utilisation is forecast to be stressed beyond the original design capacity of the network. Complexity of

network operation is increasing significantly as we rely on flexibility, Distribution System Operator (DSO)

constraint management and innovation for real-time advanced network management. The criticality of our assets

is rising as customers transition to Net Zero and this results in our network needing to connect greater numbers

of electric vehicles and heat pumps in response to the climate emergency. All of this is set against the unavoidable

and contemporaneous deterioration of our asset base.

Key Highlights The strategy adopted to modernise SP Manweb 132kV network has been science-based, with data analytics and

detailed site surveys undertaken to inform the prioritisation, optioneering and optimisation of intervention

candidates during RIIO-ED2. Lessons learnt and best practices from RIIO-ED1, including the deployment of low-

volume in-line oil regeneration technology to manage transformer insulation materials, and the use of alternative

oil containment bunding techniques and materials have been assimilated and will continue to be deployed

through the detailed design, planning and delivery phases of RIIO-ED2.

Wherever practicable, existing network and infrastructural elements that are in a safe and serviceable condition

will be reused. Refurbishment activities have been prioritised over replacement where the condition of existing

assets can be cost effectively remediated, and where supported by the Cost Benefit Analysis (CBA).

All the proposed interventions have been carefully engineered from the bottom-up, informed by CBRM and with

innovation embedded where appropriate. Network wide grouping of interventions, for a coordinated and efficient

delivery programme, has been undertaken whilst developing our plan for the RIIO-ED2 price review period. Each

132kV network intervention proposed for the RIIO-ED2 price review period has a supporting EJP, in which details

of the project’s full scope are presented. An accompanying CBA presents the financial details and a detailed review of the options that have been considered.

The main considerations associated with the selection of our RIIO-ED2 intervention candidates are summarised

in the sections below:

132/33kV Grid Transformers: The selection strategy is informed by observed and measured conditions held in our corporate data repositories. Statistical and trending analyses of oil test results have also been performed. The list of transformers requiring intervention, and the level of specific activities have been developed through CBRM, detailed site survey information and ongoing stakeholder engagement. Refurbishment candidates in the programme have been selected to return the best investment outcome, which includes the use of innovative low-volume in-line oil regeneration technology. Use of alternative insulating and cooling medium for replacement candidates has also been considered. The use of synthetic ester offers greater fire safety where necessary, and improved biodegradability.


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132kV Switchgear: The selection strategy is informed by observed and measured conditions held in our corporate data repositories. The list of circuit breakers, disconnectors, isolators and earth switches requiring intervention, and the level of specific activities have been developed through CBRM, an extensive review of equipment failure mechanisms, detailed site survey information and ongoing stakeholder engagement. By the end of the RIIO-ED2 price review period, SP Manweb will have removed all 132kV air blast and bulk oil circuit breakers from the network. This follows on from a programme of work that commenced in DPCR5 and through RIIO-ED1. Switching isolators affected by safety and operational restrictions will be removed. All new switchgear to be installed will use non-fluorinated greenhouse gases as the insulation and arc extinction medium.

132kV Cables: The selection strategy is informed by the detailed review of oil top-up and the leakage histories of cable hydraulic and pneumatic cable sections. The level of cable circuits requiring intervention, and the level of specific activities have been developed through CBRM and ongoing stakeholder engagement. Targeted cable replacement will be adopted for circuits with severe and unrepairable leaks. The strategy also includes the targeted refurbishment of cables to mitigate circuits with repairable leaks and any potential cable fitting failures. Innovation including the use of specially trained sniffer dogs and radioisotope tracking will be deployed to aid the detection of leaks.

132kV Overhead Lines: The selection strategy for steel tower and wood pole overhead lines is informed by observed and measured conditions held in our corporate data repositories. The list of conductors, towers, insulators and associated fittings requiring intervention, and the level of specific activities have been developed through CBRM, helicopter flight reports, drone images, foot patrols, conductor destructive testing and ongoing stakeholder engagement. Whole system thinking has also been embedded in this programme, with close engagement with National Grid on specific route refurbishment strategies. The strategy is to continue the targeted replacement of end-of-life Aluminium Conductor Steel Reinforced (ACSR) phase and earth wires with All Aluminium Alloy Conductor (AAAC) phase and earth wires of the required rating. Overhead lines constructed to 275kV or 400kV specifications will be modernised to a 132kV specifications unless a credible need arises for retaining the higher specification constructions.

Figure 1 shows that the total annualised forecast expenditure for our RIIO-ED2 plan is slightly lower than that for

RIIO-ED1. More details on our track record during the RIIO-ED1 price review period and the forecast for the

RIIO-ED2 price review period are covered in Chapter 7.

Figure 1: RIIO-ED1 and RIIO-ED2 annualised costs from CV7a, CV7b, CV8 and CV9 for 132kV plant and

circuits

0

2

4

6

8

10

12

14

16

Transformer Switchgear Cable Overhead Total

An

nu

al C

ost (£

m/Y

ea

r)

RIIO-ED1 (With Forecast) RIIO-ED2 Proposal


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High Level RIIO-ED2 Output Summary

• Refurbishment of three 132/33kV grid transformers

• Replacement of 11 132/33kV grid transformers

• Replacement of 13 auxiliary and earthing transformers

• Replacement of 30 132kV circuit breakers

• New installation of two 132kV circuit breakers

• Replacement of 87 132kV disconnectors and earth switches

• New installation of 49 132kV earth switches

• Replacement of 19.429km of pressurised oil filled 132kV cables

• New installation of 1.374km of non-pressurised solid 132kV cables

• Refurbishment of 1,049 unique steel towers

• Replacement of 83.140km of 132kV overhead steel tower conductor

• Replacement of 9.345km of 132kV overhead wood pole conductor

• Replacement of 1,122 three phase sets of insulators and associated fittings on steel tower lines

• Replacement of 512 three phase sets of insulators and associated fittings on wood pole lines

• Delivery of a monetised Long Term Risk benefit of £113,140,521

• Forecast expenditure of £73.673m from CV7a, CV7b, CV7c, CV8 and CV9 for plant and circuits

• Forecast expenditure of £2.398m from CV10, CV11, CV14, CV22, CV31 and CV32 associated with and in

support of plant and circuits modernisation

Benefits

The asset stewardship plan and investment strategy for the SP Manweb 132kV network during the RIIO-ED2

price review period is primarily driven by the maintenance of, and enhancements to, the resilience and reliability

of our distribution supply network. This is in line with SP Energy Networks’ commitment of improving the reliability of our networks and stewardship of Critical National Infrastructure as set out in our “Enabling the path to Net Zero” document [1]. Specifically, the strategy aims to maintain safety, integrity and performance of the network

whilst ensuring long-term sustainability as outlined in Annex 4A.4: Network Asset Risk Strategy [2] and Annex

4C.3: Environmental Action Plan [3].

Why Asset Management is important in RIIO-ED2

Our customers are

increasingly dependent

on a reliable electricity

supply as they

increasingly use

electricity for transport

and heating.

Our customers depend on

us…

Our plans will manage the

deterioration of our assets

in RIIO-ED2 by targeting

modernisation on our

poorest condition assets,

promoting life extension

where possible, and

prioritising assets with the

greatest consequence of

failure.

We are managing an

ageing and deteriorating

asset base…

The electrification of heat

and transport will

increase network power

flows. Network assets will

be operating at a higher

level of utilisation,

increasing the

deterioration (‘wear and tear’ rate) of assets.

We are pushing the

network harder…


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The key factors that have allowed us to focus our attention of specific network assets are the Asset Health Indices

for targeted equipment, with consideration given to safety, health, criticality, network dynamics and DSO

requirements. The modernisation programme will target assets that are at, or are approaching, the end of their

safe and serviceable life, as informed by CNAIM v2.1 [4] which is implemented through a software called

Condition Based Risk Management (CBRM). The intervention selection process has considered the specific

Network Asset Risk Metric (NARM) asset, as well as non-NARM assets which includes the surrounding and

supporting infrastructure. Detailed site surveys have allowed us to target specific replacement interventions and

establish, where appropriate, a controlled and cost-effective site-wide refurbishment and reuse strategy.

Within this document, details are presented that outline the specific equipment intervention strategies employed

whilst compiling our asset stewardship plan. This document summarises the targeted lead, and associated

secondary, assets that will be addressed during the RIIO-ED2 price review period. References are made to the

specific Engineering Justification Papers (EJPs) that have been produced to provide the necessary narrative and

detail for all the standalone and grouped intervention programmes that we plan to undertake during the RIIO-

ED2 price review period.

Areas of work outside the scope of this SP Manweb 132kV Plant and Circuits Strategy annex associated with the

SP Manweb 132kV network, including specific civil and flood resilience are outlined in Annex 4A.15: Civils and

Flooding Strategy [5], interventions associated with site security and fire protection are outlined in Annex 4A.18:

Legal and Safety (CV14) Strategy [6], and installation of enhanced battery and standby generator systems are

outlined in Annex 4A.17: Electricity System Restoration Strategy [7].

Customer and stakeholder input Throughout the planning for, and preparation of our SP Manweb 132kV Plant and Circuits Strategy investment

plan for the RIIO-ED2 price review period, we have consulted with, and most importantly listened to, the

investment area’s key stakeholders.

The consultation process has been driven by the need to identify and apply the appropriate level of intervention

to our most deserving lead and supporting assets. We have balanced the outputs from the discussions with our

subject matter experts against the realistic cost efficiencies we are obliged to deliver for our bill paying customers.

Our investment plan has flexed as it has been developed, often influenced by emerging opportunities to

undertake a more focused level of specifically targeted intervention. Again, this approach has been supported by

the investment area’s subject matter experts and key stakeholders.

The views of the stakeholders we have engaged with can be explored in more detail in Annex 3.1: Co-creating

our RIIO-ED2 Business Plan with our Stakeholders [8].

Delivering our Plan

The forecast expenditure for the intervention programmes of work to be undertaken during the RIIO-ED2 price

review period has been estimated based on DPCR5 and RIIO-ED1 project out-turn costs, which have been

modified to include potential efficiencies identified during the development of our plan. All forecast expenditure

is expressed on the 2020/21 price base. Summaries of detailed cost development sheets are included in the Cost

Benefit Analysis (CBA) workbooks for the standalone and grouped intervention programmes of work.

As the fine detail of each intervention is developed, during the pre-engineering activities for each project, a further

review of potential additional efficiency in delivery methods will be conducted.


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Where practical, and considered to deliver efficiencies, individual projects have been coordinated to minimise the

impact on network flexibility and availability. Potential to move intervention projects between specific delivery

years has been one of the key drivers to ensure that the programme of works scheduled for the RIIO-ED2 price

review period can be efficiently and effectively delivered.

Signpost for Ofgem’s business plan requirements

Ofgem BP Guidance No Annex Page Number N/A N/A


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2. List of Figures Figure 1: RIIO-ED1 and RIIO-ED2 annualised costs from CV7a, CV7b, CV8 and CV9 for 132kV plant and circuits .............. 4

Figure 2: SP Manweb 132kV operational regions ................................................................................................................. 10

Figure 3: SP Manweb 132/33kV transformers forecast asset Health Index (HI) movement .................................................. 14

Figure 4: SP Manweb 132kV circuit breakers forecast asset Health Index (HI) movement ................................................... 16

Figure 5: SP Manweb 132kV underground cable forecast asset Health Index (HI) movement ............................................. 20

Figure 6: SP Manweb 132kV overhead lines asset Health Index (HI) movement ................................................................. 22

Figure 7: Track record of CV7a - 132kV Transformer (GM) .................................................................................................. 24

Figure 8: Track record of CV9 - 132kV Transformer (GM) .................................................................................................... 24

Figure 9: Track record of CV7a - 132kV CB (Air Insulated Busbars) (ID) (GM) ..................................................................... 25

Figure 10: Track record of CV7a - 132kV CB (Air Insulated Busbars) (OD) (GM) ................................................................. 26

Figure 11: Track record of CV7a - 132kV CB (Gas Insulated Busbars) (ID) (GM) ................................................................ 26

Figure 12: Track record of CV7b - 132kV Switchgear - Other ............................................................................................... 27

Figure 13: Track record of CV7a - 132kV UG Cable (Non Pressurised)................................................................................ 28

Figure 14: Track record of CV8 - 132kV UG Cable (Non Pressurised).................................................................................. 29

Figure 15: Track record of CV8 - 132kV UG Cable (Oil)........................................................................................................ 29

Figure 16: Track record of CV7a - 132kV OHL (Tower Line) Conductor ............................................................................... 30

Figure 17: Track record of CV7b - 132kV OHL (Pole Line) Conductor .................................................................................. 31

Figure 18: Track record of CV9 - 132kV Tower ..................................................................................................................... 31

Figure 19: Track record of CV7b - 132kV Pole ...................................................................................................................... 32

Figure 20: Track record of CV7a - 132kV Fittings ................................................................................................................. 32

Figure 21: Track record of CV8 - 132kV Pole (Fittings) ......................................................................................................... 33

3. List of Tables Table 1: Engineering Justification Papers (EJPs) supporting the SP Manweb 132kV modernisation plan.............................. 9

Table 2: 132/33kV transformers to be addressed during the RIIO-ED2 price review period ................................................. 13

Table 3: Auxiliary and earthing transformers be replaced during the RIIO-ED2 price review period ..................................... 14

Table 4: 132kV circuit breakers to be replaced during the RIIO-ED2 price review period ..................................................... 16

Table 5: Switching Isolator – Switchgear and Equipment RVS 300 to be replaced during RIIO-ED2 ................................... 18

Table 6: 132kV plant investment expenditure summary ........................................................................................................ 18

Table 7: Cable circuits – Details of circuits to be replaced during the RIIO-ED2 price review period .................................... 19

Table 8: Overhead line routes – Details of routes to be refurbished during the RIIO-ED2 price review period ..................... 22

Table 9: 132kV circuits investment expenditure summary..................................................................................................... 23


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4. List of Engineering Justification Papers

Table 1: Engineering Justification Papers (EJPs) supporting the SP Manweb 132kV modernisation plan

Documents Title Last Issue

ED2-NLR(A)-SPM-001-SWG-EJP Trawsfynydd 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-002-SWG-EJP Wylfa 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-003-SWG-EJP Frodsham 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-004-SWG-EJP ICI Wade 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-005-SWG-EJP Halewood 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-006-SWG-EJP RVS 300 SF6 132kV Switching Isolator Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-007-SWG-EJP Lister Drive 132kV Switchgear Modernisation - Circuit Transfers Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-009-SWG-EJP Cellarhead 132kV Switchgear Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-001-SUB-EJP Gateacre 132kV Switchgear and Grid Transformer Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-001-TX-EJP Amlwch 132kV Grid Transformer T1 Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-003-TX-EJP Colwyn Bay 132kV Grid Transformers T1 & T2 Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-004-TX-EJP Lostock 132kV Grid Transformer T2 Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-005-TX-EJP Woodside 132kV Grid Transformer T2 Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-006-TX-EJP ICI Castner Kellner 132kV Grid Transformer T2B Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-007-TX-EJP Hawarden 132kV Grid Transformers Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-008-TX-EJP Rock Ferry 132kV Grid Transformers Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-009-TX-EJP Kirkby 132kV Grid Transformer T3 Refurbishment Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-010-TX-EJP Ince Local 132kV Grid Transformers T1 and T2 Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-011-TX-EJP 132kV Auxiliary and Earthing Transformer Replacement Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-001-OHL-EJP AG Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-004-OHL-EJP DB Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-005-OHL-EJP CU Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-006-OHL-EJP YS Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-007-OHL-EJP BH Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-008-OHL-EJP 132kV Overhead Line Tower and Fitting Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-009-OHL-EJP 4ZC Route 132kV Overhead Line Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-001-UG-EJP Bootle-Kirkby 132kV Cable Modernisation Issue 2.0 – Nov 2021

ED2-NLR(A)-SPM-003-UG-EJP 123kV Cable Refurbishment Issue 2.0 – Nov 2021


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5. SP Manweb 132kV Network

132kV Network Geography and Topology

The SP Manweb 132kV network provides supplies to 1,523,255 industrial, commercial and domestic load and

generation customers, with a network maximum demand of 2,674MW. The SP Manweb 132kV network secures

its connectivity to the wider transmission network directly at 17 National Grid (NG) owned and operated Grid

Supply Point (GSP) substations. There are also 132kV connections to adjacent distribution networks, including

Electricity North West in the north, Western Power Distribution (West Midlands) in the east and Western Power

Distribution (South Wales) in the south.

The SP Manweb 132kV network has 111 substations, either solely operating at 132kV or at 132/33kV. These

substations are connected at 132kV by a mix of interconnector and radial feeder circuits, comprising 1,339.1km

of overhead lines and 265.2km of underground cables.

The SP Manweb 132kV network is divided into three, centrally controlled and coordinated, geographic operation

regions.

• Merseyside – extending north from the River Mersey through the greater Liverpool conurbation to the

northerly tip of Southport, and eastwards towards the easterly edge of St Helens

• Cheshire – south of the River Mersey, encompassing the Wirral Peninsular and Chester to the south and

extending eastwards towards Radway Green, to the east of Crewe

• Wales – south of Chester down to Aberystwyth, to the east encompassing Oswestry and Wrexham, and

bounded on the west by the Irish Sea

Figure 2: SP Manweb 132kV operational regions


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Deployed 132kV Asset Overview

5.2.1 Transformers and Reactors

SP Manweb owns and operates 153 132/33kV grid transformers, along with their associated auxiliary and

earthing equipment, and four 132kV series reactors. Most of this equipment is cooled and insulated by mineral

oil; however, an increasing number of newly installed transformers utilise a synthetic ester cooling and insulating

medium.

The use of synthetic ester affords an enhanced fire protection performance over that of mineral oil filled

equipment, consequently allowing for a reduction in separately constructed fire risk mitigation measures. This

strategy, where enhanced fire protection is required, is in line with the guidance set out in SUB-01-012 [9].

5.2.2 Circuit Breakers

SP Manweb owns and operates 234 132kV circuit breakers. This asset base consists of 179 sulphur hexafluoride

(SF6), 37 bulk oil, 15 air blast and three vacuum circuit breakers.

In support of SP Energy Networks’ commitment to adopt alternatives to greenhouse gases as outlined in “Enabling the path to Net Zero” document [1], SP Manweb has made a strategic move away from the installation

of new equipment utilising SF6 as an arc extinction and insulating medium during the latter years of RIIO-ED1 on

our 132kV network [10]. Wherever practically possible, SP Manweb will continue to follow this strategy through

the RIIO-ED2 price review period and beyond. The commitment to avoid the further deployment of fluorinated

greenhouse gases has brought with it several operational and maintenance challenges. We must expand our

gas handling equipment stock to match the differing insulating and arc extinction gasses offered by equipment

suppliers.

5.2.3 Disconnectors and Earth Switches

SP Manweb owns and operates 1,297 132kV plant and circuit disconnectors and fixed earth switches.

We will continue to review the performance and operational adequacy of this equipment and only intervene when

deemed necessary to support the ongoing safe, resilient and flexible operation of the 132kV network. We will

target the deployment of remotely controllable plant items at specific network substations to support the flexible

operation of, and DSO requirements for, the 132kV network.

5.2.4 Cables

SP Manweb owns and operates 265.2km of 132kV cables. This asset base consists of 153.9km of oil filled paper

insulated, 7.4km of gas compression paper insulated and 103.9km of cross-linked polyethylene insulated cables.

The oil filled paper insulated cable base contains around 680,000 litres of potentially polluting mineral oil.

5.2.5 Overhead Lines

SP Manweb owns and operates 1,339.1km of 132kV overhead lines. This asset base consists of 1,099.4km of

steel tower lines and 239.7km of wood pole lines. It should be noted that a small number of the steel tower lines,

though operated at 132kV, were originally constructed by the Central Electricity Generating Board (CEGB) to a

275kV or 400kV standard.


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6. Asset Stewardship Throughout RIIO-ED2

Overarching Principles

The overarching principle adopted for the management of a safe, resilient, reliable and flexible 132kV network

combines an ongoing policy based inspection and maintenance regime, with a targeted intervention programme

to address specific substation plant and circuit assets that are at, or are approaching, the end of their safe and

serviceable life.

The strategies underpinning the overarching principle are set out in a suite of SP Energy Networks standards,

policies and guidance documents. These standards, policies and guidance documents are informed by many

drivers. However, the foundation for all strategic decisions are driven by the safe and cost effective operation of

a resilient, reliable and flexible 132kV network.

Throughout the asset intervention targeting process, the strategy for selection has followed the principles detailed

in Annex 4A.4: Network Asset Risk Strategy [2] for assets captured under the Network Asset Risk Metric (NARM)

framework. This consists of five key components: inspection, prioritisation, optioneering, portfolio planning and

optimisation, with innovation embedded throughout. Non-NARM assets such as insulators and fittings on wood

poles lines have also been assessed using the NARM style methodology. During the detailed intervention option

selection process, a CBA, in line with the guidance issued by Ofgem on the 8 October 2021 [11], was undertaken

to ensure the selection of the most cost-effective intervention.

132kV Plant

6.2.1 Transformers and Reactors

The investment strategy for 132/33kV transformers, series reactors and auxiliary and earthing transformers is

driven by safety, health, criticality, network flexibility and DSO requirements. The refurbishment and replacement

programme has targeted assets that are at, or are approaching, the end of their safe and serviceable life, as

informed by TRAN-02-002 [12] and CNAIM v2.1 [4]. The focus of the selection process has been on transformers,

series reactors and auxiliary and earthing transformers with poor quality insulating and cooling oil, that are

showing signs of degradation in insulating paper integrity, that have an inoperative or restrictive tap change

mechanism or are in a poor observed physical condition.

Refurbishment

Where practical, and considered to be a cost-effective intervention, selective refurbishment of transformers and

series reactors will be given preference over replacement. These refurbishment activities will include:

• The deployment of innovative in-line insulating and cooling mineral oil regeneration equipment, designed to

manage the moisture content, acids and intermediate oil and insulating paper ageing products

• The replacement of poor condition 132kV porcelain bushings

Replacement

132/33kV transformer replacement activities will specifically target the lead asset. Any closely associated

ancillary or salient primary plant and equipment that is considered to have a practical degree of safe and

serviceable life will not be automatically replaced. The retained ancillary or salient primary plant and equipment

will undergo targeted, cost-effective refurbishment and maintenance before being returned to service. Auxiliary

and earthing transformer replacements will be undertaken where the integrity of the insulating paper has

deteriorated to a point that cannot be effectively managed by the deployment of oil regeneration equipment.

Whilst undertaking the replacement of the transformer, a selective and targeted replacement of protection and

control equipment will be undertaken. Only elements of the protection and control suite that are either obsolete


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or obsolescent, as detailed in ASSET-01-025 [13], will be replaced. To facilitate network flexibility, DSO

requirements and minimise network losses, modifications will be made to the voltage control equipment. This

work will include the provision of direct tap changer position indication and control facilities to the SP Manweb

24-hour network control centre.

When adjudged to be practical and cost-effective to do so, as much of the civil and structural infrastructure

associated with the transformer to be replaced will be retained and, where necessary, remodelled for reuse.

Whilst replacing the transformer, all oil containment bunds, including those associated with the auxiliary and

earthing transformer, will have their integrity fully assessed. Where the need for remediation activities are

identified, the deployment of either a high-density polyethylene (HDPE) bund lining system or a stand-alone

HDPE bund will be prioritised over a traditional reinforced concrete installation. Any oil and water separator

equipment that does not meet the current and relevant environmental agency standards will be upgraded.

Whilst replacing the transformer, a set of 132kV and 33kV surge arrestors will be installed in line with SUB-01-

020 [14].

All replacement transformers will be compliant with the current European Union Commission Regulation (EU)

2019/1783 [15] - Eco-Tier 2 design, which supports a considerable reduction in iron and copper losses, offering

a reduction in losses in the order of 70% and 40% respectively.

The detailed discussion supporting the selection criteria for refurbishment and replacement candidates can be

found in the associated RIIO-ED2 EJPs.

To summarise, SP Manweb will be undertaking the following refurbishment and replacement work on 132/33kV

transformers as well as auxiliary and earthing transformers during the RIIO-ED2 price review period:

• Targeted refurbishment of three 132/33kV transformers

• Replacement of 11 132/33kV transformers, of which:

• Three will contain a synthetic ester (SE) insulating and cooling medium

• Eight will contain a mineral oil (MO) insulating and cooling medium

• Replacement of 13 auxiliary and earthing transformers, of which

• Nine are associated with 132/33kV transformer replacement activities

• Four will be replaced as part of a stand-alone auxiliary and earthing transformer replacement programme

Table 2 provides a high-level view of the intervention plan associated with 132/33kV transformers.

Table 2: 132/33kV transformers to be addressed during the RIIO-ED2 price review period

Substation Region Plant Activity EJP Reference RIIO-ED2 Year

Gateacre Grid Merseyside T1 Replacement – MO ED2-NLR(A)-SPM-001-SUB-EJP 2025/26

Kirkby GSP Merseyside T3 Oil Regeneration ED2-NLR(A)-SPM-009-TX-EJP 2023/24

ICI Castner Kellner Grid Cheshire T2B Replacement – MO ED2-NLR(A)-SPM-006-TX-EJP 2026/27

Ince Local Cheshire T1 Replacement – MO

ED2-NLR(A)-SPM-010-TX-EJP 2026/27

T2 Replacement – MO 2026/27

Lostock Grid Cheshire T2 Replacement – MO ED2-NLR(A)-SPM-004-TX-EJP 2025/26

Rock Ferry Grid Cheshire T1 Replacement – SE

ED2-NLR(A)-SPM-008-TX-EJP 2024/25 T2 Bushing Replacement

Woodside Grid Cheshire T2 Replacement – SE ED2-NLR(A)-SPM-005-TX-EJP 2027/28

Amlwch Grid Wales T1 Replacement – SE ED2-NLR(A)-SPM-001-TX-EJP 2025/26

Colwyn Bay Grid Wales T1 Replacement – MO

ED2-NLR(A)-SPM-003-TX-EJP 2027/28 T2 Replacement – MO

Hawarden Grid Wales T1 Replacement – MO

ED2-NLR(A)-SPM-007-TX-EJP 2024/25 T2 Oil Regeneration


14

Figure 3 shows the forecast asset Health Index (HI) profiles for 132/33 kV transformers at the end of RIIO-ED1

with interventions, at the end of RIIO-ED2 if no interventions were undertaken, and with our planned RIIO-ED2

NARM interventions. This programme for 132/33kV transformers will yield a monetised Long Term Risk benefit

of £30,967,977.

Figure 3: SP Manweb 132/33kV transformers forecast asset Health Index (HI) movement

Table 3 provides a high-level view of the intervention plan associated with auxiliary and earthing transformers.

Table 3: Auxiliary and earthing transformers be replaced during the RIIO-ED2 price review period

Substation Region Plant Activity EJP Reference RIIO-ED2 Year

Gateacre Grid Merseyside ET1 Associated with lead asset ED2-NLR(A)-SPM-001-SUB-EJP 2025/26

Speke Grid Merseyside ET1A Stand-alone replacement ED2-NLR(A)-SPM-011-TX-EJP 2023/24

ICI Castner Kellner Grid Cheshire ET2B Associated with lead asset ED2-NLR(A)-SPM-006-TX-EJP 2026/27

Knutsford Grid Cheshire ET1

Stand-alone replacement ED2-NLR(A)-SPM-011-TX-EJP 2023/24 ET2

Lostock Grid Cheshire ET2 Associated with lead asset ED2-NLR(A)-SPM-004-TX-EJP 2025/26

Rock Ferry Grid Cheshire ET1 Associated with lead asset ED2-NLR(A)-SPM-008-TX-EJP 2024/25

Saltney Grid Cheshire ET1 Stand-alone replacement ED2-NLR(A)-SPM-011-TX-EJP 2023/24

Woodside Grid Cheshire ET2 Associated with lead asset ED2-NLR(A)-SPM-005-TX-EJP 2027/28

Amlwch Grid Wales ET1 Associated with lead asset ED2-NLR(A)-SPM-001-TX-EJP 2025/26

Colwyn Bay Grid Wales ET1 Associated with lead asset

ED2-NLR(A)-SPM-003-TX-EJP 2027/28 ET2 Associated with lead asset

Hawarden Grid Wales ET1 Associated with lead asset ED2-NLR(A)-SPM-007-TX-EJP 2024/25

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

Forecast End of RIIO-ED1With Interventions

Forecast End of RIIO-ED2With No Interventions

Forecast End of RIIO-ED2With NARM Interventions

HI 1 HI 2 HI 3 HI 4 HI 5


15

6.2.2 Circuit Breakers

The investment strategy for 132kV switchgear is driven by safety, health, criticality and network flexibility. The

replacement programme will target assets that are at, or are approaching, the end of their safe and serviceable

life as informed by CNAIM v2.1 [4]. The focus of the selection process has been on circuit breakers with either

known safety or operational restrictions.

There is well documented evidence of considerable risk to health, safety and consequential secondary damage

associated with the destructive failure of high pneumatic pressure 132kV air blast (AB) circuit breakers. The

operational and safety critical observations associated with these circuit breakers are detailed in SWG-05-096

Issue 2 [16]. The replacement of this type of circuit breaker has been prioritised for the RIIO-ED2 price review

period.

A considerable number of 132kV bulk oil (BO) dead tank circuit breakers are at, or are approaching, the end of

their safe and serviceable life. There is documented evidence of the destructive circuit breaker bushing failure

resulting from moisture ingress, operating mechanism failures due to excessive wear and the strict confined

space working techniques required when undertaking routine maintenance. The operational and safety critical

observations for this type of circuit breaker are detailed in SWG-05-092 Issue 2 [17] and SWG-05-097 [18]. The

replacement of this type of circuit breaker has been prioritised for the RIIO-ED2 price review period.

In all instances, the circuit breaker replacement will be undertaken using a circuit breaker employing a non SF6

insulation and arc extinction medium [10].

Circuit breaker replacement activities will specifically target the lead asset. Any closely associated ancillary or

salient primary plant and equipment that is considered to have a reasonable degree of safe and serviceable life

will not be automatically changed. The retained ancillary or salient primary plant and equipment will undergo

practical, cost-effective refurbishment and maintenance before being returned to service.

Whilst undertaking the replacement of the circuit breaker, a selective and targeted replacement of protection and

control equipment will be undertaken. Only elements of the protection and control suite that are either obsolete

or obsolescent, as detailed in ASSET-01-025 [13], will be replaced.

When adjudged to be practical and cost-effective to do so, as much of the civil and structural infrastructure

associated with the circuit breaker will be retained and, where necessary, remodelled for reuse.

The detailed discussion supporting the selection criteria for replacement candidates can be found in the

associated RIIO-ED2 EJPs.

To summarise, SP Manweb will be undertaking the following 132kV circuit breaker replacement work during the

RIIO-ED2 price review period:

• Replace 30 circuit breakers in total, of which:

• 10 by the deployment of Air Insulated Busbar (AIB) Outdoor (OD) Ground Mounted (GM) circuit breakers

• 12 by the deployment of Gas Insulated Busbar (GIB) Indoor (ID) Ground Mounted (GM) circuit breakers

• Eight by the deployment of Air Insulated Busbar (AIB) Indoor (ID) Ground Mounted (GM) circuit breakers

• New additions of two Air Insulated Busbar (AIB) Outdoor (OD) Ground Mounted (GM) circuit breakers

• Avoided deployment of 1,639kg of fluorinated greenhouse gas

• Removal of 220,000 litres of mineral oil

• Removal of 72kg of fluorinated greenhouse gas

Table 4 summarises the interventions planned to address the network risk associated with our current fleet of

132kV air blast and bulk oil circuit breakers.


16

Table 4: 132kV circuit breakers to be replaced during the RIIO-ED2 price review period

Substation Region Plant Current Plant Type Future Plant Type EJP Reference RIIO-ED2 Year

Gateacre Grid Merseyside 120

BO AIB OD GM AIB OD GM ED2-NLR(A)-SPM-001-SUB-EJP 2025/26 –

2026/27 220

Halewood Grid Merseyside 120

BO AIB OD GM AIB OD GM ED2-NLR(A)-SPM-005-SWG-EJP 2027/28 320

Lister Drive GSP Merseyside

120

BO AIB OD GM

GIB ID GM ED2-NLR(A)-SPM-007-SWG-EJP

2023/24 –

2024/25

130

230

105

110

205

305

405

505

605

705 SF6 AIB OD GM

805

Cellarhead GSP Cheshire 305 BO AIB OD GM AIB OD GM ED2-NLR(A)-SPM-009-SWG-EJP 2025/26

Frodsham GSP Cheshire

120

AB AIB ID GM AIB ID GM ED2-NLR(A)-SPM-003-SWG-EJP 2024/25

130

230

205

705

1005

ICI Wade Grid Cheshire 120 BO AIB OD GM AIB OD GM ED2-NLR(A)-SPM-004-SWG-EJP 2026/27

Trawsfynydd GSP Wales

120

BO AIB OD GM AIB OD GM ED2-NLR(A)-SPM-001-SWG-EJP 2026/27 130

110

205

Wylfa Grid Wales 205

AB AIB ID GM AIB ID GM ED2-NLR(A)-SPM-002-SWG-EJP 2025/26 305

Figure 4 shows the forecast asset Health Index (HI) profiles for 132kV circuit breakers at the end of RIIO-ED1


NARM interventions. This programme for 132kV circuit breakers will yield a monetised Long Term Risk benefit

of £22,238,436.

Figure 4: SP Manweb 132kV circuit breakers forecast asset Health Index (HI) movement

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%






17

6.2.3 Disconnectors and Earth Switches

Wherever practically possible, disconnectors and fixed earth switches that are closely associated with the lead

assets being changed, will undergo a refurbishment and maintenance before being retained and reused. There

are several instances where this type of intervention is not practical, necessitating replacement, these include:

• Where plant items have operating mechanisms that are either inoperative or unreliable and beyond

refurbishment

• Where the plant item’s primary contacts are worn beyond a point where they can practically, and cost effectively be refurbished or replaced

• Where poor condition plant items must be removed to replace a severely deteriorated existing support

structure

• Where poor condition plant items must be removed to replace a severely deteriorated existing foundation

plinth

• When a fundamental change to a substation’s architecture is being made, for example when an air insulated

substation is being replaced by either a hybrid or fully gas insulated switchgear arrangement

When a disconnector or fixed earth switch is to be replaced, the opportunity will be taken to introduce the current

standard of local and remote-control functionality where safety and network flexibility benefits can be

demonstrated. This will support the ongoing safe, flexible operation and DSO requirements of the 132kV network.

To summarise, SP Manweb will undertake the following 132kV disconnector and earth switch replacement work

during the RIIO-ED2 price review period:

• Replace 91 disconnectors, isolators and earth switches in total, with:

• 136 dead operation air break isolators and earth switches (replacing 87 isolators and earth switches)

• Two live operation Disconnecting Circuit Breaker (DCB) arrangements (replacing four isolators and earth

switches)

• Avoided deployment of 16.7kg of fluorinated greenhouse gases

The increase in disconnectors and earth switches from 91 to 136 is a result of the deployment of additional 49

fixed earthing devices to satisfy the best practice detailed in the SP Energy Networks Safety Rules [19] and the

replacement of four isolators and earth switches (by two DCBs).

The detailed discussion supporting the selection criteria for the replacement candidates can be found in the

associated transformer and switchgear RIIO-ED2 EJPs.

Within the SP Manweb 132kV network, there are 12 SF6 switching isolators in service. These isolators have been

operating under an Electricity Association Suspension of Operational Practice (SOP–287), OPSAF-16-287 [20]

for 20 years. The SOP, which outlines the additional annual maintenance and protracted operational

requirements to allow continued safe and reliable live operation of this type of isolator, was issued following a

disruptive failure of an RVS 300 Switching Isolator at ICI Wade Grid substation in 2001. SP Manweb experienced

a further disruptive failure of this type of switching isolator at Huyton Grid substation in 2015. To remove the

ongoing risk to safety, network reliability and flexibility associated with the continued use of these switching

isolators, they will be replaced during the RIIO-ED2 price review period.

A detailed review of the 132kV network operational requirements has identified two specific locations where the

live operation facilities, afforded by the switching isolators, must be retained. At these locations, the isolators will

be replaced by the installation of a Disconnecting Circuit Breaker (DCB) arrangement. At the remaining 10

locations, where non-live operation is considered acceptable, the switching isolators will be replaced by an air

break, not live operation, disconnectors and, where necessary, associated earth switch arrangement.


18

Table 5 summarises the interventions planned to address the long-standing restrictions associated with the

Switchgear and Equipment – RVS 300 Switching Isolators.

Table 5: Switching Isolator – Switchgear and Equipment RVS 300 to be replaced during RIIO-ED2

Substation Region Plant Replacement EJP Reference RIIO-ED2 Year

Bootle Grid Merseyside 215A Dead Operation Air Break

ED2-NLR(A)-SPM-006-SWG-EJP

2025/26

Paradise Street Grid Merseyside 115 Live Operation DCB

2024/25 125 Dead Operation Air Break

Prescot Grid Merseyside 115B Dead Operation Air Break 2025/26

Dallam Grid Cheshire 115 Live Operation DCB 2027/28

Percival Lane Grid Cheshire 100 Dead Operation Air Break

2027/28 115 Dead Operation Air Break

Brymbo Grid Wales 115 Dead Operation Air Break 2025/26

Lister Drive GSP Merseyside 215 Dead Operation Air Break ED2-NLR(A)-SPM-007-SWG-EJP 2024/25

Gateacre Grid Merseyside 500 Dead Operation Air Break ED2-NLR(A)-SPM-001-SUB-EJP 2026/27

ICI Wade Grid Cheshire 115 Dead Operation Air Break

ED2-NLR(A)-SPM-004-SWG-EJP 2026/27 215 Dead Operation Air Break

6.2.4 Plant Expenditure Summary

The annual forecast financial expenditure associated with the SP Manweb 132kV network plant elements within

the Business Plan Data Tables during the RIIO-ED2 price review period are summarised in Table 6.

Table 6: 132kV plant investment expenditure summary

Cost Allocation Category Total

(£m)

Incidence (£m)

2023/24 2024/25 2025/26 2026/27 2027/28

CV7a – Asset Replacement NARM – 132kV Transformer (GM) 16.584 1.695 3.948 4.105 4.918 1.917

CV7a – Asset Replacement NARM – 132kV CB AIB OD GM 1.977 - 0.281 0.539 0.824 0.332

CV7a – Asset Replacement NARM – 132kV CB AIB ID GM 1.317 0.279 0.732 0.306 - -

CV7a – Asset Replacement NARM – 132kV CB GIB ID GM 0.604 0.302 0.302 - - -

CV7b – Asset Replacement No NARM – 132kV Switchgear - Other 2.270 - 0.405 0.845 0.685 0.336

CV7c – Asset Replacement Civils Driven – 132kV 2.319 0.272 0.520 0.455 0.477 0.594

CV8 – Refurbishment No NARM – 132kV Transformer (GM) 0.195 0.195 - - - -

CV8 – Refurbishment No NARM – Protection Systems 2.236 0.203 0.634 0.346 0.766 0.288

CV9 – Refurbishment NARM – 132kV Transformer (GM) 0.331 0.137 0.194 - - -

CV10 – Civil Work Condition Driven 0.085 - - 0.015 0.045 0.025

CV11 – Operation IT & T – RTUs 0.250 0.105 0.105 0.020 0.020 -

CV14 – Legal and Safety – Fire Protection 0.040 - 0.020 - - 0.020

CV22 – Environmental Reporting – Oil Pollution Mitigation 0.382 0.076 0.115 0.057 0.019 0.115

CV31 – Repair and Maintenance – Substation Civils 0.011 - 0.006 - - 0.005

Plant Modernisation Programme 28.601 3.264 7.262 6.688 7.754 3.633


19

132kV Circuits

6.3.1 Cables

The investment strategy for 132kV underground cables is driven by safety, health, criticality, environmental

impact, network security and flexibility. The modernisation programme will target assets that are at, or are

approaching the end of their serviceable life, as informed by CNAIM v2.1 [4]. Enhanced cable management will

be applied with integration of observed and measured conditions, focusing on refurbishing cables in a serviceable

condition and only replacing cables when refurbishment is not a practical and cost-effective option. The presence

of crystalline lead associated with the cable sheaths will be captured as an additional observed condition, in line

with CNAIM v2.1 [4].

For pressurised fluid filled cables, measured condition reports in the form of annual oil and gas top-up volumes

have been used to inform the decision to select specific hydraulic and pneumatic sections of cable for attention

in the RIIO-ED2 price review period.

Replacement – condition driven

Based on the assessment criteria outlined above, the two 132kV cables running between Bootle Grid and Kirkby

GSP have been selected for replacement in the RIIO-ED2 price review period. A detailed discussion supporting

the selection criteria and the replacement approach to be adopted can be found in the associated RIIO-ED2 EJP.

A circuit length of 19.429km of oil filled 132kV cable will be replaced in the RIIO-ED2 price review period.

The replacement of the pressurised oil filled cable circuits between Bootle Grid and Kirkby GSP, with non-

pressurised solid cable, will eliminate oil leakage from our worst performing cables. By purging the insulating

mineral oil from the decommissioned oil filled cable systems, 36,000 litres of potentially polluting material will also

be removed from the environment. This is in line with Annex 4C.3 Environmental Action Plan [3], as well as our

commitment of making a positive impact on the natural environment as detailed in “Enabling the path to Net Zero” document [1].

Circuit transfers – Lister Drive GSP

There will be cable installation work undertaken that is not specifically driven by asset condition replacement.

This activity is associated with the transfer of circuits from the existing air insulated substation to the new gas

insulated substation at Lister Drive GSP. A detailed discussion presenting the requirement to undertake this work

can be found in the associated RIIO-ED2 EJP.

Table 7 summarises the interventions planned to address the environmentally polluting nature and remove the

ongoing refurbishment cost associated with the continued use of badly leaking oil filled cables, and the new

installation associated with switchgear modernisation.

Table 7: Cable circuits – Details of circuits to be replaced during the RIIO-ED2 price review period

Circuit Name Region Length (km) Replacement Cable Type EJP Reference RIIO-ED2 Year

Bootle-Fazakerley-

Gillmoss-Kirkby Merseyside 9.941

1200mm2 Aluminium Conductor

Cross Linked Polymer Insulated ED2-NLR(A)-SPM-001-UG-EJP

2024/25 –

2025/26 Bootle-Gillmoss-

Kirkby Merseyside 9.488


Cross Linked Polymer Insulated

Lister Drive GSP –

Circuit Transfers Merseyside 1.374


Cross Linked Polymer Insulated ED2-NLR(A)-SPM-007-SWG-EJP

2023/24 –

2024/25

Figure 5 shows the forecast asset Health Index (HI) profiles for 132kV underground cable at the end of RIIO-ED1


NARM interventions. This programme for 132kV underground cable will yield a monetised Long Term Risk benefit

of £29,763,388.


20

Figure 5: SP Manweb 132kV underground cable forecast asset Health Index (HI) movement

Refurbishment (No NARM)

Based on the assessment criteria outlined at the start of this section, and historical remediation interventions, an

allowance has been allocated to the ongoing refurbishment of hydraulic sections of oil filled pressurised cable

systems. An allowance has also been allocated to address anticipated cable fitting failures for non pressurised

cable systems.

A detailed discussion presenting the requirement to make this provision can be found in the RIIO-ED2 EJP –

123kV Cable Refurbishment: ED2-NLR(A)-SPM-003-UG-EJP.

6.3.2 Overhead Lines

The investment strategy for 132kV steel tower and wood pole overhead lines is driven by safety, health, criticality,

network security and flexibility. The modernisation programme will target assets that are at, or are approaching,

the end of their safe and serviceable life, as informed by CNAIM v2.1 [4]. The overreaching inspection regime

employed for the 132kV overhead line route elements is detailed in TRANS-03-005 [21].

Conductors

A suite of observations has been collated to inform the decision to select a specific route for attention. These

observations include conductor sample destructive testing, helicopter and drone flight reports, foot patrol safety

reports as well as known and documented lifespan forecasting. This is supported and reflected in the asset life

assessment approach detailed in ASSET-01-030 [22] and the findings detailed in CIGRE 176 [23] working group

report.

Insulators and fittings

The key drivers for the assessment of suitability for continued safe and secure use are the observed conditions

gathered from helicopter and drone flight reports, foot patrol safety reports and specific localised failure

information.

Tower fabric

A combination of helicopter and drone flight reports, foot patrol safety reports and tower climbing surveys have

been employed to target the candidate towers for full or partial refurbishment. Targeted tower interventions will

include a mix of the replacement of badly corroded steel members, proprietary treatment of early signs of

corrosion, replacement of corroded step blots, upgrades to anti climb protection devices and the preparation and

application of protective coatings. The assessment regime for steel towers is based on the categorisation

methodology as summarised in OHL-03-103 [24], and further detailed in TS 3.04.31 [25].

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

45.0%

50.0%






21

Wood Poles The assessment of wood poles is detailed in OHL-17-001 [26]. The condition of the wood pole structures is

closely monitored on an annual cycle. Any remediation activities identified are undertaken on a rolling needs

case basis.

Foundations The assessment of tower and wood pole foundation integrity is informed by airborne Light Detecting and Ranging

(LiDAR) tower verticality checks, helicopter and drone flight reports as well as foot patrol safety reports. Targeted

tower foundation work will include, where necessary, the replacement of full foundations, repairs to failing

foundations, remediation and repair of foundation caps and muffs.

Route refurbishment including conductor modernisation For overhead line routes where the overhead line conductors are considered to be at, or are fast approaching,

the end of their safe and reliable service life, a full route refurbishment programme will be undertaken. These

works will include phase and earth wire replacement, targeted insulator and associated fitting replacements,

targeted tower and wood pole refurbishments and selective foundation interventions.

Resulting from the data gathered as outlined above on the SP Manweb 132kV overhead line routes, five routes

have been identified as requiring conductor replacement during the RIIO-ED2 price review period. Each of these

complete route modernisation programmes are fully detailed in the route specific RIIO-ED2 EJPs.

We have not fully evaluated optimal phasing1 within the programme. There are two specific routes, the YS Route

and the 4ZC Route, where this will be evaluated during the planning and detailed design phase of the projects,

and corrective actions taken if found to beneficial.

Route refurbishment excluding conductor modernisation

For overhead line routes where the conductors have not been identified as being at, or are fast approaching, the

end of their safe and serviceable life, a standalone overhead line fittings and tower intervention programme will

be undertaken. This programme of work is detailed in a specific, programme level, RIIO-ED2 EJP.

Summary of overhead lines work plan

To summarise, SP Manweb will be undertaking the following 132kV overhead line modernisation work during the

RIIO-ED2 price review period:

• Full refurbishment, including phase and earth wire conductor replacement, of three full steel tower and two

mixed steel tower and wood pole overhead line routes

• Targeted refurbishment, excluding phase and earth wire replacement, of 19 steel tower routes and four mixed

wood pole and steel tower routes

The full and targeted refurbishment programmes will deliver the following outputs:

• Replacement of 92.485km of overhead line conductor

• 83.140km steel tower overhead line conductor

• 9.345km of wood pole overhead line conductor

• Replacement of 1,634 three phase sets of insulators and associated fittings

• 1,122 three phase sets of steel tower line insulators and associated fittings

• 512 three phase sets of wood pole line insulators and associated fittings

• Undertake 1,447 tower refurbishment and repair interventions

Table 8 summarises the interventions planned to address the network risk associated with our 132kV overhead

line network.

1 Optimum Phasing: The arrangement of conductors on double circuit steel tower routes to minimise the radiating magnetic field.


22

Table 8: Overhead line routes – Details of routes to be refurbished during the RIIO-ED2 price review period

Route Region

Conductor

Replacement

(km)

Fittings

Replacement

Tower

Refurbishment

and Repair *

EJP Reference RIIO-ED2

Year

AG Route Cheshire 3.013 17 42 ED2-NLR(A)-SPM-001-OHL-EJP 2024/25

BH Route Cheshire - 268 465 ED2-NLR(A)-SPM-007-OHL-EJP 2023/24

YS Route Cheshire 59.854 249 77 ED2-NLR(A)-SPM-006-OHL-EJP 2025/26

CU Route Wales 5.483 38 36 ED2-NLR(A)-SPM-005-OHL-EJP 2027/28

DB Route Wales 8.905 78 3 ED2-NLR(A)-SPM-004-OHL-EJP 2026/27

4ZC Route Wales 15.230 68 - ED2-NLR(A)-SPM-009-OHL-EJP 2026/27

Standalone Towers

and Fittings **

Merseyside

Cheshire

Wales

- 916 824 ED2-NLR(A)-SPM-008-OHL-EJP 2023/24 –

2027/28

* Tower repair work includes repair to tower foundations and replacement of anti-climbing devices

** Replacement of 20 wood poles (non-NARM assets) is also included

Figure 6 shows the forecast asset Health Index (HI) profiles for 132kV overhead line conductors, towers and

fittings at the end of RIIO-ED1 with interventions, at the end of RIIO-ED2 if no interventions were undertaken,

and with our planned RIIO-ED2 NARM interventions. This programme for 132kV overhead lines will yield a

monetised Long Term Risk benefit of £30,170,719.

Figure 6: SP Manweb 132kV overhead lines asset Health Index (HI) movement

0.0%

5.0%

10.0%

15.0%

20.0%

25.0%

30.0%

35.0%

40.0%

45.0%

50.0%






23

6.3.3 Circuits Expenditure Summary

Table 9 summarises the annual forecast financial expenditure associated with the SP Manweb 132kV network

circuit elements in the Business Plan Data Tables during the RIIO-ED2 price review period.

Table 9: 132kV circuits investment expenditure summary

Asset

Type Cost Allocation Category

Total

(£m)

Incidence (£m)

2023/24 2024/25 2025/26 2026/27 2027/28

Cable

CV7a – Asset Replacement NARM – 132kV UG Cables (Non Pressurised) 18.642 1.430 9.321 7.891 - -

CV7b – Asset Replacement No NARM – Pilot Wire Underground 1.089 - 0.544 0.544 - -

CV8 – Refurbishment No NARM – 132kV UG Cables (Non Pressurised) 1.093 0.219 0.219 0.219 0.219 0.219

CV8 – Refurbishment No NARM – 132kV UG Cables (Pressurised Oil) 1.093 0.219 0.219 0.219 0.219 0.219

Cable Modernisation Programme 21.917 1.867 10.303 8.873 0.437 0.437

OHL

CV7a – Asset Replacement NARM – 132kV Tower Line Conductor 8.640 - 0.422 5.984 1.883 0.351

CV7a – Asset Replacement NARM – 132kV Fittings 6.473 1.898 0.397 2.323 1.323 0.531

CV7b – Asset Replacement No NARM – Pilot Wire Overhead 0.025 - 0.024 0.000 - -

CV7b – Asset Replacement No NARM – 132kV Pole Line Conductor 0.885 - - - 0.546 0.339

CV7b – Asset Replacement No NARM – 132kV Poles 0.115 0.023 0.023 0.023 0.023 0.023

CV8 – Refurbishment No NARM – 132kV Towers 0.059 0.002 0.052 0.002 0.002 0.002

CV8 – Refurbishment No NARM – 132kV Poles 1.634 0.264 0.264 0.264 0.579 0.264

CV9 – Refurbishment NARM – 132kV Towers – Paintwork 5.560 1.645 0.895 1.242 0.796 0.983

CV9 – Refurbishment NARM – 132kV Towers – Steelwork 0.533 0.299 0.124 0.037 0.037 0.037

CV31 – Repair and Maintenance – 132kV Towers 1.424 0.565 0.077 0.532 0.125 0.124

CV32 – Dismantlement 0.206 0.206 - - - -

OHL Modernisation Programme 25.553 4.900 2.279 10.408 5.314 2.653

Total Circuits Modernisation Programme 47.470 6.767 12.581 19.281 5.751 3.090


24

7. Track Record and Deliverability

This section provides an overview of the RIIO-ED1 track record for the deployed 132kV assets outlined in Section

5. This view is based on the six-year actual costs and output addition volumes reported in our RIIO-ED1

Regulatory Reporting Pack (RRP). A forecast of the remaining planned delivery for RIIO-ED1 has been included

for completeness. Forecast costs and output addition volumes for the RIIO-ED2 price review period are presented

on the same graphs for comparison purposes.

Transformers

Figure 7 shows the track record for CV7a Asset Replacement NARM for 132kV Transformer (GM). The average

output volume per year during RIIO-ED1 is 2.75 and will be 2.2 per year during RIIO-ED2. The average cost per

year, in 20/21 prices, is £2.360m during RIIO-ED1 and is planned to be £3.317m during RIIO-ED2.

Figure 7: Track record of CV7a - 132kV Transformer (GM)

The planned 132kV Transformer (GM) replacement activity during RIIO-ED2 is comparable to the interventions

undertaken during RIIO-ED1. The increase in average cost per year from RIIO-ED1 to RIIO-ED2 is a reflection

of the real world price increase of transformers throughout RIIO-ED1, a forecast increase in costs of raw materials

going into RIIO-ED2, and the deployment of a non-standard 100MVA unit and three synthetic ester filled units.

Figure 8 shows the track record for CV9 Refurbishment NARM for 132kV Transformer (GM). The average output

volume per year during RIIO-ED1 is 0.875 and will be 0.6 per year in RIIO-ED2. The average cost per year, in

20/21 prices, is £0.121m during RIIO-ED1 and is planned to be £0.066m in RIIO-ED2.

Figure 8: Track record of CV9 - 132kV Transformer (GM)

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There is a reduction in the planned refurbishment activities for 132kV Transformer (GM) during RIIO-ED2 when

compared to that undertaken in RIO-ED1. Refurbishment candidates have been carefully selected based on a

technical evaluation of probable lifetime extension through targeted practical and cost-effective interventions.

The RIIO-ED2 programme will focus on oil regeneration and bushing replacements. The selection of these

interventions is based on guidance set out in CNAIM v2.1 [4] and TRAN-02-002 [12]. The candidate selection

process has also been informed by detailed CBAs.

The forecast, high level, in-year delivery programme will be allowed to flex to accommodate unforeseen network

access constraints, or new load and generation connection construction work. As a result of longer design,

manufacture and delivery lead times associated with asset replacement activities, the first year of the RIIO-ED2

price review period will focus on refurbishments interventions.

Circuit Breakers

The circuit breaker modernisation programme covers the following three regulatory equipment types:

• 132kV CB (Air Insulated Busbars) (ID) (GM)

• 132kV CB (Air Insulated Busbars) (OD) (GM)

• 132kV CB (Gas Insulated Busbars) (ID) (GM)

7.2.1 132kV CB (Air Insulated Busbars) (ID) (GM)

Figure 9 shows the track record for CV7a Asset Replacement NARM for CB (Air Insulated Busbars) (ID) (GM).

The average output volume per year during RIIO-ED1 is 1.75 and will be 1.6 per year during RIIO-ED2. The

average cost per year, in 20/21 prices, is £0.249m during RIIO-ED1 and is planned to be £0.263m during RIIO-

ED2.

Figure 9: Track record of CV7a - 132kV CB (Air Insulated Busbars) (ID) (GM)

The planned replacement activity for 132kV CB (Air Insulated Busbars) (ID) (GM) during RIIO-ED2 is comparable

with that during RIIO-ED1. The programme will continue to target the removal of this category of air blast circuit

breaker to address the safety and operational issues detailed in SWG-05-096 Issue 2 [16].

7.2.2 132kV CB (Air Insulated Busbars) (OD) (GM)

Figure 10 shows the track record of CV7a Asset Replacement NARM for 132kV CB (Air Insulated Busbars) (OD)

(GM). The average output volume per year during RIIO-ED1 is 2.125 and will be 2.4 per year during RIIO-ED2.

The average cost per year, in 20/21 prices, is £0.295m during RIIO-ED1 and is planned to be £0.395m during

RIIO-ED2.

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Figure 10: Track record of CV7a - 132kV CB (Air Insulated Busbars) (OD) (GM)

The planned replacement activity for 132kV CB (Air Insulated Busbars) (OD) (GM) during RIIO-ED2 is

comparable to that during RIIO-ED1. The programme will continue to target the remaining bulk oil circuit breakers

with safety and operational issues detailed in SWG-05-092 Issue 2 [17] and SWG-05-097 [18].

7.2.3 132kV CB (Gas Insulated Busbars) (ID) (GM)

Figure 11 shows the track record for CV7a Asset Replacement NARM for 132kV CB (Gas Insulated Busbars)

(ID) (GM). The average output volume per year during RIIO-ED1 is 4.375 and will be 2.4 per year during RIIO-

ED2. The average cost per year, in 20/21 prices, is £4.470m during RIIO-ED1 and is planned to be £0.121m

during RIIO-ED2.

Figure 11: Track record of CV7a - 132kV CB (Gas Insulated Busbars) (ID) (GM)

There is a decrease in the addition volume for 132kV CB (Gas Insulated Busbars) (ID) (GM) during RIIO-ED2

when compared with that during RIIO-ED1, with a noticeable decrease in cost forecast for RIIO-ED2 when

compared to that expended during RIIO-ED1. This is due to the completion of three major gas insulated

substation projects at Kirkby GSP, Birkenhead GSP and Crewe Grid during the RIIO-ED1 price review period.

The Lister Drive GSP project will span both the RIIO-ED1 and RIIO-ED2 price review periods. Plant procurement,

the majority of the substation construction and preparation for circuit transfers will have been completed, and

funded in RIIO-ED1, with the circuit transfer and energisation work planned for the first two years of RIIO-ED2.

The Lister Drive GSP project will remove 12 132kV CB (Air Insulated Busbars) (OD) (GM) circuit breakers, with

the addition of 12 132kV CB (Gas Insulated Busbars) (ID) (GM) circuit breakers.

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27

7.2.4 Circuit Breaker Modernisation Programme

The planned activities associated with circuit breakers of the three regulatory types have been coordinated in

terms of their delivery during the RIIO-ED2 price review period. It is planned to complete the gas insulated

substation work at Lister Drive GSP in the first two years of RIIO-ED2, following extensive construction and

preparatory work during RIIO-ED1. For this reason the output delivery profile for 132kV CB (Gas Insulated

Busbars) (ID) (GM) in Figure 11 is front loaded. Work has been planned for 132kV CB (Air Insulated Busbars)

(ID) (GM) in the subsequent years as shown in Figure 9, and finally with the focus shifting to 132kV CB (Air

Insulated Busbars) (OD) (GM) as shown in Figure 10.


access constraints, or new load and generation connection construction work.

Disconnectors and Earth Switches (Switchgear – Other)

The disconnector and earth switch modernisation programme is closely associated with the circuit breaker

modernisation and transformer replacement programmes.

Figure 12 shows the track record for CV7b Asset Replacement No NARM for 132kV Switchgear - Other. This

regulatory asset type covers both disconnectors and fixed earth switches. The average output volume per year

during RIIO-ED1 is 37.75 and will be 27.2 per year during RIIO-ED2. The average cost per year, in 20/21 prices,

is £0.193m during RIIO-ED1 and is planned to be £0.454m during RIIO-ED2.

There is a decrease in the addition volume for 132kV Switchgear - Other during RIIO-ED2 when compared with

that during RIIO-ED1, with an increase in cost forecast for RIIO-ED2 when compared to that expended during

RIIO-ED1. The increase in cost is due to how the costs for disconnectors and earth switches were absorbed by

the overall programme associated with the completion of three major gas insulated substation projects at Kirkby

GSP, Birkenhead GSP and Crewe Grid during the RIIO-ED1 price review period.

The cost in RIIO-ED2 is attributed to the following activities:

• Targeted replacement of RVS 300 SF6 switching isolators

• Addition of earth switches associated with the circuit breaker replacement programme

• Addition of earth switches as a result of the deployment of fixed earthing devices to satisfy the best practice

outlined within the SP Energy Networks Safety Rules [19]

Figure 12: Track record of CV7b - 132kV Switchgear - Other


access constraints, or new load and generation connection construction work.

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28

Cables

The cables modernisation and refurbishment programme covers the following two regulatory equipment types:

• 132kV UG Cable (Non Pressurised)

• 132kV UG Cable (Oil)

7.4.1 Cable Replacement

Figure 13 shows the track record for CV7a Asset Replacement NARM for 132kV UG Cable (Non Pressurised).

The average output volume per year during RIIO-ED1 is 1.185km and will be 4.161km per year during RIIO-ED2.


RIIO-ED2.

Figure 13: Track record of CV7a - 132kV UG Cable (Non Pressurised)

The increase in the work planned for RIIO-ED2, when compared to RIIO-ED1 is a result of the replacement of

19.429km of 132kV UG Cable (Oil) between Bootle Grid and Kirkby GSP. This cable will be replaced by 132kV

UG Cable (Non Pressurised). A number of successful attempts to detect and repair several serious oil leaks have

been undertaken on these circuits during the previous and current price review periods. However, due to the

deterioration of the cable’s lead sheath, new leaks continue to develop.

There is the potential of encountering route deviations associated with the replacement of the two Bootle Grid to

Kirkby GSP cable circuits. The planned route closely follows that of the existing cable tracks; much of which is

either adjacent to or directly beneath major arterial roads. Early engagement, towards the end of RIIO-ED1, with

the three respective local authorities will help to identify any specific measures required to minimise the risk to

delivering the project within the targeted time frame. We have shared the replacement plans for these cables

with other utilities to try and identify any clashes, or opportunities to combine planned activities with a view to

minimising disruption to the general public.

An additional 1.374km of 132kV UG Cable (Non Pressurised) will be installed to facilitate the circuit transfers

from the existing Lister Drive GSP air insulated substation to the newly constructed gas insulated substation.


access constraints, new load and generation connection construction work or third party and local authority

access constraints.

7.4.2 Cable System Refurbishment

The work forecast for the RIIO-ED2 price review period is apportioned evenly between 132kV UG Cable (Non

Pressurised) and 132kV UG Cable (Oil), this reflects the RIIO-ED1 Year 1 to Year 5 out-turn for both CV8 and

CV9 activities.

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Figure 14 shows the track record for CV8 Refurbishment No NARM for 132kV UG Cable (Non Pressurised).

These interventions are primarily associated with cable joint and termination failures. The average number of

interventions per year during RIIO-ED1 is 4.598 and is forecast to be 2.200 per year during RIIO-ED2 (note that

the unit is not km). The average cost per year, in 20/21 prices, is £0.374m during RIIO-ED1 and is planned to be

£0.219m during RIIO-ED2.

Figure 14: Track record of CV8 - 132kV UG Cable (Non Pressurised)

There is a reduction in the forecast work for RIIO-ED2 as we have addressed a specific quality issue in RIIO-

ED1. We have included a scaled-back forecast to make provision for similar unforeseen equipment failures during

RIIO-ED2.

Figure 15 shows the track record for CV8 Refurbishment No NARM for 132kV UG Cable (Oil). These interventions

are primarily associated with cable system oil leak repairs. The average number of interventions per year during

RIIO-ED1 is 0.25 and will be 2.2 per year during RIIO-ED2. The average cost per year, in 20/21 prices, is £0.011m

during RIIO-ED1 and is planned to be £0.219m during RIIO-ED2.

Figure 15: Track record of CV8 - 132kV UG Cable (Oil)

As detailed in Appendix A2 of DNO CNAIM v2.0 Methodology Changes Explained [27], a change in the scope of

activities that constitutes a CV8 Refurbishment No NARM and a CV9 Refurbishment NARM for 132kV UG Cable

(Oil) intervention has been introduced. Work such as replacement, or remaking, of cable system fittings and re-

engineering of pressurising systems are to be categorised as a CV8 activity rather than a CV9 activity. For this

reason, no activities are planned for CV9 during the RIIO-ED2 price review period.

The forecast, high level, in-year delivery programme will potentially change as we advance through the RIIO-

ED2 price review period. The main refurbishment activities, such as replacement or remaking of non pressurised

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cable fittings, and pressurised cable oil system interventions are generally reactionary arising from in-service

asset failures.

Overhead Lines

The overhead lines modernisation programme covers the following five regulatory equipment types:

• 132kV OHL (Tower Line) Conductor

• 132kV OHL (Pole Line) Conductor

• 132kV Tower

• 132kV Pole – for wood pole line fittings

• 132kV Fittings – for steel tower line fittings

7.5.1 Conductor Replacement

Overhead line conductor replacement planed for the RIIO-ED2 price review period is spread across steel tower (CV7a), wood pole (CV7b) and mixed tower and pole routes.

Figure 16 shows the track record for CV7a Asset Replacement NARM for 132kV OHL (Tower Line) Conductor.

The average output volume per year during RIIO-ED1 is 33.752km and will be 16.628km per year during RIIO-

ED2. The average cost per year, in 20/21 prices, is £2.967m during RIIO-ED1 and is planned to be £1.728m

during RIIO-ED2.

Figure 16: Track record of CV7a - 132kV OHL (Tower Line) Conductor

The reduction in the work planned for RIIO-ED2, when compared to RIIO-ED1 is a result of the focus for overhead

line interventions shifting to address conductor replacement on wood pole routes, and the introduction of a

standalone programme of work to address poor condition steel towers, insulator sets and associated line fittings

on overhead line routes where the conductors are not being replaced.

Figure 17 shows the track record for CV7b Asset Replacement No NARM for 132kV OHL (Pole Line) Conductor.

The average output volume per year during RIIO-ED1 is 0.000km and will be 1.869km per year during RIIO-ED2.


RIIO-ED2.

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31

Figure 17: Track record of CV7b - 132kV OHL (Pole Line) Conductor

The increase in the work planned for RIIO-ED2, when compared to RIIO-ED1 is a result of the targeted conductor

condition assessment undertaken bringing two mixed wood pole and steel tower routes into our priority list.

7.5.2 Steel Tower Refurbishment

Figure 18 shows the track record for CV9 Refurbishment NARM for 132kV Tower. The average number of

interventions per year during RIIO-ED1 is 71.5 and will be 205.4 per year during RIIO-ED2. The average cost

per year, in 20/21 prices, is £1.649m during RIIO-ED1 and is planned to be £1.219m during RIIO-ED2.

Figure 18: Track record of CV9 - 132kV Tower

The increase in the number of steel towers that we plan to refurbish during RIIO-ED2, when compared to RIIO-

ED1, is a result of a shift in the focus away from an overhead line programme that has been predominantly

conductor replacement driven during DPCR5 and RIIO-ED1. The overarching overhead line refurbishment

programme for the RIIO-ED2 price review period will not only target the replacement of our poorest health

condition conductors; the programme reflects the importance we have placed on addressing the painting and

remediation of poor condition towers. The intervention candidate selection has been informed by a combination

of helicopter and drone flight reports, foot patrol safety reports and tower climbing surveys. This approach has

been strongly supported by our business stakeholders.

7.5.3 Wood Pole Replacement

Figure 19 shows the track record for CV7b Asset Replacement No NARM for 132kV Pole. The average number

of interventions per year during RIIO-ED1 is 2.125 and will be 4 per year during RIIO-ED2. The average cost per

year, in 20/21 prices, is £0.026 m during RIIO-ED1 and is planned to be £0.023m during RIIO-ED2.

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Figure 19: Track record of CV7b - 132kV Pole

As detailed in Section 6.3.2, condition of wood poles is closely monitored on an annual cycle with the need for

interventions identified on a rolling needs case basis. The activity planned for RIIO-ED2 is thus estimated based

on the total volume undertaken to date in RIIO-ED1.

7.5.4 Insulators and Associated Fittings Replacement

Figure 20 shows the track record for CV7a Asset Replacement NARM for 132kV Fittings, whereas Figure 21

shows the track record for CV8 Refurbishment No NARM 132kV Pole (Fittings) as defined in Ofgem RIGs Annex

A [28].

The average output volume for CV7a Asset Replacement NARM for 132kV Fittings per year during RIIO-ED1 is

132.5 and will be 224.4 per year during RIIO-ED2. The average cost for CV7a Asset Replacement NARM for

132kV Fittings per year, in 20/21 prices, is £1.064m during RIIO-ED1 and is planned to be £1.295m during RIIO-

ED2.

The average output volume for CV8 132kV Pole (wood pole line fittings) per year during RIIO-ED1 is 13.625 and

will be 102.4 per year during RIIO-ED2. The average cost for CV8 132kV Pole (Fittings) per year, in 20/21 prices,

is £0.037m during RIIO-ED1 and is planned to be £0.327m during RIIO-ED2.

Figure 20: Track record of CV7a - 132kV Fittings

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Figure 21: Track record of CV8 - 132kV Pole (Fittings)

The increase in the number of 132kV insulator sets and associated fittings that we plan to replace during RIIO-

ED2, when compared to RIIO-ED1, is a result of a shift in the focus away from an overhead line programme that

has been predominantly conductor replacement driven during DPCR5 and RIIO-ED1. The overarching overhead

line refurbishment programme for RIIO-ED2 will not only target the replacement of our poorest health condition

conductors, but also reflects the importance we have placed on addressing the replacement of end-of-life or near

end-of-life insulators and associated fittings. The intervention candidate selection has been informed by a

combination of helicopter and drone flight reports, foot patrol safety reports and tower climbing surveys. This

approach has been strongly supported by our business stakeholders.


access constraints, or new load and generation connection construction work. The overhead line modernisation

programme has been coordinated across the network, not only with regard the specific overhead line activities,

but also to accommodate broader network interventions on closely associated assets.

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8. Conclusion

The asset modernisation programme that we have planned will minimise the risk associated with the SP Manweb

132kV network through the RIIO-ED2 price review period. This is driven by cost-effective improvements to, and

ongoing management of safety, health, security of supply, criticality and network dynamics.

The overarching principles we have followed during the development of SP Manweb 132kV Plant and Circuits

modernisation programme are detailed in Annex 4A.4: Network Asset Risk Strategy [2]. This is underpinned by

an industry best practice approach to the ongoing management of asset risk and criticality, founded upon and

supported by CNAIM v2.1 [4].

We have adopted a targeted approach to our modernisation plan, only selecting assets for modernisation that

are adjudged to be in a critical need of attention. We have reviewed the closely associated and supporting

infrastructural elements, and chosen to only replace them when absolutely necessary, favouring a selective

reuse, refurbishment and remodelling intervention. This approach has allowed us to promote the best value for

money response to our obligation for maintaining a safe, reliable, resilient and secure arterial supply network.

Whenever possible, we have taken the opportunity to follow a path making use of alternative and innovative

interventions and the reuse of existing healthy infrastructural elements, to deliver the lowest carbon footprint

solution we can. This approach will minimise the deployment of fluorinated greenhouse gasses, reduce the

amount of reinforced concrete installed, reduce the potential for mineral oil pollution, whilst endeavour to extend

the safe, serviceable and environmentally friendly use of lead and supporting assets.

The forecasted expenditure to deliver our planned asset modernisation programme has been derived from known

material costs and a review of our DPCR5 and RIIO-ED1 programme out-turn costs. Throughout the delivery of

our RIIO-ED2 programme, we will seek to secure the best value for money approach available, whilst

continuously striving to identify further potential cost saving opportunities.


35

9. Bibliography

[1] SP Energy Networks, Enabling the path to Net Zero, 2021.

[2] SP Energy Networks, Annex 4A.4: Network Asset Risk Strategy, 2021.

[3] SP Energy Networks, Annex 4C.3: Environmental Action Plan, 2021.

[4] Energy Networks Association (ENA), DNO Common Network Asset Indices Methodology (CNAIM) v2.1, 2021.

[5] SP Energy Networks, Annex 4A.15: Civils and Flooding Strategy, 2021.

[6] SP Energy Networks, Annex 4A.18: Legal and Safety (CV14) Strategy, 2021.

[7] SP Energy Networks, Annex 4A.17: Electricity System Restoration Strategy, 2021.

[8] SP Energy Networks, Annex 3.1: Co-creating our RIIO-ED2 Business Plan with our Stakeholders, 2021.

[9] SP Energy Networks, SUB-01-012: Substation Fire Protection Policy, 2018.

[10] SP Energy Networks, Policy for the Procurement of SF6 Free Equipment in SP Energy Networks, SP Energy Networks, Draft Issue 1, 2021.

[11] Ofgem, RIIO-ED2 Cost Benefit Analysis (CBA) Guidance, 2021.

[12] SP Energy Networks, TRAN-02-002: Assessment of the Operational Adequacy of Transformers & Reactors (33kV & Above), 2020.

[13] SP Energy Networks, ASSET-01-025: Protection Equipment Asset Health Assessment Methodology, 2015.

[14] SP Energy Networks, SUB-01-020: Surge arrester application policy for SPEN 400kV/275kV/132kV substation equipment over-voltage protection, 2015.

[15] European Union Commission Regulation (EU) 2019/1783: Ecodesign Requirements for Small. Medium and Large Power Transformers, Official Journal of the European Union, 2019.

[16] SP Energy Networks, SWG-05-096: Operational Issues with AEI GA6 132kV Air Blast Circuit Breakers, 2019.

[17] SP Energy Networks, SWG-05-092: Operational Issues with AEI OW409, OW410 & Ferguson Pailin 132kV Bulk Oil Circuit Breakers, 2019.

[18] SP Energy Networks, SWG-05-097: Operational Issues with GEC OFA11/OFA12 132kV Bulk Oil Circuit Breakers, 2013.

[19] SP Energy Networks, Safety Rules: Scottish Power Limited Safety Rules (Electrical and Mechanical), 4 ed., 2017.

[20] SP Energy Networks, OPSAF-16-287: Suspension of Operational Practice – Switchgear and Equipment 132kV Switching Isolator Type RVS 300 (SOP 287), 2001.

[21] SP Energy Networks, TRANS-03-005: Technical Specification for Annual Transmission Overhead Line Inspections, 2020.

[22] SP Energy Networks, ASSET-01-030: in SPT Overhead Lines Technical Asset Life & CBRM Condition Rating Methodology, 2019.

[23] CIGRE, Brochure 176: Ageing of the System - Impact on Planning, CIGRE Working Group 37.27, 2000.

[24] SP Energy Networks, OHL-03-103: Specification for Painting and Steelwork Inspections of Steel Lattice Towers, 2020.

[25] National Grid, TS 3.04.31: Specification for Steelwork Inspection and Condition Assessment of Overhead Line Towers, 2013.

[26] SP Energy Networks, OHL-17-001: Inspection and Testing of Wood Poles, 2018.

[27] Energy Networks Association (ENA), DNO CNAIM v2.0 Methodology Changes Explained, 2020.

[28] Ofgem, RIIO-ED1 Regulatory Instructions and Guidance: Annex A – Glossary, 6 ed., 2020.

[29] Scottish Government, “Climate change,” [Online]. Available: https://www.gov.scot/policies/climate-change/. [Accessed 5 April 2019].

[30] Scottish Government, “Climate Change Plan. The Third Report on Proposals and Polices 2018-2032,” 2018.