Fluid Filled Cables Risk Assessment

Alan Archer CMIOSH, Asset Lifecycle Engineer

UK Electricity Network

• Owned & operated by 10 Distribution Network Operators & National Grid Transco

• •Over 836,000 km of lines & cables of which:• –344,000 km are overhead lines• –492,000 km are underground cables• •980,000 substation sites• •Have equipment containing oil in quantities ranging

from a few litres to tens of thousands of litres.

Fluid Filled Cables & The Environment

• A full range of environmental aspects and impacts:• Climate Change• –Vehicle emissions• –Energy Losses• Pollution of Land and Waste• –Oil handling & storage• –Leakage (inc 3rd party damage)• –Contaminated soil and materials• • Nuisance• –Excavation and pumping noise• –Street works–road closures• Ecological and Historic Impacts• –Potential to protected species and sites during repairs

Fluid Filled Cables• The majority of the cables were

installed in 1960’s mainly in the fast growing conurbations.

• •These system comprises: – • cable with oil which is contained

within the small spaces between the outer sheath and inner cores;

• •joints; and • •above or below ground pressurised

tanks• •Number and size of the tanks depend

on topography• •Size of cable and operating pressure

depends on voltage• •UK Power Networks: approx.

2,500km of cable -approx. capacity of 27 million litres

Cable Fluid

• Formulations have been changed over the years • The fluids are all compatible with each other and will readily mix.

– -P1/DDB : Mineral fluids or mixtures, non biodegradable, used up until the late 1960s. Use stopped due to poor availability from producers.

– -C14 : Synthetic & a by-product of the Detergent Industry, used from the late 1960’s to the late 1970’s, not biodegradable.

– -C14A or P2 : Revised structure of the C14 fluid used in the 1970’s to the late 1980’s -low biodegradability.

– -P3, C14B or T3788 : Currently used, developed to be more environmentally friendly, biodegradable.

Environmental Risk Assessment

• Challenges:• Availability of digitised cable route/section data• Point source –distance to a sensitive feature straight forward -Most cable

routes are several km’s long• Only small length of cable may be near or within a sensitive feature or there

may be a range of feature along the route• Some sections of route may also have been replaced by solid cables• There may be several cable sections along a route –may have own tanks

and split into different routes • Solution:• Generate an area sensitivity map • Route change colour as it crosses the sensitive area• Assessment can be refined from route to section level as better digitised

data becomes available.

Environmental Risk Assessment

• Requirement of the FFC Operating Code between the Environment Agency and Distribution Network Operators

• Applications of CoP ETR 135 Guidance on the operation and maintenance of FFC

• Assessment underpins the ability to comply with the required leak reporting and response requirements

• Key requirement is to identify routes in Sensitive Areas• Environment Agency defines a Sensitive Area as: • -An area within 50m of a watercourse, • -A Major Aquifer with high or intermediate vulnerability or where

groundwater is close to the surface (10 metres), • -A Source Protection Zone (SPZ) around groundwater abstractions.

Environmental Risk Assessment• Challenges:• • Availability of digitised cable route/section data• • Point source –distance to a sensitive feature straight forward -some cable

routes several km long• • Only small length of cable may be near or within a sensitive feature or

there may be a range of feature along the route• • Some sections of route may also have been replaced by solid cables• • There may be several cable sections along a route –may have own tanks

and split into different routes • Solution:• -Generate an area sensitivity map• -Route change colour as it crosses the sensitive area

– -Assessment can be refined from route to section level as better digitised data becomes available.

Environmental Risk Assessment

• Water:-• Surface Water Courses• Groundwater

• Source Protection Zone 1• Source Protection Zone 2• Source Protection Zone 3

• Source: Environment Agency, Centre for Ecology & Hydrology & British Geological Survey

Environmental Risk Assessment

• Historic:-• Scheduled

Monuments• Parks &

Gardens• Source: English

Heritage

Environmental Risk Assessment

• Nature:-• Protected sites:• RAMSAR• SAC, SPA• SSSI• Local Nature Reserve• National Nature Reserve• AONB• National Park• Source: Living Nature

Environmental Risk RankingVERY 

HIGHHIGH MEDIUM LOW VERY 

LOW

Ground

water 

SPZ1 Within 100m 

of a SPZ1 OR 

Within SPZ 

and over a 

Major 

Aquifer with 

High or 

Medium soil 

leaching 

Within SPZ2 or SPZ3 

OR Over a Major 

Aquifer or with 

100m of a Major 

Aquifer OR Within 

250m of other 

groundwater 

abstractions 

Over a 

Minor 

Aquifer 

Non‐

aquifer 

and not in 

a SPZ 

Surface 

water Less than 

50m Within 50‐

100mWithin 100‐

200m  More than 

250m 

Ecological  Less than 

50m Within 50‐

100mWithin 100‐

200m  More than 

250m 

Overall Environment Risk Map

Purple –Very High Risk

Red –High Risk

Orange –Medium Risk

Yellow –Low & V Low

Risk

Black –indicative cable

routes

Environmental Risk Assessment - Output

Fluid Filled Cable Management

• How is the data being used ?– Circuits are being assessed against range of environment & condition

risk factors for investment prioritisation including:• –Fluid pumping history• –Pumping rate• –Repair history• –Environmental route risk• –Cable condition• –Number and type of connected customers• –Physical access constraints etc.• • Determining the decommissioning strategy• • As well as the reporting and response times for leaks

Environmental Risk Route Framework

Environmental Risk Route Framework

SPN - FFC probability/consequence

0.0010.0020.0030.0040.0050.0060.0070.0080.0090.00

100.00

0.00 10.00 20.00 30.00 40.00 50.00 60.00

Environmental sensitivity

Con

ditio

n/ac

cess

ibili

ty/F

luid

lo

ss

Long Term Strategy

• Fluid filled cables require a life cycle approach to be taken

• •Need to be conscious of environmental, cost and security of supply issues• •Range of options to be considered:• •Nature of the problems or issues related to a cable• •Condition and lifecycle of cable• •Cost & environmental impact of replacement

• •Network rationalisation and upgrading can present additional replacement opportunities

Summary

• FFCs present a range of significant environmental risks to be managed.

• There are a number of competing drivers that have to be balanced when maintaining and investing in the network

• •Investment decisions need to be made in the medium to long term plan.

• •Environmental risks form a key part of the management of cables in balance with other factors.

• •We wish to manage out the environmental risks with fluid filled cables, but this isn’t simply replacement.

• Thank You

Any Questions