Memorandum submitted by Central Networks
(FL 159)
EXECUTIVE SUMMARY
1. Central Networks welcomes the opportunity
to contribute to the work of the Select Committee. We believe
it is important to identify lessons from the summer floods in
order to improve our preparedness and resilience.
2. The flooding in July 2007 was unprecedented.
The majority of the electricity distribution network was unaffected
but we experienced localised disruption to electricity supplies
in Gloucestershire. Notwithstanding this, our emergency planning
and preparedness enabled us to respond effectively and efficiently
to limit the impact on our customers and the community.
3. Working in extremely difficult conditions,
Central Networks engineers made operational decisions to disconnect
customers from our network to ensure safety and to avoid damage
to our equipment in a controlled way. This avoided a prolonged
loss of supply for customers.
4. Since the flooding in July, we have installed
Hesco Bastion flood protection to Castle Meads sub-station and
are actively assessing the risk and mitigation measures for other
key strategic sites. In addition, we are supporting a review of
flood resilience being led by the Energy Networks Association
at the request of the Department for Business, Enterprise &
Regulatory Reform (BERR).
5. Central Networks is a Civil Contingencies
Act Category 2 responder and we supported the Gold and Silver
Commands established in Gloucester during the event.
BACKGROUND
6. Central Networks distributes electricity
to 5 million domestic, commercial and industrial customers in
Central England. It is the second largest electricity distribution
company in the UK.
7. We take power at 132kV from 29 grid supply
points on the National Grid transmission system and distribute
it through an extensive network of voltage transformers, switches
and overhead and underground cables to individual customer premises.
8. Our network covers an area of 30,000
square kilometres from the Welsh borders in the West to the Lincolnshire
coast in the East, Bristol in the South to the Peak District in
the North.
9. The length of our overhead and underground
cable network is around 130,000 km and we operate nearly 100,000
substations to reduce the voltage to the levels required by customers.
Much of the network is inter-connected that allows us to switch
supplies in the event of faults on our network and thereby provide
a high degree of resilience.
10. In order to distribute electricity,
we rely on secure supplies from the National Grid transmission
system. Whilst our network is inter-connected, the extent to which
we can redirect supplies is limited. Whilst we can reduce the
impact by re-configuring supplies, a major failure on the transmission
network will inevitably cause disruption to customer supplies.
11. Security of supply is the cornerstone
of our strategy and we continually strive to improve the performance
of our network by efficient operation, careful maintenance and
targeted investment.
12. We employ 2,500 staff based at 8 sites
across our region. Our head office is at Pegasus Business Park
adjacent to East Midlands Airport on the outskirts of Nottingham.
In addition, we have offices at Tipton, Gloucester, Worcester,
Stoke, Hinckley, Sleaford and Moorgreen.
13. In addition to our own staff, we employ
approximately 3,000 contractors primarily to support delivery
of our investment programme.
14. Central Networks is owned by E.ON, the
world's largest investor owned power and gas company.
THE NATURE
OF OUR
BUSINESS
15. Our operations cover the following counties:
Gloucestershire, Worcestershire, Herefordshire, West Midlands,
Staffordshire, Warwickshire, Oxfordshire, Buckinghamshire, Northamptonshire,
Leicestershire, Derbyshire, Nottinghamshire and Lincolnshire.
16. These regions include a mixture of rural,
semi-rural and urban environments. In the rural areas, the network
is predominantly overhead whereas in towns and cities, the network
is largely underground.
17. The network was rapidly expanded in
the 1950's and many of our assets are over 50 years old. We have
a major investment programme to progressively replace the worst
performing assets. We experience faults either due to age and
condition or due to damage by third parties. Typically we experience
around 40000 faults per year on our network that are managed as
part of our day to day operations.
18. Our overhead network is particularly
susceptible to damage by extreme weather, in particular, high
winds, snow/ice and lightning. Flooding presents an additional
risk to the resilience of the network that needs to be considered
alongside other weather related risks. Major weather events can
cause significant disruption and require us to implement our emergency
planning procedures to ensure efficient and effective return to
business as usual.
PROVISIONS FOR
EMERGENCY PLANNING
19. Central Networks maintains an emergency
plan that has been developed in line with the Civil Contingencies
Act. It is routinely tested to ensure all parties understand their
roles in the event of an emergency.
20. In addition, we typically experience
one or two major incidents every year for which we implement our
emergency plan. As a consequence, our preparedness is high, enabling
effective and efficient response in the event of a major incident.
21. Central Networks is a Category 2 responder
and as such may be required to participate in wider emergency
events involving other agencies such as the flooding at Gloucester.
22. Our extensive geographic footprint necessitates
engagement with 14 Local Resilience Forums and 6 Regions.
FLOODING RESILIENCE
23. The major weather-related risk to our
network is wind, snow/ice and lightning. Flooding has not hitherto
materialised as a major risk and notwithstanding the events in
July is not as significant as wind, snow/ice or lightning.
24. Our equipment needs to be installed
close to the demand. Therefore, if development takes place in
areas at risk of flooding, we will need to extend our network
in those areas, exposing our equipment to similar risk.
25. It would not be practicable to protect
every sub-station at potential risk of flooding and indeed there
is no need to if the premises supplied by them are not themselves
protected. Therefore, our primary focus is on protecting the major
strategic sites supplying high number of customers (typically
more than 10,000).
26. We are ensuring that flood protection
is considered in the design of new facilities. An example of this
is the new substation at Port Ham in Gloucester that has been
constructed on stilts.
OUR RESPONSE
TO THE
FLOODING INCIDENTS
IN WORCESTER
AND GLOUCESTER
27. This section details the events leading
up to, during and immediately following the significant flooding
experienced in Worcestershire and Gloucestershire between 20th
July and 2nd August 2007.
Worcestershire
28. Based on forecasts from the Met Office,
Central Networks implemented its emergency plan on 19 July 2007,
raising its level of preparedness in the Worcester area.
29. At 1730 hours on 20 July, Timberdine
sub-station in Worcester experienced two faults resulting in disconnection
of 12,676 customers. The supplies were restored within 2 hours
40 minutes by reconfiguring the network and transferring load
to other circuits. The sub-station had been flooded, causing damage
to some of the equipment.
30. Timberdine was repaired once the flood
water had been pumped from the site and restored to normal operation
on 26 July.
31. Timberdine was flooded by storm water
run off (pluvial flooding) rather than river flooding (fluvial).
At present there are no reliable techniques to predict sites at
risk of pluvial flooding.
32. Silver Command supported Central Networks
by providing temporary protection and pumping at both Timberdine
and the adjacent Warden sub-station that was also at risk of flooding.
Gloucestershire
33. On 22 July, based on forecasts from
the Met Office we became aware of the risk of flooding in Gloucestershire.
Central Networks staff surveyed key sites identified as being
at risk of flooding to monitor water levels. Tewkesbury and Castle
Meads sub-stations were found to be at risk due to rising water.
34. Water levels continued to rise at Castle
Meads and we requested assistance from Silver Command. The Fire
Service and Army commenced sand bagging the 132kV control room
and pumping within trenches to keep the water away from essential
equipment. This enabled us to maintain supplies throughout 22
July.
35. In the early hours of 23 July, the water
levels at Castle Meads rose rapidly and the emergency services
could no longer protect the site from flooding. Central Networks
decided to disconnect supplies in order to avoid damage to the
equipment. At 0639 hours the site was switched out, disconnecting
supplies to five substations and 47,753 customers.
36. Supplies were progressively restored
by switching to alternative circuits and within two hours, supplies
to 33,400 customers had been restored. Supplies to the remaining
customers could only be restored once Castle Meads had been reconnected.
37. Castle Meads was re-energised and all
supplies restored by 0222 hours on 24 July.
38. Once the flood waters started to recede
we visited 23,000 electricity meters to check their integrity
and visited 20,000 premises affected and/or potentially affected
properties to check electrical safety.
39. The experience of the flooding in both
Worcestershire and Gloucestershire was unprecedented. It was the
first time Central Networks had participated fully in Gold and
Silver Command.
40. Notwithstanding this, our emergency
plan and general preparedness meant that we were able to respond
swiftly and effectively to minimise the impact on our customers
and support the management of the incident.
41. We deployed resources from across the
company and our contractors to ensure that our response was not
limited by resource. The main constraining factor was access to
affected properties and assets due to the flood water.
ADDRESSING FLOOD
RESILIENCE
42. We have invested £200k in flood
protection at Castle Meads sub-station to minimise the risk of
disruption to the site should an event of similar magnitude to
the July flood occur in the future.
43. We have identified a total of 113 substation
sites across our region which may potentially be at risk of flooding
on the basis of a 1 in 1000 year event. Of these, 81 sites are
within the 1 in 100/200 year flood risk areas. We are currently
seeking to quantify the extent of potential flooding at these
sites, commencing with the larger 132kV sites, to determine the
requirements (if any) for additional protection.
44. In order to inform the above work, we
are working to develop predictive techniques and models. We are
also co-funding with National Grid and EDF a scoping study with
the Met. Office looking at how climate change will impact the
electricity industry as a whole. We will take these findings on
board and factor them into our future network design and investment
plans.
45. The Energy Networks Association (ENA)
has been commissioned by BERR to review the flood resilience across
the industry and is due to report at the end of February 2008.
Central Networks is supporting this review.
46. We will be seeking support from Ofgem
to increase investment in flood resilience as part of the Distribution
Price Review for 2010 to 2015.
47. It is important to recognise that flood
resilience requires a long term investment and programme of work.
Central Networks
January 2008
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