Select Committee on Environment, Food and Rural Affairs Minutes of Evidence

Memorandum submitted by Central Networks (FL 159)


  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.


  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.


  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.


  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.


  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.


  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.


  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.


  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.


  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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