The new 132kV Norton substation is not only one of the first to be constructed by a customer DNO under new regulations, it is also probably the largest and most strategically important project ever undertaken by NEDL. Ray Puryer, NEDL’s project engineer, outlines how the close working partnership between ABB and NEDL is helping to ensure on-time completion of this ‘mammoth task’.
Norton 132kV substation, near Stockton on Tees, serves a population of over 250,000 – a significant part of the NEDL (Northern Electric Distribution) load base – so secure and reliable operation of the site is of vital importance. The overall site, which has a direct 400kV feed from one of Europe’s largest gas fired power stations at Redcar, is actually home to four substations ranging from NGT’s 400kV and 275kV substations to NEDL’s 132kV and 11kV local distribution network.
The current project is focused on the 132kV substation, which interconnects the National Grid and NEDL’s distribution network. The existing AIS (Air Insulated Switchgear) substation was built in the late 1930s and had reached the end of its economical working life. Previously, National Grid would have been responsible for building and project managing the replacement. However, a recent relaxation of regulations now allows a customer distribution network operator (DNO) to build the substation and have the relevant circuits transferred to National Grid on completion.
The original plan was to carry out a ‘like for like’ replacement and it was put out to tender as a turn-key project on this basis. However, ABB then came in with an alternative bid based on GIS (gas insulated switchgear) technology for around £9 million, which was about the same cost as an AIS substation .
It was clear that the GIS approach would enable us to work with a ‘green field’ site, with the main construction and installation of switchgear completed off-line and the circuits switched-in in a controlled way, so that outages could be planned well in advance. In comparison, the AIS approach involved the greater risk of working in a live compound and direction of outages would have been much more challenging. And since ABB was proposing to use its compact ELK-04 gas insulated switchgear, which was already well proven in substation projects, we decided that this represented a lower-risk option.
A further advantage of the GIS approach is that the new substation is housed indoors, in a purpose built building occupying around one sixth of the space occupied by the existing AIS substation. This will significantly improve the aesthetics of the site as we will demolish the AIS substation after it is decommissioned, and the indoor substation requires less maintenance as well as offering greater reliability. The new 132kV substation, rated at 540MVA, features 20 bays of switchgear (four of which will be transferred to National Grid) with four incoming circuits fed by supergrid transformers and 12 outgoing circuits, two of which will feed local grid transformers. It also features new transition joint technology to connect the existing fluid filled cable circuits to new XLPE cables (see opposite page).
The key to the success of this mammoth task has been in ABB/NEDL’s thorough approach to planning, coordination and attention to detail at every phase, from initial design, through civil works to installation of the equipment and commissioning. The team has been particularly strong, especially in the way that every party involved has been encouraged to work together right from the very first site meeting. It is refreshing to see that the traditional customer-supplier relationship has evolved into a true partnership between ABB and NEDL based on mutual support and flexibility. National Grid has also played a very important role by taking an equally flexible approach to its own requirements and offering help and assistance as required. For a site of this strategic importance any outages have to be planned around a year in advance.
This means that careful planning and coordination is vital to ensure that all the planned activities can be accomplished during the restricted time available and, most importantly, that power is restored on time –which is not always the case in this type of project. In fact, ABB and NEDL have worked so well together we are currently slightly ahead of schedule. This gives us added flexibility to plan additional activities for the outages. In the short-term, the success of this project has to be gauged by the commissioning phase, which is always a serious, difficult and exacting process.
We have a fantastic commissioning team on site, ably supported by NEDL, NGC and the ABB offices in Stone. We are on target to have the final 20th bay on-line for February 2005, less than two years since we broke ground on site in April 2003.
For the long-term reliability is of course vital. This can only be judged after time. But we do know that ABB has provided a tried and trusted integrated solution encompassing GIS switchgear, panels, cables and surge arresters. It also comes with an eight-year guarantee as well as a ten year maintenance contract.
Outside this contract, NEDL has also asked ABB to replace two of the grid transformers and to construct a new 11kV substation in the space created by the 132kV GIS project. So by 2006 ABB will have revamped a substantial part of the whole Norton site.
Jon Downs, ABB project manager, said: “For ABB this has truly been, and continues to be, an international effort with critical coordination and planning between focused factories in Germany, Sweden and Finland and the UK project delivery team”.