ABB to provide a switchgear retrofit service for London substations
30 July 2014
ABB has won a four-year framework agreement with UK Power Networks, the distribution network operator (DNO), to provide a retrofit service for medium voltage switchgear installed at London distribution substations.
The retrofit programme covers legacy class QA/QF oil-filled circuit breakers, which are now unsupported by their original manufacturer. As an alternative to a complete replacement of the switchgear panels, which would require considerable capital expenditure by UK Power Networks, as well as major civil works and long network outages, ABB is project managing the installation and commissioning of an innovative retrofit methodology developed by its OEM partner, P&B Switchgear.
For UK Power Networks, there are two key drivers for the retrofit approach. First, the substations play a critical role in meeting London’s ever-growing demand for electrical power. This means that outages must be kept as short as possible and planned a long time ahead so there are important operational reasons for upgrading rather than installing new equipment. Second, space is at a premium, which also makes the construction of new substations challenging.
The P&B Switchgear method is based on the fact that the original fixed switchboard equipment, such as the housing and busbars, remains in good condition. Installing a new state-of-the-art circuit breaker will bring the switchboard up to modern safety and reliability standards while offering a life extension of 20 years or more. Network downtime is also reduced as site disruption is minimised and there is no need to disturb or replace cabling.
The replacement circuit breaker design deployed for UK Power Networks is based on an existing type-tested, Energy Networks Association assessed design developed by P&B Switchgear. It has required some modification to be compatible with the unique shuttering mechanism. To assist with the final design and test phases, including partial discharge testing, UK Power Networks has made obsolete housings available.
The ABB retrofit philosophy will help UK Power Networks meet Ofgem’s RIIO (Revenue = Incentives + Innovation + Outputs) model, which encourages network operators to invest efficiently for continued safe and reliable services and innovate to reduce network costs. Under the model, Ofgem is rewarding operators for investing efficiently and extending the life of existing assets.
The first project within the UK Power Networks framework is scheduled for delivery by ABB by the end of this year. This is for a 28-panel board, around 40m wide and more than 2.5m high. It represents a good example of the advantages of retrofitting, since the exercise will be completed within a one-week outage.
Replacing this very large board with new equipment would have required a major logistical and civil engineering project, both to remove the old switchboard and to install the new one, involving building modifications, new foundations and cabling work.
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