Andrew Pallett, SCADA project manager for EDF Energy Powerlink, reports on ABB's SPIDER network management solution
London Underground’s power supply system is now controlled by an integrated SCADA (Supervisory Control and Data Acquisition) system based on ABB’s SPIDER network management solution. Andrew Pallett, SCADA project manager for EDF Energy Powerlink, reports.
The London Underground (LU) comprises some 250 miles of track, with 12 lines and 275 stations serving around one billion passenger journeys each year, and its annual demand for power exceeds 1TWh.
LU’s power supply system is continuously managed by control room engineers and operators responsible for the safe and reliable operation of a 22kV sub-transmission system with load delivered via an 11kV system to 158 delivery points. Local transformer rectifiers provide 630V DC for the train motive power as well as lower voltage supplies for auxiliary services such as signalling, lighting and ventilation. The DC supply is switched off at night, to allow track maintenance work to be carried out safely while trains are not running, and this typically results in over 500 switching operations each day.
PRIVATE FINANCE INITIATIVE (PFI)
In August 1998, LU signed a 30-year, £1 billion Power Private Finance Initiative (PFI) contract with EDF Energy Powerlink - a consortium jointly owned by EDF Energy, Balfour Beatty and ABB - to operate, maintain, finance and renew the Underground’s high-voltage power supply system. One of ABB’s main roles has been the design, installation and commissioning of a new integrated, high performance, SCADA (Supervisory Control and Data Acquisition) SPIDER system to provide overall control of the power distribution network for four out of seven LU regions (Eastern, Western, Victoria and Metropolitan) as well as the primary 22kV distribution network. It replaces six previous SCADA systems that were either at the end of their working life or were temporary installations.
TWO CONTROL CENTRES
The SPIDER SCADA system is fully integrated with LU’s communications system. Control of the network is centralised in two replicated command centres (main and emergency), with dual application servers interconnected by a high-speed fibre-optic communications link.
RTUs (remote terminal units) provide the local interface with the power network equipment (transformers, switchgear, SVCs and so on), and they are linked into the SCADA system by copper lines converging on six data concentrators. One of the key technical challenges in the project was in developing the protocol conversion software that enabled the legacy RTUs to communicate with the new SCADA system.
PROJECT MANAGEMENT
From the initial stages, a great deal of attention was paid to ensuring the involvement and commitment of the end users and clients from both companies. A joint implementation team was set up to formulate the functional design specification and to take the project through the installation, testing and commissioning phases. Commissioning of the SPIDER system, which was completed in 2006, was progressive to ensure no interruptions to supply as control was switched over from the existing SCADA systems. A particular challenge was that access to the network was restricted to a short shut-down window in the small hours of the morning.
THE VERDICT
The SPIDER system has proved its capability to ensure a high level of power availability to meet LU’s stringent operating targets. In particular, greater visibility of the power system enables any issue to be flagged and identified, so that early action can be taken to prevent it escalating into a fault.