Powering the Azumas
The rapid withdrawal of LNER’s HST fleet was made possible by the commissioning of Potteric Carr OLE feeder station, which feeds both Hitachi’s new Azuma depot at Doncaster and provides additional clean power for the East Coast main line. Prior to then, HSTs had to run through Doncaster as there was insufficient power for a full electric service.
This 25kV traction feeder station is fed from the local 33kV distribution network operator (DNO) network. It is the first in the UK for Network Rail to use a power electronics based ‘PCS 6000 Rail’ 50MW Static Frequency Converter (SFC), supplied by ABB Power Grids under a £14 million contract.
The Potteric Carr SFC feeder station was successfully commissioned into commercial operation by ABB on the ECML end of October 2019, following the completion of Network Rail product and system acceptance tests and the issuance of trial certification.
One key advantage of this technology is that it enables connection to the utility grid at lower voltages (compared to normal 132kV and above for the range of power required). It also potentially eliminates neutral sections on the railways and enables the power utility to see a ‘balanced’ supply into the railway power infrastructure. Based on an earlier engineering and option selection scheme by Network Rail, it is estimated that the chosen SFC solution, which eliminates the need for a costly high-voltage grid connection, reduces the cost of a new feeder station by 60 per cent. High-voltage grid connections were previously needed, as a single-phase 25kV OLE supply would otherwise result in an unacceptable phase imbalance in the grid supply.
This is not a problem with an SFC, which takes a three-phase supply, converts it to DC and then into a clean single phase 25kV supply for traction OLE and depot use. As a result, it is possible to take a three-phase balanced load from a local distribution network 33kV supply to power the single-phase 25kV OLE system.
ABB Power Grids has already installed SFC feeder stations in Brisbane and Queensland, Australia, as well as several other European countries.
SFCs were developed to interconnect power networks operating at incompatible frequencies. A typical example of this is a cruise ship, with a 60Hz on-board network that may have to be connected to a 50Hz shore supply. Other examples in the UK for 60Hz to 50Hz connection include interconnectors within the Western Power Distribution network area and the Maygen Renewable Generation project in Scotland.
Further power supply enhancements are required to maximise electric running on the ECML, and these are being delivered by phase two of Network Rail’s ECML power supply upgrade. This includes the commissioning of a new feeder station and 132kV connection at Hambleton Junction, near Selby, to provide resilience of supply, as well as two static frequency converter compounds at 132kV supply points and the upgrade of the feeder station at Marshall Meadows, immediately south of the Scottish border.
It is the Marshall Meadows feeder station that won’t be upgraded until at least 2021. Until then, some LNER services and all the new TransPennine Express services (30 trains a day) will have to operate on diesel power for the 64 miles between Longniddry and Chathill.
