ELECTRIFICATION
Pictured: Willow Park Autotransformer Feeder Station (ATFS)
Protection testing associated with the North West Electrification Autotransformer System – Phase 1
Ashley Jordan, testing and commissioning director for WJ Project Services Ltd, a ‘Level A’ nominated person on Network Rail’s infrastructure, has a detailed knowledge of the 25kV AC Overhead line system (both Autotransformer and Classic feeding arrangements) along with the 33kV / 750VDC traction system used widely in the south east.
he North West Electrifi cation Project – Phase 1 is part of a programme of works to install new OLE on the Chat Moss lines between Liverpool and Manchester and reinforce the electrifi cation infrastructure on the West Coast Main Line (WCML) at Newton-Le-Willows. The traction power supply system has been installed to a 12kA fault level 25kV – 0 – 25kV Autotransformer (AT) system. Phase 1 of the project involved the
T installation
of two new substations, Ordsall Lane Mid-Point Autotransformer Station (MPATS) and Willow Park Autotransformer Feeder
Station
(ATFS). The initial implementation was
protection is provided by Siemens Siprotec 7ST61 and Schneider P143 Relays.
The initial works included moving the
132/25kV railway in-feeds from the existing Parkside Feeder Station to the new Willow Park ATFS substation. This was followed by the transfer of all track feeders feeding the WCML during a nine-day blockade of the line.
The long-term plan is to use the 400kV/50kV/25kV derived supply from Weaver Junction ATFS on the WCML to provide a full AT supply to the Liverpool to Manchester scheme, as the WCML Phase 3B project works progresses.
Typical autotransformer feeding arrangement
limited to a 6kA fault level ‘AT lite’ system.
Testing and commissioning works associated with the new substation equipment involved using OMICRON CMC 353 / CMC 356 secondary injection equipment to carry out testing of the protection scheme, and has progressed to supporting the Network Rail Electrifi cation and Plant Design Group (EPDG) in setting the IEC 61850 standard, which is to be rolled out on future Network Rail projects.
Autotransformer system
The traction power supply system specifi cation called for a 12kA fault level 25kV – 0 – 25kV Autotransformer (AT) system, but with initial implementation as a 6kA fault level Autotransformer 25kV system (derived from the single phase 132kV/25kV incoming supply at Willow Park ATFS).
The two new autotransformer substations at Willow Park ATFS and Ordsall Lane MPATS are modular substation buildings with Siemens 8DA12 gas insulated switchgear. Willow Park ATFS is a 36 Panel Siemens 8DA12 substation. Ordsall Lane MPATS is a 26 Panel Siemens 8DA12
Substation. Circuit / equipment 46 | rail technology magazine Jun/Jul 14
Control is carried out using a conventional Siemens (formally Invensys) Supervisory Control and
Data Acquisition (SCADA) system, but it also has the capability of being controlled via the IEC 61850 network system functionality, which is being trialled in parallel.
Factory acceptance testing
During the FAT stage, WJ Project Services Ltd was brought in to support the testing of the modular substation arrangements. Particular areas of testing that were carried out were Current Transformer (CT) testing; Voltage Transformer (VT) testing; HV Pressure testing; and Contact resistance testing.
Time constraints during the FAT stage meant that the testing methods used needed to be effi cient. Due to other installation and testing works being carried out, there was limited access to the HV switchboard, which caused concern over the conventional CT testing methods the client had called for. From experience, carrying out separate ratio / polarity tests / magnetisation curves / resistance / knee point tests on the 122 protection CTs would have taken an estimated eight days of engineers’ labour. A further three days would also have been needed to process the results into a report format and plot the required magnetisation
Aside from saving considerable time, other benefi ts of using the CT Analyser were:
• •
Consistency in testing methods to achieve identical testing methods
Standardised test report format for all results
• Less room for error and retesting requirements
• •
• Accuracy of the test results
Traceability of the test results – being date and time stamped
Ensuring CTs were always left in a demagnetised state following testing
• Automatic CT Class identifi cation Site acceptance testing
Once the substation modules were transported and positioned at their fi nal locations, the SAT stage began. With little more than fi ve months
curves.
A quicker and more consistent CT testing method was needed, and from previous project works with Balfour Beatty and Babcock International, OMICRON’s CT Analyser was suggested to the client as a quick and effi cient solution. Although there were additional costs for the hire of the CT Analyser equipment, these were offset against the time saved in engineering resources.
The use of the CT Analyser reduced the testing time by some 40%, to an overall total of seven days for both the testing to be carried out and the reports to be printed for handover to the client.
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