Bringing more power to Merseyrail

Merseyrail will be introducing new trains to its network around the Liverpool City Region from next year, replacing the current fleet of electric multiple units which are now approaching 40 years old.

Built and maintained by Swiss manufacturer, Stadler, the trains will be modern, fast and comfortable. They will also be able to carry more people, more quickly, helping support the growth of the City Region with the potential to run beyond the current ‘third rail’ to places like Wrexham, Skelmersdale and Warrington in the future.

To improve passenger safety, and make the network more accessible to all, the new trains will have a sliding step that will allow level access.

Merseytravel, which oversees the operation of the Merseyrail network, will own the new trains on behalf of the Liverpool City Region Combined Authority, which has set aside a reserve to help fund the project. Merseytravel will then lease the trains to Merseyrail.

Of course, there is more to the project than simply buying a fleet of new trains. The £460 million project includes provision for power upgrades to the network and work on platforms and track to help manage the gap between the train and platform. There will also be major refurbishment of the depots in Kirkdale and Birkenhead, so they can be adapted to maintain modern trains, moving to more computer-based diagnostics.

More power

Although modern trains are more efficient than those built 40 years ago, they also have additional electrical requirements.

For example, they demand more electrical power for traction and auxiliaries, such as air conditioning. Regenerative braking pushes power back into the 750V DC supply network, which has to be capable of accepting it (for example by having another train in section which is demanding power). If the system is not receptive, then the train’s onboard batteries will be charged.

The power supply network therefore had to be upgraded. This was required to meet the demands of the new fleet but will also eradicate existing DC issues at the fringes of the network, which had often caused delays on the Southport service.

Contractually, the situation is somewhat complex. Network Rail is undertaking the work, funded by Merseytravel. VolkerRail is the delivery contractor, employing AECOM as the lead designer.

The substation work needed was almost equally complex. Seven were to be upgraded (three on the Wirral lines and four on the Northern lines) by the provision of high-voltage (HV) switchgear modules, auxiliary transformers and isolation transformers. 

One track paralleling hut (TPH) would be converted to become a full DC substation by the provision of an HV switchgear module, a DC rectifier module, a transformer rectifier, an auxiliary transformer and an isolation transformer.

In addition, three completely new HV / DC substations would be built, each including HV switchgear modules, DC switchgear modules, DC rectifier modules, transformer rectifiers, auxiliary transformers and isolation transformers.

All this would draw down more power from the distribution network operator (DNO), so three new substation buildings would be required, constructed in accordance with Scottish Power Energy Networks’ specification, to accommodate a 33kV power supply and a 33kV/11kV transformer to suit the demands of Network Rail’s upgraded substations and equipment.

HV feeders

Modelling of the existing Network Rail distribution system identified several areas of weakness within its existing HV feeder network. Based on these findings, AECOM recommended the introduction of new HV supplies to the proposed new substation sites at Long Lane and Aughton as well as HV cable modifications at Aintree.

These HV feeder enhancements included the provision of three new HV feeders. One will be between Walton and Long Lane, another at a site still to be determined between Maghull North and Town Green stations. There will also be one between the new DNO substation building at Birkenhead North and the upgraded substation at Bidston. 

Modifications to the existing High Voltage (HV) route at Aintree substation required the existing HV cable to be cut and redirected into the existing substation to create two separate HV feeders.

In addition, electrical traction equipment (ETE) enhancements include upgrades to the existing along-track continuity bonding, impedance bonds, negative DC track feeder cables and track isolation switches.

Ongoing design

AECOM has now completed outline designs (GRIP 3) for the HV feeders and ETE works and is carrying out the detailed design (GRIP 4/5) for the HV, ETE and substation works.

It’s a complex job, requiring both preparatory work and the interfacing of several different design disciplines.

Before design could commence, topographical surveys were undertaken on all of the substation, under-track crossing (UTX) and under-road crossing (URX) sites. In addition, ground investigation works, including soakaway testing, were undertaken for all substations, UTX and URX sites.

The design itself brought in the skills of AECOM’s experts in:

• Civil and structural engineering (foundation designs, ancillary civils works, cable management / containment systems, UTXs, URXs, brickwork and DNO buildings);
• Telecoms (SCADA connections for new substations);
• Geotechnical (ground investigation factual and interpretive reporting, slope stability analysis, slope remedial works and retention structures);
• Highways (road access for new substation sites, including road safety audits);
• Drainage (flood risk assessments, SuDS (sustainable drainage systems) suitability assessments);
• Environmental and ecological surveys and management.

In addition, consideration had to be given to the key external interfaces with both Scottish Power Energy Networks and Siemens Switchgear.

Smooth progress?

In the main, the design process went smoothly. AECOM principal engineer Azadeh Ghadamgahi, who has over 12 years of experience in the design and management of power systems and electrification projects, commented: “The design submission was comprehensive and received only minor comments back from the client. The team was aware of the programme and deadlines by having effective/good communication.

“While going through the technical quality review process, everyone, whether they are a designer, checker, CRE or lead verifier, was accountable for their own work, which helped us to have a successful submission.

“As there are several sites within this project, with a multitude of designers, our aim was to maintain consistency of approach in order to produce a standardised product.

“As with any major project, there have been requested changes to the design from the client later in the process, which we have integrated faultlessly.”

One of the features of this project was the number of young designers working on the team. One such was Luke Thurgood, who started his career as a rail design engineering apprentice and has learnt his trade through the support of senior engineers around him. He now has a strong knowledge of the design of heavy-rail electrification systems, mainly focused around third-rail contact systems, negative bonding and points heating supply and distribution.

In the past year, Luke has obtained Engineering Technician (EngTech) status with the IET and continues to develop his academic knowledge while working by undertaking further studies (HND) at London South Bank University. All his studies have been funded through the government’s apprenticeship scheme – AECOM is a keen supporter of this initiative.

This article first appeared in Issue 177 of Rail Engineer, Aug/Sep 2019.