URGENT RECTIFIER TRANSFORMER REPLACEMENT FOR DLR
Docklands Light Railway
Following the malfunction of two rectifier transformers, Docklands Light Railway (DLR) required critical installation of two new 2167kVA rectifier transformers at Royal Mint Street. Already being the primary contractor for three DLR projects, Enable Infrastructure was contracted in to restore stable power supply to DLR’s busiest line.
The design phase involved arrangement drawing, a cable interconnection diagram, and wiring termination schedules. The two projects were scheduled three/ four weeks apart, within a seven-day timeline. Isolation and permit-to-work were issued on a Thursday morning, with the new rectifier transformers being fit for operation seven days later, following a 12-hour soak period.
The project
DLR/KAD required an approved design, method statement, and ITP that detailed all safety and technical aspects of the works. This project involved works including isolation, decommissioning, diversion of power to the generator, removal, installation, pre-commissioning, commissioning, and testing of the rectifier transformers. Due to the lower specifications of the tertiary windings on the new transformers, Enable installed a temporary backup generator for essential LV supplies.
Enable, Tower Hamlets Council and Transport for London (TfL) coordinated a road closure on Royal Mint St and on the Cycle Superhighway 3 to deliver works safely. This was the first major undertaking on the DLR network since the Poplar Substation fire. Therefore, it served as a crucial test for the network’s resilience and had strict time constraints.
For the first rectifier transformer, KAD conducted the isolation test 48 hours before the works began to ensure the stability of peak load times without the transformer in service.
Construction commenced on Friday morning after site set-up on Thursday. All cables were disconnected, and alarms/indication wiring were tested, prior to removing existing transformer on Sunday. The existing HV cable was cut and replaced with new HV cable. With road closure in effect, the existing transformers were safely removed using a HIAB crane and low-loader. The new transformers were then lifted into place and accurately positioned using pre-drawn markings and a laser level. The redundant transformers were transported to the designated storage location for refurbishment.
The challenge
- The initially accepted programme of works had spanned three weeks, but because of the urgency of the project, this had to be reduced.
- During the transformer lift, the road closure was put in place by a subcontractor, with Cycle Superhighway 3 also closed. There were multiple access points, and some members of the public ignored the signage and moved cones to gain access.
The solution
- Enable Power Systems teams increased resource in order to condense the programme into just seven days for each transformer.
- Enable Infrastructure and the contractor involved halted all work until the problem with the influx of people was resolved. Each individual access point was manned to prevent access until the lift was complete, enabling the works to be carried out safely and without any accidents or further incidents.
The deliverables
- Site set-up, authorised working perimeter located and barriered
- Road closure approval from TfL & Tower Hamlets
- Supply and installation of temporary back-up generator for essential LV supplies
- Design for installation of two rectifier transformers at Royal Mint Street
- Installation of 45m HV cable
- Installation of 150m anode cable
- Removal and delivery of 2 x 2MW rectifier transformers
- Two 2MW transformers fully commissioned into service
- Handover back to DLR/KAD
Gallery
“This site is key to maintaining and supporting the integrity of the railway operation. Enable Infrastructure delivered the works in two text-book operations, on programme and without compromising site or personal safety, despite being under much scrutiny due to potential operational consequences. Great performance all around!” - DLR
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