Scope of works included electrical construction and testing works involving:
Construction and commissioning of a new high voltage switchroom comprising of a 2-bus 11kV switchboard (with provisions for a third bus section), and a 2-bus 33kV switchboard.
Decommissioning of all existing 11kV and 33kV circuit breakers and cut existing feeders into new board.
Relocating 33/11kV transformers TR1 and TR2 onto new elevated platforms and cut into new transformer circuit breakers in the new switchroom.
Re-conductor portions of 110kV overhead feeders F817 and F818 onto TR5 and TR6.
Relocating 110/33kV TR5 andTR6 marshalling cubicle, AC board and cooler control cubicle to new platform, above IRFL 9.2M, adjacent to each transformer.
Cutting TR5 andTR6 into new protection panels in new control room.
Installing new communications and SCADA panels in new control room.
Commissioning new station transformers TR8 &TR9, 2 x RMUs, 2 x AFLC and new AC and DC schemes as per design.
The main issue faced throughout the project has been the balancing of load during scheduled outages. Temporary bus ties were introduced on both the 11kV and 33kV bus to maintain network security whilst the transformers and overhead bus were relocated and recommissioned.
As an example, both the 33/11kV transformers were decommissioned and relocated onto concrete platforms above the flood level, at different times. When one was out of service, a mobile substation was employed with a temporary 33kV feed from the newly commissioned 33kV switchgear, to supply a second 11kV feed to the network. Once the transformer was commissioned into the new 11kV switchgear, a temporary bus tie was installed to join the old 11kV switchgear to the new before the second transformer was taken off line. This effectively lengthened the 11kV bus to encompass all the old 11kV feeders, and the 16x new 11kV circuit breakers, all fed from two incoming 11kV feeders within the substation.
This was a big challenge due to the strict timelines for scheduled outages. Significant planning and organisation ensured that the cut-overs were completed within the allotted timeframes.
Energex permit systems are an important aspect of their contract model. Due to the staged nature of the project, a thorough understanding of the permits was essential in ensuring the appropriate resourcing of tasks within specified work areas.
Redesigning of the cable support systems
The initial design of the transformer enclosures were designed for standard installation, with a single run of cable ladder to house the multicore cables. However, due to the relocation of the control cubicles, and the introduction of submersible junction boxes on the transformers, the number of multicores almost tripled. Zinfra designed and upgraded the cable support system on both of the 110/33kV transformers (TR5 and TR6), offering a neat and practical solution to the problem, while adhering to Energex’s structural and earthing standards.
The project was unique in both size and scope which required a staged approach to successfully deliver the project within the nominated timeframes.
After 9,000 man hours the project is currently MTI and LTI free. Regular audits by Energex coordinators have noted a high level of appreciation for the project team’s work ethic and attention to safety. The project has successfully passed three separate audits by a senior member of the Energex HSE Team, a visit from the ESO and QLD Health and Safety, and two audits by Energex ETU representatives, with only minor improvements being recommended. Paperwork, application of PPE and safe approach to tasks have been commended throughout these audits.