Rosebery 44kV Substation Disconnector Upgrade
- Client
- TasNetworks
- Principal Contractor
- Zinfra
- Location
- Rosebery Substation, west coast Tasmania, TAS
- Voltage
- 44 kV
- Asset Type
- Substation Upgrade
- Project Type
- Asset replacement and protection upgrade on a live operational site
- Duration
- Site outages completed March 2025; final as-built documentation May 2025; variations closed out September 2025
- Megavar Scope
- Primary design support, secondary systems design and modification, relay logic and settings changes, HV withstand testing, functional testing, and commissioning sign-off
Overview
Rosebery Substation sits on Tasmania’s remote west coast, supplying the mining townships and industrial loads that define this part of the state. It is a congested older switchyard, built up progressively over decades, with limited spare space and a network layout that has to be understood in detail before any modification can be safely executed.
TasNetworks engaged Zinfra as principal contractor to replace a set of ageing 44 kV disconnectors, upgrade associated protection, and return the site to service with its reliability and safety performance improved. Megavar was brought in by Zinfra to deliver the high voltage design inputs, the secondary systems modifications, and the full testing and commissioning scope.
The work had to be executed on a live operational substation within tightly controlled outage windows. Any delay or rework would have flow-on effects across the west coast network, so the project was planned around short, well-defined outages with minimal tolerance for schedule slip.
Scope of Work
- Primary design support for the replacement 44 kV disconnector installations, including interface review against the existing switchyard layout and clearance verification
- Secondary systems design and schematic modifications covering the new disconnector motor drive units, interlocking, and position indication wiring
- Protection relay logic and settings modifications to accommodate the new disconnectors, targeting the Siemens 7SJ82 (B299) feeder protection relay and the Siemens 7UT86 (E499) transformer differential relay
- Point-to-point wiring checks and interlock verification of the new disconnector motor drive cubicles, including DC supply, trip and close coil testing, and position auxiliary contact proving
- Contact resistance (micro-ohm) testing of the new disconnector main contacts using a DLRO100
- 58 kV AC withstand testing of the new disconnectors E429C and E429D using a BK 130 HiPot test set
- Insulation resistance testing at 5 kV DC across disconnector and wiring insulation using a Megger insulation tester
- Protection secondary injection testing and scheme logic functional testing using an Omicron CMC 356 to verify modified relay settings, trip paths, and interlocking
- Switching and energisation support during the outage windows, with commissioning engineers supporting TasNetworks operations personnel through return-to-service
- Final as-built documentation, test records, and site handover package
Equipment
Commissioned
- 2 x new 44 kV disconnectors (E429C and E429D) including motor drive units
- Siemens 7SJ82 feeder protection relay (B299) with modified logic and settings
- Siemens 7UT86 transformer differential relay (E499) with modified logic and settings
- Associated interlocking, DC supply, and position indication circuits
Megavar Test Equipment Deployed
- Megger DLRO100 micro-ohmmeter for disconnector contact resistance testing
- Megger 5 kV insulation resistance tester
BK 130 HiPot test set for 58 kV AC withstand testing - Omicron CMC 356 protection relay test set for secondary injection and scheme functional testing
Team: A multi-discipline Megavar team was mobilised from our Tasmanian offices, covering primary design input, secondary design, testing and commissioning. The on-site execution team included commissioning engineers working from EWPs for visual inspection and termination checks, and protection engineers based at the relay panels for wiring verification, logic modification, and secondary injection.
Challenges and Approach
The biggest constraint on this project was not the equipment, it was the site. Rosebery is a congested older switchyard where the existing 44 kV network layout severely limits how and where new equipment can be installed. Clearances are tight, access around live plant is restricted, and every outage window had to be used without wasted time.
Megavar’s response was to invest up front in planning. The primary design review was used to flush out the installation constraints before mobilisation. The secondary design and protection settings work was sequenced so that as much of it as possible was desktop-verified and test-simulated before any site outage was called. Interlock logic and protection modifications were pre-proven against the scheme drawings so that site time was spent verifying, not investigating.
On site, the team worked the outages in a carefully staged sequence. EWPs were used for visual inspection and clearance checks around the new installations while panel-based engineers ran the wiring verification and secondary injection testing in parallel. The HV withstand and contact resistance testing was slotted into the sequence so that each test either cleared the equipment for energisation or identified an issue early enough to be corrected within the outage.
QA processes were deliberately tightened after early scope reviews to reduce the risk of rework. Test records were cross-checked against the protection settings and schemes at the end of each day, so any discrepancy was caught and resolved before the next step was authorised. That discipline carried through to the as-built documentation and final handover, which were delivered in a form that TasNetworks operations could accept without lengthy revision cycles.
Outcomes
The Rosebery disconnector upgrade was delivered on time against its outage milestones and in full compliance with the applicable technical and safety standards. The new disconnectors and associated protection were commissioned without any return-to-site events, and the site was handed back to TasNetworks operations cleanly at the end of each outage window.
Despite the complexity of the existing switchyard and the tight access conditions typical of older west coast Tasmanian sites, the work was executed in a well-planned and professional manner. The front-loaded design and QA effort paid back through faster client approvals and fewer document revision cycles, which is the hardest thing to measure on a project like this but the most valuable.
- All site outages completed within their planned windows, with no rollovers into subsequent outage periods
- Full compliance with TasNetworks technical standards, Megavar ISO procedures, and site safety requirements through the entire execution phase
- Tightened QA processes reduced rework and produced cleaner test records, leading to faster client sign-off on commissioning milestones
- Final as-built documentation delivered May 2025 with minimal revision required; post-project variations closed out by September 2025
- Modified Siemens 7SJ82 and 7UT86 protection settings proven in service, with the disconnectors E429C and E429D in reliable operational use since energisation
Need High Voltage Testing or Equipment?
Talk to our engineers about your project requirements.
Get In TouchFrequently Asked Questions
What does a 44 kV substation disconnector upgrade involve?
Why is 58 kV withstand testing used on a 44 kV disconnector?
What test equipment is required for HV disconnector commissioning?
Why was the Rosebery substation upgrade important to TasNetworks?
Rosebery Substation supplies the west coast Tasmania network, including mining loads and regional communities. Replacing the ageing disconnectors and upgrading the associated protection improved the reliability and safety of a critical piece of the west coast network, and reduced the risk of unplanned outages on an asset that is expensive to access and mobilise to. TasNetworks was the asset owner, with Zinfra as principal contractor.
What challenges are typical on Tasmanian west coast substation projects?
Does Megavar provide HV commissioning services across Tasmania?
Explore Our other services
SCADA engineering and integration for substations and renewable energy projects. RTU configuration, IEC 61850, DNP3, cybersecurity, and end-to-end commissioning across Australia.
Substation maintenance services: preventive, corrective, and condition-based maintenance for HV transformers, switchgear, protection, and SCADA across Australia. Omicron test equipment.
HV earthing design and testing: earth grid design, EPR calculations, step and touch voltage analysis, soil resistivity surveys, and compliance testing per ENA EG-0 across Australia.
Trusted by top enterprises for exceptional results
Explore the latest insights
We’re incredibly excited to share a big milestone in Megavar’s story—we’ve officially opened our new Newcastle branch, located at 22 Gavey Street, Mayfield,
