Chapel Street Substation: 11 kV Switchgear Replacement and Commissioning
- Principal Contractor
- RBD Electrical
- Location
- Tasmania, TAS
- Voltage
- 110 / 11 kV
- Project Type
- Substation
- Duration
- 12 months
- Megavar Scope
- Testing and commissioning of four new 11 kV bus sections (ABB UniGear ZS1), associated feeder, incomer, bus coupler and bus zone protection schemes, integration with existing 110/11 kV transformers T5 and T6, SCADA integration to TasNetworks NOCS, and 11 kV cable VLF and PD testing.
Overview
Megavar was engaged by RBD Electrical to deliver the testing and commissioning scope for the replacement of all four 11 kV bus sections at TasNetworks’ Chapel Street Substation. The works replaced legacy switchgear with new ABB UniGear ZS1 cubicles across Buses A, B, C and D, while the 110/11 kV transformers T5 and T6 remained energised and the substation stayed in service. The project ran for twelve months and completed in April 2026.
Chapel Street feeds nearby utilities and suburban distribution load. Taking the site fully out of service was not an option. The work was therefore staged so that one bus at a time was isolated and replaced, while the alternate bus supplied by the same transformer winding remained live. Megavar’s scope covered factory acceptance testing, primary and secondary site testing, SCADA integration with the National Operations Control System, and final on-load commissioning checks.
Scope of Work
- Stage-wise DC isolation and relocation of two AC distribution boards (ACDBs) within the existing control room while the substation remained in service.
- Stage-wise secondary isolation of each 11 kV bus to allow safe removal of primary equipment.
- Factory acceptance testing of 30 × Siemens 7SJ82 feeder, incomer, bus coupler and bus zone protection relays.
- Site acceptance testing and integration of new 11 kV switchgear with the existing 110/11 kV substation.
- Stage-wise SCADA testing and end-to-end signal verification to TasNetworks’ National Operations Control System (NOCS).
- Final commissioning checks, energisation and on-load measurements across all four 11 kV buses.
- Cable VLF withstand and partial discharge (PD) testing on 11 × 11 kV cables.
- As-commissioned protection setting files uploaded to TasNetworks StationWare and as-built drawing package issued at handover.
Equipment
Commissioned
- 4 × 11 kV incomer cubicles, 2 × 11 kV bus couplers, 4 × 11 kV bus metering cubicles, 24 × 11 kV feeder cubicles (ABB UniGear ZS1).
- 4 × 11 kV busbars, 30 × 11 kV vacuum circuit breakers, 32 × 11 kV earth switches.
- 32 sets of three-phase 11 kV current transformers, 22 toroidal CTs and 8 sets of three-phase 11 kV voltage transformers.
- 4 × 11 kV incomer protection schemes, 2 × bus coupler protection schemes, 4 × bus zone protection schemes and 24 × feeder protection schemes, each based on Siemens 7SJ82 multifunction relays.
- Integration with existing 110/11 kV transformers T5 and T6, including 2 × GE T60 transformer protection relays and 2 × Siemens 7UT86 differential protection relays, with setting modifications and stability testing on each transformer.
- 1 × 150 kVA dry-type station service transformer (ST-3) and associated low-voltage distribution.
- 11 × 11 kV cables, VLF withstand and partial discharge testing.
Full SCADA point-to-point testing and integration to NOCS.
Megavar Test Equipment Deployed
- Omicron CMC 500 and CMC 356 protection relay test sets for secondary injection.
- Omicron CPC 100 and TESTRANO 600 for primary injection and transformer tests.
- Omicron MPD 600 and CIBANO 500 for partial discharge measurement and circuit breaker analysis.
- Omicron CT Analyser with switch box for current transformer ratio, polarity and excitation testing.
Three-phase variac for controlled primary energisation tests. - HV Diagnostics HVA 60 kV VLF cable test set for 11 kV cable withstand and PD-on-VLF testing.
- Phenix 6CP50 (50 kV) AC withstand set.
Megger MIT 515 (5 kV) insulation tester and DLRO 600 micro-ohmmeter.
Team: Project Manager: Zeeshan Afzal. Lead Engineer: Saif Ur Rehman. Testing team: Johannes Scheepers, Max Thrope, Doug Smith and Muhammed Waseem. The site team was sized at two to three test engineers, scaled across the twelve-month programme to match each staging window.
All works delivered to TasNetworks technical specifications and substation standards. Settings, asset records and as-commissioned data delivered through TasNetworks StationWare.
Challenges and Approach
Maintaining supply during ACDB relocation
Both AC distribution boards needed to be relocated to a new location within the existing control room without interrupting protection on the live substation. Megavar’s site team developed a procedure to parallel the DC circuits of the two ACDBs, isolate one ACDB safely for RBD to relocate it, verify circuits, restore the isolated ACDB, then repeat the same sequence on the second board. Substation protection remained operational throughout.
Staging T5 and T6 outages with minimum risk
The original design proposed cutting the 11 kV cables on the transformer side and leaving sealed live ends in place during staging. The Megavar team reviewed this approach and proposed an alternative: isolating the 11 kV cables at the transformer cable boxes instead of cutting them. The proposal was assessed by TasNetworks and the design contractor and adopted. The revised methodology produced a safer outage and a more efficient staging sequence within the same overall timeframe.
Integrating new assets into a live substation scheme
Each new 11 kV bus had to be integrated with the existing 110/11 kV substation while three of the other four buses continued to supply load. Test engineers familiar with TasNetworks protection schemes and documentation completed the secondary modifications and verified each interface before energisation. Setting changes on T5 and T6 were implemented and stability-tested for every staging configuration.
Outcomes
Chapel Street is a working distribution hub serving suburban and utility load. Replacing four bus sections inside a live substation, while maintaining supply through the alternate winding of each transformer, is the type of work where the planning carries the project. Megavar’s contribution was as much about staging the engineering as it was about the testing itself. The team proposed a safer cable isolation method, worked with TasNetworks and the design contractor to revise the staging, and deployed engineers who already understood the asset owner’s standards. The technical work was conventional. The way it was sequenced and delivered is what kept the substation in service.
- All four 11 kV buses (A, B, C, D) and the associated 24 feeders were tested and commissioned in line with the agreed programme.
- 4 × new 11 kV ABB UniGear ZS1 buses, 11 × 11 kV cables and 1 × 150 kVA station service transformer were energised in a staged, one-bus-at-a-time sequence to keep the substation in service throughout the programme.
- Existing 110/11 kV transformers T5 and T6 were re-stability-tested and returned to service after each staging step.
- As-commissioned settings, test reports and ITP records issued through StationWare and to RBD Electrical for inclusion in the final asset documentation.
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Get In TouchFrequently Asked Questions
What does 11 kV switchgear commissioning involve?
11 kV switchgear commissioning is the structured process of testing primary equipment, secondary protection schemes, control wiring and SCADA signals, then energising the switchgear under controlled load. The work covers factory acceptance testing of protection relays, primary injection of CTs and circuit breakers, secondary injection of relay schemes, point-to-point SCADA verification, and on-load checks once the bus is live. At Chapel Street, Megavar commissioned four 11 kV bus sections this way, one stage at a time, while the substation remained in service.
How is switchgear replaced in a live substation without losing supply?
Which protection relays did Megavar test at Chapel Street?
Megavar tested 30 Siemens 7SJ82 multifunction relays across feeder, incomer, bus coupler and bus zone protection schemes, plus two GE T60 and two Siemens 7UT86 transformer protection relays on T5 and T6. Each relay was factory acceptance tested before delivery to site, secondary injection tested through Omicron CMC 356 and CMC 500 sets, then end-to-end verified through to the SCADA signals before the bus was energised.
What does end-to-end primary plant and SCADA commissioning include?
End-to-end primary plant and SCADA commissioning includes primary injection of CTs and circuit breakers, polarity and ratio checks on every CT, contact resistance and timing checks on every CB, secondary injection of every protection element, point-to-point verification of every SCADA point through to the control centre, and on-load checks with the bus live. At Chapel Street the SCADA signals were verified all the way through to TasNetworks’ National Operations Control System (NOCS).
How does Megavar approach staged outages on live substations?
What was delivered at the Chapel Street substation upgrade?
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