Rangebank BESS: 220 kV GIS Testing and Substation Commissioning

Rangebank is a 200 MW / 400 MWh battery energy storage system in Rangebank Business Park, Cranbourne West, in Melbourne's outer south east. Developed by Eku Energy and Shell Energy Australia, it connects at 220 kV through a feeder bay at the adjacent Cranbourne Terminal Station and was completed in December 2024. The site substation steps 220 kV down to 33 kV, where two switchboards collect the battery feeders.

Megavar was engaged by RJE Global, the balance of plant contractor, for HV testing and secondary commissioning of the substation. The work ran as separate packages: protection relay testing in February 2024, HV withstand and partial discharge testing of the 220 kV gas insulated switchgear in April 2024, and substation commissioning from late May to mid July 2024, with crews of up to seven testers on site in the peak weeks.

The scope covered the 220 kV GIS and its voltage transformers, duplicated X and Y protection on the 220 kV line, the 220/33 kV transformer and both 33 kV buses, and HV, contact resistance and circuit breaker timing tests on the 33 kV switchboards. It adds to Megavar's renewables and battery storage experience on substations across Australia.

• 220 kV GIS: outdoor gas insulated switchgear with circuit breakers and disconnectors, tested as one circuit
• 220 kV voltage transformers: 3 x single phase inductive VTs, 220 kV primary with four secondary windings each
• 220 kV line protection: Siemens 7SL87 (X protection) and GE L90 (Y protection)
• Transformer protection: GE T60 (Set X) and SEL-487E (Set Y)
• 33 kV bus protection: GE Multilin B90 (X protection) and SEL-487B (Y protection), one relay per phase
• Neutral earthing transformer monitoring: Littelfuse SE-700 relays
• 33 kV switchboards: two boards with two incomers, 16 BESS feeders and two auxiliary transformer feeders

Flashover during the first 33 kV withstand

During the first HV withstand attempt on the 33 kV switchboard in June 2024, a flashover occurred at about 38 kV on the red phase cone bushing of one circuit breaker, where the cable boot would later terminate. Testing stopped immediately. After rubber insulation tubes over the exposed cones did not hold the voltage, Megavar, RJE Global and Fluence agreed to pause HV testing until the switchboard manufacturer provided a test procedure, rather than risk further damage to new plant.

Completing the switchboard test with the right accessories

With test boots fitted to the exposed cones, both 33 kV switchboards were retested over the weekend of 13 to 14 July 2024 at 56 kV for one minute, with insulation resistance measured before and after. One bushing boot cap failed on the blue phase of Switchboard 1 during the test; it was replaced and the board retested successfully, so both boards were proven before energisation.

Voltage transformers on the GIS

The 220 kV VTs could not be driven to the 127 kV conditioning voltage because of their inductive nature. They were withstand tested at 101 kV for one minute, a value verified and approved by the GIS manufacturer's representative on site, and then ratio, polarity, phase shift and secondary winding resistance tests were completed on every winding.

Wiring errors found during protection testing

Site acceptance testing of the transformer X protection found current inputs wired to the 5 A rather than the 1 A terminals, neutral CT currents drawn to the wrong inputs, crossed neutral CT wiring that failed restricted earth fault testing, and a circuit breaker status input on the wrong contact. Each fault was corrected, drawings were marked up, and the affected functions were retested before the relay was signed off.

Holding a compressed commissioning window

Commissioning ran from late May to mid July 2024 across four protection platforms from three manufacturers. To hold the programme, the crew was increased to seven testers in the peak weeks, after hours work was added in the week of 8 July at the client's request, and the 33 kV HV testing was completed over a weekend.