Michael Bradbery, Planning Systems Manager at TransGrid, described to EcoGeneration how the location of the Capital Wind Farm, and the lengthy switching station design process ultimately led to grid-connection success.

Location, location, location

The Capital Wind Farm is located near Bungendore in New South Wales, spreading across the Hammonds, Ellendon and Groses Hill ridgelines – wind rich and less than one kilometre from TransGrid’s Canberra to Kangaroo Valley 330 Kilovolt transmission line.

The proximity of the Capital Wind Farm to existing TransGrid infrastructure meant that only a small section of transmission line was required to join the farm’s switching station to the distribution network, explains Mr Bradbery.

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Additionally, the Capital Wind Farm is located a close distance from an existing TransGrid communications network at Black Mountain. The small distance between the wind farm and the communication network at Black Mountain means that a single microwave tower can be used to link the Capital switching station to the network, which facilitates remote operation and control of the switching station.

The switching station

Where things became more challenging, Mr Bradbery explains, is in the design and construction of the switching station.

“TransGrid’s engineers were faced with the challenge [of designing a switching station] to connect a large renewable and intermittent generating source for the first time, while also maintaining flexibility for future connections and expansion,” says Mr Bradbery.

Furthermore, TransGrid engineers had to ensure that the design, construction and performance of the switching station complied with the minimum access and performance standards defined in the National Electricity Rules (NER) prior to connection.

These include:

  • Reactive power capability
  • Quality of electricity generated and its continuous and uninterrupted operation
  • The generating units response to disturbances in frequency, voltage and contingency events
  • Protection of power system disturbances, trip plant and any impacts on system security
  • The ability for remote monitoring.

In addition, TransGrid needed to ensure that the switching station would be compatible with existing TransGrid assets, while adopting the most cost-effective design and maximising generator performance.

It took several years of detailed planning, conducted in collaboration with Infigen and the Australian Energy Market Operator (AEMO), for TransGrid to finally arrive at a suitable design for the Capital Wind Farm switching station.

Switching station specifications

In the end, a compact three breaker mesh design was selected for the switching station. Such a system allows for moderate future expansion at a lower cost than a significantly expandable design, says Mr Bradbery. While simpler connections were researched, such as a tee connection, these were incompatible with the standards of reliability required by TransGrid.

The switching station was built by Infigen Energy and then transferred to TransGrid for testing and commissioning.

Connection success

The Capital Wind Farm achieved grid connection via the switching station in November 2009. The Capital Wind Farm switching station is an integral part of TransGrid’s transmission network, says Mr Bradbery – a network that achieved a reliability level of over 99.99 per cent in 2009-10.