Transpower is currently exploring the possibility of replacing gas-insulated circuit breakers with vacuum circuit breakers (VCBs).
VCBs use a combination of dry air or nitrogen as an insulating medium with a vacuum interrupter, instead of SF6. SF6 is the greenhouse gas currently used in the circuit breakers, and makes up over a third of Transpower’s carbon emissions.
Replacing gas-insulated circuit breakers with VCBs will not only significantly reduce Transpower’s carbon footprint, it is also safer for both the environment and maintenance crews (as the dry air can be released back into the atmosphere, rather than the crews having to handle and dispose of toxic material), and requires much less maintenance.
Currently, Transpower is entering the detailed design phase of trialling a 72.5 kV VCB (supplied by Alstom Grid) on the Islington-Papanui1 circuit. The trial will provide information on the performance of VCBs, such as whole of lifecycle and cost benefits compared with the existing SF6 circuit breakers, before a decision is made to apply the technology on a wider scale.
The trial is set to be in place before the end of November 2012.