In a DCB the disconnecting function is integrated in the breaker chamber which provides several benefits such as high reliability, simplified substations and space saving. The technical solution, pioneered by ABB, recently celebrated 10 years in the field and is a standard solution in Sweden. Today it is accepted and used in more than 25 countries.
One of the key buying criteria for Transpower was to minimise their maintenance. With the DCB solution, the maintenance requirements, compared to a conventional substation with disconnectors, will be significantly reduced to almost a third. The climatic conditions in New Zealand demands high quality switchgear to maximise the power availability for consumers. The vast majority of the substations are close to the sea and will be exposed to wind borne salt, promoting corrosion in open air contacts that are used in disconnectors. In addition, New Zealand has geothermal areas with Hydrogen Sulphide contamination which also promotes corrosion and requires careful selection of materials. With the DCB solution, all open air contacts are eliminated since the interrupter fulfils the requirement of a disconnector.
As New Zealand is subject to earthquakes and high levels of seismic activity can take place in areas that were not thought to be of high risk, Transpower has adopted the IEEE 693-2005 HIGH standard for all their switchgear. ABB therefore verified the seismic requirements through calculations and a shake table test which will be performed this year.
The DCB solution provides customer value in the form of increased availability, reliability and safety. It will also reduce capital expenditures due to fewer apparatuses and smaller footprint of the substation, and lower operating expenditures as a result of significant reduction in maintenance requirements.
