BLadewig,
I want to share with all of you an inconclusive discussion with the factories while I was serving in ABB in regards to a report from a Sweden utility that found that their disconnect switch designed for the IEC market have more maintenance requirement than modern SF6 circuit breakers.
This originated the design of new breakers with disconnect switches integrated similar to the GIS switch unit to be more reliable and less expensive to maintain. We understood the benefit of the new apparatus in term of performance and space saving in the substation but we had hard time to extrapolate this switch experience to the US market.
After many internal debates, the idea to introduce this concept in the US market was abandoned for the following reasons:
* Lock of reliable database from utility and private owner substations. Most people in the utility were happy we the disconnect switch performance even though we found in several sites the switch was very seldom operated.
* US disconnect switches design are more robust than the European counterpart in regards to seismic performance, ice break capability and, heavy duty parts and mechanisms.
* The winter environment conditions in Sweden are more severe than the average site in the US.
* Market resistance to accept new apparatus without track record experience.
* Engineering culture, code requirement(NESC) and maintenance practice mandate visible isolation of the disconnect switch blade making difficult to accept a breaker-switch combo even with side glass or external position indicator.
I hope you or any of our colleagues bring new light and fresh data to this issue.