Solid Insulation Switchgear - 15kV

Although I don't have any direct experience, as you requested, with solid insulated switchgear, I found some info to peruse while you wait for somebody who does....

..."All live parts in the main circuit are molded with epoxy and then covered with a conductive layer connected to the earth. The complete solid insulation method will prevent a one-line earth fault, if it occurs, from developing into a between-phase short-circuit incident."...

...."The footprint is nearly 50% of that of conventional cubicle type switchgear, allowing the whole switchgear panels to be transported. Technologies to achieve high reliability and labor-saving will reduce the frequency of regular inspections that requires the shut-down of the main circuit down to once every six months ."...

https://www.meidensha.com/products/energy/prod_01/prod_01_04/prod_01_04_01/index.html

I have specified & installed with contract electricians 15kV switchgear since about 1974, many lineups, GE and Westinghouse, some Allis-Chalmers, and seen many more, all between 500 and 1000MVA interrupting rating. These all have solid insulation systems which were trouble free for decades. 15kV seems awful low for a gas insulated system, I always assumed the complexity & cost would only make sense at 69kV and up, unless you had a serious space problem. These breakers, air magnetic, may have a softer interruption than vacuum breakers, but the application of surge arresters necessary to protect load equipment would always be required, so there was no consideration necessary for the switchgear insulation. So not sure what would drive an engineer to specify a GIS at 15kV level? I think 15kV switchgear insulation was typically rated 95kV BIL.

Thanks for the replies, we do a lot of IEC spec SF6 MV switches as they are very compact units. When space allows we also do ANSI metalclad air insulated gears with air magnetic CB´s.

We are concerned of the service life for the 15kV class SIS switchgears.

Thanks for the links to the writeups, I had read them prior to posting and found them very informative.

Is the insulation system different than earlier designs from 40+ years ago? Typical installation included air conditioned room with filtered air makeup, positive pressure room, and in extreme cases, charcoal filtered air systems.