Good company for electronic soft starter.

For 11kV, it would be Solcon. Pretty much most of the ones you will find are made by one of 3 manufacturers;

Solcon is the most predominant because of their world-wide presence. Besides having their own sales and support offices all over the world, Solcon makes them for Siemens and most of the rest of the smaller suppliers you will find on web searches. But be wary of Chinese knock off versions. If they look like Solcon but say they are made in China, they are probably illegal copies and not as good.

Motortronics, who brand labels them for ABB, GE, Toshiba, Schneider, Saftronics / Emerson, Emotron and Elletronica Santerno. There is also a Chinese copy of the Motortronics product out there as well.

Benshaw, who brand labels to Teco and a few other small mfrs in India, South Africa and Australia.

Allen Bradley, Aucom and Eaton / Cutler Hammer (who each brand label to nobody else) do make MV soft starters but do not make 11kV versions as far as I know. A-B might by now, but you would be a guinea pig for them if they do, because they will have virtually no experience. I heard a couple of years ago that Aucom was developing one, but again, if they succeeded they would not have much experience yet.

Of all of the above, I think Solcon has the best product and the most experience right now. Motortronics and Benshaw are focussed on the US market (expect through their brand label deals) but are struggling to survive this economic situation and may end up getting bought out. Support for their products outside of North America is through one of the brand label deals (i.e. ABB, Schneider or Toshiba) who tend to not be very responsive because it is not really their product. Most of them have cut staff and rely upon Motortronics or Benshaw to fly technicians out of the US to take care of problems, and the resulting down time can end up being expensive.