Why PT's?

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Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

Here's a question I've always wondered about.  As I understand it,
potential transformers are devices designed to step down a 14.4kV or
whatever transmission line to a more manageable 120V signal that can be
more easily read by the utility companies, so they can see what's
happening on their HV lines.  Basically a step-down transformer with a
precise turns ratio and a minimal power handling capability, but happily
enough so that it's useful in "our" application.

These are big, heavy devices.  I would think that a solid state
optically isolated equivalent could be easily produced.  Why are these
dinosaurs still used by the utility companies?  And why a 120V output?
I'm grateful that these devices work so well for our application but...

Gary Lau
MA, USA