I really don't understand the downvotes, this was a sincere question. Please note, the OP states:

>"Until the 1990s, Grand Central Station in New York had almost everything - 60Hz commercial power, 40Hz LIRR power (Pennsylvania Railroad standard) 25Hz NYC Subway power, 700VDC Metro North power, 600VDC subway third rail power, and some old Edison 100VDC power."

and then subsequently states:

."In the 1990s, Grand Central was rewired, and everything except railroad traction power was converted to 60Hz."

I am asking because I am trying to make sense of the entire comment. They also mention 4 or 5 other electrical frequencies and voltages, so there's a lot packed into that comment. I am genuinely interested in the comment and trying to learn something.