Not being an electrical person, I have to find my way in the dark, so to
speak (pardon the pun), but I'm curious about the power supply issue that's
said to place limits on Melbourne's tram operation.

I can mainly only draw comparisons with the system I know best in intricate
detail, Prague, and between the two I have some comparative figures that
are not telling me much and perhaps somebody can provide a little more
detail.

From the various sources I've consulted, including YT, Melbourne has some
60 substations (output not known) and a fleet of 500 trams of various sizes
(thus tonnages) from 30 metres down to 15 metres. YT states that a W class
requires about 500 amps of power and an E class about 1,500 amps.

Prague has 41 substations (smaller system area I guess), with a combined
output of over 200MW, and the system does about twice the work of
Melbourne's. There is a fleet of about 800 regular service trams (plus
museum and service stock), but since the older 15 metre cars almost
entirely run in coupled sets, that could be regarded as a fleet of about
570 30 metre passenger trams or consists. Both systems are 600 volts DC and
both use regeneration. I don't know if there are any other issues I should
cover.

Does anybody know the total output of Melbourne's substations and what is
the issue that leads to the calls to build more substations, or,
alternatively, the decision to fit batteries to the G class to help with
power peaks?

Tony P