Basil Jet wrote:
On 08/02/2019 15:54, Anna Noyd-Dryver wrote:
Marland wrote:

Or use twin conductors like a trolley bus.
There was a short section In Greenwich when the Royal Observatory was
still located there where stray current even from normal track would have
affected some instrumentation.
They were rare though and I don’t immediately recall another UK
installation.
Having gone to the trouble of avoiding overhead returning a few years later
and putting up twice as much would hardly be popular.

That would necessitate use of trolley poles, where pantographs are the
current standard fitment for new tramways.

No, trolley poles were needed because trolley buses wander over the
road. A tram could use dual pantographs similar to those sported by
trains using three-phase electrification.


As I said in the text which you snipped:

"I suppose you could have twin pantographs as fitted for 3-phase on certain
mountain railways, though you might get polarity issues on single track
sections, plus I suspect the OLE then needs to be aligned more accurately,
thus making it more intrusive."


Anna Noyd-Dryver