Can someone explain why most PRR catenary towers were so tall? I am assuming that the wires at the top were high powered transmission lines, but was it really necessary to put them that far above the catenary wires?
John
IIRC, electrical designers want a 10’ radius around a 69kV line to prevent arcing
Have you seen pictures of the ex-Reading commuter lines in and out of Philadephia? They have BIG and TALL transmission towers; they look much more like modern high-tension line towers out in the country than a squarish cat. tower.
It is practice right down to your local telephone pole that the highest voltage line goes at the top and progress downward. the reason is if it was the other way and your phone line or cable line broke it could fall on the high voltage line and zap you or the wiring in your house when it came in contact with the lower voltage stuff. Not to say it couldn’t happen the other way a round but it does offer a degree a safety
PRR High Tension Transmission was at 132kv @ 18’ radius from Other High tensions wires
Height does vary… because of high way overpasses and airplane rights of way … ex BWI lancaster airport, Newark airport
There’s a rather famous - or at least often-reproduced - diagram of the PRR catenary installation that is basically a photo of it looking down the track towards a pair of towers, with all of the components labeled. One version can be found in the Winter 2007 edition of The Railway & Locomotive Historical Society’s NEWSLETTER (Vol. 27, No. 1), the article on “Railroad Standardization: The Special Problem of Electrification” by William D. Middleton, pgs. 5- 10, at the top of pg. 9, an HTML version of which can be found on-line at:
http://rlhs.org/rlhsnews/htms/nl27-1.htm
The high-tension lines are indeed labeled as “132,000 Volt Transmission” per the post above, and with just “eyeball” scaling (based on the track centers), the distance from those wires down to the catenary certainly seems to be in the 18 ft. range as suggested above.
I’m also familiar with the Reading Railroad lines and the catenary towers along them. They’re especially large in the Manayunk / “Connelly Curve” / Flat Rock Tunnel area on the west side of the Schuylkill Expressway (now I-76 there), where multiple main line tracks run between some of the towers’ legs. I believe those towers were called an “overbuild” because oddly enough, those tracks were never electrified - they’ve always been freight-only - the Reading’s electrification was strictly for the commuter routes only. Some day when I’m down there with seom spare time, I’ll try to get a few photos - without getting run over !
- Paul North.