16.7Hz is not correct by the way; it is 50Hz divided by 3, so it is 16 2/3 Hz. Normal AC in Europe is 50 Hz, not 60 Hz as in the US, Canada and quite a few other places. The history of the why for the old Pennsy's 25 Hz, I don't know. Likewise, I have no idea why the ex New Haven 11.5 kV 25 Hz was converted to 12.5 kV 60 Hz and the ex Pennsy side was not. I would suspect that the New Haven side when changed was not changed to be 25 kV to match the new electrification north of New Haven due to electrical clearance issues.
16 2/3 vs 16.7 hz. From Wikipedia:
Probably boils down to cost/benefit ratio...is it "worth it" to upgrade?
I am going to guess you mean smaller voltages require larger wire sizes to carry the same power? P=VI
O Kkkkkkk. Duly noted. First time I heard this.
Constant tension catenary can actually have much longer span distances these days. Siemens Sicat SX, good for speeds up to 250 kmh (so almost all of the NEC), can have a span distance of 112 m, and the limit at this distance is wind. This was successfully deployed in Denmark, and in the UK with a 102 m span distance (good at wind speeds up to 61 mph), and in Hungary with 99 m span distances. For higher speeds, Siemens Sicat HA, good for speeds up to 350 kmh, has a span distance of 70 m. An in-between system good for ~300 kmh and ~90 m spans should be possible and would cover the whole NEC without needing to rebuild any catenary poles.
Exactly my thoughts on constant tension catenary. Maybe the concept of shorter spans was because the tension was not high enough? With higher tension the uplift from the pantograph is reduced as is lateral sway of the wire itself. For those that think in US Customary units, 300 km/hr = 186 mph, and 90 m = 295 feet. Therefore, I have not understood why the spans could not safely be longer with constant tension than with fixed catenary.
I don't recall the catenary being problematic during high winds, but I will ask around. I have experienced a cancellation once when the wires were brought down by a pantograph due to hot weather. (I got a free taxi ride from London to Harwich out of that, so not a complete disaster.
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This is where constant tension catenary shows its major advantages. You simply have to make the available travel distance for the weight sufficient for the temperature swings. My inclination if designing such would be, take the lowest known temperature in the area, use a number at least 10 degrees F lower and make that the location for the top of the travel path for your tensioning weight. Then for the highest known temperature, add solar heating plus say at least 20 degrees F higher and make that the location of the bottom of the travel path for your tensioning weight. The reason for the greater allowance on the high temperature end is that if the weight bottoms out the wire loses tension and you begin to get slack wire issues. For the low temperature, if the weight hits the top of its path you get an increase in wire tension which is likely to be of no significance. But, if you are generous with your travel limits, neither should happen.
Most of New York to Washington DC and all of Philly to Harrisburg is not constant tension. There is all of less than 30 miles of constant tension south of New York. So the most heavily used by Amtrak part of the NEC does not have constant tension.
