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| Re: LIRR: Third rail vs. catenary (335342) | |||
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Re: LIRR: Third rail vs. catenary |
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Posted by WillD on Tue Nov 7 16:13:40 2006, in response to Re: LIRR: Third rail vs. catenary, posted by RonInBayside on Mon Nov 6 18:55:23 2006. Come on Ron, find a friggin physics book. You're comparing apples and oranges, or rather light rail and heavy rail systems, to develop an incoherent, pointless argument. The latter three examples you cite are all light rail lines with power needs low enough that the higher current required by a low voltage DC system is not a significant impediment. However, if you try to run a heavy rail car developing somewhere between 800 and 1200hp off a narrow wire with a high current and low voltage you'll probably turn that wire into the basic equivilant of a toaster heating element.Philadelphia 30th St Station has plenty of room under it to accomodate high voltage AC catenary with plenty of room to spare, and as you should know, accounts for just two blocks of 'tunnelling'. Thus the higher cost of providing clearances for catenary were minimal especially when compared to the massive costs of building substations every mile from NYC to Washington DC. And that, despite your many attempts at creating straw men is the crux of the issue with respect to the LIRR's power infrastructure. The only advantage a third rail installation holds is in low clearance areas, while it is severely hampered by long distances and high power demands, which is exactly the problem with electrifying the eastern end of Suffolk county. The Philadelphia and Western was incorporated in 1902 and didn't begin operating until 1907. At that time the only AC system was the New Haven's experiment with 11.5kv catenary. As I said elsewhere the Miami Metro system was built as a copy of the Baltimore subway system. By the 1980s our quite conservative transit doctrine had the idea of subways using third rail firmly ingrained. Look at all the trouble BART went through to to keep third rail, when a 3000vdc catenary installation probably would have been much better. So ground losses are independent of underground right? If you do not understand ground losses you need to stop participating in this discussion. You can whine about how I "don't have experience", but at least I have a technical basis in this discussion. Ground losses have ABSOLUTELY nothing to do with a conductor being above or below ground. Ground losses are the loss of power transmitted over a condutor to the neutral return. This is why third rail is preferable for a close clearance area, low voltage DC power is less capable of jumping from the conductor to the nearest non-insulated point than high voltage AC power. It also just happen to be why high voltage AC catenary needs to be suspended high in the air and heavily insulated from the grounded supports. |
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