25 Hz power stated as challenge to opening NYP tunnels

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25 Hz power stated as challenge to opening NYP tunnels

  • Today's announcement from Amtrak of the Friday opening of all NYP tunnels, they state that the use of 25 Hz power is limiting capacity because the power needs to travel an excessively long distance in order to bypass the out-of-service Kearny substation.

    Since all trains can use 60 Hz current, and Kearny is severely damaged, would it not be advantageous to replace this equipment with 60 Hz current to allow more opportunities for local power supplies? Or does it cost less to generate and transmit 25 Hz power from Safe Harbor dam?

    More: http://www.amtrak.com/ccurl/10/874/Amtrak-to-Re-open-Three-NYC-Tunnels-ATK-12-104.pdf

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  • aegrotatio
    Today's announcement from Amtrak of the Friday opening of all NYP tunnels, they state that the use of 25 Hz power is limiting capacity because the power needs to travel an excessively long distance in order to bypass the out-of-service Kearny substation.

    Since all trains can use 60 Hz current, and Kearny is severely damaged, would it not be advantageous to replace this equipment with 60 Hz current to allow more opportunities for local power supplies? Or does it cost less to generate and transmit 25 Hz power from Safe Harbor dam?

    More: http://www.amtrak.com/ccurl/10/874/Amtrak-to-Re-open-Three-NYC-Tunnels-ATK-12-104.pdf

     

    The motors can use 12.0 kv 25 Hz, 25 kv 60 Hz,  and 12.5 kv 60 Hz interchangably either automatically when  coasting thru a phase break area (usually about 100 ft in case both pans on a motor are extended ) or by the engineer turning a rotary switch to switch what the power the loco is receiving.. However the NJ TRANSIT EMUs  with a few exceptions cannot switch frequencies on the fly without the operator going on the ground and manually switching frequencies &/or voltages.  (some NJT CAT is 25 kv 60 hz   So the EMUs from Trenton may not be able to take an on the fly change from 25 Hz to 60 Hz even though the voltage is  ~~  the same .. 

    The real problem is all the land based equipment that uses the 25 Hz.  this formist does not know what station mechanicals are off the 25 Hz yet.  we do know that signal power uses frequency multipliers to convert the 25 Hz to 100 Hz signal power every 15 - 25 miles. there is an AMTRAK project to eventually have back up signal power at each signal location provided by a frequency converter that will use comercial 60 Hz 110. / 220v to provide 100 Hz power to  each signal bungalow. as far as known that project is not complete.  

    Wha t would help is a conversion  to 12.5 from of the line from south of the NJT Morrisville yard to NYP BUT that will be a long term project.

  • Safe Harbor  is a whole another question.  It actually generates both 25 Hz single phase and 60 Hz 3 phase commercial power current. I believe that there is a priority for the RR 25 Hz. Imagine that the 25 Hz is similar to the power going into your home transmitted as 69 Kv each leg to ground and 138 Kv leg to leg. That is steped down to 12 Kv CAT power  using auto transformers . If  you look at the transmission lines of AMTRAK you will notice that the25 Hz power lines are in multiples of 2 - 4 - 6. PRR did sell an easement to a commercial power line that is 3 phase 60 Hz above the 25 Hz. Sometime in the past the primary voltage was raised from 132 Kv to 138 Kv  and with out changing any transformers the CAT voltage went from 11.5 Kv to 12 Kv nominal voltages.

  • Yes and Amtrak retains ownership of an abandoned rail line just to keep the transmission lines in service, and I think that's the one that originates at Safe Harbor. My understanding is that they are renovating this line, too.

    Another detail that I didn't mention that Blue Streak did is the 100 Hz signalling system. Evidently its clock is timed so it fits into the multiples of 25 Hz. There is another thread here that describes it in deep detail, too.

    I guess it's not as easy as it looks. They want to restore service as soon as possible, too.

  • I get the impression Amtrak would like to upgrade the entire system to 60 Hz to avoid future problems like this emergency compatibility, but (according to another railfan forum) SEPTA is the final holdout.

  • MidlandMike

    I get the impression Amtrak would like to upgrade the entire system to 60 Hz to avoid future problems like this emergency compatibility, but (according to another railfan forum) SEPTA is the final holdout.

    SEPTA may / should not be a big problem as the silverliner - 5s are being built to work on both 25 and 60 Hz. Power is taken directly from the  -- 5s  pan to a 25 / 60 Hz transformer, output to  rectifier(s), then those output( s ) to inverters to provide the various traction motors and auxlliaries.  Although not installed there is provision for SEPTA to add an automatic center tap on the transformer for future 25 Kv CAT transitions on the NEC or Harrisburg line or for thru operation on the AMTRAK New Haven  -- Boston line or even the line south to WASH.  No other provision for dual 25 / 60 Hz equipment on the  -- 5s as the 2 frequencies are essentially the same voltage.

    Now the conditions of how the dual frequencies on silverliner  -  4s would operate are unknown to this formist. Remember the earlier silverliners have just recently been retired.

    The dual frequency has some interesting characteristics.  A transformer originally built for 25 Hz will accept 60 Hz.  However a transformer built for 60 Hz will not operate very well on 25 Hz. A 25 Hz transformer is much more heavy for the same power output than a 60 Hz transformer of the same power.  Also a 25 hZ syncnorous motor is much bigger and heavier than a 60 Hz motor of the same horsepower. That is partially the result of the maximum speed of a 2 pole 60 Hz motor is 1800 RPM where as a 25 Hz motor is 750 RPM.  These same restrictions apply to the power generators at safe harbor requiring much bigger generators for the same power output.

    If the USA had to build an electrical system from scratch today it probably would be 100 Hz + / - as the same scale ups would apply to the higher frequencies (max 3000 rpm) .  That may be why PRR signaling was made 100 Hz because they used a lot of motors originally in their signal systems.  

  • blue streak 1

    If the USA had to build an electrical system from scratch today it probably would be 100 Hz + / - as the same scale ups would apply to the higher frequencies (max 3000 rpm) .  That may be why PRR signaling was made 100 Hz because they used a lot of motors originally in their signal systems.  

    I'd disagree - 50/60 Hz seems to a better compromise between the needs of long distance transmission and circuit breker operation versus the desires for smaller, lighter motors and transformers. The circuit breaker problem may be the most significant as 100 Hz would nearly halve the time around the current zero crossing point which is important for helping to extinguish the arc. 25 Hz is even better in that regards and that was brought in articles in such diverse rags as "Electric Lines" and "IEEE Spectrum" during early 90's discussion on converting the NEC to 60 Hz.

    You are correct about 25 Hz motors and transformers being heavier than their 60 Hz counterparts.

    - Erik

    P.S. If we go to 3kVDC, we can run the traction inverters directly off the catenary voltage and thus get rid of the transformer.Mischief

    P.P.S. The earliest AC distribution systems in the US ran on 133 Hz.

  • My question is, then, that since the PRR system served so well with the ability to feed the whole system from Wilmington DE to Sunnyside Yards when needed with only a slight reduction in efficiency, stood and operated well for its entire life...lots still serving today in fact...then why does the whole system have to be thrown out and a completely new and different system have to replace it?  Ok..catenary has to change for higher speeds, but after that?

    RIDEWITHMEHENRY will plan and escort railfan rides in and around the NY Metropolitan and Philadephia areas: no mode of transportation is untouched. Guaranteed railfan fun!

  • I'm not a technical expert about the theory and practice of electric traction motors, Henry.  I do know historically they have used different kinds of electricity.  Relatively low voltage DC (600 volts) was once common and my still be used on the New York subways.  The Delaware Lackawanna and Western used 3,000 volts DC but I do not know of any other systems that used DC at that high voltage.  The New Haven  used split phase AC motors at 25,000 volts I think.  I don't know why the Pennsylvania picked 25 hertz; perhaps one one who knows the theory can explain.  

    But in the American electrical system 60 hertz is standard and you can get it pretty much any place you are.  I bet this has a lot to do with the decision.  

  • Where the 25 Hz cat supply taps into the 60 Hz grid, there is the extra step of phase conversion.  PRR used rotary converters, an electro-mechanical device.  I believe some are still working, and some have been replaced by solid state devices, but either way it could be eliminated by adopting 60 Hz cat,  Also the voltage would be doubled, which could use lighter cat.  Basically the old system is obsolete.

  • Thank you for the note about rotary converters, Mike.  What strikes me is not that 25Hz AC is obsolete today but that it was also obsolete in the 1930's when the PRR first electrified their lines.  60Hz was standard at that time.  So I wonder my the PRR used 25Hz in the first place.  

  • MidlandMike

     PRR used rotary converters, an electro-mechanical device.  I believe some are still working, and some have been replaced by solid state devices, but either way it could be eliminated by adopting 60 Hz cat,  Also the voltage would be doubled, which could use lighter cat.  Basically the old system is obsolete.

    well if the rotary converters are obsolete why is AMTRAK rebuilding the rotary converters ? You can find it on the monthly reports and the FY 2012 , 2011, 2010 budgets.  AMTRAK is adding new solid state converter devices as well. The rotaries are being rebuilt in place because they are so massive due to the low rpm they have to operate. Has to be a divisor of both 60 Hz and 25 Hz. (3600 & 1500 rpms).

    The cat voltage cannot be easily doubled to 25 Kv until the cat is rebuilt with 25 Kv insulators. south of Newark to south of Trenton is the only place as  of now that the cat is scheduled for rebuilding and will not be completed until 2017 ? as well all circuit breakers and old PRR 25Hz transformers ( PCBs) will require replacing.  It may be the rebuilding  ( if necessary ? ) of the Kearney substation that was flooded will be of the dual frequency / voltage type.  Voltage cannot be increased in NYP & its tunnels, Newark, 30th St, ( wilmington ? ) Baltimore, WASH cannot be raised at this time due to clearance increases needed for the higher voltages.  The present CAT is too close to overhead structures. most stations except NYP, 30th st, BAL can eventually increase clearances but I would expect that is 10 - 20 years in the future.  However  

     

  • John WR
    25Hz AC is obsolete today but that it was also obsolete in the 1930's when the PRR first electrified their lines.

    What development made it obsolete? Was it obsolete when PRR first used it circa 1915? Can motors like GG1s and MP54s had use 60 Hz AC?

  • timz

    John WR
    25Hz AC is obsolete today but that it was also obsolete in the 1930's when the PRR first electrified their lines.

    What development made it obsolete? Was it obsolete when PRR first used it circa 1915? Can motors like GG1s and MP54s had use 60 Hz AC?

    When mainline electrification was being developed in the early 1900s, power companies were not really able to supply the needs of this scale, so RRs generally built their own power plants.  For the early AC motors, 25 Hz was optimal, so the RRs built as such.  By the mid century, rectifiers and DC motors made the  supply cycle rate unimportant.  Modern solid state electronics make the cycle rate irrelevant.  Nevertheless, until the system is converted to 60 Hz, the old rotary converters, of substitute electronics must be maintained. 

    I had forgotten about the tunnel insulation clearance problems that would have to be resolved, as pointed out.  Rebuilding the cat for double the voltage would indeed need heavier insulators, but the wire could be lighter which allows faster speeds.  Also, while supply off the grid would be at the right Hz. it is 3 phase, and the cat would be single phase.  Some have said this would cause a phase imbalance in the grid, but others have said the problem is manageable.

  • timz

    John WR
    25Hz AC is obsolete today but that it was also obsolete in the 1930's when the PRR first electrified their lines.

    What development made it obsolete? Was it obsolete when PRR first used it circa 1915? Can motors like GG1s and MP54s had use 60 Hz AC?

    Answering Tim's question to John...

    The GG1's and MP54's used AC series (universal) motors, and were designed to run on 25 Hz. 60 Hz series motors top out at a few tens of HP, which is substantially less than the ratings for the motors used in either the GG1 or MP45.  Competing single phase AC electrification technologies in the 1930's were phase converter locomotives as used by the N&W and VGN (which operated at two fixed speeds), and motor generator locomotives as used by the GN. Neither approach was suitable for the MP54 and a motor generator "GG1" would have been heavier and much more expensive than the GG1 as built.

    Some experimental rectifier locomotives were built prior to WW1, but on-board rectifiers weren't used in quantity in the US before the early 1950's - first on an order of NH MU's and then on the VGN EL-3 (E-33's).

    My $0.02 worth,

    - Erik