Phase reversal would but it would be a slow meter reader who didn’t notice the disk turning the wrong way to say nothing of accounting wondering why they owed SEPTA $50,000 this month!
Bill
Railroad Forums
Corridor Electric Power Generation and Distribution
- Discussion related to Amtrak also known as the National Railroad Passenger Corp.
Moderators: GirlOnTheTrain, mtuandrew, Tadman
by Bill West
Regarding the Jamesburg Branch, it had single 132kv circuits from Monmouth and South Amboy supplying Helmetta sub. Monmouth of course had the full 4 circuit mainline and SA was supplied by two circuits from Rahway. So although the branch's lines are still there they don't have a role anymore.
Bill
Bill
by PRRTechFan
The 132kV feeders from SA heading down the Jamesburg Branch are severed. They cross over the Garden State Parkway just south of the Raritan River Bridge, which is only a mile or two from the sub at SA. The lines over the Parkway were cut some time ago...
...The photographs of the 30th Street Load Dispatch and Power Director's boards that Bill West provided links to show this line out of service and grounded, if you download the correct high-resolution image and zoom in... What is even more interesting about these images (taken in 1997?) is that in many cases, you can still see abandoned feeders and substations and still read many of the names and designations that have been "painted over" after they have been abandoned. FYI, some of those pictures also show details of the 100Hz signal power distribution, including the M-G sets that sourced the 100Hz power.
One of my frequent tasks as an electrical engineer is to redraw or correct one-line diagrams of electrical facilities; many times we have to go in and physically survey substations and feeders in order to create the one-line. I have begun to create a one-line diagram from the 1997 photographs. It will be a "spare-time as available" project, and I will try to include as much of original but now out of service feeders and equipment as I can discern from the photos. When I have gone as far as I can, I will post a "pdf" file for comments, additions and corrections.
...The photographs of the 30th Street Load Dispatch and Power Director's boards that Bill West provided links to show this line out of service and grounded, if you download the correct high-resolution image and zoom in... What is even more interesting about these images (taken in 1997?) is that in many cases, you can still see abandoned feeders and substations and still read many of the names and designations that have been "painted over" after they have been abandoned. FYI, some of those pictures also show details of the 100Hz signal power distribution, including the M-G sets that sourced the 100Hz power.
One of my frequent tasks as an electrical engineer is to redraw or correct one-line diagrams of electrical facilities; many times we have to go in and physically survey substations and feeders in order to create the one-line. I have begun to create a one-line diagram from the 1997 photographs. It will be a "spare-time as available" project, and I will try to include as much of original but now out of service feeders and equipment as I can discern from the photos. When I have gone as far as I can, I will post a "pdf" file for comments, additions and corrections.
by Ken W2KB
Bill West wrote:Phase reversal would but it would be a slow meter reader who didn’t notice the disk turning the wrong way to say nothing of accounting wondering why they owed SEPTA $50,000 this month!I handled a theft of service case about 15 years ago when a meter reader found a meter that was plugged in upside down in the meter pan socket so it would run backwards. The meter reading schedule had been revised unbeknownst to the customer. We calculated that the customer had it inverted on week out of a month so the bill was approximately halved.
Bill
Even a sleepy meter reader couldn't miss that one!
~Ken :: Fairmont ex-UP/MP C436 MT-14M1 ::
Black River Railroad Historical Trust :: [/url]
Black River Railroad Historical Trust :: [/url]
by Ken W2KB
PRRTechFan wrote:The 132kV feeders from SA heading down the Jamesburg Branch are severed. They cross over the Garden State Parkway just south of the Raritan River Bridge, which is only a mile or two from the sub at SA. The lines over the Parkway were cut some time ago...My vague recollection is that the Jamesburg lines were de-energized after a trespasser contact incident.
...The photographs of the 30th Street Load Dispatch and Power Director's boards that Bill West provided links to show this line out of service and grounded, if you download the correct high-resolution image and zoom in... What is even more interesting about these images (taken in 1997?) is that in many cases, you can still see abandoned feeders and substations and still read many of the names and designations that have been "painted over" after they have been abandoned. FYI, some of those pictures also show details of the 100Hz signal power distribution, including the M-G sets that sourced the 100Hz power.
One of my frequent tasks as an electrical engineer is to redraw or correct one-line diagrams of electrical facilities; many times we have to go in and physically survey substations and feeders in order to create the one-line. I have begun to create a one-line diagram from the 1997 photographs. It will be a "spare-time as available" project, and I will try to include as much of original but now out of service feeders and equipment as I can discern from the photos. When I have gone as far as I can, I will post a "pdf" file for comments, additions and corrections.
The one-line drawings will be interesting to see.
~Ken :: Fairmont ex-UP/MP C436 MT-14M1 ::
Black River Railroad Historical Trust :: [/url]
Black River Railroad Historical Trust :: [/url]
by Jersey_Mike
I posted Mr. West's captioned images on the PAOLI power board and Philly power dispatch center at:
http://acm.jhu.edu/~sthurmovik/Railpics ... oliLOC.jpg
http://acm.jhu.edu/~sthurmovik/Railpics ... PwrBd2.jpg
http://acm.jhu.edu/~sthurmovik/Railpics ... oliLOC.jpg
http://acm.jhu.edu/~sthurmovik/Railpics ... PwrBd2.jpg
by farecard
I'm in a discussion in another forum re: the eventual NE Corridor move from 11KV/25Hz to 25KV/60Hz.
In the course of that the detail emerged that the 25KV is deployed as center-tapped 50KV, with periodic autotransformers.
This is called "2x25KV" I'm told. I was given these links:
http://indianrailways.gov.in/financecod ... 1_data.htm
http://www.iit.upcomillas.es/docs/03EPF02.pdf
http://www.iit.upcomillas.es/docs/00EPF01.pdf
It looks like this:
Feed xfmr
A
O|o-----cat
O|o
O|o
O|o
O|o-----Rail/return
O|o
O|o
O|o
O|------Feeder
B
Where A & B are connections to a primary feed, say 132Kv.
The secondary is 25-0-25.
Then you have autotransformers distributed every few miles:
|o-----cat
|o
|o
|o
|o-----Rail/return
|o
|o
|o
|------Feeder
The claim is that the scheme reduces the sag and cuts the I^2R loss 75% in the network. I'm trying to wrap my head around that, and not there. I'm contrasting the I^2R drop to that of just paralleling the same size feeder and cat, and running on ordinary single-ended 25KV.
The other cited reason for 2x25 was since the current is ~equal in each leg, and opposite; the parallel cables will cancel out a lot of EMI.
I looked back in this group but didn't see any discussion of 2x25 systems. Is anyone here familiar with them?
In the course of that the detail emerged that the 25KV is deployed as center-tapped 50KV, with periodic autotransformers.
This is called "2x25KV" I'm told. I was given these links:
http://indianrailways.gov.in/financecod ... 1_data.htm
http://www.iit.upcomillas.es/docs/03EPF02.pdf
http://www.iit.upcomillas.es/docs/00EPF01.pdf
It looks like this:
Feed xfmr
A
O|o-----cat
O|o
O|o
O|o
O|o-----Rail/return
O|o
O|o
O|o
O|------Feeder
B
Where A & B are connections to a primary feed, say 132Kv.
The secondary is 25-0-25.
Then you have autotransformers distributed every few miles:
|o-----cat
|o
|o
|o
|o-----Rail/return
|o
|o
|o
|------Feeder
The claim is that the scheme reduces the sag and cuts the I^2R loss 75% in the network. I'm trying to wrap my head around that, and not there. I'm contrasting the I^2R drop to that of just paralleling the same size feeder and cat, and running on ordinary single-ended 25KV.
The other cited reason for 2x25 was since the current is ~equal in each leg, and opposite; the parallel cables will cancel out a lot of EMI.
I looked back in this group but didn't see any discussion of 2x25 systems. Is anyone here familiar with them?
by David Benton
Fare Card , the same system is used in NZ . i have taken 20 years to fiqure out how the 50kv becomes 25 kv , and still dont completely comprehend it ! i have a booklet on it that i could scan , and post .
The answer to the 75% part is in the equation IR2 . power = current * resistance SQUARED . this means if the current is doubled , or the resistance is doubled , then the power used goes up by 4 times . in this case it is the power loss , because the voltage is doubled , the current is halved , so the power loss in the 50 kv goes down by 200% , however you then have the 25 kv section the train is occupying , depending on where the train is in the section in relation to the auto transformer feed , it may be 100% loss , or 10 % loss in that section , so i would say the 75% is an averaging out .
sorry i dont think ive made that very clear at all . but the answer is to do with the squared part of the IR2 formula .
The answer to the 75% part is in the equation IR2 . power = current * resistance SQUARED . this means if the current is doubled , or the resistance is doubled , then the power used goes up by 4 times . in this case it is the power loss , because the voltage is doubled , the current is halved , so the power loss in the 50 kv goes down by 200% , however you then have the 25 kv section the train is occupying , depending on where the train is in the section in relation to the auto transformer feed , it may be 100% loss , or 10 % loss in that section , so i would say the 75% is an averaging out .
sorry i dont think ive made that very clear at all . but the answer is to do with the squared part of the IR2 formula .
Moderator worldwide railfan , Rail travel & trip reports
The only train trips I regret are the ones I didn't take.
The only train trips I regret are the ones I didn't take.
by farecard
>but the answer is to do with the squared part of the IR2 formula
Oh, that's obvious.. What's not is the how.
The 2x25 has two size n conductors of equal length, each carrying half the needed current. Their voltage drop will be the same. So the drop is (0.5I^2)*R.
If you just parallel the same two conductors in a single-ended 25Kv system, you have again half the needed current in each [assuming perfect balance...] and each has the same (0.5I^2)*R drop, as far as I can see.
So I assume I'm missing something in my mental model.
I asked about an unbalanced design: make the feeder 75KV, the cat still 25, and the autoformers with a 25% tap, not a center tap. THAT would cut the current in the feeder significantly. But the reply was to the effect that adjacent structures suffered from the unbalanced current. I infer that refers to induced, not ground return, but I'm not sure.
That makes me think the real win of the 2x25 is external issues, not I^2R loss, but maybe another EE will weigh in and enlighten me.
BTW, there's an irony here. RR RoW was/is popular for buried utilities, including telco/data, and in some places, pipelines. This was tempered by the fact that railroads and petro pipelines were always enemies; the railroads thinking all that product should go by tanker on their trackage. [Fat chance....but].
I can't imagine how you could keep either pipe or buried conductors intact around the NE corridor, given the ground return currents. But for fiber, no problem.
Oh, that's obvious.. What's not is the how.
The 2x25 has two size n conductors of equal length, each carrying half the needed current. Their voltage drop will be the same. So the drop is (0.5I^2)*R.
If you just parallel the same two conductors in a single-ended 25Kv system, you have again half the needed current in each [assuming perfect balance...] and each has the same (0.5I^2)*R drop, as far as I can see.
So I assume I'm missing something in my mental model.
I asked about an unbalanced design: make the feeder 75KV, the cat still 25, and the autoformers with a 25% tap, not a center tap. THAT would cut the current in the feeder significantly. But the reply was to the effect that adjacent structures suffered from the unbalanced current. I infer that refers to induced, not ground return, but I'm not sure.
That makes me think the real win of the 2x25 is external issues, not I^2R loss, but maybe another EE will weigh in and enlighten me.
BTW, there's an irony here. RR RoW was/is popular for buried utilities, including telco/data, and in some places, pipelines. This was tempered by the fact that railroads and petro pipelines were always enemies; the railroads thinking all that product should go by tanker on their trackage. [Fat chance....but].
I can't imagine how you could keep either pipe or buried conductors intact around the NE corridor, given the ground return currents. But for fiber, no problem.
by JimBoylan
PRRTechFan wrote:The 132kV feeders from SA heading down the Jamesburg Branch are severed. They cross over the Garden State Parkway just south of the Raritan River Bridge, which is only a mile or two from the sub at SA. The lines over the Parkway were cut some time ago...The broken feeder wires just SouthEast of the New Jersey Turnpike were spliced (with U bolts?) in early 2009, then almost immediately broke 1 or 2 poles more to the East.
by David Benton
ok , then im sure it is to do with the lenght of the section of 25kv , and 75 % is an average fiqure .
here the sections are quite long , where there is an auto transformer to whereever the locomotive in the section will govern the overall power loss or efficency . if the locomotive has just entered the section , then it is pretty much 50 kv all the way to the locomotive and the efficeny gain over a straight 25 kv system would be close to 200 % . but if the locomotive is near the end of the section , then it may have a similiar distance of 25 kv between it and the auto transformer , to the distance between the auto transformer and the supply substation which is at 50 kv . then efficency gain would be less than 100% , and is where the 75% fiqure comes from as an average .
without knowing the relative distances , it is hard to fiqure it out mathematically .
here the sections are quite long , where there is an auto transformer to whereever the locomotive in the section will govern the overall power loss or efficency . if the locomotive has just entered the section , then it is pretty much 50 kv all the way to the locomotive and the efficeny gain over a straight 25 kv system would be close to 200 % . but if the locomotive is near the end of the section , then it may have a similiar distance of 25 kv between it and the auto transformer , to the distance between the auto transformer and the supply substation which is at 50 kv . then efficency gain would be less than 100% , and is where the 75% fiqure comes from as an average .
without knowing the relative distances , it is hard to fiqure it out mathematically .
Moderator worldwide railfan , Rail travel & trip reports
The only train trips I regret are the ones I didn't take.
The only train trips I regret are the ones I didn't take.
by electricron
Some basic electric math involved, and points to remember. You got to recognize that there was a history of changes/modifications to the old PRR NE corridor.....
The 25Hz system was originally built by the Pennsylvania Railroad with a nominal voltage of 11.0 kV. The nominal operating voltages were later raised and are now:
Catenary (Traction) Voltage : 12.0 kV
Transmission Voltage: 138 kV
Transmission Lines
All transmission lines within the 25Hz system are two wire, single-phase, 138kV. The center tap of each 138kV/12kV transformer is connected to ground, thus the two transmission lines are tied to +- 69kV with respect to ground and 138kV relative to each other.
Transmission Voltage
<--------------------138kV------------------->
<--69kV-->ground (center-tap)<--69kV-->
|TRANSFORMER|
Traction Voltage
<--12kV-->
Generally two separate two-wire circuits travel along the rail line between substations. One circuit is mounted at the top of the catenary poles on one side of the track; the second circuit runs along the other side.
The arrangement of catenary supports and transmission wires gives the overhead structure along former Pennsylvania Railroad lines its characteristic 'H' shaped structure. As the system has lines operating at very high voltages, they are also much taller than the overhead electrification structures on other electrified American railroads.
Common commutating electric motors can also be fed AC (universal motor), because reversing current in both stator and rotor does not change the direction of torque. However, inductance of the windings makes large motors impractical at standard AC distribution frequencies. Five European countries, including Germany, Austria, Switzerland, Norway and Sweden have standardized on 15kV 16⅔ Hz (one-third the normal mains frequency) single-phase AC. In the United States (with its 60 Hz distribution system), 25 Hz (an older, now-obsolete standard mains frequency) is used at 12kV between Washington, DC and New York City and between Harrisburg, Pennsylvania and Philadelphia. A 12.5kV 25 Hz section between New York City and New Haven, Connecticut was converted to 60 Hz in the last third of the 20th century.
So, why did PRR choose to use 25 Hz vs 60 Hz power? Their existing electric locomotives had DC Universal motors, and therefore had commutating rotors with huge windings. Additionally, Universal motors can be powered with DC or AC. To minimize inductance losses (XL) with the old electirc locomotives, they used 25 Hz AC (XL=2ttFL). New AC locomotives today use the much lighter induction motors, because they use can rotors without heavy windings. That's why new traction systems can use 60 Hz.
Back in the 1930s the plastics industry was new. Wire insulation for using higher voltages wasn't available, most high voltage systems required using oil for insulation. It was much cheaper to use 12kV for the locomotives. The higher voltages for transmission solved the distance problems.......
So, why do modern traction systems use higher voltages and higher Hz? I think I've already answered this earlier, but to keep it simple, here it is again. Higher frequencies can be used with induction motors because they have lightweight (relatively) can rotors. Higher voltages can be used because the plastic industry has matured over the last 80 years and standard motors are built for higher voltages today.
So, what would be the advantages for Amtrak to modernize the old PRR traction systems to 25kV and 60 Hz since all the old 1930 era locomotives have been retired long ago? A doubling of the traction voltage would cause the halving of the traction current to each locomotive. (P=IE; since P <->, ^ E means I v)
(P=I^2R; since R <->, I v means power losses due to heat v by a factor of 4)
So, why did PRR use single phase AC power vs three phase? Most three phase AC motors are almost twice as efficient as single phase. But Universal motors don't need three phases, they work on single phase. Therefore, the single phase motor only requires one catenary wire, making it very simple to use a single pantograph disc. Three phase traction power would have required three catenary wires and three pantograph discs, either on one pole or three. Again, it's much cheaper having just one!
Since modern induction motors require three phase AC to work internally, how do they make three phase AC from single phase AC? First, the single phase AC is rectified to DC, which is them inverted into three phase AC, which is then applied to the AC traction motor. Additionally, traction motors can be DC too.
I hope that answers all the questions....
The 25Hz system was originally built by the Pennsylvania Railroad with a nominal voltage of 11.0 kV. The nominal operating voltages were later raised and are now:
Catenary (Traction) Voltage : 12.0 kV
Transmission Voltage: 138 kV
Transmission Lines
All transmission lines within the 25Hz system are two wire, single-phase, 138kV. The center tap of each 138kV/12kV transformer is connected to ground, thus the two transmission lines are tied to +- 69kV with respect to ground and 138kV relative to each other.
Transmission Voltage
<--------------------138kV------------------->
<--69kV-->ground (center-tap)<--69kV-->
|TRANSFORMER|
Traction Voltage
<--12kV-->
Generally two separate two-wire circuits travel along the rail line between substations. One circuit is mounted at the top of the catenary poles on one side of the track; the second circuit runs along the other side.
The arrangement of catenary supports and transmission wires gives the overhead structure along former Pennsylvania Railroad lines its characteristic 'H' shaped structure. As the system has lines operating at very high voltages, they are also much taller than the overhead electrification structures on other electrified American railroads.
Common commutating electric motors can also be fed AC (universal motor), because reversing current in both stator and rotor does not change the direction of torque. However, inductance of the windings makes large motors impractical at standard AC distribution frequencies. Five European countries, including Germany, Austria, Switzerland, Norway and Sweden have standardized on 15kV 16⅔ Hz (one-third the normal mains frequency) single-phase AC. In the United States (with its 60 Hz distribution system), 25 Hz (an older, now-obsolete standard mains frequency) is used at 12kV between Washington, DC and New York City and between Harrisburg, Pennsylvania and Philadelphia. A 12.5kV 25 Hz section between New York City and New Haven, Connecticut was converted to 60 Hz in the last third of the 20th century.
So, why did PRR choose to use 25 Hz vs 60 Hz power? Their existing electric locomotives had DC Universal motors, and therefore had commutating rotors with huge windings. Additionally, Universal motors can be powered with DC or AC. To minimize inductance losses (XL) with the old electirc locomotives, they used 25 Hz AC (XL=2ttFL). New AC locomotives today use the much lighter induction motors, because they use can rotors without heavy windings. That's why new traction systems can use 60 Hz.
Back in the 1930s the plastics industry was new. Wire insulation for using higher voltages wasn't available, most high voltage systems required using oil for insulation. It was much cheaper to use 12kV for the locomotives. The higher voltages for transmission solved the distance problems.......
So, why do modern traction systems use higher voltages and higher Hz? I think I've already answered this earlier, but to keep it simple, here it is again. Higher frequencies can be used with induction motors because they have lightweight (relatively) can rotors. Higher voltages can be used because the plastic industry has matured over the last 80 years and standard motors are built for higher voltages today.
So, what would be the advantages for Amtrak to modernize the old PRR traction systems to 25kV and 60 Hz since all the old 1930 era locomotives have been retired long ago? A doubling of the traction voltage would cause the halving of the traction current to each locomotive. (P=IE; since P <->, ^ E means I v)
(P=I^2R; since R <->, I v means power losses due to heat v by a factor of 4)
So, why did PRR use single phase AC power vs three phase? Most three phase AC motors are almost twice as efficient as single phase. But Universal motors don't need three phases, they work on single phase. Therefore, the single phase motor only requires one catenary wire, making it very simple to use a single pantograph disc. Three phase traction power would have required three catenary wires and three pantograph discs, either on one pole or three. Again, it's much cheaper having just one!
Since modern induction motors require three phase AC to work internally, how do they make three phase AC from single phase AC? First, the single phase AC is rectified to DC, which is them inverted into three phase AC, which is then applied to the AC traction motor. Additionally, traction motors can be DC too.
I hope that answers all the questions....
Last edited by electricron on Mon Dec 07, 2009 9:15 pm, edited 3 times in total.
by farecard
electricron wrote:Some basic electric math involved, and points to remember.
Per Wikipedia, the ex-PRR sections of the NE corridor have this electric feed.
The 25Hz system was originally built by the Pennsylvania Railroad with a nominal voltage of 11.0 kV. The nominal operating voltages were later raised and are now:
Catenary (Traction) Voltage : 12.0 kV
Transmission Voltage: 138 kV
Transmission Lines
All transmission lines within the 25Hz system are two wire, single-phase, 138kV. The center tap of each 138kV/12kV transformer is connected to ground, thus the two transmission lines are tied to +- 69kV with respect to ground and 138kV relative to each other.
Transmission Voltage
<--------------------138kV------------------->
<--69kV-->ground (center-tap)<--69kV-->
|TRANSFORMER|
Traction Voltage
<--12kV-->
The above is talking a) about 25Hz sections. b) about the primary side, not the secondary.
My interest is in the 2x25Kv sections that replace 25 Hz with 60 Hz at higher voltage.