Q: How much "power" in overhead catenary systems?

i wonder what the power factor (efficiency) of the electric motors on the GG1's were? We need to know that to accurately calculate how much 'juice' or amps they would use at 11kVolts.

Assume a 0.8 power factor for the motors I calculate 720 amps of 11kV to make 8500 hp.  

@Steims posted:

Assume a 0.8 power factor for the motors I calculate 720 amps of 11kV to make 8500 hp.  

This is just me spitballing here, but I would think there is a practical limit on the pantograph contact point to the wire. One major reason for going high voltage is to reduce the current- it both reduces transmission losses- but more so in this case more power can cross the limited contact patch between the round wire and the actual sliding contact point.

Hey look- some relevant info on that from a manufacturer of the pantographs https://www.mersen.com/sites/d...e-mersen-en-1601.pdf

Looks like there is a range of 6-22 Amps per mm of contact length.

There is also a tradeoff- a pantograph as it gets wider and heavier is bad for system performance.

Another in depth document from DOT https://railroads.dot.gov/site...GLE%20AND%20DUAL.PDF

@Homey B posted:

Looking through my models, I have three different engines that use Catenary power.  The PRR GG-1, of course, but also the NH EP-5 and the VGN EL-C.  They all use the same 11kVA@25Hz to power them.  And they all called the East Coast home, but that's just because most (if not all) of the heavily electrified railroads were there.  And still are!

So, I wondered just how much "oomph" could be found in the wires.  According to Wikipedia, the GG-1 could do 4620 horsepower pull, with a peak of 8500hp.  Could you put three GG-1s together and have them pulling at 8500hp without tripping the breaker at the local power distribution center?  The loads we see today (either the Metro North M-7 commuter cars, the Acela or even the NJT engines across the Hudson)  certainly can't pull down as much as juice as those older monsters could.

So, if I wanted to (figuratively speaking) pull England closer to the US using only GG-1 power, how many could I get on-line before we black out the system?

I have operated 3 GG-1s all in service pantographs up. There was always more than enough juice in the overhead. During the rush hour you could have 4 to 6 trains all leaving Penn Station again drawing from the overhead. The power desk could switch power around and in high demand push as much as required. There was plenty of redundancy build in to the system.

It doesn't seem as though the pantograph contact area is really the issue, because the GG-1s obviously were designed to draw enough power through the their own separate contacts to allow them to generate maximum horsepower. In the case of operating three GG-1s together, each would be drawing the necessary power from its own separate pantograph, so there would not be any issue of overloading a contact. The limiting factor would be how much juice the power desk could provide to the overhead, as ThatGuy pointed out.

I am not an electrical engineer, but here is a rough power calculation derived from the basic formula "amps x volts = watts." A GG-1 had twelve 385hp/287 Kw motors that operated on 400 volts AC (stepped down from the 11Kv catenary supply). Total maximum watts would have been 12 x 287Kw = 3,444,000 watts at 400 volts, which implies 8,610 amps total at 400 volts. However the current was being fed to the locomotive's transformers at 11,000 volts, so the total amps drawn from the trolly wire by one engine would have been 3,444,000 watts divided by 11,000 volts = 313 amps. So far, I haven't been able to find information on total power capacity for the PRR system (or sections of it) but if you consider the power needed to operate three GG-1s together on just single train on the four-track mainline, or consider the amount of power required to take six trains out of Penn Station, then the system must have been extremely robust with plenty of redundancy.

Some interesting info here:

Amtrak's 25 Hz traction power system

This is a fascinating article with a great deal of detail. One thing that caught my attention was the statement that the generating capacity is about twice what is required by Amtrak and that the excess is sold commercially. Just briefly, the catenary is divided into sections about 10 miles long fed at each end by substations that drop the 138Kv carried throughout the system to 12Kv (Amtrak raised it from the original 11Kv), so that no train on the line is ever more than 4-5 miles from a substation. The 25 Hz system was put in place before the North American Grid was established with a 60 Hz standard.

To quote the article "the remainder is sold to the regional railroads that operate their trains along the corridor, including NJ Transit, SEPTA and MARC" which use it to power their engines.

@B Smith  Your power calculations seem off to me.  Watts are a measure of energy over time, plugging numbers into equations does not always provide a "true" answer. I took electrical engineering power courses a long time ago and only remember every time I tried to do what you are doing I got the answer wrong.  For Electrical applications 1 horse power is defined as 0.7457 kilowatts. Now to make things confusing horse power is 550 ft⋅lbf/s yet we consume KWs in terms of hours.  Good thing there are 3600 seconds in a hour.  (foot pounds force per second, not pounds as in weight or British currency)

Luckily for us railroad fans the unit was developed so James Watt could compare the work his steam engine was capable of doing versus the number of horses (draft type) need to do the same amount of work.  My brain hurts trying to re-remember this stuff, so I am done here. 

Thanks for posting this, Scouting Dad. I was just trying a  very simplistic estimate, which is probably wrong, as you point out! At any rate, the answer to the original question in this thread about operating three GG-1s together seems to have been answered: Yes, there was plenty of power available in the system to do that.

@wjstix posted:

Some interesting info here:

Amtrak's 25 Hz traction power system

As that article point out, the GG1s, as well as the New Haven electrics that inspired them used "Universal Motors" which were able to operate on low frequency AC as well as DC current. Indeed, the New Haven engines did just that by using third rail DC from Woodlawn to Grand Central and AC everywhere else, including over the **** Gate Bridge to both Penn Station and to the car float terminal at Bay Ridge. GG1s were never equipped for DC operation.

Interestingly, during the 1939-1940 Worlds Fair, some PRR trains operated through to the World's Fair station. The trains, including their GG1s, were hauled by LIRR DD1 locomotives while on the LIRR. The inaugural run of the Silver Meteor began at the World's Fair Station in Queens. Lots of info with pictures here.