I have looked this up before and did not find an concrete answer.
I was watching a video of the TGV when it was going for it’s 2007 speed record and for a brief time the pantograph was lowered and then raised again. I do not think the other pantograph on the train set was raised either, but I can not be sure, which leads me to this question.
Can an electric locomotive operate without the pantograph making contact with the overhead wires? If so, for how long?[*-)]
When the pantographs are dropped, the locomotive is coasting since it doesn’t have any way of drawing power. Some of the auxiliaries may cut over to battery power but there would be no means of propulsion.
The Northeast Corridor (New Haven Line) buys 3 phase AC power. To balance the power lines, different sections are fed from different phases.
MNR General Orders: At “Phase Breaks/Phase Gaps” , “All electric trains must have controller in coast/off posistion ----”
Thanks, CCS
I am a little confused by your statement. Sorry I am just not familiar with electric rail operations.
The essence of the DMUinCT post is this: Think of two regions of track fed by two different power sources. These sources are not identical and cannot be connected together without causing overloads to both. If a train has two locomotives, each with pantographs up, there exists an electrical path between the electrical “blocks” as the first locomotive enters the new block while the second locomotive remains in contact with the old. Similarly, with only one locomotive, if the pantograph width is greater than the gap between the two catenary circuits, then the possibility of connecting them together is high. Drop pantograph(s) for a few seconds when passing the point of demarcation from one source to the other and there’s no problem.
klahm,
Ok, I understand. Thanks for the description. [8-|]
Temporary drop orders can be issued when maintenance work is being performed on the catenary or an overpass is being built over the tracks. I remember a temporary drop order on the South Shore at the Ford City overpass near 130th and Torrence. New catenary supports were being installed on the overpass and that stretch of the catenary was de-energized by use of insulators and devices similar to phase breaks. All trains had to drop pantographs prior to entering the de-energized section and couldn’t raise them again until the section was cleared. Needless to say, the speed of the trains dropped appreciably while they coasted through.
The reason for the Drop Pantograph order is because it is possible for a locomotive under power to drag an arc from the live section into the neutral “dead” section, energizing it. Normally dropping the pantograph also opens the main circuit breaker automatically.
DPO’s are also to avoid hitting a damaged section with a good pantograph.
A electric train can coast till it runs out of speed or out of air, without the juice the Compressor won’t run 
Pans can be slightly away from the contact wire. usually it is only about 2.5 cm per 10Kv. so if the pan bounces slightly off you may see a spark from the contact wire to the pan. Amazing enough the spark can also be heard sometime nearby on FM radios. Used to happen a lot around the Wilmington, De area when flying overhead. Could see the flashes as a welder sounding buzz came over our radios. Some of the GG1s Pan may not have been working too well.
A retired colleague of mine, at an earlier time in his railroad career, worked as a Milwaukee Road train dispatcher out of Tacoma. A portion of his territory included the mainline electrification between Seattle/Tacoma and Othello. On occasion when maintenance work was being performed on portions of the catenary, he would issue a “DROP PANS AND DRIFT” order - and those almost always applied only to trains that were moving on a descending grade. So thinking about this situation and the fact that the locomotive had to keep the air brakes pumped up, a question comes to mind.
Could the regenerative braking feature of the Milwaukee Road’s electric locomotives produce electric power independent of contact with the overhead catenary - at least enough to keep the headlights working, the class lights on, and the air compressor running?
With the main reservoirs up to 135 psi or so, you’d be able to keep the 80 psi brake pipe up quite a while. Once the MR drops to the trainline pressure, you’d better get the compressor going again.
There is one circumstance where an.electric engine could remain under power with no pantograph operating and that is an engine set up for third rail power. The NYC engines only used a pantograph for complex trackwork and ran third most of the time.
A nice thought, Oltmannd, applicable to a more perfect world perhaps. But with dozens of microleaks present in any trainline, especially at pipe joints and between coupled gladhand castings, that 135psi main reservoir pressure would probably be diminished in relatively short order.
On a passenger train the air can drop pretty fast, it sometimes only takes a few passengers to flush toilet or the airbags to ajust in a curve and train ends in emergency
Som electric switchers had an "extension cord’ arrangement to extend operation a short way into an interchange yard.
And other switchers, NYCentral and North Shore, had battery power as well.
Re the TGV, I would imagine a train going 200 MPH or whatever could coast a LONG way…
[;)]
And you would think that if such an event were fairly common, that there would be the provision for a friction clutch and shaft drive of a compressor to keep the brakes pumped up a bit? It would eat into the momentum, but so would grade change to positive, windage, and so on. I expect, though, that coasting between side or overhead power was only a stop-gap for highly transient events.