In NSW the catenary has always been 1.5kv DC BUT there has been something that has been puzzling me

Whats the Differnce between this ?



And This?



I know that its the same story in other places like France & Spain With there DC systems so what differance does the second contact wire do??

Cheer  

Instead of rushing in here for an obvious answer why dont you think about your problem and come up with your own answer.  Its much more satisfying.  For instance, what current can a small cross section wire carry compared to a larger cross section wire.  Its really all low level high school physics and really quite simple.

Cheers

Rod Gayford

First one is more efficient.  Each pantograph for an M set carries well over 500 amps, so the voltage drop getting to the panto is not negligible.

Its really all low level high school physics and really quite simple.

F.Y.I. Im only in year 10 and im doin physics next year......

First one is more efficient. Each pantograph for an M set carries well over 500 amps, so the voltage drop getting to the panto is not negligible

Now that I didn't know  

Whereas a QR IMU only draw's 40 amps through the panto.

There is really no difference to the actual structure that carries the overhead, but a thicker top wire can carry more current (Thus move a bigger train faster, or allow more trains into the section or futher out into the section) and double contact wires provides less wear on the carbon strips in the panto's.

I am confused as to why in NSW there is double catenary on some sections for kilometers long (eg EAST HILLS line). I fully understand the arguments about high DC voltage, but I have never seen this in European rail that carry trains at up to 400 km per hour. Is this because European rail uses only AC for high speed?

I am confused as to why in NSW there is double catenary on some sections for kilometers long (eg EAST HILLS line). I fully understand the arguments about high DC voltage, but I have never seen this in European rail that carry trains at up to 400 km per hour. Is this because European rail uses only AC for high speed?

NSW runs twin wires to double the amperage available for the modern 4G trains that have AC motors. 25kv AC only needs a single wire and that is why you don't see double wires in europe outside of short sections where a set of wires ends and another begins.

To do the physics

Your train pulls say 1400kW at full power (150kW per traction motor x 8 + Aux load, lets assume across 1 pano).


25kV train = 56 amps per pano

1.5kV train = 933 amps per pano

The cross sectional area of the pano wire is driven by how much amps it has to carry.

Also remember arc of the pano with wire causes oxidation of both and loss of metal over time. If the arcing is bad enough you risk melting the wire.

Hence two contacts are better than one. Less wear and tear, longer life, more consistent current draw.

AC power is a newer thing.  High speed rail is also a fairly new thing.  That's why the HS lines in europe and japan mostly use 25KV at 50/60Hz.
While getting a bit deeper, AC power also has the potential to deliver far more power than DC, even with the same voltage.

Once upon a time the State of NSW had electric locomotives and when run as multiple units they could overtax the overheads ability to supply sufficient current to feed them properly .
Coal trains ran on the West and Illawarra with four 86s on them and they could only run one pan up each and in limited power combinations ie series .
Twin or dual feeders gave better current feeding abilities and doubled the potential contact area .
Elec locos are virtually a memory now but the appetite of EMU tin cans has grown considerably in the past 20 years .

Once upon a time the State of NSW had electric locomotives and when run as multiple units they could overtax the overheads ability to supply sufficient current to feed them properly .
Coal trains ran on the West and Illawarra with four 86s on them and they could only run one pan up each and in limited power combinations ie series .
Twin or dual feeders gave better current feeding abilities and doubled the potential contact area .
Elec locos are virtually a memory now but the appetite of EMU tin cans has grown considerably in the past 20 years .

The Blue Mountains had double wire catenary when I travelled that way in 1966, long before the 86 class. I would imagine it was built that way, for the 46 class.

Once upon a time the State of NSW had electric locomotives and when run as multiple units they could overtax the overheads ability to supply sufficient current to feed them properly .
Coal trains ran on the West and Illawarra with four 86s on them and they could only run one pan up each and in limited power combinations ie series .
Twin or dual feeders gave better current feeding abilities and doubled the potential contact area .
Elec locos are virtually a memory now but the appetite of EMU tin cans has grown considerably in the past 20 years .

The Blue Mountains had double wire catenary when I travelled that way in 1966, long before the 86 class. I would imagine it was built that way, for the 46 class.

The BM line does not have twin contact wires but has the normal large feeder cable with a smaller feeder cable suspended from the hangers. A single contact wire is then suspended from the lower power cable. To service the NIFT cars a number of power sub stations are being upgraded to provide better power output.

Although an enhanced power supply will be available, in regard to electric locomotives, forget about their re-introduction until 25KVAC power replaces the 1500 VDC and that aint likely to happen any time soon if ever.

The BM line does not have twin contact wires but has the normal large feeder cable with a smaller feeder cable suspended from the hangers. A single contact wire is then suspended from the lower power cable. To service the NIFT cars a number of power sub stations are being upgraded to provide better power output.

Although an enhanced power supply will be available, in regard to electric locomotives, forget about their re-introduction until 25KVAC power replaces the 1500 VDC and that aint likely to happen any time soon if ever.

It was more than 50 years ago. Sorry for leading people down the garden path. You are right. There is an extra wire, but it's not a contact wire.

The Blue Mountains had double wire catenary when I travelled that way in 1966, long before the 86 class. I would imagine it was built that way, for the 46 class.

Not quite. The Blue Mountains OHW had two catenary wire (one major and one minor) and only one contact wire.

Where confusion may have happened is at Crossovers, Points and Section breaks where there are TWO contact wires in play but only for as long as needed.

For may years there were publications available about the Blue Mountains Electrification because it was still regarded as a major undertaking and the Railway's were quite proud of what had been done.
These publications described in detail of what had to be done to electrify the line and why it was done the way it was.

It was a HUGE step going from slow running Steam to firstly the 46 class hauled passengers but once the single Decker Interurban's were introduced, it opened up a whole new era of transport.

Once upon a time the State of NSW had electric locomotives and when run as multiple units they could overtax the overheads ability to supply sufficient current to feed them properly .
Coal trains ran on the West and Illawarra with four 86s on them and they could only run one pan up each and in limited power combinations ie series .
Twin or dual feeders gave better current feeding abilities and doubled the potential contact area .
Elec locos are virtually a memory now but the appetite of EMU tin cans has grown considerably in the past 20 years .

It was very common during the era of Electric locomotives for a 'Down Train', Penrith to Lithgow to 'Pull the Power' because the system was and still is inadequate to handle both heavy and FAST loads.
The system was 'monitored' from the Prince Alfred sidings Electrical Branch Depot and every night with the passage of 261 Interstate Goods, Coal Stage Lithgow would get a call from the operator asking for number of a recently arrived Train as it had 'Pulled' or 'Overloaded' the system ascending the Mountains.
This was 261 as it was a 'Timetabled Train' and ran with a fixed load at a specific speed, too heavy and too fast if the Driver wasnt really careful when accelerating.

At Valley Heights signal box was a table of times that you were to use to keep 'Down Trains' apart (mainly Goods) so they didnt over load the system.