• Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!

Neutral Sections

Status
Not open for further replies.
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
And to add too this for the OP, you'll hear these breakers in various stock. On the 350's there is a very pronounced *thunk* and the air conditioning drops out (the train at this point is running entirely on battery power, so some high voltage draw kit is dropped)

Listening for the air conditioning stopping is one way to identify the neutral sections.

This was the cause of some controbersy when the Mk3-based sleeping cars were introduced about 35y ago. The loss of the sound of the ventilation every few minutes is noticeable and intrusive.

BR's answer to concerns was that the overall noise level in the compartment including the air conditioning was less than in the old sleeping cars.
 

Joseph_Locke

Established Member
Joined
14 Apr 2012
Messages
1,878
Location
Within earshot of trains passing the one and half
AFAIK the contact wire at a Neutral Section has a section of Glass Fibre inserted.

I presume this makes the short section dead?

Yes, but only enough to insulate against twice the peak traction voltage, or 50kV. At 33kV/cm for dry air that's a tiny gap; I think they have about 300mm of insulation in them (I've never got close enough to measure). Neutral sections are placed to avoid areas (on the approach to signals, in stations, etc.) where trains are likely to stop regularly.
 

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
I had a look at the SA for the southern WCML once and they were about every 13 miles if I remember correctly.

I think the length of line supplied by one grid supply point is about 25-30m and that there is usually a neutral section at the supply point and 1/2 way in between.
 
Last edited:

Beebman

Member
Joined
17 Feb 2011
Messages
640
I've noticed a similar gap on a lifting bridge near Den Holder, also in Netherlands.

Can be seen here:
https://goo.gl/maps/UYQevBmEmVk

Interesting to see a classic Dutch bridge used on a railine

There are also air gaps separating the Dutch 1500v system from the Belgian 3000v one. There are two, one south of Roosendaal on the line to Antwerp, and the other is between Randwyck and Eijsden on the Maastricht-Liege line. (Eijsden station is just inside the Netherlands and uniquely for the NS network has 3000v electrification.)

This page in Dutch has pictures of each of these two air gaps ('Spanningssluis'): http://www.energievoorziening.info/spanningssluis/spanningssluis.htm
 

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
Yes, but only enough to insulate against twice the peak traction voltage, or 50kV. At 33kV/cm for dry air that's a tiny gap; I think they have about 300mm of insulation in them (I've never got close enough to measure).

I seem to recall that the original Mk1 OHLE had much longer neutral sections than the later Mk 3 which reduced it to a short insulator. There were if I understand it rightly 2 insulators with an earthed section of contact wire in between.
 

The Planner

Veteran Member
Joined
15 Apr 2008
Messages
15,836
. Neutral sections are placed to avoid areas (on the approach to signals, in stations, etc.) where trains are likely to stop regularly.

Really? We have some absolute crackers then if that is the case! There are several close to stations that sit nicely in the acceleration curve on the WCML.
 

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
Really? We have some absolute crackers then if that is the case! There are several close to stations that sit nicely in the acceleration curve on the WCML.

There are, but they are not sited at places where the train would have to stop. Thus the train has the momentum to coast through, but won't get "gapped".
 

Whistler40145

Established Member
Joined
30 Apr 2010
Messages
5,911
Location
Lancashire
IIRC some Feeder Stations/Track Section Cabins if out of service for maintenance could mean that the Neutral Section is bypassed in some cases?

Sent from my SM-G920F using Tapatalk
 

driver9000

Established Member
Joined
13 Jan 2008
Messages
4,230
IIRC some Feeder Stations/Track Section Cabins if out of service for maintenance could mean that the Neutral Section is bypassed in some cases?

Sent from my SM-G920F using Tapatalk

No because the wire is physically dead at the neutral section and the dead section doesn't conduct electricity.
 

Railsigns

Established Member
Joined
15 Feb 2010
Messages
2,488
No because the wire is physically dead at the neutral section and the dead section doesn't conduct electricity.

It would be possible to have a switched jumper connecting the live wires on either side of the neutral section. I'm not saying that this is actually done; however, it is possible.
 

Whistler40145

Established Member
Joined
30 Apr 2010
Messages
5,911
Location
Lancashire
Sorry if I wasn't clear.

What I meant was e.g if a Feeder Station was out of order, the Neutral Section would be bypassed to another location.

Sent from my SM-G920F using Tapatalk
 

The Planner

Veteran Member
Joined
15 Apr 2008
Messages
15,836
There are, but they are not sited at places where the train would have to stop. Thus the train has the momentum to coast through, but won't get "gapped".

Yes, but not ideal if you are trying to accelerate away from a station and then have to back off shortly affer.
 

highdyke

Member
Joined
29 Dec 2015
Messages
678
Sorry if I wasn't clear.

What I meant was e.g if a Feeder Station was out of order, the Neutral Section would be bypassed to another location.

Sent from my SM-G920F using Tapatalk

Yes, you do some interesting feeding arrangements, apart from the remotely operated switches and circuit breakers, there are hand operated switches. The ECO needs to take great care how these are set up.
 

ComUtoR

Established Member
Joined
13 Dec 2013
Messages
9,398
Location
UK
Cool, thanks - but I was meaning the 'air gap' principle i.e. has that idea ever been considered here or would it even be feasible/suitable/appropriate/cheap enough etc? I'm guessing not as I'm not aware of any of these in the UK...

No worries. The units I drive have the ADD I assumed this was a common safety feature of all our pantographs.

If we had that air gap our pants would detect the missing wire and drop. The train would come to a grinding halt. It would have to be changed on our units if there was an air gap introduced. I think its because I'm dual voltage that the protection is needed.

I wonder what kind of pantograph protection they have. When ours come down for any reason the train would be protected by the ADD. If the wires came down towards an tunnel and the pan stayed up...
 

Bald Rick

Veteran Member
Joined
28 Sep 2010
Messages
29,070
I can imagine it can get rather confusing to Drivers.

Sent from my SM-G920F using Tapatalk

Not at all. A neutral section is a neutral section, and the driver is informed of each by signs.

Everything else - switches, sections, overlaps etc is not a requirement for drivers to know about.
 

Railsigns

Established Member
Joined
15 Feb 2010
Messages
2,488
Lineside signs for neutral sections were only introduced in 1988 and there are still some that aren't currently signed. Their locations should all be contained in the Sectional Appendix though.
 

Philip Phlopp

Established Member
Joined
31 May 2015
Messages
3,004
Sorry if I wasn't clear.

What I meant was e.g if a Feeder Station was out of order, the Neutral Section would be bypassed to another location.

Sent from my SM-G920F using Tapatalk

Yes, but it's difficult to explain.

This is why there are track sectioning cabins (TSC) and mid point track sectioning cabins (MPTSC). They enable one section of OLE to be isolated without the entire feeder section to be isolated, and they allow various different configurations of feeding arrangement to accommodate a feeder which has failed.

The neutral section at the end of each feeder section is the MPTSC, there's usually an additional neutral section at the feeder point itself, which enables adjacent feeders either side of the affected feeder/section to feed half the affected section each, rather than one feeder having to feed the whole affected section, though that depends on what the alternative feeding arrangements are in the event of a feeder going out of service.

Oh, and they get new names if the OLE is using AT feeding, and things can be a little different transitioning between AT and conventional feeding arrangements.
 
Last edited:

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
Yes, but not ideal if you are trying to accelerate away from a station and then have to back off shortly affer.

That certainly is the case leaving Stafford or Crewe heading North. It doesn't cause any problems except that it takes longer for the train to accelerate to line speed.
--- old post above --- --- new post below ---
If we had that air gap our pants would detect the missing wire and drop.

That should make an interesting display. :D
 

The Planner

Veteran Member
Joined
15 Apr 2008
Messages
15,836
That certainly is the case leaving Stafford or Crewe heading North. It doesn't cause any problems except that it takes longer for the train to accelerate to line speed.

Which in my game is a problem! Doxey is one of the worst, even though it is/was meant to be coming out.
 

MisterT

Member
Joined
12 Oct 2014
Messages
403
Location
The Netherlands
There's a video on t'internet. From memory, it's a pan down/pan up gap.
The air gaps are a common thing in the Netherlands. Many bridges have them, and therefor do not need special constructions for the wires when opening the bridges.

https://youtube.com/watch?v=0h3OH1ZH17k

This is one of the many air gaps. It's just outside the Maassluis station, between the Hook of Holland and Rotterdam.
 

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
The air gaps are a common thing in the Netherlands. Many bridges have them, and therefor do not need special constructions for the wires when opening the bridges.

https://youtube.com/watch?v=0h3OH1ZH17k

This is one of the many air gaps. It's just outside the Maassluis station, between the Hook of Holland and Rotterdam.

Astonishing the pantograph isn't lowered for the transit of the bridge.
 

Rick1984

Member
Joined
23 Aug 2012
Messages
1,030
On the point of Neutral Sections near stations I'm always intrigued by this gap in 3rd rail at Ryde Esplanade
ryde_esplanade_06.jpg

It surprises me the trains can pull off without getting gapped.
 
Last edited:

QueensCurve

Established Member
Joined
22 Dec 2014
Messages
1,904
On the point of Neutral Sections near stations I'm always intrigued by this gap in 3rd rail at Rude Esplanade.

Sounds like a good place for a saucy seaside postcard. :lol:

That, incidently is a "section gap" not a neutral section.
 

ComUtoR

Established Member
Joined
13 Dec 2013
Messages
9,398
Location
UK
In DC land you typically need 2 gaps in the juice for a unit to become "gapped" a DC gap needs all shoes to drop into gaps.
 

mr_moo

Member
Joined
7 Sep 2009
Messages
514
Location
Cambridgeshire
Don't forget that 3rd rail trains nearly always have a shoe on each end, and sometimes more in the middle too depending how they are made up. Thus, as long as the gap is less than the biggest distance between any two shoes on the train it will still have power.

With pantographs (or pants!) you often have only one, sometimes 2, rarely more, so gapping is a bigger issue.
 

ComUtoR

Established Member
Joined
13 Dec 2013
Messages
9,398
Location
UK
With pantographs (or pants!) you often have only one, sometimes 2, rarely more, so gapping is a bigger issue.

Not really. In DC land gaps are freaking everywhere and there are regular gapping incidents. On AC I've never heard of a unit being gapped in a neutral section. I'm sure its happened I just can't recall any.

Neutral sections are usually well placed and not at places where you bring your unit to a stand and they are usually placed on a gradient so you can gravitate out. Its our first instruction for neutral sections.

On DC I worry about gapping, on AC I rarely, if at all, think about it.
 
Status
Not open for further replies.

Top