"Charles Ellson" wrote in message
...
the DC line is 650v which ISTR has been stencilled on many trackside
cabinets for years. OTOH the native trains have been able to run on
750v since at least the c.501 if not also the immediately preceding
LMS trains. ATM there doesn't seem to be an "official" confirmation
which leaps to the front of the Google queue.

I noticed as I was travelling on the GW main line between Didcot and
Paddington that there are lineside cabinets labelled "650V" miles away from
the sections where the London Transport lines run alongside - or even where
the line is OHLE electrified. From memory I think I saw them around the
Maidenhead-Twyford area. What are they for?

On 13/04/2010 08:06, Mortimer wrote:
"Charles Ellson" wrote in message
...
the DC line is 650v which ISTR has been stencilled on many trackside
cabinets for years. OTOH the native trains have been able to run on
750v since at least the c.501 if not also the immediately preceding
LMS trains. ATM there doesn't seem to be an "official" confirmation
which leaps to the front of the Google queue.

I noticed as I was travelling on the GW main line between Didcot and
Paddington that there are lineside cabinets labelled "650V" miles away
from the sections where the London Transport lines run alongside - or
even where the line is OHLE electrified. From memory I think I saw them
around the Maidenhead-Twyford area. What are they for?

they will either be for signalling equipment or for the GSM R
transmitters or they could be for the proposed GW line electrification.

"Hugo Rogers" wrote in message
...
On 13/04/2010 08:06, Mortimer wrote:
"Charles Ellson" wrote in message
...
the DC line is 650v which ISTR has been stencilled on many trackside
cabinets for years. OTOH the native trains have been able to run on
750v since at least the c.501 if not also the immediately preceding
LMS trains. ATM there doesn't seem to be an "official" confirmation
which leaps to the front of the Google queue.

I noticed as I was travelling on the GW main line between Didcot and
Paddington that there are lineside cabinets labelled "650V" miles away
from the sections where the London Transport lines run alongside - or
even where the line is OHLE electrified. From memory I think I saw them
around the Maidenhead-Twyford area. What are they for?

they will either be for signalling equipment or for the GSM R transmitters
or they could be for the proposed GW line electrification.

Would signalling or GSM use such high voltages? I'd expect low voltages for
anything that didn't require large amounts of power and would therefore
incur I-squared-R losses. I thought that the proposed GW electrification
would be OHLE, so why would it need 650V supplies?

"Mortimer" wrote

Would signalling or GSM use such high voltages? I'd expect low voltages
for anything that didn't require large amounts of power and would
therefore incur I-squared-R losses. I thought that the proposed GW
electrification would be OHLE, so why would it need 650V supplies?
What voltage do point motors run at?

Peter

"Mortimer" wrote in message
...
"Hugo Rogers" wrote in message
...
On 13/04/2010 08:06, Mortimer wrote:
"Charles Ellson" wrote in message
...
the DC line is 650v which ISTR has been stencilled on many trackside
cabinets for years. OTOH the native trains have been able to run on
750v since at least the c.501 if not also the immediately preceding
LMS trains. ATM there doesn't seem to be an "official" confirmation
which leaps to the front of the Google queue.

I noticed as I was travelling on the GW main line between Didcot and
Paddington that there are lineside cabinets labelled "650V" miles away
from the sections where the London Transport lines run alongside - or
even where the line is OHLE electrified. From memory I think I saw them
around the Maidenhead-Twyford area. What are they for?

they will either be for signalling equipment or for the GSM R
transmitters or they could be for the proposed GW line electrification.

Would signalling or GSM use such high voltages? I'd expect low voltages
for anything that didn't require large amounts of power and would
therefore incur I-squared-R losses. I thought that the proposed GW
electrification would be OHLE, so why would it need 650V supplies?

650 V is the standard lineside power supply for signalling and comms, so
nothing new at all really. Already needed for all the 'non-traction' loads.

Paul S

On Tue, 13 Apr 2010 09:08:00 +0100
"Peter Masson" wrote:
"Mortimer" wrote

Would signalling or GSM use such high voltages? I'd expect low voltages
for anything that didn't require large amounts of power and would
therefore incur I-squared-R losses. I thought that the proposed GW
electrification would be OHLE, so why would it need 650V supplies?
What voltage do point motors run at?

I can't imagine them running at 650V would be very healthy for the track
maintenance staff!

B2003

On Tue, 13 Apr 2010 08:59:03 +0100 someone who may be "Mortimer"
wrote this:-

Would signalling or GSM use such high voltages? I'd expect low voltages for
anything that didn't require large amounts of power and would therefore
incur I-squared-R losses. I thought that the proposed GW electrification
would be OHLE, so why would it need 650V supplies?

650V, which is low voltage, is the standard signalling supply and
has been used since at least the 1960s as part of power signalling
schemes. It is used for the same reason that higher voltages are
used in electricity distribution systems, to minimise losses and
conductor cost.

The voltage is reduced and rectified as necessary for use with
signalling equipment.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000...#pt3-pb3-l1g54

On 13 Apr, 10:21, David Hansen
wrote:
On Tue, 13 Apr 2010 08:59:03 +0100 someone who may be "Mortimer"
wrote this:-

Would signalling or GSM use such high voltages? I'd expect low voltages for
anything that didn't require large amounts of power and would therefore
incur I-squared-R losses. I thought that the proposed GW electrification
would be OHLE, so why would it need 650V supplies?

650V, which is low voltage, is the standard signalling supply and
has been used since at least the 1960s as part of power signalling
schemes. It is used for the same reason that higher voltages are
used in electricity distribution systems, to minimise losses and
conductor cost.

The voltage is reduced and rectified as necessary for use with
signalling equipment.

Why choose an odd Voltage like 650V? What frequency? Single or three
phase?

On Apr 13, 12:20*pm, Stephen Furley wrote:

Why choose an odd Voltage like 650V? *What frequency? *Single or three
phase?

Like a lot of things on the railway, its origins are historical. 650 V
was the highest value of "medium" voltage under the old Factories Act,
which meant that (at that time) a permit-to-work system was not
required for "live" work. Such a system of work would these days be
illegal under the Electricity at Work Regs, of course.

It is single-phase at 50 Hz and it, by the definitons of BS 7671, an
"IT" (earth-free) system. This allows the system to continue to
operate in the event of a first earth fault, until such time as it can
be fixed.

Modern signalling power installations have some form of insulation
monitoring equipment to measure the resistance between the two
conductors (as it's earth-free, we can't really call them "live" and
"neutral", of course!) and if it drops below a certain level, an alarm
is sent. On electrified lines, this is usually to the electrical
control room; on non-electrified lines, to the signal box.

The WCML modernisation scheme uses (mostly!) 400 V three-phase, but
this has not been a great success owing to the higher currents (and
therefore greater number of sources of supply, known as Principal
Supply Points or PSPs) required.

The 650 V distribution system supplies power to locations known as
"Functional Supply Points" from which a spur feeder is taken to a
650/110 V transformer and thence at 110 V into the signalling location
cases (the grey boxes you see everywhere and generally referred to as
"locs"). On the Western, the FSPs are usually separate from the
signalling locs and are identified as such with a yellow stripe.
Elsewhere, the 650 V equipment is within the signalling loc case.

The policy for main lines now is that the distribution systems have
either a PSP at each end (WCML practice) or a PSP at one end and an
auxiliary PSP (APSP) at the other (Western practice), to enable
resupply in the event of a failure. In particular, a dual-fed system
will allow a faulted cable section to be isolated and the two sections
to be fed from each end.

PSPs have two sources of supply. On DC electrified lines the principal
source of supply is from the 33 or 11 kV system that supplies the
traction substations, via a step-down transformer to 400 V (which also
supplies the local substation loads); usually the signalling supply is
taken from one phase (usually red) and stepped up to 650 V. The
standby supply is from the mains.

On AC electrified lines, the principal source of supply is the mains,
with back-up from the 25 kV OLE via a step-down transformer and
voltage regulator. This latter is, in effect, a 1:1 auto-transformer
with automatic on-load tapchanger, to maintain the output voltage at
650 V. More modern installations use an Uninterruptible Power Supply,
which uses a DC link inverter to produce a steady 650 V. These can be
seen, for example, on the electrified section of the MML at, for
example, Kentish Town, Silkstream Junction, Radlett, St Albans, Luton,
Legrave and Bedford. (They look like a small container from the
outside.)

On non-electrified lines, tjhe principal source of supply is from the
mains, with the secondary from a diesel generator. A UPS is used on
SSI routes to ensure there is no break in the supply. (Like most
electronic equioment, SSI cannot tolerate any significant interruption
in supply, whereas a relay interlocking can tolerate the short blip
betwen the mains going down and the genny starting up.) At some sites,
the genny is three-phase, and at others single-phase, but (except in
Scotland), all distribution takes place at 650 V. The Scots have a
slightly different system whereby distribution takes place at 400 V
and is stepped up to 650 V on each individual feeder. The main reason
for this is that given that much of Scotland is sparsely populated, it
is easier to hire a 400 V generator in an emergency to connect to the
distribution board at a remote site than to keep a stockpile of 650 V
gennies, which is the practice elsewhere (especially on the Western).

APSPs don't have a standby genny but do have provision for a mobile
genny to be brought in.

Traditionally, PSPs were located in brick buildings and usually
adjacent to a relay room, or in the ground floor of a PSB (eg Exeter,
Peterborough, Trent). This is particularly noticeable on the Western,
where they often look like a small chalet. On the Eastern and former
LMR, they tended to be next to the relay room but in a separate
building, with the transformers in a compound in between. (Eg Welwyn
Garden City, Hitchin, Royston, Grantham, Newark Northgate, Todmorden
(Hall Royd Junction), St Helens Junction.) On the WCML and the early
GE and Glasgow schemes, they were an integral part of the feeder
station or Track Sectioning Cabin, and not necessarily by a relay
room. On the Southern and other DC lines, they are also co-located
within the substation. Modern installations tend to be containerised
and there is now a move to replacing existing PSPs with containers as
the equipment becomes life-expired. Examples of these can be seen at
Charfield, Ashchurch and Weston-super-Mare; completely new examples
can be found at Wrexham General and Trowell Junction, among others.

HTH.

On Apr 13, 10:48*am, The Gardener wrote:
On Apr 13, 12:20*pm, Stephen Furley wrote:



Why choose an odd Voltage like 650V? *What frequency? *Single or three
phase?

Like a lot of things on the railway, its origins are historical. 650 V
was the highest value of "medium" voltage under the old Factories Act,
which meant that (at that time) a permit-to-work system was not
required for "live" work. Such a system of work would these days be
illegal under the Electricity at Work Regs, of course.

It is single-phase at 50 Hz and it, by the definitons of BS 7671, an
"IT" (earth-free) system. This allows the system to continue to
operate in the event of a first earth fault, until such time as it can
be fixed.

Modern signalling power installations have some form of insulation
monitoring equipment to measure the resistance between the two
conductors (as it's earth-free, we can't really call them "live" and
"neutral", of course!) and if it drops below a certain level, an alarm
is sent. On electrified lines, this is usually to the electrical
control room; on non-electrified lines, to the signal box.

The WCML modernisation scheme uses (mostly!) 400 V three-phase, but
this has not been a great success owing to the higher currents (and
therefore greater number of sources of supply, known as Principal
Supply Points or PSPs) required.

The 650 V distribution system supplies power to locations known as
"Functional Supply Points" from which a spur feeder is taken to a
650/110 V transformer and thence at 110 V into the signalling location
cases (the grey boxes you see everywhere and generally referred to as
"locs"). On the Western, the FSPs are usually separate from the
signalling locs and are identified as such with a yellow stripe.
Elsewhere, the 650 V equipment is within the signalling loc case.

The policy for main lines now is that the distribution systems have
either a PSP at each end (WCML practice) or a PSP at one end and an
auxiliary PSP (APSP) at the other (Western practice), to enable
resupply in the event of a failure. In particular, a dual-fed system
will allow a faulted cable section to be isolated and the two sections
to be fed from each end.

PSPs have two sources of supply. On DC electrified lines the principal
source of supply is from the 33 or 11 kV system that supplies the
traction substations, via a step-down transformer to 400 V (which also
supplies the local substation loads); usually the signalling supply is
taken from one phase (usually red) and stepped up to 650 V. The
standby supply is from the mains.

On AC electrified lines, the principal source of supply is the mains,
with back-up from the 25 kV OLE via a step-down transformer and
voltage regulator. This latter is, in effect, a 1:1 auto-transformer
with automatic on-load tapchanger, to maintain the output voltage at
650 V. More modern installations use an Uninterruptible Power Supply,
which uses a DC link inverter to produce a steady 650 V. These can be
seen, for example, on the electrified section of the MML at, for
example, Kentish Town, Silkstream Junction, Radlett, St Albans, Luton,
Legrave and Bedford. (They look like a small container from the
outside.)

On non-electrified lines, tjhe principal source of supply is from the
mains, with the secondary from a diesel generator. A UPS is used on
SSI routes to ensure there is no break in the supply. (Like most
electronic equioment, SSI cannot tolerate any significant interruption
in supply, whereas a relay interlocking can tolerate the short blip
betwen the mains going down and the genny starting up.) At some sites,
the genny is three-phase, and at others single-phase, but (except in
Scotland), all distribution takes place at 650 V. The Scots have a
slightly different system whereby distribution takes place at 400 V
and is stepped up to 650 V on each individual feeder. The main reason
for this is that given that much of Scotland is sparsely populated, it
is easier to hire a 400 V generator in an emergency to connect to the
distribution board at a remote site than to keep a stockpile of 650 V
gennies, which is the practice elsewhere (especially on the Western).

APSPs don't have a standby genny but do have provision for a mobile
genny to be brought in.

Traditionally, PSPs were located in brick buildings and usually
adjacent to a relay room, or in the ground floor of a PSB (eg Exeter,
Peterborough, Trent). This is particularly noticeable on the Western,
where they often look like a small chalet. On the Eastern and former
LMR, they tended to be next to the relay room but in a separate
building, with the transformers in a compound in between. (Eg Welwyn
Garden City, Hitchin, Royston, Grantham, Newark Northgate, Todmorden
(Hall Royd Junction), St Helens Junction.) On the WCML and the early
GE and Glasgow schemes, they were an integral part of the feeder
station or Track Sectioning Cabin, and not necessarily by a relay
room. On the Southern and other DC lines, they are also co-located
within the substation. Modern installations tend to be containerised
and there is now a move to replacing existing PSPs with containers as
the equipment becomes life-expired. Examples of these can be seen at
Charfield, Ashchurch and Weston-super-Mare; completely new examples
can be found at Wrexham General and Trowell Junction, among others.

Thank you for your comprehensive explanation.

Appreciated.