Electrical clearances

[Greg Gritton]

I am trying to figure out electrical clearances for 25kV AC railway
electrification, and am getting a some contradictory information,
so perhaps someone in news-land knows better.

Perhaps the clearest document on the Web I have found is the UK railway
group standard GE/RT8025 "Electrical Protective Provisions for
Electrified Lines". It lists normal clearance to infrastructure on
the order of 270mm, or just under 11". This seems consistent with
some European clearances. For example, continental Europe's largest
standard loading gauge, GC, has a "kinematic envelope" (clearance including
possible movements) of 4.7m high. Meanwhile, the lowest catenary limit
is 5.0m, a difference of 0.3m (300mm).

The space between the catenary and the locomotive is higher.
For example, with the TGV, the locomotive is 4.1m high, almost 1m
below the 5.08m high catenary.

So far, so good, however, applying this to the US situation gets more
complex. I haven’t found a source like the UK one that gives a good
overall explanation of electrical clearances. In addition, most sources
I have found seem to desire very large clearances. For example, the
CalTrain electrification project plans on a contact wire height of
23 feet (7.01m) compared to a Plate-H height limit of 20'2" (6.15m),
a difference of 0.86m. The Transport Cooperative Research Program's
Report 52 on Joint Operation of Light Rail Transit or Diesel Multiple
Unit Vehicles with Railroads, lists the desired catenary height
23-26 feet (7.01m-7.92m). Given that the highest clearance is
Plate-H, used for double-stack, this gives very large clarances
to catenary, and the need of a really, really high pantograph.

It is even trickier finding the clearance above a catenary to a bridge
above. Does it require the same high clearance as that implied
above the trains? For example, CalTrans requires a 6 foot clearance
to infrastructure for 25kV electrical lines. On the other hand,
there are some indications that much lower clearances would be
required. For example, in "Specific Requirements for Working on
the Reading Blue Mountain & Northern Railroad Right of Way" about
bridge height being 23' (7.01m) normally, or 24' 6" (7.46m) for an
electrified line or where future electrification could be expected,
a difference of only 1' 6" (0.45m). Also, according to the
"Cross Harbor Freight Movement DEIS", the freight tunnels being
possibly planned for freight access to Manhattan will have a
vertical clearance of only 22' 6" (6.85m), which, according to that
proposal, is supposed to be enough for double-stack service and
future electrification, although only diesel traction is initially
planned. This gives 2' 4" (711mm) above the top of the stack
cars, or 2' (610mm) above their dynamic envelope, which seems
tight even by European standards.

Does anyone out there have any more insights?

Sincerely,

Greg Gritto

[montcharmont.f]

GB allows , low clearences than France especially since the ECML was
electrified .
Bigfoot . Den Norsker Fransken togfarer

Post by Greg Gritton
I am trying to figure out electrical clearances for 25kV AC railway
electrification, and am getting a some contradictory information,
so perhaps someone in news-land knows better.
Perhaps the clearest document on the Web I have found is the UK railway
group standard GE/RT8025 "Electrical Protective Provisions for
Electrified Lines". It lists normal clearance to infrastructure on
the order of 270mm, or just under 11". This seems consistent with
some European clearances. For example, continental Europe's largest
standard loading gauge, GC, has a "kinematic envelope" (clearance including
possible movements) of 4.7m high. Meanwhile, the lowest catenary limit
is 5.0m, a difference of 0.3m (300mm).
The space between the catenary and the locomotive is higher.
For example, with the TGV, the locomotive is 4.1m high, almost 1m
below the 5.08m high catenary.
So far, so good, however, applying this to the US situation gets more
complex. I haven't found a source like the UK one that gives a good
overall explanation of electrical clearances. In addition, most sources
I have found seem to desire very large clearances. For example, the
CalTrain electrification project plans on a contact wire height of
23 feet (7.01m) compared to a Plate-H height limit of 20'2" (6.15m),
a difference of 0.86m. The Transport Cooperative Research Program's
Report 52 on Joint Operation of Light Rail Transit or Diesel Multiple
Unit Vehicles with Railroads, lists the desired catenary height
23-26 feet (7.01m-7.92m). Given that the highest clearance is
Plate-H, used for double-stack, this gives very large clarances
to catenary, and the need of a really, really high pantograph.
It is even trickier finding the clearance above a catenary to a bridge
above. Does it require the same high clearance as that implied
above the trains? For example, CalTrans requires a 6 foot clearance
to infrastructure for 25kV electrical lines. On the other hand,
there are some indications that much lower clearances would be
required. For example, in "Specific Requirements for Working on
the Reading Blue Mountain & Northern Railroad Right of Way" about
bridge height being 23' (7.01m) normally, or 24' 6" (7.46m) for an
electrified line or where future electrification could be expected,
a difference of only 1' 6" (0.45m). Also, according to the
"Cross Harbor Freight Movement DEIS", the freight tunnels being
possibly planned for freight access to Manhattan will have a
vertical clearance of only 22' 6" (6.85m), which, according to that
proposal, is supposed to be enough for double-stack service and
future electrification, although only diesel traction is initially
planned. This gives 2' 4" (711mm) above the top of the stack
cars, or 2' (610mm) above their dynamic envelope, which seems
tight even by European standards.
Does anyone out there have any more insights?
Sincerely,
Greg Gritton

[BH Williams]

Post by Greg Gritton
I am trying to figure out electrical clearances for 25kV AC railway
electrification, and am getting a some contradictory information,
so perhaps someone in news-land knows better.
Perhaps the clearest document on the Web I have found is the UK railway
group standard GE/RT8025 "Electrical Protective Provisions for Electrified
Lines". It lists normal clearance to infrastructure on the order of
270mm, or just under 11". This seems consistent with
some European clearances. For example, continental Europe's largest
standard loading gauge, GC, has a "kinematic envelope" (clearance including
possible movements) of 4.7m high. Meanwhile, the lowest catenary limit
is 5.0m, a difference of 0.3m (300mm).
The space between the catenary and the locomotive is higher.
For example, with the TGV, the locomotive is 4.1m high, almost 1m
below the 5.08m high catenary.
So far, so good, however, applying this to the US situation gets more
complex. I haven't found a source like the UK one that gives a good
overall explanation of electrical clearances. In addition, most sources
I have found seem to desire very large clearances. For example, the
CalTrain electrification project plans on a contact wire height of 23 feet
(7.01m) compared to a Plate-H height limit of 20'2" (6.15m),
a difference of 0.86m. The Transport Cooperative Research Program's
Report 52 on Joint Operation of Light Rail Transit or Diesel Multiple
Unit Vehicles with Railroads, lists the desired catenary height 23-26 feet
(7.01m-7.92m). Given that the highest clearance is
Plate-H, used for double-stack, this gives very large clarances
to catenary, and the need of a really, really high pantograph.
It is even trickier finding the clearance above a catenary to a bridge
above. Does it require the same high clearance as that implied
above the trains? For example, CalTrans requires a 6 foot clearance
to infrastructure for 25kV electrical lines. On the other hand,
there are some indications that much lower clearances would be
required. For example, in "Specific Requirements for Working on the
Reading Blue Mountain & Northern Railroad Right of Way" about bridge
height being 23' (7.01m) normally, or 24' 6" (7.46m) for an electrified
line or where future electrification could be expected,
a difference of only 1' 6" (0.45m). Also, according to the
"Cross Harbor Freight Movement DEIS", the freight tunnels being
possibly planned for freight access to Manhattan will have a
vertical clearance of only 22' 6" (6.85m), which, according to that
proposal, is supposed to be enough for double-stack service and future
electrification, although only diesel traction is initially planned. This
gives 2' 4" (711mm) above the top of the stack
cars, or 2' (610mm) above their dynamic envelope, which seems
tight even by European standards.
Does anyone out there have any more insights?
Sincerely,
Greg Gritton

I'm no expert on catenary, though I know a few (where is Richard Catlow when
you need him?). I'm pretty certain that contact-wire > car-body clearances
at Eurotunnel are lower than those you suggest, with our Shuttles being
close to your double-stack in terms of loading gauge.
To what are the Caltrans clearances related? If it's the distance between
any point where a member of the public might have access and the contact
wire, then it doesn't seem too different to European standards- 3.1 metres
rings a bell. If, however, it refers to the distance between the underside
of an overline structure and the contact wire (or other energised part of
the OCS), then it is way in excess of UK, and almost certainly other
European, standards. I'll cross-post your inquiry to UK rail, in the hope of
some rather more precise figures from Mr C or others.
Brian

[Greg Gritton]

Hello BH,

Post by BH Williams
To what are the Caltrans clearances related? If it's the distance between
any point where a member of the public might have access and the contact
wire, then it doesn't seem too different to European standards- 3.1 metres
rings a bell. If, however, it refers to the distance between the underside
of an overline structure and the contact wire (or other energised part of
the OCS), then it is way in excess of UK, and almost certainly other
European, standards.

The CalTrans standards are generic, non-rail standards. The document
I got them from dealt with placing power lines over highways. However
the distances seem similar to US standards I have found other places.

It may come from the General Electrical Safety Code. Unfrotunately,
like too many US standards (and it seems unlike many European ones),
this is a proprietary standard that isn't avaiable for free, and thus
on the web.

Greg Gritton

[g***@yahoo.com]

Post by Greg Gritton
The CalTrans standards are generic, non-rail standards. The document
I got them from dealt with placing power lines over highways. However
the distances seem similar to US standards I have found other places.
It may come from the General Electrical Safety Code. Unfrotunately,
like too many US standards (and it seems unlike many European ones),
this is a proprietary standard that isn't avaiable for free, and thus
on the web.

Also known as "National Electric Code".

I've been told that our NEC is far more conservative than any other
national equivalent. Several people involved in the railroad industry
have told me that if their equipment were required to meet the National
Electric Code, railroad transport would quickly become uneconomical
because railroad car and locomotive electrical equipment would be double
the size that it is now. However, the code does not apply to mobile
equipment. Stationay electrical systems, unfortunately, in most cases
must meet it.

[Philip Nasadowski]

Post by g***@yahoo.com
I've been told that our NEC is far more conservative than any other
national equivalent.

It's pretty tough. Also, NEMA rated electric stuff tends to be built
more heavily. A NEMA size 0 starter's pretty big vs an IEC equivalent,
though most places will allow either in industrial stuff. I don't know
exactly what the code says, though heck, even Square-D sells IEC rated
equipment, so it must be legal somewhere.

Post by g***@yahoo.com
Several people involved in the railroad industry
have told me that if their equipment were required to meet the National
Electric Code, railroad transport would quickly become uneconomical
because railroad car and locomotive electrical equipment would be double
the size that it is now.

But of course. Should the RR industry be held to ANY modern safety
standard, it'd quickly become uneconomical. That's why we should look
the other way, accept train crashea, and just keep upping the buff
strength and putting on louder horns!

I don't see how the NEC would be an anchor on the industry - heck, it'd
likely allow some stuff the FRA frowns on (such as high voltage
connections between cars).

Post by g***@yahoo.com
Stationay electrical systems, unfortunately, in most cases
must meet it.

Well, why wouldn't they? The only exceptions I can think of are
traction power and maybe signaling. Even the former might not. But any
station or other public place darn well BETTER meet the code.

In any case, the NEC's not difficult to read or figure out. It's not
even that much of a book anyway, and it's pretty well laid out. I think
the bigger shock to the RR industry if they had to conform to it would
be seeing what a real, workable, and successful set of safety
regulations look like, as opposed to the arbitrarilly silly FRA stuff...

[g***@yahoo.com]

Post by Philip Nasadowski

Post by g***@yahoo.com
Several people involved in the railroad industry
have told me that if their equipment were required to meet the National
Electric Code, railroad transport would quickly become uneconomical
because railroad car and locomotive electrical equipment would be double
the size that it is now.

But of course. Should the RR industry be held to ANY modern safety
standard, it'd quickly become uneconomical. That's why we should look
the other way, accept train crashea, and just keep upping the buff
strength and putting on louder horns!
I don't see how the NEC would be an anchor on the industry - heck, it'd
likely allow some stuff the FRA frowns on (such as high voltage
connections between cars).

Supposedly the much larger electrical equipment, as opposed to IEC, would
take up far more space and thus leaves less room for other vital
components such as passengers.

[Philip Nasadowski]

Post by Greg Gritton
It may come from the General Electrical Safety Code.

Do you mean the National Electric Code?

The NEC doe not define standards for rail equipment or catenary. That's
the AAR's ball of wax, though I doubt the AAR's even aware anymore what
catenary is, or that you can power trains by something other than a
diesel engine.

There might be guidelines, but they're followed loosely at times - the
clearances at Penn Station NY are notoriously tight - they've been known
to bump-lock pantographs on trains. On the flip side, Long Branch has
the wire up darn near the max running height of the pan, which gives a
few feet between the roof and wire.

Pans also have different reaches - the PRR's was higher than the New
Haven's, and the current Metra Electric line is a tad higher, still, I
think. LRV lines tend to be lower.

Post by Greg Gritton
Unfrotunately,
like too many US standards (and it seems unlike many European ones),
this is a proprietary standard that isn't avaiable for free, and thus
on the web.

Actually, it's supposed to be (more or less) law of the land and you can
get it in the US quite readily (though not free, I don't understand
why). Most better libraries have it, and bookstores might, too. It's a
very useful book, in any case.

[James Robinson]

Post by Greg Gritton
I am trying to figure out electrical clearances for 25kV AC railway
electrification, and am getting a some contradictory information,
so perhaps someone in news-land knows better.

Clearances are defined in the Railway Engineering Association manual,
which most states would use as a starting point for their regulations.

The minimum clearances consider a number of factors, including catenary
sag and uplift, the depth of the catenary contact system, vehicle bounce
and sway, track geometry tolerance, air clearance, altitude, and some
additional values for insurance. The resulting minimum clearance will
vary depending on the specifics chosen for each of these factors.

The minimums are just that, minimums. Most railroads would not build to
those values except in unusual circumstances. They would normally want
additional clearances to reflect the realities of everyday operation.

As an example, they might add some additional clearance to the minimum to
make it easier to accomplish track maintenance. Adding ballast (ballast
lift) is a common maintenance technique to bring a track back into good
geometry. The catenary would need to be a few inches higher than the
minimum to permit one or two ballast lifts without getting into trouble
with clearances.

When designing for 25kVAC, the absolute minimum clearance above the load
would be about 18 or 19 inches, using typical values. "Normal" minimum
clearance would be closer to two feet. As mentioned above, additional
clearance would probably be added to ease maintenance requirements.