Topics

Short Protection in Yards


Vollrath, Don <dvollrath@...>
 

Allan's advice makes a lot of sense. Each operator should be isolated by mistakes of others.
Make the yard a separatly protected power district, isolated from main tracks where other operators would be working.
If the yard is double ended and worked by two operators, make each end a separate district.
Likewise, make other industrial switching areas separate districts from main tracks.
Isolating each track is overkill. If you have unknown shorts, find & fix before you attempt operating sessions.
DonV

-----Original Message-----
From: WiringForDCC@...
[mailto:WiringForDCC@...]On Behalf Of wirefordcc
Sent: Monday, January 16, 2006 8:04 PM
To: WiringForDCC@...
Subject: [WiringForDCC] Re: Short Protection in Yards


You could make the entire yard a single protected zone or you could
protect each individual turnout. In between is everything you can
imagine.

With a yard, if you get a short, you will likely know why. Chances
are you are in the middle of a movement and are staring right at the
cause of the short.

So what purpose is served by short protection? Probably the most
useful purpose is to not shut down other operators. So protecting
the whole yard as a single unit is probably enough. If you have
more than one yard operator or a double-ended yard being operated
from both ends, maybe protecting the yard as two zones is
appropriate.

Probably the second most important function served by short
protection is limiting the amount of railroad that is rendered
inoperable. Suppose you have a short and can't identify why. Or
you found the problem, but the middle of an operating sessions isn't
the time to fix it. So maybe you break your double-ended yards into
say four zones. Now if you have a short you can't fix, it only
immobilizes a portion of your yard.

You could certainly protect each individual track, but that results
in a rats nest of wiring and may not be worth it.

I hope these thoughts help.

Allan






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wirefordcc <wire4dcc_admin@...>
 

You could make the entire yard a single protected zone or you could
protect each individual turnout. In between is everything you can
imagine.

With a yard, if you get a short, you will likely know why. Chances
are you are in the middle of a movement and are staring right at the
cause of the short.

So what purpose is served by short protection? Probably the most
useful purpose is to not shut down other operators. So protecting
the whole yard as a single unit is probably enough. If you have
more than one yard operator or a double-ended yard being operated
from both ends, maybe protecting the yard as two zones is
appropriate.

Probably the second most important function served by short
protection is limiting the amount of railroad that is rendered
inoperable. Suppose you have a short and can't identify why. Or
you found the problem, but the middle of an operating sessions isn't
the time to fix it. So maybe you break your double-ended yards into
say four zones. Now if you have a short you can't fix, it only
immobilizes a portion of your yard.

You could certainly protect each individual track, but that results
in a rats nest of wiring and may not be worth it.

I hope these thoughts help.

Allan


Earl T. Hackett <hackete1@...>
 

I've heard of so many schemes to minimize the effect of shorts that I can't remember them all - but none, including automatic reversing boosters, appeared to really solve the problem. My approach to the whole short circuit problem is to simply eliminate the possibility of a short ever occurring - or at least reduce the probability of such an occurrence to an acceptable level. You can take a look at the file I recently uploaded on reverse loop wiring in the files section to see a detailed description of the approach I usually take.

There are two basic causes for a short to occur during normal operation, a derailed metal wheel bridges the gap between two rails of opposite phase or a wheel or conductive truck bridges an insulating gap separating rail segments of opposite phase.

In facing point movements, the threat is from derailed wheels bridging gaps between adjacent rails. That is easily eliminated by insuring that rails of opposite phase have spacing between them much wider that the wheel thickness. To eliminate this problem, I extend the electrical continuity of the frog at least 1.25" in both directions from the point of the frog. With commercial turnouts this could be difficult to achieve, but it results in rails of opposite phase being well separated from each other (at least 1/4" or 6 mm) so a metal wheel can not bridge the gap.

In trailing point movement, there is the potential that an operator will mistakenly run through a turnout with the points thrown against him. All my turnouts have a DPDT switch operated with the movement of the points. One pole controls track power to the frog of the switch. The other pole is used to set signal aspects. As on the prototype, operators are expected to obey signal aspects. If you don't have signals, the second pole could be to control power to a length of rail on the approach to the frog that is at least 1 1/2 times the length of your longest locomotive. If an operator tried to run against the switch while pushing cars, the cars would derail at the points but no short would occur. If he tried to run against the switch with the loco in the lead, the dead rail would cause the loco to stop until the points were aligned properly.

The above relates to conventional turnouts. Double slips and crossings are special problems and elimination of shorts is a bit more complicated, but not particularly difficult.

----- Original Message -----
From: minaret5
To: WiringForDCC@...
Sent: Monday, January 16, 2006 7:16 PM
Subject: [WiringForDCC] Re: Short Protection in Yards


Earl,

As I stated in my original post, I'm just setting up short circuit
protection in the yards, so there is no specific problem now to
relate. All I want to know is if the entire yard is protected
together, where in the event of a short caused by derailment or
anything else,


minaret5 <Minaret5@...>
 

Earl,

As I stated in my original post, I'm just setting up short circuit
protection in the yards, so there is no specific problem now to
relate. All I want to know is if the entire yard is protected
together, where in the event of a short caused by derailment or
anything else, the whole yard, and all its tracks, stops until
resolved or do you have the individual tracks protected separately to
limit multiple engines on different tracks from all stopping in the
event of a short on another track. Yards ARE more prone to shorts
due to the increased number of close proximity T/O's that someone
might accidentally derail on if not lined properly from inattention,
etc.

Thanks. Fred



--- In WiringForDCC@..., "Earl T. Hackett"
<hackete1@c...> wrote:

I'm not quite sure why a yard should be more prone to shorts than
anywhere else. As long as there is good separation between rails of
opposite polarity or phase, there shouldn't be any problem. I hand
lay 95% of my track and have never had a shut down due to a short
during normal operation.

If you have a particular problem with a reversed polarity problem
in the yard area, some more detail about the actual problem would
make it easier for us to provide assistance.
----- Original Message -----
From: minaret5
To: WiringForDCC@...
Sent: Monday, January 16, 2006 3:45 PM
Subject: [WiringForDCC] Short Protection in Yards


Greetings,

I am in the process of setting up short circuit protection on a
club-
sized layout. I will be using short circuit modules that
provides
protection to 4 sub-districts.


[Non-text portions of this message have been removed]


Mark Gurries
 

I'm not quite sure why a yard should be more prone to shorts than
anywhere else. As long as there is
good separation between rails of opposite polarity or phase, there
shouldn't be any problem. I hand
lay 95% of my track and have never had a shut down due to a short
during normal operation.

If you have a particular problem with a reversed polarity problem in
the yard area, some more detail
about the actual problem would make it easier for us to provide
assistance.

It is best to instal power districts where people tend to concentrate
their activities. Main line vs yard vs branchline ect.

Although you may not have lots of problems due to your excellent track
construction and car inspections meeting NMRA standards ect...a lot of
others live with less than perfection. More often than not, they tend
to be associated with areas that have lots of track switches...such as a
yard. The point being that derailments are an unfortunate common enough
event in most model train layouts that the shorts often created by them
can really impact the enjoyment of the layout when more than one
operator is involved. As such the strategy is to isolated large
sections of the layout track logically into working areas. By keeping
the working areas electrically isolated, electrical accidents only
bothers the one dealing with the cause as opposed to the other innocent
operators.

Best Regards,

Mark Gurries
Linear Technology
Power Supply & Battery Charger Applications Engineer/Manager
---------------------------------------------------------
Model Railroad Club and NMRA DCC presentations are at:
http://www.siliconvalleylines.com/index.html
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Audio Enthusiast (Love SAE equipment)
http://members.ebay.com/aboutme/gurriesm/
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Earl T. Hackett <hackete1@...>
 

I'm not quite sure why a yard should be more prone to shorts than anywhere else. As long as there is good separation between rails of opposite polarity or phase, there shouldn't be any problem. I hand lay 95% of my track and have never had a shut down due to a short during normal operation.

If you have a particular problem with a reversed polarity problem in the yard area, some more detail about the actual problem would make it easier for us to provide assistance.

----- Original Message -----
From: minaret5
To: WiringForDCC@...
Sent: Monday, January 16, 2006 3:45 PM
Subject: [WiringForDCC] Short Protection in Yards


Greetings,

I am in the process of setting up short circuit protection on a club-
sized layout. I will be using short circuit modules that provides
protection to 4 sub-districts.


minaret5 <Minaret5@...>
 

Greetings,

I am in the process of setting up short circuit protection on a club-
sized layout. I will be using short circuit modules that provides
protection to 4 sub-districts.

My question to you experts out there is how much protection is
generally installed within the confines of yards or what type of
criteria did you use? Are you protecting each classification track or
passenger terminal track individually; a pair of tracks; or some other
combination?

Protecting each track in a large yard tends to eat up a lot of circuits
and I was curious about what the larger layouts are doing for short
protection in active, busy yards.

Thanks.
Fred