Sparking on the rails
 

Snow had collected on the conductor rails on the piccadilly line this
morning (presumably Tubelines were still asleep since arn't they
supposed to clear them?). Anyway , the shoes were sparking nicely and
the lights and other systems were going on and off. Does constant on/
off of the juice do the train systems any harm in the same way
constantly flicking a PC on/off would eventually kill it? Am I right
in suspecting this will probably affect the newer trains with
electronic control systems more than the old electro mechanical ones?

B2003

Sparking on the rails
 

On 8 Feb, 15:24, "Boltar" wrote:
Snow had collected on the conductor rails on the piccadilly line this
morning (presumably Tubelines were still asleep since arn't they
supposed to clear them?). Anyway , the shoes were sparking nicely and
the lights and other systems were going on and off. Does constant on/
off of the juice do the train systems any harm in the same way
constantly flicking a PC on/off would eventually kill it? Am I right
in suspecting this will probably affect the newer trains with
electronic control systems more than the old electro mechanical ones?

B2003

I expect more erudite people will come in here, but I can't resist
sticking my two penn'orth in. It wouldn't have hurt a 4-SUB much, I
daresay. I remember the lights used to go dim when the driver started
away. Perhaps the shoes will need replacing earlier? I don't think the
electronics are run directly off the traction supply anyway. The DC
off the juice rail has a fair amount of ripple, and jumps up and down
a fair bit and carries a fair amount of noise anyway. Nearby trains
with commutators (still present on older stock) would present a
problem too. I think that essential control and safety electronics
would be fed from a filtered supply derived from batteries charged in
some way from the traction supply eg by motor generators. The ICMUs on
Eurostars and Networkers etc had to be tuned to avoid tripping because
of the electrical noise from shoe arcs, but that is another story.

Sparking on the rails
 

On Feb 8, 10:24 am, "Boltar" wrote:
Snow had collected on the conductor rails on the piccadilly line this
morning (presumably Tubelines were still asleep since arn't they
supposed to clear them?). Anyway , the shoes were sparking nicely and
the lights and other systems were going on and off. Does constant on/
off of the juice do the train systems any harm in the same way
constantly flicking a PC on/off would eventually kill it? Am I right
in suspecting this will probably affect the newer trains with
electronic control systems more than the old electro mechanical ones?

B2003

Ice and snow on the power rails is a common occurrence on most
systems.
The wayside power delivery system and the train-borne power collection
system are designed to handle the interruptions and intermittent
contact. Some newer electronic propulsion control units may trip out
if too many on-off cycles occur in a short time frame but are easily
reset. Most trains have more than one collector shoe per car so that
one shoe may be interrupted and spark while the other carries current.

Ray