ballast resistance on a track circuit

[Archie]

Hi there, as I explained on my previous thread a couple of weeks back I am just starting out in the world or signalling, so excuse me for being simple minded for a while.

My question is as follows: changing of ballast resistance, what effects does this have on track circuits.

Any info would be greatly appreciated.

[PJW]

Hi there, as I explained on my previous thread a couple of weeks back I am just starting out in the world or signalling, so excuse me for being simple minded for a while.

My question is as follows: changing of ballast resistance, what effects does this have on track circuits.

Any info would be greatly appreciated.

When the ballst is wet the resistance reduces so more current leaks away from the rails and hence drop shunt increases; indeed it may be that the track cannot pick at all and thus fails after the passage of the train- rightside failure. Cnversely if in this condition the techs go an adjust the track tro reduce feed resistance to get the track up again, this is fine until the ballas dries out but potentially the drop shunt is now so low that a train wouldn't be detecteed- wrongside failure.

Hence in a word, effect vcan be "dramatic"

[Archie]

Hi there, as I explained on my previous thread a couple of weeks back I am just starting out in the world or signalling, so excuse me for being simple minded for a while.

My question is as follows: changing of ballast resistance, what effects does this have on track circuits.

Any info would be greatly appreciated.

When the ballst is wet the resistance reduces so more current leaks away from the rails and hence drop shunt increases; indeed it may be that the track cannot pick at all and thus fails after the passage of the train- rightside failure. Cnversely if in this condition the techs go an adjust the track tro reduce feed resistance to get the track up again, this is fine until the ballas dries out but potentially the drop shunt is now so low that a train wouldn't be detecteed- wrongside failure.

Hence in a word, effect vcan be "dramatic"

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Hi there, many thanks for your reply. I just wanted to get a heads up as I am starting BS1 on my return from Christmas and I believe that question goes over that and thanks for the answer.
I have just passed my 'Electrical Installation Signalling Skills' assessment, which was nice just before the holidays.