2002 Track Circuit Calculation

[adikarina]

Hi Peter,
Please see the attached attempted Track Cirucit calculation question for 2002.

For Part B, the comments are below:-

Wet weather has caused the increase in the ballast resistance from 5 Ohms to 40 Ohms, therefore, the current through the ballast resistance has reduced from 52mA to 6.5mA. The current through the relay resistance and feed resistance is the same, hence the additional current flows through the drop shunt resistance (i.e. the train wheels), hence the new drop shunt resistance value is lower than the original. The prsence of the train causes the track relay to de-energise and drop away its current.

Please provide your feedback.

Thanks
Regards
Aditi