Dynamic Imbalances and Conducted Interference in Double-Rail Impedance Bond Track Circuits

AC propulsion trains can cause ac conducted emissions in the traction supply line, which can have EMI effects on signal equipment. To better characterize actual EMI susceptibility of typical signal equipment, the authors measured dynamic dc and ac imbalance currents in double-rail power frequency track circuit impedance bonds. DC imbalance currents of 15% of rated current had negligible effect on impedance bond inductance. Dynamic measurements while in service showed ac imbalance currents of 5% over a broad frequency range. At a location where the cross-bonding was irregular, the maximum sustained AC imbalance current was 22%.