Evaluation of the Electromagnetic Effect of Traction Rolling Stock on Track Circuits

The regulations regarding railways currently in force in Bulgaria require that each new type of locomotive, to get access to railway infrastructure, must undergo a procedure for checking its electromagnetic effect on functioning of track circuits. The relevant testing was carried out for seven types of AC and DC track circuits and for six types of locomotives intended to be put into operation (five electric locomotives and a diesel locomotive). Schematic diagrams of testing conditions are presented. During the tests the voltage waveform, frequency, and level rates at the terminals of the track receiver (on the track relay coil) were recorded for a free (normal (common) mode) and occupied (shunt mode) track circuit during the action of return traction current of electric locomotives, as well as during the action of impacts caused by operation of electrical equipment located in the body and under the frame of the diesel locomotive. For electric locomotives, the tests were carried out during the shunting of track circuits (of a tested one and of the track circuit adjacent to it), starting from the rest, lowering and raising pantographs. For a diesel locomotive, tests were carried out in a stationary mode, when inner wheelsets shunted the insulating joints of two adjacent track circuits and for different cases of arrangement of the equipment of the relay and receiver ends. During the tests, the state of the armature and contacts of track relays was monitored. The amplitude of the recorded interference was compared with voltage of reliable switching off/ on of track relays/track receivers. It was found that during the shunt mode, the recorded residual voltage in the track receiver under the action of the electric locomotive was 50 or more times lower than the reliable operate voltage and 33 or more times lower than the reliable drop-out voltage of the receiver. For a diesel locomotive, the results turned out to be similar, except for the case of shorter DC track circuits, where the amplitude of the interference was higher, but without a dangerous effect on the shunt mode. Based on the results of the tests, it was established that all types of track circuits used on the railways of Bulgaria are resistant to electromagnetic interference emanating from tested samples of traction rolling stock.