# Research on Interference Mechanism of 25 Hz Phase Sensitive Track Equipment from Unbalanced Current
## 4 Analysis of Track Circuit Misoperation Test
### Analysis of Hanging Ground Wire Test  
After clarifying the mechanism of the red ribbon phenomenon caused by the unbalanced current generated by hanging the ground wire, the ground wire test was carried out on the site. Considering the influence of the ground wire on the adjacent track and the degree of interference, the track signal circuit of one sending and one receiving track is selected for monitoring. The monitoring quantity mainly includes the voltage and current in the front and back stage circuits of the grounding wire. The purpose is to observe the influence of the unbalanced current generated in the circuit on the track circuit when the turnout crosses the regional grounding wire, and to monitor and collect the signal. The layout of the probe is shown in Figure 21.  
Figure 20: Unbalanced current in track circuits under different conditions. (**a**) Monitoring road section waveform when small unbalanced current is generated in track circuit; (**b**) Adjacent track section waveform when small unbalanced current is generated in track circuit; (**c**) Monitoring road section waveform when transient impulse unbalance current exists; (**d**) Adjacent track section waveform when transient impulse unbalance current exists; (**e**) Monitoring road section waveform when steady-state unbalanced current exists; (**f**) Adjacent track section waveform when steady-state unbalanced current exists.  
Figure 22a shows the voltage and current flowing through the rail when the track circuit is not grounded. At this time, the track circuit is in normal working condition. It can be seen that the unbalanced current flowing in the rail is small, which is 0.8 A. The unbalanced small current is mainly caused by the unbalanced track impedance.  
Figure 21: Field probe layout diagram.  
Figure 22: Choke transformer and relay grounding wire test waveform. **(a)** The track circuit is not grounded; **(b)** The position of grounding wire is close to the monitored position; **(c)** The grounding wire is far from the monitored position; **(d)** Waveform distortion during grounding wire hanging.  
In order to explore and analyze the influence of the distance between the grounding wire and the monitoring point, the positions near and far from the monitoring point are set up for the grounding wire test. When the position of the grounding wire is close to the monitoring point, it can be found from Figure 22b that the grounding wire has a great influence on the monitoring point, the waveform distortion is serious, and the unbalanced current generated reaches 14 A. When the position of the grounding wire is far away from the monitoring point, the waveform of the choke transformer is shown in Figure 22c. Under the influence of the grounding wire, although there are some waveform glitches, the effective value of the unbalanced current in the track is low, only 1.7 A. Therefore, the grounding wire will lead to the appearance of an unbalanced current, and the value of the unbalanced current is also affected by the distance between the grounding wire and the monitoring point. When the grounding wire is close to the monitoring point, the unbalanced current is larger, and vice versa.  
In the process of hanging the grounding wire, the waveform of the track coil side is also disturbed due to the serious distortion of the waveform, as shown in Figure 22d. It can be seen that the voltage waveform of the track coil side drops from the original 22 V voltage to 2.97 V. At this time, the track circuit has produced a red ribbon, and there has been misoperation.