# A Network-Based Method to Analyze EMI Events of On-Board Signaling System in Railway
## 4 Case Study
### Analysis and Discussion
#### 4.3.2 Path B  
1. \(A_{v5}\) of the node \(v_{5}\)  
As the description in Section 3.1.1, the conductive EM disturbances from the channel of \"pantograph--traction transformer--converter--power line--ground device\" will make the interactions between the power system and OTCS equipment. The factory workers may lay the cable between DMI device \(v_{15}\) and the OTCS kernel \(v_{20}\) at the installation space together with the power cables inside the train body for saving space. However, this condition leads to the EMI event in path B occurs.  
The waveform in Figure 16 is selected as the attribute of \(A_{v5}\) as the equivalent conduction disturbance from the railway system by measurement [27]. The amplitude voltage of the actual measurement transient signal is about 5.3 V. Thus, the disturbance showed in Figure 16 with 2.5 \(\upmu\)s duration is regarded as one signal in \(A_{v5}\).  
Figure 15: The evaluation criterion for Av26 of the node v26 with the relationship throughput and SNR.  
2. \(A_{e13\text{-}16}\) of the edge \(e_{13\text{-}16}\)  
According to the layout of the EMU, the power wire \(v_{5}\) is a long cable with the 220 V, 50 Hz AC, and the resistance at both ends is 50 \(\Omega\). The DMI cable \(v_{16}\) is placed parallel to \(v_{5}\). Therefore, the signal in \(v_{5}\) is the source of the EMI path and the terminal at \(v_{20}\) will receive the disturbance signal. Considering the basic shape of the EMU, a rectangular body is used to simulate the train body. The size of the train is set at 25 m \(\times\) 4 m \(\times\) 4 m with 0.03 mm material aluminum in thickness. The DMI cable is close to the sidewall of the train body, 30 cm away from the ground and the sidewall. The power line and the DMI cable are routed in parallel, and the length is 20 m, as shown in Figure 17. Then, the core of the power cable is 0.75 mm\({}^{2}\), and the core of the DMI cable is 0.5 mm\({}^{2}\), and the shielding thickness of them is both 0.5 mm. The terminal \(v_{20}\) is connected to the 120 \(\Omega\) load, and the terminal  
however, the communication function between nodes \(v_{15}\) and \(v_{20}\) is still normal due to the low received disturbance level.  
In the second scene, the disturbance in Figure 17 is superimposed on the power cable with a 220 V AC signal, and the result at node \(v_{20}\) is shown in Figure 19a. The figure shows that the power cable has an impact on the signal of the DMI cable. Assuming that the transmission is the differential mode of RS485, thus, the difference between the two cores determines the terminal signal. It can be found in the figure that the voltage difference between cores has reached about 7 V, which obviously exceeds its normal decision level. Thus, it may cause the fault detailed in \"communication interruption error\".  
To verify the analysis results, the measure results in time-domain at the port of node \(v_{20}\) in OTCS is shown in Figure 19b. Taking into account the actual cable length, the amplitude of the disturbance and the protective measures, the waveform of the measured result is relatively smooth than the simulation. However, the amplitude received has reached the same level in Figure 19a, which exceeds the normal judgment amplitude.  
The simulation and measurement results verify the validity of the path \(v_{5}\to v_{20}\). Thus, the EMI event of \(v_{5}\to v_{13}\to v_{16}\to v_{20}\) in the EN model of the OTCS has been analyzed and the results show that the disturbance from the traction system would affect the communication between \(v_{15}\) and \(v_{20}\) if the power cable is nearby.  
Figure 19: The results at node \(v_{20}\) with the disturbance. (**a**) The power cable with the disturbance source; (**b**) The signal measured at the port of node \(v_{20}\) in OTCS.  
Figure 18: The results at node \(v_{20}\). (**a**) No power cable near the DMI cable; (**b**) The signal received at the node \(v_{20}\) when the power cable is nearby.