# A Network-Based Method to Analyze EMI Events of On-Board Signaling System in Railway
## 4 Case Study
### Analysis and Discussion  
#### 4.3.1 Path A  
1. \(A_{v2}\) of the node \(v_{2}\)  
The pantograph arcing is selected as the attribute of \(A_{v2}\). To obtain the actual waveform of the pantograph arcing during the operation of the EMU, a measuring probe is installed at the position of the train roof (see Figure 10(a)). As shown in the figure, the horizontal distance between the pantograph and the measurement antenna is 2.5 m and the antenna is 0.4 m in height above the roof. A coaxial cable is fixed on the outside of the train for connecting the instrument temporarily. The receiver and oscilloscope are set inside of the train under the control of the computer for data collection. The single waveform of the EM disturbance from the pantograph arcing that is measured on-site is shown in Figure 10(b). The duration of the single discharge is within 1 \(\upmu\)s and the rise time is at nanoseconds (ns) level. However, the length of a symbol is around tens of \(\upmu\)s in the communication system, i.e., the length of a symbol is about 72 \(\upmu\)s in FDD-LTE (Long-Term Evolution Frequency-Division Duplex) with OFDM (Orthogonal Frequency-Division Multiplexing). Thus, the single waveform cannot cover the useful signals completely. It should be noted that most of the pantograph arcing from the off-line discharge is not a single pulse signal. There will be multiple arcing phenomena while the off-line between pantograph and catenary occur by sliding contact. The reason is that the off-line is continuous until the displacement difference between them is no longer zero. Therefore, it is assumed that the pantograph arcing disturbance is composed of multiple independent pulse signals like the waveform in Figure 10(b). To get the time interval (TI) of the pulse, statistical analysis of the TI in  
Figure 10: The path of case B.  
Figure 9: The path of case A. 50 sets of scanning results is done based on the Weibull distribution. Thus, the continuous disturbance composed of the waveform in Figure 11b with about 0.17 ms TI is regarded as the attribute of \(v_{2}\). 2. \(A_{e14\text{-}17}\) of the edge \(e_{14\text{-}17}\)  
In general, there are two kinds of radiated parts from the structure including pantograph, contact wire, and train roof while the arc discharge happens. The primary direct radiation is from the arc itself and the other is the secondary radiation generated by the induced current in the pantograph and contact wire. Therefore, the signal in \(v_{2}\) is the excitation of the structure of the pantograph-contact wire and the energy will be radiated by the equivalent antenna. Considering the large dimension in the longitudinal direction of the contact wire in a catenary, the equivalent antenna can be regarded as the Traveling Wave Wire Antenna. Thus, \(A_{e14\text{-}17}\) of the edge \(e_{14\text{-}17}\) can be represented by the model of the whole structure including pantograph, contact wire, and train roof in CST software as shown in Figure 12.  
In the model in Figure 12, the excitation is modeled as a discrete source between contact wire and pantograph with the continuous disturbance from \(v_{2}\), and the gap between pantograph and contact line is built as 5 mm. \(v_{17}\) is the receiver at the end of the roof. In this model, the size of the train roof is set at 25 m \(\times\) 4 m \(\times\) 0.03 m with the material aluminum. Since the roof is the main reflective structure, the carriage is simplified and represented by the roof. The height of the contact line and the roof is set to 2 m. The vertical distance between the contact line and the roof is set at 2 m. Since the actual length of the contact line is much longer than the train, the load is added on the contact line terminals at a quarter-wavelength position to avoid the influence in the simulation. Based on the above analysis, the node of \(v_{17}\) is simulated as a receiving probe corresponding to the function in OTCS.