## 4 Case Analysis  
In order to verify the feasibility of the method proposed in this paper, 20 working conditions were randomly selected for testing under different breakage types in the local area of the DC grounding electrode. The measurement results were counted, and the measurement accuracy and error of the proposed method were judged. (1) Calculation model and parameters  
According to the DC grounding electrode model shown in Figure 18, the basic parameters are set as shown in Table 1, among them, the total number of grounding electrodes \(Q\) = 434 and the number of measurement points \(P\) = 98. In the figure, \(l_{k1}\), \(l_{k2}\), \(l_{k3}\)\(\ldots\), \(l_{km}\) = 0, which represents the distribution current value of the feeder rod at the continuous breakage position. When m = 2, it represents the type of two broken feeder rods. Under this type, 20 operating conditions under different breakage positions are randomly selected as case one. Similarly, when m = 3-6, 20 sets of operating conditions are designed for testing and verification under each breakage type. In summary, a total of five kinds of grounding electrode breakage conditions were designed for case calculation. As shown in Table 7. \begin{table}
\begin{tabular}{c c} \hline
**Fault Type** & \(K_{EC}\) \\ \hline Two feeder rods broken & \(k_{1}-1\leq K_{1}\leq k_{2}+1\) \\ Three feeder rods broken & \(k_{1}-1\leq K_{1}\),\(K_{2}\leq k_{3}+1\) \\ Four feeder rods broken & \(k_{1}-1\leq K_{1}\),\(K_{2}\),\(K_{3}\leq k_{4}+1\) \\ \(\ldots\) & \(\ldots\) \\ m feeder rods broken & \(k_{1}-1\leq K_{1}\),\(K_{2}\)\(\ldots\)\(K_{m-1}\leq k_{m}+1\) \\ \hline \end{tabular}
\end{table} 
Table 6: Evaluation coefficient \(K_{EC}\) under different fault types. 2. Results analysis  
According to the OSDM method proposed in this paper, the above five kinds of grounding electrode breakage cases are calculated, and the breakage conditions that conform to the evaluation coefficient \(K_{EC}\) in 20 groups of working conditions in each case are counted. The ratio of the number of samples that conform to the evaluation coefficient \(K_{EC}\) to the total number of samples is recorded as the measurement accuracy rate \(\gamma\). Taking Case 1 as an example, the measurement results are as follows. According to the results in Figure 19, \(k_{1}\) and \(k_{1}+1\) represent the actual breakage position under each working condition. The red dotted line range is the interval that satisfies the corresponding evaluation coefficient \(K_{EC}\). There are 19 groups that meet the conditions, and only the 18 th group of measurement results were not within the evaluation range. The measurement accuracy rate is \(\gamma=95\%\). The mean value of the measurement error coefficient of all working conditions that do not meet the \(K_{EC}\) standard in Case 1 is calculated, \(\overline{K_{ME}}=3\). Under the condition of inaccurate measurement in Case 1, the distance between the measured position and the actual breakage position of the feeder rod is an average of three feeder rods. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Fault Type** & \(K_{EC}\) \\ \hline case1 & Two feeder rods broken & \\ case2 & Three feeder rods broken & \\ case3 & Four feeder rods broken & 20 \\ case4 & Five feeder rods broken & \\ case5 & Six feeder rods broken & \\ \hline \end{tabular}
\end{table} 
Table 7: Grounding electrode broken case. Figure 19: Case1 measurement results. Figure 18: Calculation model of DC grounding electrode. Similarly, the corresponding measurement accuracy \(\gamma\) value and the corresponding measurement error coefficient mean \(\overline{K_{ME}}\) in the above five cases are counted. The specific results are shown in Figure 20:  
According to the measurement results of five cases of DC grounding electrode, the detection accuracy of the OSDM method proposed in this paper is between 80% and 95%.