# Fault Diagnosis System of Power Grid Based on Multi-Data Sources
## 5 Example Analysis  
### Description of Example and Running Process of Fault Diagnosis System  
The fault diagnosis system and related algorithms have been implemented in the Pycharm2020 programming environment. In order to test the reliability and efficiency of the system in the face of rather complex fault problems, the IEEE 30 bus system, whose protection is configured according to the requirements of 330-500 kV power grid in a province of China, is simulated in PSCAD. The partial wiring diagram of the IEEE 30 bus system is shown in Figure 10. The overall wiring diagram of the IEEE 30 bus system is too large to be displayed clearly. Some electrical elements unrelated to fault diagnosis are hidden in Figure 10. All electrical elements have been numbered. The fault example used in this paper considers the simultaneous faults of three \(V\_e\) class elements. Although the simultaneous faults of three \(V\_e\) class elements are very likely to lead to unstable operation of the power system, the purpose of this example is to simulate extreme grid fault conditions to demonstrate the process and performance of this fault diagnosis system. Fault description is as follows: Line L3 fault occurs. L3 mainline protection acts.CB6 refuses to trip. Remote backup protection on the B1 side of line L2 acts to remove the fault. At the same time, line L6 fault occurs. L6 mainline protection acts. CB15 refuses to trip. The fault is removed by the remote backup protection on the B6 side of line L8 but causes near backup protection on the B7 side of line L8 maloperation. At the same time, the bus B15 fault occurs. B5 bus protection acts. CB58 refuses to trip, and the fault is removed by the remote backup protection on the B18 side of line L28. Figure 9: Batch processing system flow chart. The accident-level information received by the dispatching center includes action protections RBP_L2_B1, MP_L6, NBP_L8_B7, RBP_L8_B6, BP_B15, RBP_L28_B18 and tripping circuit breakers CB4, CB18, CB19, CB55, CB56, CB57, CB71. Due to loss of partial accident-level information, tripping of CB7 and action of MLP_L3 are unknown. The real-time processing system in the dispatching center is started first. In the fault pre-diagnosis process, the initial set of suspicious faulty elements (_V_e1_ = {L2, B3, L3, L6, B7, L8, B15, L28, L21, L22, L27}) and the set of suspicious faulty elements (_V_e2_ = {L6, L8, B15})) are obtained by Algorithm 2. The initial set of faulty elements (_V_e3_ = {L6, L8, B15}) is obtained by constructing Petri nets and iterative calculations. In the stage of fault diagnosis and information missing analysis, according to the Algorithm 3, the calculated correctness values are L6\(p\) = 0.9325, L8\(p\) = 0.0773, B15\(p\) = 0.933. The operation statuses of related protections are calculated and judged to show in Table 9. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Name** & **MP\_L6** & **NBP\_L8\_B7** & **MP\_L8** & **NBP\_L8\_B6** & **RBP\_L8\_B6** & **BP\_B15** \\ \hline Action & 0.9139 & 0.0698 & 0.0758 & 0.0698 & 0.9030 & 0.9097 \\ \hline Actual action & \multirow{2}{*}{1} & \multirow{2}{*}{1} & \multirow{2}{*}{0} & \multirow{2}{*}{0} & \multirow{2}{*}{1} & \multirow{2}{*}{1} \\ value & & & & & & \\ \hline Difference & \(-0.0861\) & \(-0.9302\) & 0.0758 & 0.0698 & \(-0.0970\) & \(-0.0903\) \\ \hline \multirow{3}{*}{Judgment} & Operate & \multirow{3}{*}{Maloperation} & Operate & Operate & \multirow{3}{*}{Operate } & \multirow{3}{*}{Operate } \\ normally, no & & normally, no & refuse- & refuse- & & normally, no \\ \cline{1-1} \cline{5-5}  & & & operation & operation & & maloperation \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Judgment of operation statuses of related protections. Figure 10: IEEE 30 bus system partial wiring diagram. The set of faulty elements is _V_e4_ = [L6, B15]. Maloperation protection set is \(P\)1_ = {NBP_L8_B7}. Refuse-operation protection set is \(P\)2_ = {}. Maloperation circuit breaker set is _CB_1_ = {}. Refuse-operation circuit breaker set is _CB_2_ = {CB58, CB15}.