## 4 Overcurrent Protection Coordination Results, Analysis and Discussion
### Protection Coordination Results in Scenario 2
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**The OCRs**} & \multirow{2}{*}{**50P**} & \multirow{2}{*}{**50G**} & \multirow{2}{*}{**51P**} & \multirow{2}{*}{**51G**} & \multirow{2}{*}{**51G**} & \multirow{2}{*}{**50G**} & \multirow{2}{*}{**GA**} & \multirow{2}{*}{**GSA**} & \multirow{2}{*}{**PSO-GSA**} & \multirow{2}{*}{**GA**} & \multirow{2}{*}{**GSA**} & \multirow{2}{*}{**PSO-GSA**} \\ \cline{5-10} \cline{8-10} \multirow{4}{*}{\begin{tabular}{c} The REC \\ Can-Thanh 36 \\ OCR \\ \end{tabular} } & \multirow{4}{*}{\(I_{f}\)} & \multirow{4}{*}{20,076 A} & A & 6.71 & 52.45 & 126.51 & A & 9.23 & 33.59 & 73.50 \\  & & & & & & 2.31 & 2.31 & 2.07 & B & 1.74 & 1.82 & 2.50 \\  & & & & & & C & 0.09 & 0.93 & 0.02 & C & 0.11 & 0.98 & 1.50 \\ \cline{2-10}  & & & & & & TDS & 0.73 & 0.09 & 0.03 & TDS & 0.024 & 0.01 & 0.01 \\ \cline{2-10}  & \multirow{4}{*}{\(t_{trip}^{defined}\)} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{\(t_{trip}^{defined}\)} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{\begin{tabular}{c} The tripping time of the relay for the typical fault at Bus 3: \\ \end{tabular} } \\ \cline{5-10} \cline{8-10}  & & & & & & & \(t_{trip}\) & 0.65 s & 0.62 s & 0.65 s & \(t_{trip}\) & 0.65 s & 0.62 s & 0.65 s \\ \hline \multirow{4}{*}{\begin{tabular}{c} The REC \\ Can-Thanh \\ 163 OCR \\ \end{tabular} } & \multirow{4}{*}{\(I_{f}\)} & \multirow{4}{*}{2186 A} & \multirow{4}{*}{\(I_{f}\)} & \multirow{4}{*}{2755 A} & A & 7.77 & 44.37 & 0.60 & A & 0.01 & 30.55 & 0.01 \\  & & & & & & 2.46 & 1.79 & 2.28 & B & 0.60 & 2.19 & 1.75 \\ \cline{1-1} \cline{8-10}  & & & & & & C & 0.47 & 0.28 & 0.02 & C & 0.89 & 0.79 & 0.74 \\ \cline{1-1} \cline{8-10}  & \multirow{4}{*}{\(t_{trip}^{defined}\)} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{\(t_{trip}^{defined}\)} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{\
\begin{tabular}{c} TDS \\ \end{tabular} } & \multirow{4}{*}{0.26} & \multirow{4}{*}{0.03 s} & \multirow{4}{*}{1.26} & \multirow{4}{*}{TDS} & \multirow{4}{*}{0.37} & \multirow{4}{*}{0.01} & \multirow{4}{*}{0.46} \\ \cline{5-10} \cline{8-10}  & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & & \\ \hline \multirow{4}{*}{
\begin{tabular}{c} The REC \\ Can-Thanh \\ 163 OCR \\ \end{tabular} } & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{\(t_{trip}^{defined}\)} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{0.01 s} & \multirow{4}{*}{TDS} & \multirow{4}{*}{0.01} & \multirow{4}{*}{TDS} & \multirow{4}{*}{0.01} & \multirow{4}{*}{0.01} & \multirow{4}{*}{0.01} & \multirow{4}{*}{0.01} \\ \cline{5-10} \cline{8-10}  & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & & \\ \cline{1-1} \cline{8-10}  & & & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Optimal protection coordination results of the OCRs in Scenario 2 and their tripping time when the fault is at Bus 3.  
tripping-current threshold of 50P/G protection functions of the REC Can-Thanh 163 OCR. By further considering the REC Can-Thanh 163 OCR, the tripping current \(I_{f}\) of its 50G function is set to 2501 A as shown in Table 5. Thus, this tripping current is considered as a terminated point of the inverse-time characteristic curve of the 51G function in the same REC Can-Thanh 163 OCR. Similarly, the tripping current \(I_{f}\) of the 50G function of the REC Can-Thanh Hao-Vo OCR which is 2755 A is considered as a finishing point of the inverse-time characteristic curve of its 51G function, as clearly illustrated by the curve of Relay 2, i.e., a red curve of the plots at the left-side of Figure 12.