## 4 Overcurrent Protection Coordination Results, Analysis and Discussion  
### Reliable Fault-Current Calculation Results  
As summarized from Section of An Adaptable Fault Analysis Technique, instead of using a fixed fault-current value for each fault type with the unconsidered reliability, this paper has contributed an adaptable fault analysis technique to calculate the minimax confidence interval of fault current for each different fault type. The maximum and minimum confidence thresholds of fault current are used to select tripping and pick-up thresholds of definite-time and inverse-time OC functions in the OCR of the DG-integrated DN, respectively. By considering a feeder only supplied by the 110/22 kV Can-Gio power substation from a real 22 kV DG-based distribution network, Table 2 shows the fault analysis results of this feeder. It is noted that Bus 5 is the end bus of the feeder. Three OC relays are used to protect this feeder including a 471 Hao-Vo OCR, a REC Hao-Vo OCR, and a REC Can-Thanh 163 OCR. The maximum fault currents can be seen by the OCRs in the  
Figure 10: A simplified single-line diagram of the real 22 kV DG-integrated DN.  
DN when the various fault types occur at their protected zones/lines. Specifically, the REC Can-Thanh 163 OCR operates as the primary protection for faults at Bus 5. The maximum fault-current value of each fault type such as 3 ph-G, 2 ph-G, ph-ph and 1 ph-G faults at Bus 5 is seen by this REC Can-Thanh 163 OCR, which is also shown in Table 2. Similarly, the REC Hao-Vo OCR operates as the primary protection for faults at Bus 13. The maximum fault-current value of each fault type such as 3 ph-G, 2 ph-G, ph-ph and 1 ph-G faults at Bus 13 is seen by this REC Hao-Vo OCR. In addition, the 471 Hao-Vo OCR operates as the primary protection for faults at Bus 2. The maximum fault-current value of each fault type such as 3 ph-G, 2 ph-G, ph-ph and 1 ph-G faults at Bus 2 is seen by this 471 Hao-Vo OCR.  
As mentioned in Section 3, after a 3 ph-G fault at Bus 2 of the feeder is cleared, three feasible FISR plans are proposed. Table 3 presents the maximum fault-current calculation results observed by the OCRs corresponding to four different operating scenarios of the DN, including:  
* Scenario 1-the DN topology before the fault occurs at Bus 2, i.e., the feeder supplied by the 110/22 kV Can-Gio power substation, as referred to the dashed line (a) in Figure 10.
* Scenario 2-the DN topology for the first FISR plan, as referred to the dashed line (c) in Figure 10.
* Scenario 3-the DN topology for the second FISR plan, as referred to the dashed line (d) in Figure 10.
* Scenario 4-the DN topology for the third FISR plan, as referred to the two dashed lines (c) and (d) in Figure 10.  
Moreover, the OCR triple for each topology including one primary relay and two backup relays is also shown in Table 3. It is noted that some faulted locations can be only detected and cleared by the OCR pairs. The maximum fault-current values which are calculated from four different fault types at the buses of the real 22 kV distribution network are indicated in this table by an order-based format, specifically [_the maximum 3 ph - G fault current;the maximum 2 ph - G fault current;the maximum 1 ph - G fault current; the maximum ph -  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{3}{*}{**Fault Types**} & \multicolumn{3}{c}{**Maximum Fault Currents Detected by the OCRs**} \\ \cline{2-4}  & **Maximum Fault Currents at Bus** & **Maximum Fault Currents at Bus** & **Maximum Fault Currents at Bus** \\  & **2 Are Detected by a 471** & **13 Are Detected by a REC** & **5 Are Detected by** \\  & **Hao-Vo OCR** & **Hao-Vo OCR** & **a REC Can-Thanh 163 OCR** \\ \hline
3 ph-G fault & 25,796 A & 11,911 A & 4902 A \\
2 ph-G fault & 24,347 A & 10,742 A & 4426 A \\
1 ph-G fault & 22,340 A & 10,316 A & 4246 A \\ ph-ph fault & 20,469 A & 6488 A & 2340 A \\ \hline \end{tabular}
\end{table}
Table 2: Numerical fault-current calculation results are seen by the OCRs in a considered feeder of the DG-based DN.