## 3 A Real 22 kV DG-Integrated Distribution Network: A Case Study  
A real 22 kV DG-contained distribution network of Ho Chi Minh City, Vietnam is simulated by the ETAP software for evaluating the reliable fault analysis results and validating the proposed ASPC approach of OCRs, as seen in Figure 9. It is worth noting that the real 22 kV DG-integrated distribution network is used for this study instead of standard IEEE distribution systems. To explain that, the use of real-time load data of this DN is completely appropriate to determine the min-max confidence thresholds of load power at each load bus, the min-max confidence thresholds of load current, the min-max confidence interval of bus voltages, and the min-max confidence interval of fault currents contributed by the grid and the DG units as presented in Section 2.3.3. In the steady-state (normal) operation mode, the ASPC approach is performed to give the optimal solution of TDS multiplier and \(A\), \(B\), and \(C\) coefficients for inverse-time OC functions and to select tripping and pick-up current thresholds respectively for the definite-time and inverse-time  
Figure 8: A flow chart of GA applied to the proposed ASPC approach of OCRs in the DN. OC functions in the OCRs of a feeder supplied by the 110/22 kV Can-Gio power substation such as a 471 Hao-Vo OC relay, a REC Hao-Vo OC relay, and a REC Can-Thanh 163 OC relay. Moreover, the relay coordination in the real distribution network is discussed only in radial topologies. As seen in Figure 9, the feeder supplied by the 110/22 kV Can-Gio power substation is separated from the feeder supplied by the 110/22 kV An-Nghia power substation through opening a LBS (load breaker switch) Can-Thanh 97 to be operated in the radial topology. In Vietnam, the radial distribution systems are used for the normal (long-term) operation mode, while the ring-type distribution systems are only established for ancillary services or post-fault service restoration scenarios (the short-term operation mode). Therefore, the protection coordination solutions of OCRs are mostly analyzed for the radial systems, while the coordination solutions of DOC relays in the ring-type systems are limited in this case study. Figure 10 shows a simplified single-line diagram of the real 22 kV DG-integrated DN so that pre-fault and post-fault DN topologies can be indicated more clearly. Noted that a 3 ph-G fault is given at Bus 2 of the DN. More clearly, at the pre-fault operation mode, a LBS (load breaker switch) Can-Thanh 97 is normally opened, the real 22 kV DN operates with two separate feeders. One feeder is supplied by the 110/22 kV Can-Gio power substation; and a power flow of this feeder is indicated by a dashed line (a). The other feeder is supplied by the 110/22 kV An-Nghia substation; and its power flow direction is shown by a dashed line (b). When the 3 ph-G fault occurs at Bus 2, a 471 Hao-Vo relay and a REC Hao-Vo relay will give the tripping signals to the related circuit breakers, namely a 471 Hao-Vo circuit breaker and a REC Hao-Vo recloser, to isolate the fault at Bus 2. After clearing the fault, according to the proposed FISR plans [10,11], the protection coordination results of the related OCRs will be updated by the ASPC system through the SCADA function. By specifically considering the given fault at Bus 2, there are three feasible FISR plans which will be the basis to find the optimal parameter settings of the related OCRs. The first FISR  
Figure 9: A real 22 kV DG-based distribution network is supplied by two power substations, namely, the 110/22 kV Can-Gio substation and the 110/22 kV An-Nghia substation, three IBDGs (DG\({}_{1}\), DG\({}_{2}\), and DG\({}_{3}\)), and one RBDG (DG\({}_{4}\)). plan is to use an adjacent distribution feeder to restore the power for interrupted customers through closing the LBS Can-Thanh 97 device and opening a circuit breaker controlled by a CB GEN relay. The power flow direction of the first FISR plan is indicated by a dashed line (c).