## 6 Conclusions  
Development of an adaptive current differential protection and fast auto-closing system for application in 10 kV electricity distribution networks in China Southern Power Grid has been carried out. The system uses 4G LTE wireless communication network for its current differential protection and  
\begin{table}
\begin{tabular}{c l l} \hline \hline
**Flt** & \multicolumn{2}{c}{**Operation Sequence of Equipment**} & **Load Switch/CB Opening Time** \\ \hline \multirow{4}{*}{f1} & 1. Diff. protection between RMU1 and RMU2 operates & \\  & 2. CB F36 trips & \\ \multirow{2}{*}{f1} & 3. 604 at RMU1 and 604 at RMU2 open & At RMU1, 604 opening time: 870 ms \\  & 4. CB F36 reclose & At RMU2, 604 opening time: 870 ms \\  & 5. 601 at RMU2 closes & \\ \hline \multirow{4}{*}{f2} & 1. Diff. protection between RMU3 and RMU4 operates & \\  & 2. CB 9105 trips & At RMU3, 601 opening time: 860 ms \\  & 3. 601 at RMU3 opens & At RMU4, 9105 opening time: 370 ms \\  & 4. 601 at RMU2 closes & \\ \hline \multirow{4}{*}{f3} & 1. Diff. protection between F05 and RMU5 operates & \\  & 2. CB F05 trips & At RMU5, 601 opening time: 870 ms \\  & 3. 601 at RMU5 opens & \\  & 4. 601 at RMU2 closes & \\ \hline \multirow{4}{*}{f4} & 1. Busbar protection of RMU4 operates & \\  & 2. CB F05 and CB 9105 trip & \\ \cline{1-1}  & 3. 604 at RMU5, 9103 at RMU4 and 601 at RMU3 open & At RMU4, 9103 opening time: 870 ms \\ \cline{1-1}  & 4. CB F05 reclose & \\ \cline{1-1}  & 5. 601 at RMU2 closes & \\ \hline \hline \end{tabular}
\end{table}
Table 2: Test results of fault isolation time.  
Figure 9: 10 kV Network used for the test.  
control function. The system can locate and isolate faults in less than one second, while conventional overcurrent protection has no fault location capability. Manual locating and isolation of power system faults may take minutes or even hours. The system improves the accuracy of fault location of the power system, reduces the fault outage time, and improves the power supply reliability of the distribution network by implementing the differential protection function and the fast auto-closing function. As it can detect the change of the topology of the primary distribution network, the differential protection can adaptively change its configuration settings to suit the new topology of the distribution network. The settings are changed automatically according to the change of the topology of the primary circuit, whilst traditionally the setting change is done manually. This saves time for site operating and maintaining of the system. As it can quickly locate and isolate the power system faults and restore the power supplies to the healthy part of the distribution networks in less than one second, this improves the reliability of the power supplies to customers. The system has been factory tested to demonstrate the effectiveness of the system. The communication network data transmission and time synchronization are satisfactory for its application. It is expected that, with the application of the system, faults in the 10 kV distribution networks can be located and isolated quickly. It shortens the outage time of the important load and can improve the reliability of power supply significantly.  
Conceptualization, H.S.C.; Formal analysis, X.J. ([PERSON]); Investigation, W.A. and X.J. ([PERSON]); Resources, H.Y.Z.; Writing - original draft, J.J.M. All authors have read and agreed to the published version of the manuscript.  
This research was funded by China Southern Power Grid Co. Ltd.  
The authors declare no conflict of interest.