Research On Fault Location Technology In Active Distribution Network

According to the rapid development of clean energy technology, distribution generation (DG) with highly increasing penetration rate has been integrated into the distribution network these years, which make the conventional single-supply distribution network change into the multi-supply active distribution network (ADN). Meanwhile, the operation management and fault analysis of the ADN become more complicated than conventional approaches. As a significant function for the distribution automation system, fault location technology is highly critical to ensure the reliability and stability of the ADN.Based on the aforementioned considerations, the fault location technology for the AND consists of optimal placement of feeder terminal unit (FTU), fault region location algorithm and fault distance measurement algorithm have been thoroughly studied in this thesis. The main researches of this thesis are as follows:Firstly, an optimal FTU placement algorithm considering the integration of DG is proposed based on the consideration of the fault location technology for ADN. According to the characteristics of network in active distribution network, the accuracy of state estimation can be achieved by means of optimal FTU placement. Moreover, FTUs can usefully isolate the fault region when a fault occurs, and the effects of FTU placement on the power supply failure loss in the ADN are analyzed. A scheme of optimal FTU placement based on genetic algorithm (GA) was proposed in this thesis, with the objective of keeping the FTU numbers at minimum, while meeting the accuracy of state estimation and power supply failure loss in the ADN. Case simulations demonstrate the feasibility and effectiveness of the proposed optimal FTU placement algorithm.Then, a fault region location algorithm is proposed for the situation that fault occurs in the AND with multiple DGs. The characteristic of fault in ADN is analyzed and the network can be divided into many regions according to the FTUs’ placement in the ADN. Depending on the ports’ type of each FTU and the fault current detected by each FTU, the fault region in ADN can be located precisely by fault location criterion. Simulation results show that the fault region can be located correctly regardless of the fault occurs in which region of ADN. Moreover, the fault region location algorithm is not affected with the changes of DG’s output power capacity.At last, a further fault distance measurement algrothim is proposed in order to measure the fault distance in the ADN. The fault region can be viewed as a network model with multi-ports, then the voltage equation can be established according to all the fault information collected by FTU ports of the fault region, and the nonlinear fault distance measurement equation can also be established by the mathematical derivation. The Newton-Raphson method is used to solve the nonlinear fault distance measurement equation and the fault point can be determined directly. Note that the fault distance measurement procedure needs to be repeated if there are some branches in the fault region. Simulation results show that the proposed methodology can locate the fault point accurately and the results aren’t influenced by the transition resistance. Hence, the proposed methodology has high accuracy and it could be applied widely in the ADN.