In the low-voltage (LV) distribution network, a three-phase unbalance problem often exists. It does not only increase line loss but also threaten the safety of the distribution network. Therefore, the author designs a residential load transfer device for a LV distribution network that can deal with a three-phase unbalance problem by changing the connecting phase of the load. It consists of three parts: user controller for phase swapping, central controller for signal processing and monitoring platform for strategy calculation. This design was based on message queuing telemetry transport (MQTT) communication protocol, and Long Range and 4th Generation mobile telecommunications (LoRa + 4G) communication mode is used to realize the wireless connection between equipment and monitoring platform, and a control scheme is proposed. The improved multi-population genetic algorithm (IMPGA) with multi-objective is used to find the optimal swapping strategy, which is implemented on the monitoring platform. Then the phase swapping is realized by remote control, and the function of reducing three-phase unbalance is realized. The practical experimental result shows that the method can help to reduce the three-phase unbalance rate by changing the connection phase of the load, and the simulation results verify the effectiveness of the algorithm in the phase-swapping strategy.Energies 2019, 12, 2842 2 of 18 often unbalanced. Therefore, in order to protect equipment, ensure the quality of the power supply and reduce losses, an economic and effective solution is needed to solve the three-phase unbalance problem.In China, the LV feeders are usually three-phase four-wire systems, and have single-phase and three-phase power supply modes. In the LV distribution system, the main methods to reduce three-phase unbalance rate are power compensation and load transfer. However, although reactive power compensation can reduce the three-phase unbalance by increasing the power factor, when the three-phase unbalance is very serious, the reactive power compensation will not completely solve the three-phase unbalance problem [7], and reactive power compensation device need high cost [8]. The most direct and effective techniques to deal with the unbalanced distribution of load is to dynamically change the connection phase of single-phase users according to the unbalanced rate, so that the unbalanced rate of three-phase is within the prescribed range. Traditionally, the three-phase unbalance problem has been solved by manually to adjust the users' phase connection, but this method will cause the temporary power lose. And at the same time, due to the uncontrollable customer's power consumption, three-phase unbalance may occur in a short time. Therefore, manual adjustments require high labor costs and make the poor user experience.Power companies strive to innovate and add new elements of automation and intelligence to traditional distribution networks.[9] pointed out that the electric power distribution network is very complex, and not suitable for the...

At present, the detection methods on series arc faults are mainly based on the current of the main circuit, which probably results in misjudgment because of the singularity of the normal working current in a nonlinear load. What's worse, is the arc fault characteristic in the small power branch is easily ignored in the current of the main circuit, which leads to missed judgment. To solve these problems, a detection method based on coupling signal acquisition and higher-order cumulant identification is presented, through the electromagnetic coupling mechanism of high frequency current. By analyzing the coupling signal of the high-frequency current and using the higher-order cumulant algorithm during arcing process, the kurtosis of the coupling signal is calculated. In this paper, the unified threshold value on the kurtosis in various conditions is obtained. The results show that the novel method can be effectively used to detect and identify the series arc faults.INDEX TERMS Coupling, higher-order cumulant, kurtosis, series arc faults.

Fault arc detection is an important technology to ensure the safe operation of electrical equipment and prevent electrical fires. The high-frequency noise of the arc current is one of the typical arc characteristics of almost all loads. In order to accurately detect arc faults in a low-voltage alternating-current (AC) system, a novel differential high-frequency current transformer (D-HFCT) sensor for collecting high-frequency arc currents was proposed. The sensitivity and frequency band of the designed sensor were verified to ensure that the acquisition requirements of the high-frequency current were satisfied. A series arc fault simulation experiment system was built, and resistive, inductive, and non-linear load and high-power shielding load experiments were carried out. Experiments showed that the sensor output signal was close to zero in the non-arc state, and the sensor output response was a high-frequency glitch in the arc state. The results were consistent for different loads, and the discrimination between normal and fault states was obvious, which proved that the sensor is suitable for series arc fault detection.