As a result of small fault current, high level of noise and a large penetration of distributed generators (DG), in the neutral non-effectively grounded medium-voltage (MV) distribution networks, it is quite difficult to locate the faulted line section for single phase to ground faults. In this paper, using a technique based on synchronized measurements in distribution networks, a fault location method based on the analysis of the energy of the transient zero-sequence current in the selected frequency band (SFB) is proposed. The equivalent impedance of the distribution network with lateral branches is studied with an equivalent network, and the phase-frequency characteristics of the equivalent impedance are analyzed. The SFB, within which the transient energy of the faulty line section is larger than that of the healthy line sections is determined. A combined fault-section location criterion is proposed and the implementation scheme is illustrated with the distribution level phasor measurement units. Numerical simulations of the IEEE 34 node system and the field experiments of a 10kV distribution network validate the feasibility and effectiveness of the proposed method.

Grounding arc fault (GAF) happening in the medium-voltage (MV) distribution system may result in great damages to devices and human security. However, difficulties still exist in identifying those faults with higher grounding impedances due to the weaker feature and the varieties when grounded with different surfaces. This paper presents an integrated algorithm to detect the high impedance arc faults (HIAFs) with high-resolution waveform data provided by distribu-tion-level PMUs (D-PMUs) deployed in the system. An im-proved arc model is proposed which can continuously imitate the randomness and intermittence during the ‘unstable arcing period’ of arc faults. The integrated algorithm consists of two branches. Firstly, the variations of HIAFs during unstable arcing period is identified with the unified harmonic energy and global randomness index, which can unify the scale of harmonic content in different fault situations and enlarge the disparities from non-fault conditions. Then, the waveform distortions of HIAFs during the stable arcing period are identified with discrete wavelet transform (DWT) to extract the detailed distribution characteristics. The reliability and security of the proposed algorithm is verified with numerical simulations and field tests in a 10kV distribution system.

Detection of the high impedance fault (HIF) in distribution systems is significant for power utilization safety. However, many HIFs are challenging to be identified due to low currents and diverse characteristics. Particularly, the slight nonlinearity during weak arcing processes, the distortion offset caused by various heat dissipations, and the interference of noises could lead to malfunctions of traditional algorithms. This paper proposes a distortion-based algorithm to improve the reliability of HIF detection. Firstly, the challenges brought by the diversity of HIF characteristics are illustrated with field experiments in a 10kV real-world system. HIFs are classified into five types according to their various distortions. Secondly, an interval slope is defined to describe waveform distortions. The interval slope is extracted by linear least square filtering (LLSF) and Grubbs-criterion-based robust local regression smoothing (Grubbs-RLRS), so that distortions under different fault conditions can be uniformly described. Thirdly, an algorithm is proposed to judge the features presented by the interval slope, and distinguish from non-fault conditions. Finally, the reliability and security of the proposed algorithm are thoroughly analyzed with real-world HIFs and the simulated HIFs in IEEE 34-bus and IEEE 123-bus systems. Improvements of the proposed algorithm are shown by comparing with other algorithms.

The accurate modelling of the arc is significant for the researches on the high impedance arcing fault (HIAF), which performs sig-nificant variations of nonlinearity under different fault conditions. The diversity of the waveform distortions during HIAFs is rarely investigated previously. This paper proposes a black-box HIAF model to simulate the nonlinear current distortions with im-proved controllability and higher accuracy. Firstly, with field HIAF faults experimented in a 10kV distribution network, three major characteristics varying in the distortions of the fault cur-rent are summarized and illustrated, including the offset, extent, and duration. Secondly, a distortion-controllable (DIST-C) HIAF model is proposed based on the heat balance equation of the arc after reasonable assumptions and transformations. The three characteristics of distortions can be independently and directly controlled. Then, the implementation of the DIST-C model in PSCAD is detailedly illustrated. An automatic parameter deter-mination method using particle swarm optimization in a Py-thon-PSCAD-MATLAB co-simulation platform is presented. Finally, the controllability and accuracy of the proposed model are verified by comparing it with the other existing typical black-box models.

With the fast development of renewable energy resources, harmonics in the modern distribution system become more serious due to the wide adoption of power electronic devices. Nowadays, the distribution-level phasor measurement units (D-PMUs), which can provide synchronized harmonic data with high time resolution, are under fast development. To take advantage of the D-PMUs, a hierarchical harmonic contribution (HC) determination method is proposed in this paper for systems with multiple harmonic sources. The HCs are determined by the widely linear complex partial least squares (WL-CPLS) method which is both accurate and efficient. In the actual power system, the D-PMUs are not fully installed at all buses and the harmonics monitored by each D-PMU are actually the aggregate effects of multiple harmonic sources in the subarea. Based on the above consideration, a hierarchical HC strategy is proposed to locate the main harmonic contributors layer by layer. The proposed method can be applied to the radial distribution system with any number of D-PMU placement. The methodologies are illustrated and verified by the IEEE 37-bus system.

Battery energy storage (BES) systems play an increasingly important part in power system operation because of their high efficiency and decreasing cost. This article proposes a mixed integer linear programming (MILP) model of battery degradation considering both depth of discharge (DoD) and state of charge (SoC), which can reflect the battery degradation mechanism. To improve computational efficiency for the economic scheduling of power system, a novel one-dimensional linearization is proposed to linearize this two-variable function, which significantly reduces computation burdens without loss of accuracy. Considering the battery degradation cost, a day-ahead economic scheduling model is built and a MILP algorithm is applied to solve it. The effectiveness of the MILP-based battery degradation model for economic scheduling is validated using the modified IEEE 30-bus system. For comparison, other existing battery degradation models are also implemented in the same system.