Neutral Point Grounding Modes Research Articles

Current spectral norm and phase variation based fault region identification for active distribution network

The paper presents a fault region identification method for the active distribution network (ADN) with limited PMU. First, PMU configuration and region division strategies are proposed based on the network topology. Next, the difference in three-phase current variations between the normal and fault regions of the ADN is analyzed. A multi-dimensional state monitoring matrix is built using the measured current data. The spectral norm ratio coefficient is constructed based on the 2-norm to lower the complexity of the multi-dimensional state monitoring matrix and quantify the difference in state changes before and after the fault occurs in each region. Then, the fault region is identified by combining each region’s spectral norm ratio coefficient and the change of the current phase. Finally, an IEEE 33-node simulation model is created to simulate faults under different working conditions. According to the simulation results, the suggested approach is less impacted by fault type, neutral point grounding mode, and transition resistance. Furthermore, even if the communication does not match the rigorous synchronization requirements, the proposed method can still complete the fault identification of the distribution network correctly and has high robustness.

Research on distribution network fault processing technology based on knowledge of graph

Safety and reliability are the basis of the development of a distribution network. To analyze the risk transmission process in the distribution network and ensure the safe and reliable operation of the power system, this paper intends to use the knowledge graph method to realize the risk analysis of the distribution network information system. Firstly, the knowledge graph method is used to extract and integrate the risk knowledge of the multi-dimensional information collected by the distribution network. Secondly, the knowledge graph model of distribution network risk analysis is constructed, and the multi-dimensional distribution network fault handling and knowledge graph construction oriented to the feeder and platform area are designed. The distribution line parameters of the low-voltage distribution network model, neutral point grounding mode, and different fault types are analyzed, and the non-planned island is searched based on the knowledge graph adjacency matrix. Finally, combined with the simulation experiment, it is verified that the proposed method can effectively depict the information risk process of the distribution network. The structure of this paper starts from the multi-node complex distribution network, combined with a knowledge graph and deep learning method, which can solve the distribution network fault more quickly.

Study on Dynamic Characteristics of Single-Phase Grounding Fault of 1000 MW Hydro Generator under Different Grounding Modes

The continuous operation of 1000 MW large hydro generators in China is of great value to the implementation of “double carbon strategy” and power grid safety. However, with the continuous increase of single unit capacity of the hydro generator, the problems of unit fault grounding current and neutral point voltage drift become more and more prominent, and the traditional analysis methods cannot accurately obtain the fault dynamic data. Therefore, starting from the neutral point grounding mode of the large hydro generator, taking a 1000 MW hydro generator as the research object, this paper establishes the single-phase grounding fault model under the condition of three-phase parameter asymmetry of stator winding and analyzes the dynamic characteristics of fault current, transient overvoltage, and neutral point voltage drift under different grounding modes by using transient analysis method; the influence of frequency offset on neutral voltage drift and the dynamic characteristics of single-phase grounding fault of the large hydro generator under different grounding modes are also obtained. Finally, according to the analysis results, the selection and optimization method of neutral grounding parameters are proposed, which provides a reference for the selection of neutral grounding mode and the research of protection strategy of the large hydro generator.

Research on neutral point grounding mode and single-phase earth fault location of medium voltage island microgrid

For medium voltage islanding microgrid, the voltage clamp of the main network neutral arc suppression coil or small resistance is lost. Multiple PTs parallel operation will occur because different entities of a microgrid independently measure the voltage. It is necessary to consider the influence of multi PTs ferroresonance on the neutral grounding mode of islanding microgrid. The neutral point ungrounded, neutral point grounded by arc suppression coil and neutral point grounded by small resistance are analyzed respectively, considering multi PTs ferroresonance and single-phase earth fault location, it is determined that the islanded microgrid adopts neutral point grounded by small resistance. On this basis, the zero sequence current distribution is used to locate the single-phase earth fault. Finally, a simulation example is built to verify the correctness of the proposed method.

Fault Location Algorithm in Distribution Networks Considering Distributed Capacitive Current

In recent years, with the expansion of urban scale and construction of energy infrastructure, more cities construct underground cables to replace overhead lines from the perspective of environment and safety. Thus, more distributed capacitive current flows back to distribution networks under fault conditions and affects the accuracy of fault locating. This paper proposes an iterative modification method of capacitive current to decrease the uncertainty of complex equations with micro synchronous phasor measurement unit (μPMU) data. Firstly, the initial fault location is calculated by using phasor measurement data without the shunt effect of grounding capacitance. Then, the capacitive current is estimated by the initial fault location distance, and the location result is modified by an iterative strategy. Finally, after iteration modification, a more accurate real number solution for complex equations can be obtained for complicated distribution networks with the uncertain capacitive current. The simulation results of a real underground distribution network and a modified IEEE 33 node test feeder in MATLAB/Simulink show that the proposed algorithm has higher accuracy than the traditional methods which do not have the iterative modification method of capacitive current under different fault locations, fault resistances, fault types and the neutral point grounding modes.

The Research of High Voltage Auxiliary Power System Neutral Point Grounding Modes between the Nuclear Power Plant and Conventional Fossil Fuel Power Plant

<p>Currently, in power plants, the application of the extinction coil in high voltage auxiliary power system neutral point is less experienced. A research done on nuclear power plant and conventional fossil fuel power plant proved that using an auxiliary power system’s different characteristics was leading to different demands of the grounding modes. Thus, this research was done by selecting the grounding mode of high voltage auxiliary power system neutral point on the main nuclear power plants and the partial fossil fuel power plants together with the calculation of practical engineering, and optimal design schemes. The high voltage auxiliary power system neutral point grounding modes have been induced in the large-scale into the nuclear power plant and the conventional fossil fuel power plant. Methods in determining the neutral point grounding modes are used by analyzing the principles commonly used grounding modes and requirements of related codes. First, choose the suitable grounding mode according to the calculation result of capacitive current. Then, choose more conducive grounding mode to the operation of power plant according to the operation of technology equipment. The power is required from the configuration, connection of auxiliary power and the cut from the accident of auxiliary power. As some power plants which are under-construction will be putting into operation one after another, the whole set of perfect security arrangements and operating experiences will also be accumulated inevitably. As a conclusion, high voltage auxiliary power system neutral point grounding modes directly affect the running of the auxiliary power system and even affect the security of the nuclear safety and the operation of the power plant. I hope this article can play a role for reference on the selection of the auxiliary power system grounding modes.</p>

The Research of High Voltage Auxiliary Power System Neutral Point Grounding Modes between the Nuclear Power Plant and Conventional Fossil Fuel Power Plant

<p>Currently, in power plants, the application of the extinction coil in high voltage auxiliary power system neutral point is less experienced. A research done on nuclear power plant and conventional fossil fuel power plant proved that using an auxiliary power system’s different characteristics was leading to different demands of the grounding modes. Thus, this research was done by selecting the grounding mode of high voltage auxiliary power system neutral point on the main nuclear power plants and the partial fossil fuel power plants together with the calculation of practical engineering, and optimal design schemes. The high voltage auxiliary power system neutral point grounding modes have been induced in the large-scale into the nuclear power plant and the conventional fossil fuel power plant. Methods in determining the neutral point grounding modes are used by analyzing the principles commonly used grounding modes and requirements of related codes. First, choose the suitable grounding mode according to the calculation result of capacitive current. Then, choose more conducive grounding mode to the operation of power plant according to the operation of technology equipment. The power is required from the configuration, connection of auxiliary power and the cut from the accident of auxiliary power. As some power plants which are under-construction will be putting into operation one after another, the whole set of perfect security arrangements and operating experiences will also be accumulated inevitably. As a conclusion, high voltage auxiliary power system neutral point grounding modes directly affect the running of the auxiliary power system and even affect the security of the nuclear safety and the operation of the power plant. I hope this article can play a role for reference on the selection of the auxiliary power system grounding modes.</p>

并网型光伏发电站中性点接地方式分析

太阳能是人类取之不尽用之不竭的可再生能源，具有充分的清洁性、绝对的安全性、相对的广泛性、确实的长寿命和免维护性、资源的充足性及潜在的经济性等优点，在长期的能源战略中具有重要地位。本文综述电网中性点不同接地方式的比较，为光伏电站中性点选择合适的接地方式，并以某光伏电站为实例，计算中性点接地电阻值，以供以后的工程参考。 Solar energy is a kind of inexhaustibile clean energy. It has sufficient cleanliness, adequacy and potential economic security of absolute and relative breadth, really long life and maintenance-free property, resources etc., and plays an important role in the long-term energy strategy. In this paper, the comparison of different neutral point grounding modes of power network is summarized to select the appropriate neutral point grounding for the photovoltaic power station. Taking a photovoltaic power station as an example, neutral grounding resistor is calculated to offer the values for reference value in the future.

Study on Decision Method of Neutral Point Grounding Mode for Medium-Voltage Distribution Network

The neutral grounding mode of medium-voltage distribution network decides the reliability, overvoltage, relay protection and electrical safety. Therefore, a comprehensive consideration of the reliability, safety and economy is particularly important for the decision of neutral grounding mode. This paper proposes a new decision method of neutral point grounding mode for mediumvoltage distribution network. The objective function is constructed for the decision according the life cycle cost. The reliability of the neutral point grounding mode is taken into account through treating the outage cost as an operating cost. The safety condition of the neutral point grounding mode is preserved as the constraint condition of decision models, so the decision method can generate the most economical and reliable scheme of neutral point grounding mode within a safe limit. The example is used to verify the feasibility and effectiveness of the decision method.

Distribution Grid Fault Location Applying Transient Zero-mode Current

To aim at the puzzles on faults location in distribution grids, the paper analyzed the distributing characteristics of transient zero-mode currents as the faults occurred, with the aid of correlation theory, a new fault circuit-selection and fault-location method was proposed based on transient zero model current for power distribution grid faults. The method is based on such a fact that the RMS was maximum of fault line transient zero-mode current, and the inner products between it and other line transient zero-mode current were less than zero, in addition, the transient zero-model currents at two sides of the fault point possessed opposite polarity and diverse waveform, and as well as small correlation coefficient closer to zero. In the end, the simulation results show that the proposed method on circuit-selection and fault-location for power distribution grids fault based on transient zero- mode current is correct and effective, and not affected by voltage epoch angle, and grounding resistance, and as well as neutral-point grounding modes. DOI: http://dx.doi.org/10.11591/telkomnika.v10i5.1289

Study of Electric Power System Neutral Point Grounding Using PSCAD/EMTDC

Neutral point grounding which is related to voltage level, network structure, insulation, communication and relay protection is very important problem to power system. Nowadays, the choice of neutral point grounding mode mainly relies on operation experiences or theoretical analysis which could not give a direct view of the dynamics of electric power system during disturbances. Therefore, this paper has established the simulation model of electric power system neutral point grounding with PSCAD/EMTDC to show the dynamics of neutral point grounding when disturbed by single-phase grounding in transmission lines, and the application of each neutral point grounding mode has been analyzed according to simulation results. The dynamic model of neutral point grounding in this paper is meaningful to the analysis of high-order, non-linear transients of power system as well.

Identifying Single-Phase-to-Ground Fault Feeder in Neutral Noneffectively Grounded Distribution System Using Wavelet Transform

A scheme of single-phase-to-ground fault feeder identification in distribution networks with the application of a wavelet transform technique is presented in this paper. The scheme uses zero-sequence current traveling waves to identify the faulted feeder, and the busbar residual voltage to determine an event caused by fault or switch operation. The current traveling waves measured by zero-sequence current transducers are decomposed using wavelet multiresolution analysis. The local modulus maxima of the wavelet transform are extracted to determine the time of the initial traveling wave. The wavelet transforms on all feeders at the time are compared in magnitude and polarity with each other to identify the faulted feeder. The feeder identification is independent of the network neutral-point grounding mode. The proposed scheme was implemented and verified using Electromagnetic Transients Program (EMTP)-generated signals. The scheme proved to be robust against transients generated during normal events, such as feeder energizing and de-energizing as well as capacitor bank switching.

High-Impedance Fault Detection in Distribution Networks With Use of Wavelet-Based Algorithm

A new simple and effective algorithm of arcing fault detection in distribution networks with the application of a wavelet transform technique is presented in this paper. The protection algorithm developed observes the phase displacement between wavelet coefficients calculated for zero-sequence voltage and current signals at a chosen high-level frequency. The final decision in regards to feeder switching off (or alarm issuing) is met either with a deterministic logic scheme or with the use of a neural net trained especially for that purpose. The developed wavelet-based high-impedance fault (HIF) detector has been tested with Electromagnetic Transients Program-Alternative Transients Program (ATP)-generated signals, exhibiting better performance than traditionally used algorithms and methods. The protection method proposed may be used for HIF detection independent of the network neutral-point grounding mode. The scheme proved to be robust against transients generated during normal events such as feeder energizing and de-energizing as well as capacitor bank switching