Short circuit current forecast of large scale power grid based on improving BP Artificial Neural Network combined with Genetic Algorithm

The need for electrical energy is changing and increasing, requiring system flexibility always to be changed and developed. On the other hand, changes in the configuration of the electric power system due to the addition of components or sub-systems also change system parameters such as impedance or level of fault current (short circuit current). This paper presents a study of changes in the fault current caused by adding a new generating bus to an electric power system. This paper aims to determine the change in short-circuit current due to the addition of generators on new buses connected to existing buses to identify the most suitable location for adding these generators based on short-circuit current levels. Three-phase short circuit faults are simulated and analyzed on the IEEE 14 bus standard system using ETAP software with a base MVA 615 MVA. The addition of generators was carried out at five locations with varying generating capacities. The research results show that the short circuit current will change significantly when adding a generator bus to bus 13, with an average percentage change of 5,656%. The smallest change occurs when adding a generator to bus 2, with an average percentage change of 2,417%. The research results conclude that connecting a generator to a new bus linked to an existing generator bus (PV bus) is more effective than connecting it to a new bus associated with a load bus (PQ bus).

Today, Ukraine and the world face important issues related to solving the problems of the energy sector, including electricity. In networks of different voltages of power systems the level of short-circuit currents is constantly growing, while the requirements for electrical devices, live parts, power transformers and switchgear designs are becoming more stringent. There is a problem of optimal coordination in the dynamics of electrical equipment parameters and power system requirements or coordination of electrical equipment parameters with existing short-circuits current levels. The growth of short-circuit currents in electrical networks of all voltage classes makes it important to develop new effective methods and devices designed to reduce them. The article considers the issues of comparing the current of single-phase and three-phase short-circuit, average regional power system, the integrated parameters of electrical networks of such a system. Limitations of currents of single-phase short-circuits are analyzed in detail in problem nodes where autotransformers are installed. The conducted researches allowed to recommend the improved methods of calculations of electric devices and current-carrying parts on electrodynamic and thermal stability at short-circuit, including at single-phase. Recommendations for creating a mathematical model for calculating a nonlinear system in the presence of flexible conductors are given, because most of the damage (in the form of short-circuit) on high-voltage overhead power lines and switchgear is accompanied by an electric arc with parameters that change over time. In addition, significant short-circuit currents cause mechanical displacements of flexible wires in space, which leads to changes in the phase distances and inductive resistances of overhead lines of forward and reverse sequences. All these listed factors have a mutual influence during s.c. In addition, when operating electrical installations, an important factor is the switching life of switches, which affects the reliability of the installation and its technical and economic performance. The criterion for decommissioning the circuit breaker may be the residual life of the circuit breaker at the level of one tripping of the full tripping current of the circuit breaker. The analysis showed that it is necessary to take into account when calculating the short-circuit currents additional thermal action of various energy sources and the power system as a whole, synchronous generators and compensators, synchronous and asynchronous motors.

The short-circuit current level has become the most prominent constraint for composite power grid. Consequently, it is of unprecedented necessity to adopt specific measures to limit the short-circuit current levels in transmission network planning. A multi-objective model is proposed in this paper to configure current limiting measures. The proposed model is risk-based which considers both the occurrence probabilities and consequence severity levels of short circuit events. NSGA-II is utilized to solve the Pareto proposed model, which provides a Pareto set of optimal current limiting solutions, rather than a single solution. This proposed method effectively enhances both the cost-effectiveness and decision flexibility in current limiting planning.

Existing state-of-the-art realizable RC reduction methods may not be suitable for scalable power grid reductions due to the fast growing computational complexity and the large number of ports. In this work, we present a scalable power grid reduction method for reducing large-scale flip-chip power grids based on recent spectral graph sparsification techniques. The first step of the proposed approach aggressively reduces the large power grid blocks into much smaller power grid blocks by properly matching the effective resistances of the original power grid networks. Next, an efficient spectral graph sparsification scheme is introduced to dramatically sparsify the relatively dense power grid blocks that are generated during the previous step. In the last, an effective grid compensation scheme is proposed to further improve the model accuracy of the reduced and sparsified power grid. Since reduction of each power grid block can be performed independently, our method can be easily accelerated on parallel computers, and therefore expected to be capable of handling large power grid designs as well as incremental designs. Extensive experimental results show that our method can scale linearly with power grid sizes and efficiently reduce industrial power grids sizes by 20X without loss of much accuracy in both DC and transient analysis.

The integration of Distributed Generation (DG) in electric power systems has brought about the need for the improvement of the existing protective relaying principles used in distribution systems. This is because the integration of DG transforms the conventional single-source radial distribution system to a bidirectional multisource distribution system. Therefore, it is necessary to analyse the new short circuit fault current level, the general requirements for the integration of DG units, the requirement under abnormal conditions, power quality requirements, and the protection requirements. This chapter presents the impact of DG units on the short circuit current level and protective relaying in distribution systems. An overview of protection in conventional distribution system is first described. Afterwards, the impact of DG on the short circuit fault current and the protection of a distribution system integrated with DG are presented. Also, case studies and simulation examples on protective relaying in a distribution system integrated with DG are presented. Furthermore, some emerging technologies that can be applied to improve the protective relaying schemes in a DG-integrated distribution system are highlighted.

The distance for AC and DC dense transmission channels is very long, the transmission capacity is large, and the number of crossing points for 220kV and above are large. Multiple faults are prone to occur in extreme weather, natural disasters and so on, which seriously endangers the security of the power grid. The transmission sections are generally the weak links of power grid, and the rapid search of key transmission sections considering the influence of multiple faults is of great significance to the protection and control of power grid. The current research focuses on the influence of natural disasters on transmission equipment and transmission section search methods such as grid cut search and network contraction. But the impact of multiple faults on security and stability characteristics of power grid and the weak transmission sections haven’t been analyzed. In this paper, a key transmission section identification method considering multiple preconceived faults is proposed. Multiple faults are divided into three types, which are multiple AC line faults, multiple DC line faults and AC / DC line mixed faults. And the impact of the multiple faults on power grid security is analyzed. Then, the key section identification method considering multiple fault disturbances and the weak section identification method after topology changes due to multiple faults are studied. The validity of the proposed method is verified in scenarios with multiple expected faults by using AC/DC hybrid power grid data. Identification of critical sections under multiple faults is an important basis for on-line risk early warning and decision-making of multiple faults in large power grid, which has important practical value.

The increase in the levels of short-circuit currents in the power system of the Republic of Belarus requires the study of the parameters of the electrodynamic stability of the main structural elements of electrical installations with flexible conductors. In case of a short circuit in the network, currents tenfold exceeding the rated one hundreds of times can flow through the current-carrying part of the device. When the magnetic fields formed by these currents interact, significant electromagnetic forces arise, which have a destructive effect both on the current-carrying parts themselves and on the structural elements of electrical installations, viz. support insulators, switching devices, measuring equipment. The movement of the wires in a short-circuit mode leads to the appearance of significant dynamic loads in them, which, in turn, are transmitted to the portals, support insulators and electrical devices. A topical problem is the occurrence of unacceptable mechanical forces in the main structural elements that can cause their destruction. Thus, the analysis of the physical and mechanical parameters and geometric dimensions of the flexible busbar of switchgear shows that a violation of the condition of electrodynamic resistance to tension is unlikely due to the high mechanical strength of the large-section steel-aluminum wires used. At the same time, span-limiting portals, support insulators and other electrical devices have significantly lower permissible bending loads. When exposed to dynamic forces, the conductors bend and transfer the load to the structural elements which have certain elasticity. Thus, a reliable determination of dynamic loads, taking into account the current-carrying parts acting on the supporting structures, is possible only if a dynamic task is set. The article describes the methods of mathematical modeling and computational experiment for analyzing the parameters of the electro-dynamic stability of the main structural elements which are determined using coefficients that depend on the natural frequencies of oscillations and the nature of changes in dynamic forces over time. To solve these problems, mathematical models are compiled and boundary value problems are formulated for calculating the electrodynamic stability of structural elements, taking into account the possible coincidence of the frequencies of natural and forced oscillations of structural elements taking into account the probable coincidence of the frequencies of forced and natural vibrations of structural elements.

This paper deals with problems connected to the distance protection of double-circuit transmission lines. Because of the zero sequence mutual coupling of parallel circuits, the relay "sees" incorrect impedance. In this paper, the authors develop an adaptive model which solves problems of single-line-to-ground faults on a single line. Different operation modes change short circuit currents (I/sub k1/ - phase-to-earth short circuit current and I/sub k3/ - three-phase short circuit current) on both ends. In fact, the parameters of the active network will be changed. The idea was to develop an adaptive model with different independent Kohonen networks. Each network is trained with short-circuit examples according to the switching mode and operation mode. Input parameters are voltage, current, switching mode and operation mode. The developed adaptive model was tested on a double-circuit 400 kV transmission line.

Distributed generation (DG) has gained popularity among electricity end users who are determined to contribute to a cleaner environment by conforming to green and sustainable energy sources for various daily needs. The power system impact of such trends (e.g. roof-top solar-PV) need thorough investigation, such as impact on fault current levels on the distribution network. Varying fault current levels could adversely affect the operation of protection relays, which may lead to localized blackouts. Therefore, it is imperative to avoid localised blackouts due to mal-operation of protective relays under high penetration of DGs in distribution network. The focus of this research is to study the importance and implications of protective relays and over-current protection in the presence of distributed generation; where the impact of distributed generation on distribution network is identified. Relay coordination is observed to determine their operation characteristics to avoid mal-operation with the presence of DGs (e.g. solar-PV). This paper uses the UK generic distribution network model to simulate different scenarios in DIgSILENT Power Factory. The resulting power quality measures, such as voltage levels, short-circuit current levels and frequency are presented and discussed in the paper. The research highlights that small-scale DG penetration allows for existing protection infrastructure to continue operation and expensive upgrades for overall network are not required as fault levels remain the same.

This letter presents a correlation between the reduction of the saturation current level and increase of on-state resistance and the top-metal ageing of normally ON SiC junction gate field effecttransistors. For this study, ageing has been obtained using repetitive short-circuit operations. Among monitored parameters during ageing, on-state resistance and short-circuit current level are those, which have the strongest evolution. The top-metal degradation has been characterized via the on-state resistance measurement during ageing. In particular, we clearly show that the top-metal restructuration due to ageing leads to an additional voltage drop between gate and source terminals and results to a lower gate-source junction voltage.

The aim of this study was to estimate the efficiency of photovoltaic modules (PVM) used at solar power plants (SPP) in the Russian Federation territory and to analyze how adequate the procedure adopted for selecting protective devices in the PVM circuits is. In carrying out the study, a solar power plant analysis model developed in the PVSyst software environment using the SolarGIS weather database was used. The currently effective State Standard GOST R 56978-2016 (IEC/TS 62548: 2013): Photovoltaic Arrays. Specifications, which stipulates the procedure for selecting protective devices in the PVM circuits, is analyzed for sufficiency of the considered in it factors influencing the levels of currents in these circuits. Based on the modeling results, the values of the specific generated power were obtained, and the capacity utilization factor (CUF) values of SPPs were calculated for various regions of Russia. The data obtained can be used in performing the feasibility studies of constructing solar power plants in the Russian Federation territory, including those to be used for the consumers own needs. This data may also be needed in elaborating/updating the methodology for selecting protective devices in the PVM circuits. A conclusion can be drawn based on the obtained study results that the PVM operation features high efficiency in the Russian Federation territory. There is also a need to develop a procedure for selecting protective devices in the PVM circuits that would take into account the influence of insolation level, temperature and degradation of modules on the levels of short circuit currents in their circuits.

The ever-growing demand for advanced energy storage devices in portable electronics, electric vehicles and large scale power grids has triggered intensive research efforts over the past decade on lithium and sodium batteries. The key to improve their electrochemical performance and enhance the service safety lies in the development of advanced electrode, electrolyte, and auxiliary materials. Ionic liquids (ILs) are liquids consisting entirely of ions near room temperature, and are characterized by many unique properties such as ultralow volatility, high ionic conductivity, good thermal stability, low flammability, a wide electrochemical window, and tunable polarity and basicity/acidity. These properties create the possibilities of designing batteries with excellent safety, high energy/power density and long-term stability, and also provide better ways to synthesize known materials. IL-derived materials, such as poly(ionic liquids), ionogels and IL-tethered nanoparticles, retain most of the characteristics of ILs while being endowed with other favourable features, and thus they have received a great deal of attention as well. This review provides a comprehensive review of the various applications of ILs and derived materials in lithium and sodium batteries including Li/Na-ion, dual-ion, Li/Na-S and Li/Na-air (O2) batteries, with a particular emphasis on recent advances in the literature. Their unique characteristics enable them to serve as advanced resources, medium, or ingredient for almost all the components of batteries, including electrodes, liquid electrolytes, solid electrolytes, artificial solid-electrolyte interphases, and current collectors. Some thoughts on the emerging challenges and opportunities are also presented in this review for further development.

Electrical power systems are different in their sizes because of their amount of generation power stations, substations, transmission lines and loads. Therefore, these factors may impact on short circuit levels values. Capacity of power stations and dummy transmission lines in Extra high voltage grid (400kV) of the Iraqi Electrical power grids cause high short circuit levels values such that exceed both rating of the peak and breaking capacity of switchgear equipment's. Reduction of short-circuit levels by using Fast-acting Flexible Alternating Current Transmission Systems (FACTS) types devices in power grids maintain the operation of power grids with acceptable value of short circuit levels for their electrical equipment's and preventing cascading event outages which may lead to blackouts. This paper mainly studies strategies on how to add Short Circuit Current Limiter (SCCL) device by determining its number, value and location of connection in power grids by programing with (PSS™E version 30.3 Package Program). IEEE 25-bus system is used for testing the adding series SCCL at power transmission lines method procedure. The results of adding series SCCL with power transmission lines give significant reducing short circuit levels for the stations have highest short circuit levels in order to prevent the blackouts of overall power grid.

The world's first set of 220kV SF6 fast circuit breaker with flexible short-circuit current suppression has been commercialized. In view of this, the basic principle of flexible suppression of short-circuit current is explained, and the coordination sequence and action strategy of fast circuit breaker and conventional circuit breaker are proposed. In order to realize fast opening, the fast eddy current drive technology and the fast identification technology of short circuit fault are introduced. In order to verify the effectiveness of the proposed action sequence and control strategy, a single-phase artificial short-circuit test of 220kV line was carried out. The test results show that when a single-phase short-circuit fault occurs on the 220kV line of the Tianyi substation, the fast circuit breaker realizes the system splitting operation within 20ms and the short-circuit current is reduced from 30.8kA to 24.2kA, which effectively reduce the short-circuit current level. The protection action time of the fast circuit breaker is shortened by 78% and the full breaking time of the fast circuit breaker is shortened by 64.4% compared with the conventional circuit breaker. The research results provide an important reference for the effective development of short-circuit current suppression and 550kV fast circuit breaker.

Object-oriented logic configuration platform design for large power grid security and stability simulation