Short-circuit Current Calculation Research Articles

The significance of frequency-dependent overhead lines for the calculation of HVDC line short-circuit currents

In this paper the short-circuit current of overhead transmission lines is analyzed at a short circuit in an HVDC transmission network. The analysis focuses solely on the current contribution of the transmission line at a line-to-earth or a line-to-line short circuit. In this context it is shown which impedance is effective at the corresponding fault case. Special attention is given to the frequency dependence of the line parameters and how they affect the short-circuit current. The frequency of the current is derived with a simplified method. Finally, it is presented how the resulting time course of the short-circuit current can be determined based on travelling wave theory. The analysis covers different HVDC grid topologies.

Comparative Analysis of the Calculation Results of Online Short-Circuit Current Based on PSASP and Fault Wave Recording

In daily operation process,the results of online short-circuit current calculation and fault wave recording is different, the differences between the two results affected the dispatcher’s decision. In-depth analysis of the calculation process and finding the possible causes of the differences should be done. The on-line PSASP short-circuit current calculation based on power flow and scheme was studied. The boundary conditions and calculation models of two methods were studied, the influence of the modeling scope and equivalent circuits to the short-circuit current was also studied. Fault wave recording calculated short-circuit current through forward calculation, the middle to both sides calculation and backward calculation, and the differences of the three calculation mode were also analyzed. Through the above analysis and comparison, online data equivalent to 220kV high voltage side of the transformer greatly impacts short-circuit current, but effective value calculation method of fault wave recording has a little impact on the short-circuit current, mainly in the following reasons, the first one is that non-dispatching power plant is equivalent to a load, the second one is that several different types of load is equivalent to a load using one load model, the third one is that all devices connecting to low voltage side of the 220kV transformers are equivalent to 220kV. Conclusions of the analysis can provide the basis for the practical work of online short-circuit current calculation.

Short-Circuit Current Calculation of a Power System with a Grid-Connected Inverter

This paper analyzes the difference between conventional power supply and inverter power supply short circuit characteristics, pointing out that the short circuit current does not contain transient DC component. The inverter power supply can be regarded as AC current source with sudden change of current at moment of short-circuit to calculate the current periodic component. The method to calculate the short circuit current of power grid with both conventional rotating generator and inverter power supply is proposed and evaluated.

Relay Protection Setting Calculation and Analysis of Auxiliary Power System for Hydropower Plants

The configuration and setting calculation of auxiliary power protection are directly related to the regular and safe operation of the equipments, thereby affecting the security and stability of the power plant. The system features are analyzed in depth according to the operational requirements of auxiliary power system protection in Xiangjiaba hydropower plant ,the system model is built on the basis of the actual project, and a variety of short-circuit current calculations are carried out. At last, the setting of the auxiliary power system relay protection is completed. This thesis also proposes solutions to the emerging problems in the process of protection setting. The results of the setting have been applied to the actual operation and no misoperation or maloperation caused by improper constant setting value has occurred so far in Xiangjiaba hydropower plant.

Calculation and Analysis of Three-Phase Transformer Short-Circuit Current

Analysis the important significance of transformer short-circuit current calculation for the stable operation of power system. Lead to three different types of transformer short-circuit current calculation methods, this literature uses a simplified example to compare the characters among three methods. Meanwhile, calculation by using the theory to get a quantitative range of simplified method. The calculation results and theory support each other, finally, summarizing the application range of the three methods, and offering a reference for reasonable selection of short-circuit current methods.

Study of Short-Circuit Currents Around Dĕtmarovice Power Station

The calculation of short-circuit currents is important for power systems operation and restoration, and for determining the means to protect human lives and properties. In this paper, a part of a power system network, around the Dĕtmarovice power station in Czech Republic, was simulated by the well known program EMTP-ATPDraw (Electromagnetic Transients Program-Alternative Transient Program), and short-circuit currents and voltages were calculated at different points in the electric network and presented as a time function by the PlotXY program. Calculations were done just for phase-to-ground, and for the three-phase short-circuit at the Kuncice substation. The results were important for determining the characteristics of the equipment required to withstand or break the short- circuit current; for this reason, the calculations were repeated using earth-fault resistances only for the case of busbar KUN shown in Figs. 5 and 6.

IEC 60909에 의한 삼상 고장계산

This paper analyzes how to calculate the three phase short circuit current calculation procedures used in the IEC 60909 short circuit. It presented the new procedure of the fault current for the interrupting capacity of the circuit breaker. This procedure is applied to the future power system and calculates the fault current. Power demands are increased because of the growth of the economy for this reason, the fault current of the power system is largely increased and the fault current procedure for the proper interrupting capacity calculation of the existing or the new circuit breaker is essential. How to calculate the three phase short circuit current for ac electrical system and select the high voltage and low voltage circuit breaker based on IEC 60909 standards.

Calculation of Short Circuit Current Based on Equipment Graphics Database

According to the structural characteristics of the electrical one-line diagram at substation, Its proposed that designing the database which stores electrical properties and graphics properties of the equipment in the paper. And an intelligent graphical modeling and automatic implement of main electrical connections are achieved based on the database. By means of the graph database integrated platform, a topology analyzing method based on bus for main electrical connections is presented, which is capable of not only computer graphics processing easily, but also describing accurately and reliably the topological structure of the main electrical connections. Finally the node admittance matrix is generated and the calculation of short circuit current is completed automatically.

Calculation of Initial Short-Circuit Currents in Medium Voltage Networks According to the Standard PN-EN 60909

Determining the short-circuit currents is usually conducted by network analyses. An important feature of this calculation is carried out according to the recommendations of the standard PN EN 60909. This paper describes the models of the basic elements of the network with the method of determining the impedance parameters including correction factors introduced by the standard. Thevenin’s method connected with the nodal method are presented and used to determine the initial short-circuit for the example medium voltage network. Results are compared with the ones obtained without taking into account the correction factors.

Parameterization of a synchronous generator to represent a full-scale converter generator for fault studies

This paper addresses the representation of the full-scale converter generator technology by equivalent operational impedances valid for short-circuit current calculations. Modern wind power plants are required and designed to ride through faults in the network, subjected to fault clearing. Accurate knowledge of the wind turbine short-circuit current contribution is needed for component sizing and protection relay settings during faults within the wind power plant collector system or in the external networks. The industry standard employs software packages where generators are represented by their equivalent synchronous generator operational impedances, calculated according to standards or for electromagnetic simulation models, when studying fault currents and protection settings for wind power plant installations. Hence, it is of importance to represent non-synchronous wind generators also by an equivalent synchronous generator. The effectiveness of the proposed method has been validated by simulation and site measurements. Copyright © 2013 John Wiley & Sons, Ltd.

Enhanced light absorption in thin-film solar cells with light propagation direction conversion

Enhancement of optical absorption in thin-film solar cells (TF-SCs) has been the long-lasting issue to achieve high efficiencies. Grating couplers have been studied for the conversion of incident light into guided modes propagating along TF-SCs to extend optical path for higher optical absorption. However the wavelength band for the efficient conversion remained relatively narrow and the overall improvement of TF-SC efficiencies has been limited. This paper demonstrates that the grating height design as well as the phase matching condition is important for the enhancement of optical absorption in TF-SCs with the calculation of short-circuit currents as a figure of merit for optimization. The influence of the light absorption coefficients and grating coupling strengths on the light absorption bandwidth is also discussed.

CHARACTERISTICS OF EMERGENCY OPERATION OF FREQUENCY CONVERTERS OF WINDPOWER INSTALLATIONS WITHOUT MULTIPLYING GEAR

The article studies functioning of the scheme of transformation power through the converter wind-power installations during emergency operation. The main types of emergencies for this converter are considered. An approach to the calculation of short-circuit current of a synchronous generator and short-circuit current of an LC-circuit is presented. Protection elements (voltage limiters, fuses, fast current sensors) are given for circuit protection and the reliability in emergency conditions is offered. Unlike classic circuit diagrams for wind-power installations, the circuit diagrams without multiplying gear for turbo-generator wind-рower installations have a self-stabilization effect of electromechanical system under optimal conditions in a wide range of a wind flow. In order to improve its effectiveness and implement an offline mode, you need to use converters to match the frequency of the generator voltage and that the frequency of network. Circuit diagrams of such converters have a complex structure, they contain a number of power supplies and rectifiers, capacitive storages, pulse converters and multi-level inverters.

The Development of a Graphical Open-Ended Integrative Platform for Short-Circuit Calculation and Relay Setting of Power System

To improve the efficiency and accuracy of relay setting calculation of power system, this paper proposed and developed a schematized and open-ended software platform in integrative relay setting. Through the advanced development of the Visio software, the graphical input of the target system topology and component parameters are made possible. The platform can automatically generate PSCAD simulation model according to the topology information and device parameters through an interface program to PSCAD, and use this power system simulation software to improve the accuracy of short-circuit current calculation. With the help of the Bookmark mechanism of WORD software, the platform provides a setting template with general protection components, which forms the basis to realize the open-ended platform. The platform also uses the API interface provided by WORD software to automatically generate the final relay protection setting report document according to the results of short-circuit current calculation and the selected protection setting components. This paper gives in detail the overall framework of the proposed platform, as well as the principle and practice of all the above parts. Moreover, the validity and practicality in improving the automation degree of the relay setting of power plant are shown through practical applications.

Features of the short-circuit current calculations of the ac graphitization power electrical complex

Method of identification of short circuit electrical parameters of AC graphitization complex, taking into account the application design features and temperature regimes is proposed. The calculation and analysis of the short-circuit peak currents, taking into account the power system characteristics, graphitization technological regimes and reactive power compensation are presented.

The Building of Offshore Facilities Power System’s Equivalent Circuit Model

With the development of technology, the power system of offshore facilities (for short: power system) is increasingly complex, short-circuit current calculation process also becomes more complex. The simple recursive algorithm can not meet the requirements of short-circuit current calculation in complex power system. The paper, basing on the principle of short-circuit current calculation, taking modeling ideas, created an equivalent circuit model of power system for short-circuit current calculation. The equivalent circuit model can be used to simplify the progress of calculation and meet the needs of the power system development.

THE RATE OF CURRENT CHANGE DURING A SHORT CIRCUIT IN THE POWER CIRCUITS OF THE ELECTRIC ROLLING STOCK WITH REGARD TO EDDY CURRENTS

In the article the issue of influence of vortical currents on rate of change of short circuit current is considered, a mathematical model for the calculation of short circuit currents in the traction mode in the power circuits of DC electric rolling stock is presented, and the research results are given.

Feasibility Study of Superconducting Current Limiter Application in a Cogeneration Plant

Fault current limiters (FCL) have been developed using high temperature superconductors. Possible applications of FCL are medium and high voltage energy supply systems. In this field conventional protection against high currents often cause high expenses. Using a superconducting FCL gives an economic advantage, if technical problems can be solved at lower costs or if the usage of a FCL makes savings in other equipment possible. This work deals with possible applications of a superconducting fault current limiter in a medium voltage auxiliary power network of a typical small cogeneration power plant. For possible installation locations in the existing energy supply system of Braunschweig, Germany, calculations of short circuit currents were made. It is investigated, whether the power plant can be expanded while staying or becoming short-circuit-proof. One result of the work is that the auxiliary power system of the power plant is an especially interesting installation location for a FCL. Advantages of a FCL compared to conventional strengthening of the installations are discussed.

Second-order model for remote and close-up short-circuit faults currents on DC traction supply

A technique to calculate the current waveform for both close-up and remote short-circuit faults on DC supplied railways and subways is presented. Exact DC short-circuit current calculation is best performed by sophisticated computer transient simulations. However, an accurate simplified calculation method based on second-order approximation which can be easily executed with the help of a calculator or a spreadsheet program is proposed.

Study of Generator Source Short-Circuit Currents with Respect to Interrupting the Duty of Generator Circuit Breakers, EMTP Simulation, ANSI/IEEE and IEC Methods

Large generators have high effective X/R ratios and combined with other generator time constants and parameters, a current zero may not be obtained at the time of contact parting, i.e., the dc component of the short-circuit current at the contact parting time is higher than the peak ac component. This is well documented in the current literature. The paper presents calculations of the generator source short-circuit currents of a 234 MVA generator using ANSI/IEEE and IEC standards and EMTP simulation. The results are compared and the application of a generator breaker to meet the requirements of calculated duties are discussed. It shows considerable differences in the results, depending upon the method of calculation.

Load modelling for steady-state and transient analysis of low-voltage DC systems

The modelling of loads for low-voltage (LV) DC system studies is treated. Results from measurements on 63 different loads supplied with DC are presented. The measurement results are used to derive simplified load models, which can be used for steady-state and transient analysis of LV DC systems. These load models extend existing standards for load flow and short circuit current calculations.