Three-phase Short Circuit Current Research Articles

A research report on the phase-domain trajectories of fault recording and their mathematical models

In currently known theories and algorithms of fault recording analysis and application, there is little literature where fault feature parameters are mined deeply from electrical physical quantities themselves. In this report the calculation method of the phase angles of the reference point and sample points is obtained, which ensures the correspondence of the time-domain waveform of digital fault recording with its phase-domain trajectory. The relationship between the initial phase angle of a sinusoid and the position of its trajectory, the characteristics of the trajectories of three-phase short-circuit currents containing dc components and the mathematical models of these trajectories are analyzed. Taking a rectangular wave current and a triangle wave current as example, the characteristics of the trajectories of non-sinusoidal and periodical waveforms containing harmonics are analyzed as well as their mathematical models. The research results show that the relationship between the initial phase angle of a sinusoid and the position of its circular trajectory is definite; the dc components have no impact on the positions of the trajectories of the short-circuit currents, but on their sizes and shapes; the harmonics have an impact on the shapes of the trajectories, and their positions are decided by the initial phase angles of the ac fundamental components in the waveforms. Subsequent study of the algorithm of fault recording analysis will be spread based on the contents in this report.

Calculated Values of Three-phase Short-circuit Currents in the Power Supply System of the Synchronous Generator Excitation System

In this article, the calculated values of three-phase short-circuit currents in the power supply system of the excitation system of the STS type are considered-2100-250-2,5 UHL4 synchronous generator type SV-1130-220-44- UHL4.

PROTECTION COORDINATION OF PHOTOVOLTAIC POWER PLANT IN THE TIME DOMAIN

The safety of workers and equipment in the power grid requires the shutdown of power plants in case of maintenance or malfunction. The shutdown relies on protective devices that must be properly coordinated to isolate only the part of the grid affected by the malfunction. Using the DIgSILENT PowerFactory software, an analysis was conducted on a model of an accurate real grid integrating a photovoltaic power plant with a capacity of 390 kW. Protection coordination testing was carried out for three-phase, two-phase, and single-phase short circuit currents at arbitrarily selected locations at medium and low voltage levels. Protection in the time domain is coordinated on lines and busbars to determine the speed and selectivity of protective devices. The analysis results indicate that adequately adjusting the three-phase short circuit at the main transformer output 110/10 kV with an impedance of 0 Ω and an allowed protection operation time of up to two seconds can be correctly addressed within 36.7 ms.

Analysis of a Balanced Short Circuit on a Sulbagsel Electrical System by Using The FFA-ABC Method Approach

Fault studies are an important part of electrical power system analysis. The purpose of this study was to determine the amount of line current at the point of disturbance when a three-phase balanced fault occurs in the real Sulbagsel electrical system. In this paper, a new hybrid FFA-ABC (Fruit Fly Algorithm-Artificial Bee Colony) method is proposed, which is one of the new methods used to calculate balanced three-phase short circuit currents in electric power systems, especially in the real Sulbagsel electrical system of South Sulawesi, Indonesia. The real electricity system of Sulbagsel was chosen as the research object because this system consists of 15 generators, 44 buses, 52 transmission lines, and 29 load buses with system voltages varying from 30 kV, 70 kV, 150 kV, and 275 kV so that this system is included in the complex system category. To test the effectiveness of the proposed FFA-ABC method, it was implemented on a real electric power system, namely the Sulbagsel System. In addition, it can also be applied to IEEE electrical systems or other real electric power systems. The results of the new hybrid FFA-ABC method of the balanced short circuit analysis of the Sulbagsel electrical system are then compared using the FFA method, the ABC method, and the deterministic method (in this case, the bus impedance matrix (BIM) method). The simulation results obtained show that the FFA-ABC hybrid method is able to solve the problem of balanced short circuit analysis in the Sulbagsel electrical system in South Sulawesi, Indonesia which the largest fault current occurs when the fault is close to the slack bus generator (bus 2=Sidrap) of 18.9697 p.u, and the smallest fault current occurs when the fault is farthest from the slack bus generator (bus 44=Poso) of 0.8457 p.u.

Impact of the Short-Circuit Current Value on the Operation of Overhead Connections in High-Voltage Power Stations

This paper focuses on determining the effects of short-circuit current values on the operation of high-voltage substations. The analyses performed focused on the dynamic and thermal effects on the short-circuit current for different input data configurations. The analyses of the dynamic effects of short-circuit current were performed in two ways. First, calculations were executed using the procedures contained in “IEC 60865-1:2012 Short-circuit currents, calculations of the effects of short-circuit currents. Part 1: Definitions and calculation methods”. Analytic calculations were accomplished for different values of the initial three-phase short-circuit current, the type of short circuit, the static tension force of the conductors, the stiffness of the structure and the methods of attaching the lashing chains. Secondly, the same analysis was performed using PRIMTECH 3D software. The connections were modeled in computer software, for which the calculations were implemented according to normative recommendations. After obtaining the results, an analysis was performed using the model based on the input data. Performing the analysis in two ways made it possible to compare the results with each other and develop conclusions. An analysis of the thermal effects of the short-circuit current was also provided. The results of the calculations showed that the choice of conductor cross sections according to the value of the initial short-circuit current was correct. Particular attention has been paid to rigid conductors and flexible conductors, which are directly affected by the short circuit and have an impact on the selection of the complete equipment for the high-voltage switchgear.

Study on Short Circuit Current Calculation of EHV Overhead Line-GIL Hybrid Line

GIL electrical parameters are different from overhead lines. With the increasing application of GIL in actual projects, the influence of GIL needs to be considered when calculating the short-circuit current of the power grid. In this paper, the calculation of three-phase short-circuit current is carried out for the EHV double-circuit overhead line on the same tower with GIL. First, the electrical parameters of EHV GIL are calculated. The positive sequence resistance, reactance and capacitance values of a typical GIL are calculated. Secondly, EMTP-ATP software is used to modelling and simulation. The influence of GIL length on the short-circuit current and the position of short-circuit fault is studied respectively. Finally, the influence of the GIL unit length modelling accuracy and the grounding mode of the metal shell on the short-circuit current is studied. The research results of this paper can provide a theoretical reference for GIL simulation modelling and the evaluation of the impact of system short-circuit current.

Analysis of the influence factors of VSC–HVDC on AC three-phase short-circuit current level

PurposeThis paper aims to clarify voltage sourced converter’s (VSC’s) influence rules on the alternating current (AC) short-circuit current and identify the key factors, so as to propose the short-circuit current suppression strategy.Design/methodology/approachThis paper investigates the key factors which impact the short-circuit current supplied by the VSC based on the equivalent current source model. This study shows that the phase of the VSC equivalent current source is mainly affected by the type of fault, whereas the amplitude is mainly decided by the control mode, the amplitude limiter and the electrical distance. Based on the above influence mechanism, the dynamic limiter with short-circuit current limiting function is designed. The theoretical analysis is verified by simulations on PSCAD.FindingsThe short-circuit current feeding from VSC is closely related to the control mode and control parameters of the VSC, fault type at AC side and the electrical distance of the fault point. The proposed dynamic limiter can make VSC absorb more reactive power to suppress the short-circuit current.Research limitations/implicationsThe dynamic limiter proposed in this paper is limited to suppress three-phase short-circuit fault current. The future work will focus more on improving and extending the dynamic limiter to the fault current suppression application in other fault scenarios.Practical implicationsThe research results provide a reference for the design of protection system.Originality/valueThe key influence factors are conducive to put forward the measures to suppress the fault current, eliminate the risk of short-circuit current exceeding the standard and reduce the difficulty of protection design.

Penentuan Kapasitas PMT SF6 Pada Bus 70 KV Menggunakan Simulasi Program ETAP

The electric power system consists of several components, namely generation, distribution, transmission and load. Along with the rapid development of technology in the field of electricity today, a protection system is installed at substations, one of which is a powerbreaker (PMT) at each substation. In the event of a disturbance, the protection relay will detect and instruct the breaker to open or disconnect the circuit from the disturbance, then a circuit breaker will receive a signal from the relay and in the end will decide the circuit according toits current rating. Based on the type of PMT isolation media, PMT is divided into 4 types, one of which is the SF6 gas isolation media type. This type of PMT can be used to cut currents up to 40 KA and in circuits with a voltage of 765 KV. It must be noted that if the current is very large at the time of short circuit, then the thing that must be considered is the capacity of thebreaker itself. To determine the breaker capacity, it is sought from the largest short-circuit current, namely a three-phase short circuit. In finding a three-phase short circuit current can be simulated using the ETAP (Electric Transient Analysis Program) program. ETAP can simulatepower flow and short circuit current. The results of the calculation of the PMT capacity on the 70 KV bus are 0.324 KA and from the results of the calculation and analysis of the PMT it is included in the rating of 12.5 KA where the PMT with the rating value can decide the fault current from 0.9 KA -7.74 KA

РАСЧЁТ РЕЖИМА ТРЁХФАЗНОГО КОРОТКОГО ЗАМЫКАНИЯ В ЭЛЕКТРИЧЕСКОЙ СЕТИ 10 КВ С УЧЁТОМ ВЛИЯНИЯ ТОКОВ НАГРУЗКИ

Abstract. The load current aff ects the value of the short-circuit current in the electric network and, consequently, the voltage value. In some cases, this infl uence must be taken into account for the correct choice of switching devices, remote monitoring the operating modes of electric networks, and determining the modes. It is possible to disconnect loads connected through magnetic starters and contactors. Failure to consider the infl uence of the load current can lead to an incorrect interpretation of the identifi ed grid operating modes during remote monitoring and, as a result, incorrect dispatcher’s decisions. In addition, it is also insuffi cient to specify the choice of switching devices in the 10 kV feed network. The article describes a method for analyzing the three-phase short circuit mode in a 10 kV feed network, taking into account the infl uence of load currents. The method is exemplifi ed by the case of an actual electric network – the 10 kV ring feed network containing reclosers and receiving power from diff erent sections of lowvoltage buses of the “Kulikovskaya” 110/35/10 kV substation, belonging to the Branch of PJSC «DGC of Center”-“Orelenergo.” For this network, the values of the three-phase short-circuit currents at points with diff erent distances from the substation buses have been determined. The authors have fi guredout the values of the load currents and their shares in the total short-circuit current. The voltage values at different points of the network in the case of short circuits have also been determined. The research proves that the effect of the load current on the total short-circuit current should be taken into account for the case of remote short circuits.

Analysis of Split-Tooth Stator Slot PM Machine

In this article, split-tooth stator slot permanent magnet (PM) machines, which have high fault-tolerant capability, are proposed. Compared with the existing 12-slot 10-pole (12S10P) stator slot PM machine, the torque can be improved by 66% by properly choosing the split tooth number and other geometric parameters. It is found that two split teeth stator slot PM machine (ST2) shows the best torque characteristics among the stator slot PM machines with different split tooth number. To further illustrate the merits and demerits of ST2, a conventional 6S4P surface mounted PM machine (SPMM) and a 6S4P variable flux reluctance machine serve as the benchmarks to compare with the 6S11P ST2, at both open circuit condition and load condition. The 6S11P ST2 shows 68% higher torque over the 6S4P VFRM. Although the torque of the 6S11P ST2 is around half of the 6S4P SPMM, the former has 70% higher torque per PM volume than the latter. Furthermore, demagnetization analyses under three-phase short-circuit and pure d-axis currents show that the 6S11P ST2 has much better demagnetization withstand capability over the 6S4P SPMM. A Prototype is manufactured and tested to validate the theoretical analyses.

Practical Calculation Method for the Short-Circuit Current of Power Grids with High Temperature Superconducting Fault Current Limiters

With the expansion of the power grid scale and the enhancement of network structure interconnection, the short-circuit current of power grids is increasingly close to the upper capacity limit of circuit breakers. The fault current limiter is effective in suppressing the short-circuit current of power grids, and with the mature development of superconducting technology, high-temperature superconducting fault current limiters (HTS-FCLs) have been widely used in power grids. Due to the nonlinear impedance–current characteristic of HTS-FCLs, the traditional short-circuit current calculation method is inapplicable to power grids with HTS-FCLs. First, based on the establishment of the electromechanical transient model and the short-circuit calculation model, the short-circuit current calculation procedure for power grids with HTS-FCLs is proposed. Second, the calculation methods for three-phase and single-phase short-circuit currents at the substation bus in power grids with HTS-FCLs are analyzed. Finally, three-phase and single-phase short-circuit currents at the 500 kV Xijiang substation bus in the Guangdong power grid are calculated as the study case. Simulation results show that compared with the situation where there is no HTS-FCL installed, the short-circuit current on the 500 kV bus decreases from 65.34 to 58.31 kA in terms of the three-phase short-circuit fault, and decreases from 54.56 to 46.62 kA in terms of the single-phase short-circuit fault, thus verifying the effectiveness and practicability of HTS-FCLs in suppressing the short-circuit current, which is significant for the safe, stable and reliable operation of the power grid.

THE EFFECT OF ELECTROMAGNETIC COUPLING BETWEEN WIRES DOUBLE- CIRCUIT OVERHEAD LINE AND THE GROUND ON TRANSIENTS

Abstract. A method is proposed for calculating the initial value of the periodic term of the short- circuit strength of a dual-circuit overhead transmission line using multiphase replacement circuits. The method takes into account the electromagnetic connections between the wires of the dual-circuit overhead line and the ground to transient modes. The calculation model will allow to take into account the influence of the internal properties of the dual-circuit overhead line when calculating the three-phase short-circuit currents at the design stage, which will significantly improve the accuracy of the choice of relay protection settings and line automation. The model was tested in Matlab Simulink.

Sudden Short-Circuit Test of 22-kV YBCO Triaxial Superconducting Cable

For the power line between a power generator and a step-up transformer, isolated power bus (IPB) is generally used. The present IPB has a normal cylindrical conductor made of aluminum or copper at the center of the outer jacket and generates very huge Joule loss. To decrease it, superconducting buses have been developing. In this study, a 22-kV 3-kA triaxial superconducting bus was designed and fabricated with YBa2Cu3O7-d (YBCO) tapes and the various kinds of properties were investigated. Previously, the ac and lightning impulse withstand voltage test, critical current Ic test, and ac loss measurement were conducted and it was shown that the developed triaxial superconducting cable met the designed specifications. In this paper, a sudden short-circuit test of a 2-m-long triaxial cable was carried out by using a 200-MVA short-circuit generator. For protection, each phase of the cable was connected to a XLPE cable with a length of 3 m and a cross-sectional area of 250 mm 2 in parallel. Three-phase short-circuit current of 25 kA was applied to every phase of the cable bath-cooled with liquid nitrogen at 77 K for 2 s. As a result, the following tremendous phenomenon was demonstrated. Any phase of the triaxial cable kept a flux-flow state and did not quench. Short-circuit current was shared between the superconducting cable and the connected XLPE cable, and the branch current ratio varied even during one period of 60 Hz. The numerical simulation was also conducted to explain the phenomenon theoretically. That should contribute to the instantaneous recovery to a normal operation after a short-period interrupt of the circuit.

Local online adaptive technique for optimal coordination of overcurrent relays within high voltage substations

Summary The optimal coordination of overcurrent relays is an important task in the field of power system protection. Traditionally, this problem is solved with the assumption of the grid being in maximum or minimum loading and dominant topology, that is, the topology in which the grid operates most of the time. However, the grid condition changes during the time because of many reasons. In this paper, by sampling voltage and load current phasors at the high-voltage (HV) bus of a substation, an online method, based on an evolutionary algorithm, is introduced to estimate the grid's Thevenin equivalent viewed from the HV bus. Then, the Thevenin equivalent together with the connection status and short-circuit model of local power transformers and local distributed generations are used to estimate three-phase short-circuit currents in the existing condition of the grid. Finally, these fault currents are used for adaptive optimal coordination of overcurrent relays of the HV substation, such that the optimal coordination of the relays is preserved in all the grid conditions. Case studies, performed on the overcurrent protection of a typical 230/20 kV substation connected to a 9-bus grid, prove desired performance of the proposed online adaptive setting method. Furthermore, this method needs no telecommunications and represents a step toward self-adjusting overcurrent relays. Copyright © 2016 John Wiley & Sons, Ltd.

Rotor Current Analysis on Transient Performance of Low Voltage Ride-Through of Doubly Fed Induction Generator

From a theoretical perspective, this paper develops a systematic approach to analyze the transient characteristics of the low voltage ride through in three-phase short-circuit rotor current. Firstly, the steady state current mathematical model of the system is described. And then, the short-circuit rotor current dynamic characteristic during the low voltage fault is analyzed, the resistance value and switching strategy of crowbar are discussed. Finally, the simulation results and the theoretical analysis manifest that appropriate crowbar reactance value and switching time can improve LVRT control characteristic and grid stability.

Research of Installing Small Reactors on Neutral Points of 500 KV Autotransformers and the Analysis of Overvoltage

Because of the extensive application of autotransformer in 500 kV power grid, the value of single-phase short-circuit current is generally greater than that of three-phase short-circuit current, or even greater than the maximum rated through current of the breaker. In order to reduce single-phase short-circuit current and avoid implement of bus split, this paper proposes to install small reactors on neutral points of 500 kV autotransformers. By analyzing and calculating the effect on short-circuit current limitation, the most suitable impedance value of small reactor is proposed. In addition，the overvoltage of the neutral point and insulation coordination are particularly discussed.

Analysis on the Short Circuit Current of a Low Voltage Direct Current(DC) Distribution System using PSCAD/EMTDC

In this paper, we analyzed the short circuit current of a low voltage direct current distribution system. For the analysis, we performed the modeling of the low voltage direct current distribution system with a 6-pulse three-phase thyristor rectifier using the PSCAD/EMTDC, surveyed impedance of sources, transformers and distribution lines to run a simulation. A result of the simulation is that short circuit currents of the direct current distribution system with the rectifier decreased due to a thyristor-ON-resistance(Ron). But in case of the low thyristor-ON resistance, output fault current of the rectifier increased over three-phase short circuit current of an AC power system without a rectifier by regular ratio of the rectifier. Because the output fault current of the rectifier can increase over interrupting the capacity of circuit breakers, studying short circuit currents of a low voltage direct current distribution system with a rectifier is necessary for introducing the direct current distribution systems.

The Problem of Coordination of Levels of Short-Circuit Currents in Power Systems

The problem of coordination of short-circuit (fault) currents is considered. Data on the dynamics of variation of the levels of single-phase and three-phase short-circuit currents (their highest values) in networks rated for different voltage are presented for a long-term period. The main factors (integral parameters of the networks) affecting the values of short-circuit currents are listed. Statistics of variation of rated parameters of electrical equipment in past years and in the recent period is presented and predictions for the future are made. Basic methods and means for limiting short-circuit currents are discussed. A method of automatic and stationary network separation and a method of circuit design are described in detail. The efficiencies of different methods are compared. The effect of integral parameters of the network on the maximum level of short-circuit currents is shown. The aspects of the switching life of breakers and of allowance for probabilistic characteristics of faults and for the risk factor of decision-making are considered. It is shown that coordination of the levels of short-circuit currents is a possible means for raising the reliability of power installations and systems.

Calculation of sudden three-phase short-circuit current of turbine generators by 3D magnetic field analysis

Sudden three-phase short-circuit current of a turbine generator was calculated by a three-dimensional magnetic field analysis. That analysis takes into account the rotation, magnetic saturation, and eddy current at a rotor part. To compare test results and calculated results, a method was proposed for short-circuit phase estimation at sudden three-phase short-circuit test by line voltage waveform of the test results. The calculated results of short-circuit current waveform are in good agreement with the test results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(1): 54–62, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20110

Calculation of Sudden Three-Phase Short-Circuit Current of Turbine Generator by 3D Magnetic Field Analysis

Sudden three-phase short circuit current of a turbine generator was calculated by a three-dimensional magnetic field analysis. That analysis takes into account the rotation, magnetic saturation, and eddy current at a rotor part. To compare test results and calculated results, we proposed a method for short-circuit phase estimation at sudden three-phase short-circuit test by line voltage waveform of the test results. The calculated results of short-circuit current waveform are good agreement with the test results.