Phase Short Circuit Fault Research Articles

Artificial Neural Network Application in Optimal Coordination of Directional Overcurrent Protective Relays in Electrical Mesh Distribution Network

Directional Overcurrent relays (DOCR) applications in meshed distribution networks (MDN), eliminate short circuit fault current due to the topographical nature of the system. Effective and reliable coordination’s between primary and secondary relay pairs ensures effective coordination achievement. Otherwise, the risk of safety of lives and installations may be compromised alongside with system instability. This paper proposes an Artificial Neural Network (ANN) approach of optimizing the system operation response time of all DOCR within the network to address miscoordination problem due to wrong response time among adjacent DOCRs to the same fault. A modelled series of DOCRs in a simulated IEEE 8-bus test system in DigSilent Power Factory with extracted data from three phase short circuit fault analysis adapted in training a custom ANN. Hence, an improved optimized time is produced from the network output to eliminate miscoordination among the DOCRs.

TRANSIENT STABILITY ANALYSIS ON A MULTI-MACHINE SYSTEM IN PSAT

Modern power system are subject to large disturbances such as three phase short circuit faults. When a fault occurs on a system the generators rotor angle becomes unstable and thus it losses synchronism with the system and it becomes unstable. Thus transient stability analysis can be performed on a system in order to understand the generators performance when subjected to a short circuit fault. When the system is subjected to a fault the generator experiences transient oscillations in rotor speed and angle which can be effectively suppressed with the incorporation of Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS). The simulations have been performed using the MATLAB/PSAT software.

Investigation of fault‐tolerant capability of five‐phase doubly salient electromagnetic generator

A new topology of five-phase fault-tolerant doubly salient electromagnetic generator (FTDSEG) is proposed for high reliability applications in this paper. The analysis of no-load and loading operations shows the potential fault-tolerance capability. On the basis of comparative analysis on structure characteristics between five-phase non-FTDSEG (NFTDSEG) and five-phase FTDSEG, the variation of rotor pole number from NFTDSEG to FTDSEG is revealed. Meanwhile, the flux linkage and electromotive forces (EMFs) of five-phase NFTDSEG and five-phase FTDSEG are investigated with finite element method and five faults of five-phase FTDSEG are analysed in detail. Especially when single phase short-circuit fault happens, the magnetic field of the motor, flux linkage of short-circuit phase and short-circuit currents without load are investigated in four different short-circuit moments and the fault is in consideration of armature winding resistance. The ultimate variation trend of flux linkage is irrelevant to moment when the short-circuit fault happens. The flux linkage and EMF of short-circuit phase are also analysed. The laws of fault operating influence on external and power characteristics of FTDSEG are researched in five faults with different exciting currents. The fault-tolerant ability of five-phase FTDSEG has been demonstrated by the experimental results.

Stabilizing Controller Design for Transient Stability Improvement of Power Systems

This paper presents a nonlinear excitation controller for power system. The non-linearity and interconnections in power system are eliminated by using direct feedback linearization technique. With this compensator design, only the bounds of the generator and the network parameters are to be known. The resulting feedback linearizing excitation controller guarantees the overall transient stability of the power system. Simulation results on the model depicts that the proposed controller can greatly enhance the power system transient stability regardless of the network parameter variations. In power system, fault is the main reason which transforms the system from stable to unstable. Few of the main parameters to be monitored during fault condition are power angle and terminal voltage whichcan depict the system behavior. The major objective is to prevent power system from losing synchronism after sudden fault and to restore the terminal voltage to pre-fault value. Power system is characterized with nonlinear behavior. The nonlinearity existing in power system is mainly due to the system elements. Direct feedback linearization is the technique which isused for linearizing the nonlinear power system. Here three phase short circuit fault is considered which occurs on one of the transmission line. Different controllers designed for stabilizing the linearized system has been discussed in this paper and comparative results have been shown in this paper through simulation results.

English

When integrated to the power system, large wind farms pose stability and control issues. A thorough study is needed to identify the potential problems and to develop measures to mitigate them. Although integration of high levels of wind power into an existing transmission system does not require a major redesign, it necessitates additional control and compensating equipment to enable recovery from severe system disturbances. This paper investigates the use of a Static Synchronous Compensator (STATCOM) along with wind farms for the purpose of stabilizing the grid voltage after grid-side disturbances such as a three phase short circuit fault, temporary trip of a wind turbine and sudden load changes. The strategy focuses on a fundamental grid operational requirement to maintain proper voltages at the point of common coupling by regulating voltage. The DC voltage at individual wind turbine (WT) inverters is also stabilized to facilitate continuous operation of wind turbines during disturbances.

The Influence Analysis of Rectifier Side Control Mode on Commutation Failure in UHVDC

This paper studies the influence of different control modes in the rectifier side (constant current control, constant power control) on commutation failure in UHVDC transmission system. The study is based on Yunnan-Guangdong ±800kV UHVDC transmission system and simulated in PSCAD/EMTDC. A wealth of simulation results indicate that the control ability of the constant current control on commutation failure caused by the critical voltage ratio of inverter transformer increased is worse than the constant power control; the control ability of the constant current control on commutation failure caused by three-phase grounding fault happens at inverter side AC bus is worse than the constant power control; The control ability of the constant current control on commutation failure caused by phase to phase short circuit fault or single-phase ground fault happens at inverter side AC bus is worse than the constant power control.

EVALUATION OF REACTANCES AND TIME CONSTANTS OF SYNCHRONOUS GENERATOR

For any power equipment the control system and protection system plays an imperative role as the dependency on the power equipment in any industry will be very high. Thus for the Generator the Reactances and Time Constants becomes controlling parameter and hence protecting it is necessary for prolonged usage. In general reactance shall be defined as “non-resistive component of impedance in an AC circuit, arising from the effect of inductance or capacitance or both and causing the current to be out of phase with the electromotive force causing it”. In other word it can also be defined as the imaginary part of the impedance in any power circuit. There are various Reactances and Time Constants which contributes during the selection of control systems and protection scheme for any Generator. Therefore practical evaluation of those parameters shall also be super critical same as those are by calculation. More accurate measurement or the calculation of reactance shall certainly give us more stabilized error free system and hence ensuring a healthy control system. As there are different tests or different methods to measure and calculate the Reactances and Time Constants, in this context we are considering Line to Line fault (L-L fault), Double line to Ground fault and Sudden three phase short circuit fault to determine the Negative Sequence reactance, Zero Sequence reactance, Sub-transient and Transient reactance and time constants respectively. The fault condition will be demonstrated with the 40MW, 11KV, 2624A, 4pole, 50 Hz synchronous generator and above mentioned parameters are calculated based on references available.

A Comprehensive Evaluation Method on Dynamic Simulation Accuracy of Power System

In order to overcome the shortcomings of the present accuracy assessment methods of power system dynamic simulation, this paper focuses the permanent single phase short-circuit fault which occurs in a large probability in power grids,and selects the typical electrical quantities which is very concerned in engineering after the fault happened. A time-scale based error criteria on simulation validation is proposed, and a comprehensive error criteria according to the average errors between simulation data and actual data is proposed to evaluate objectively the simulation accuracy of the typical electrical quantities. Considering the variation characteristics of the electrical quantities, the simulation accuracy evaluation of a single electrical element is expended to the simulation accuracy evaluation of the entire network, so not only the comprehensive evaluation about the model and its parameters but also the information for model modification and parameter correction can be obtained. The effectiveness of the proposed method is verified by the numerical results on the New England 10 Unit 39 Bus powers system.

Short Circuit Fault Analysis of Electrical Power System using MATLAB

The objective of the present study is to simulate short circuit faults on different buses of a power system network and to estimate the state of the power system before and after a fault, which includes various bus voltages and current flow on various transmission lines. The analysis before the fault is carried out by solving non-linear load flow problem by using numerical iterative technique of Newton-Raphson method. State estimation after short circuit fault is carried by using algorithm of short circuit current computation. The short circuit currents dictate the rating of circuit breakers to be employed at various buses and in various lines of the network. The effect of three phase short circuit faults on power system has been studied in terms of post-fault conditions and pre-fault conditions. In this paper, three phase short circuit fault is simulated on the standard IEEE 11bus and IEEE 30 bus system and fault current level is calculated and short circuit MVA rating for the circuit breaker has been chosen. The analysis of power system under faulty conditions is important to determine the values of system voltages and currents during faulted conditions, so that protective devices may be set to minimize the harmful effects of such contingencies.

A Novel Wind Turbine Concept Based on an Electromagnetic Coupler and the Study of Its Fault Ride-through Capability

This paper presents a novel type of variable speed wind turbine with a new drive train different from the variable speed wind turbine commonly used nowadays. In this concept, a synchronous generator is directly coupled with the grid, therefore, the wind turbine transient overload capability and grid voltage support capability can be significantly improved. An electromagnetic coupling speed regulating device (EMCD) is used to connect the gearbox high speed shaft and synchronous generator rotor shaft, transmitting torque to the synchronous generator, while decoupling the gearbox side and the synchronous generator, so the synchronous generator torque oscillations during a grid fault are not transmitted to the gearbox. The EMCD is composed of an electromagnetic coupler and a one quadrant operation converter with reduced capability and low cost. A control strategy for the new wind turbine is proposed and a 2 MW wind turbine model is built to study the wind turbine fault ride-through capability. An integrated simulation environment based on the aeroelastic code HAWC2 and software Matlab/Simulink is used to study its fault ride-through capability and the impact on the structural loads during grid three phase and two phase short circuit faults.

Introducing an improved bidirectional charger concept for modern residential standalone PV systems

The increasing electrical energy price worldwide and generally the liberation of Electrical Energy Markets, has highlighted the standalone residential PV systems as a potentially viable commercial product, especially for remote areas (islands, rural territories etc). Critical values for the success of these systems are the initial required capital for such an investment, the payback period and the compatibility with national and international directives on the low voltage electrical installations and on the power quality. To this direction, an improved standalone bidirectional battery charging system for residential applications is introduced in this paper. Extended Matlab/Simulink results are validating the advantages of the proposed configuration, especially in cases of three phase short circuit faults.

Study on Dynamic Response of Torsional Vibration of Turbo-Generator Unit Caused by Short Circuit Fault

When short circuit faults happen near power plant or generator terminal, severe transient torque shock will act on the shaft system, which seriously affects the safe and stable operation of the unit. Using the increment transfer matrix method, the dynamic responses of torsional vibrations are calculated in this work. Combined with the complex Morlet wavelet and time-frequency contour map, the time-frequency domain characters of dynamic torque are analyzed. The analyzed results show that the torque value caused by three phase short circuit fault is largest. The order of torque value from high to low is two phase short circuit to ground, two phase interphase short circuit and single phase short circuit. The electric distance between short circuit point and generator is more short, and the torsional vibration is more serious.

Investigation of Wind Farm Interaction with Ethiopian Electric Power Corporation's Grid

Ethiopia is planning to use wind power plants in addition to the existing hydropower plants to supply the increasing load demand to insure sustainable development. Consequently, large scale wind farms are going to be integrated to EEPCO's (Ethiopian Electric Power Corporation's) grid. This paper is concerned with investigation of interaction of wind farm with EEPCO's grid under transient operating condition. It is mainly concerned with Fault Ride-Through (FRT) capability, which includes voltage recovery at the wind turbines terminal; active and reactive power behaviour of the wind turbines after the fault is cleared. Recently planned wind farms of Ethiopia like Adama and Aisha use Permanent Magnet Synchronous Generator Wind Turbine (PMSG WT). As a result dynamic model of PMSG WT is developed by DIgSILENT PowerFactory simulation tool. Then Adama phase-1 wind farm with 34 PMSG WTs is modelled by using aggregated modelling approach. This model is used to investigate FRT capability and, active and reactive power behaviour of the wind farm by applying three phase short circuit fault. Promising response is observed from the Adama wind farm with PMSG WT when fault occurs on the grid terminal near to the wind farm.

Control of Wind Turbine Equipped with DFIG after Fault in Power Grid

grid connected wind turbine is daily increasing .a problem in power grid is grid faults.most problem is system stability after faults, also a probable problem of new energy sources in connection with grid is Islanding due to faults.in this condition loading mismatch between generation and load ‏consumption in isolated part of system can cause voltage and frequency cross it’s allowable limit.too in the case of over generation rotor will accelerate.so these lead to turbine interruption.in this paper wind turbine equipped with doubly fed induction generator is controlled for uninterrupted operation during fault to achieve more stability and rapid voltage recovery. Authority of DFIG grid side converter and Dstatcom effect after three phase short circuit fault are compared. results shows that with combination Dstatcom with grid side converter, voltage regulation in normal operation is beter.also after a fault more voltage stability and rather voltage recovery is achieved.too a suitable control will be presented for sake that wind turbine be able under Islanding operation to feeding local load at rated voltage and rated frequency.ability of control strategy in Islanding operation is investigated and simulation results Illustrate control strategy ability.

A NEW METHOD IN POWER SYSTEM SIMULATION TO APPROXIMATE TRANSIENTS OF THE SYNCHRONOUS MACHINES STATOR

Abstract This paper presents a new method to approximate the effects of synchronous machines stator transients in power system transient stability simulations. The method can approximate the DC offset currents which arise from the stator and network transients during three phase short circuit faults. However, the method is based on the traditional model with stator and network transients neglected.

Transient Stability Studies of AC/DC Power Systems

This paper presents the layout of a computer prgram capable of investigating the transient stability problems of AC and AC/DC power systems following the occurrence of symmetrical three phase short circuit faults. In the developed program, a high degree of flexibility is allowed in the representation of the various components of power systems. Special attention is focused on the modeling of synchronous machines., Two basic models; namely, the inertial model and the frequency response model,' are. identified. Also, the program includes a versatile load model which simulates different load-voltage characteristics. In addition, six various modes of control of the HVDC transmission are available.The developed program is applied to investigate the transient stability of a two-machine system with an AC/DC parallel network. The emphasis is focused on the effect of the HVDC transmission on the system stability with and without DC power modulation.