Two-phase Short Circuit Research Articles

Analysis of Measures that Exclude the Non-Selective Actions of Differential Collecting Busbar Protection in External Two-Phase Short Circuits with the Saturation of Current Transformers Included in Fault-Free Phases

An analysis is made on the non-selective actuation of the differential protection of busbars with a voltage of 110 kV of an electrical distribution system substation in the transition mode of an external two-phase short circuit. The protection effect is found to be due to the saturation of the transformer cores of class P current included in fault-free phases. Methods are also analyzed to ensure the correct operation of protection in the considered mode, and methods for calculating the protection parameters at which these methods are workable are proposed.

ANALISIS GANGGUAN HUBUNG SINGKAT PADA JARINGAN PEMAKAIAN SENDIRI PLTU BOLOK PT. SMSE (IPP) UNIT 3 DAN 4 MENGGUNAKAN SOFTWARE ETAP 12.6.0

Bolok Steam Power Plant has its own 6.3 kV usage network to service loads such as Feed Water Pump and Circulating Pump Feed. This self-use network is expected to supply unit loads at the Bolok coal-fired steam power plant without any interference. The presence of disturbances such as short circuit in the electric power system can cause problems such as damage to electrical equipment and the emergence of a power outage. Therefore problems that arise like this require an analytical study to determine the short circuit current that will occur while reducing the consequences that arise.
 This study aims to determine the largest short circuit fault current with the help of ETAP 12.6.0 software. Short circuit simulation results with ETAP 12.6.0 will be compared with manual calculations based on positive, negative and zero sequence impedance values from the point of disturbance location. 
 Based on the results of the research that has been done, it is known that the type of two-phase short circuit interference to the ground is the largest type of interference, which is equal to 10,615 kA on the generator bus. Whereas for the smallest type of short circuit interference is the type of disturbance one phase to the ground that is equal to 3,967 kA on the OutGoing II bus. From the results of the simulations conducted, it can also be seen that changes in the value of short circuit fault currents are affected by changes in the number of operating loads. The more load that operates the positive and negative sequence impedance the smaller and the value of the short circuit current will be greater, while the zero sequence impedance does not affect the amount of load operating, as well as the opposite.

Analysis of periodic processes of electrical energy devices on the basis of matrix of transition of the states

The mathematical model of the synchronous machine, the differential equations of which are presented in the normal form of Cauchy, an accelerated method of obtaining periodic processes on the basis of the transition matrix of states is proposed, and the algorithm for calculating periodic processes is given. Thanks to the calculation of the state transition matrix, the method of finding the initial conditions that lead to a periodic process is expanded to analyze the modes of power devices with saturated magneto resources. In addition, the efficiency of the method is described by the calculation of the electromechanical process, which is the two-phase short circuit of the synchronous generator.

Dynamic response of large turbogenerator stator end winding under fault conditions

The electromagnetic fields of a 600MW turbogenerator stator end region under three-phase short circuit and two-phase short circuit are calculated by numerical simulation base on a three-dimensional electromagnetic model. The variation of electromagnetic force density can also be obtained in the same time. Then the dynamic responses consist of deformation and stress distributions of end winding under three-phase short circuit are numerically analyzed by the fine finite element model which is set up in ABAQUS software. The presented numerical models and method can in turn be used to study the dynamic responses and safety of the end structure under various operation conditions.

Analysis of power system operation at asymmetrical load

The paper presents a mathematical model of a power system (PS) consisting of a generating unit (with a synchronous generator) connected by a high voltage (transmission) power line to a bus. The state and output equations of the generator are expressed in the coordinate system d, q, 0 and with the use of phase quantities of the generator stator, the bus and the power line, which is especially useful in the analysis of asymmetrical states. A disturbance of the steady state in the form of a two-phase short-circuit in the transmission line was taken into account in the made calculations. The influence of the excitation system and angular speed control system of the generator as well as the impact of selected generator model parameters on the waveforms were investigated.

Учёт сопротивления заземляющего устройства и сопротивления металлосвязи оборудования при расчёте токов двухфазного короткого замыкания на землю

Учёт сопротивления заземляющего устройства и сопротивления металлосвязи оборудования при расчёте токов двухфазного короткого замыкания на землю

DETERMINING A TYPE OF A DAMAGE IN THE CURRENT PROTECTION OF POWER LINES OF 6–35 KV

The methods to identify types of phase-to-phase short circuits that can be used to improve technical excellence by speed-current line protection of distribution networks of 6–35 kV are considered. As a result of the assessment of the appropriateness of their application in current protection, the choice was made in favor of the method based on the control of the relative current unbalance. The influence of contact resistances and load currents of various levels on the magnitude and character of the change of relative unbalance taking into account the errors of measuring transformers of current has been studied with the aid of the method of numerical experiment. It is demonstrated that in a lot of cases of arch short circuits in the loaded power line and in idle mode, the control only asymmetry is insufficient for reliable determination of the type of damage. A better algorithm has been proposed for determining phase-to-phase short circuit based on the control and the analysis of the two relative unbalance currents determined by the current values of the differences of the phase currents of the line. Its serviceability was evaluated. It was found out that in all the modes being considered, the proposed method – when boundary conditions are properly chosen – makes it possible to fix three-phase and two-phase short circuit on the protected line, and in the area of remote redundancy. The dynamic properties of the proposed method are investigated for different modes of the line. It is established that in the worst case, the determining of the damage is provided during the time not exceeding 25 ms.

Determination of high power synchronous generator subtransient reactances based on the waveforms for a steady state two-phase short-circuit

In the paper, there is presented an analysis of the waveforms at the stator winding terminals of a high power synchronous generator for a steady state two-phase short-circuit. The analysis was performed by the finite element method based on a 2D generator model taking into account higher spatial and time harmonics of the magnetic field as well as the impact of eddy currents in the rotor damping circuits. The used FE model was experimentally verified. For the steady state two-phase short-circuit, the waveforms determined by the FE method were compared with the approximated waveforms calculated using analytical formulas. The analytical formulas were derived from the machine equations written in the stator fixed coordinate system (α, β, 0), using normalized transformation of coordinates and the Heaviside operational calculus. The higher time harmonics obtained based on the FFT analysis of the waveforms of the short-circuit current and open phase voltage were used for determining subtransient reactances in the d and q axes of a 200MW generator. The thus determined generator reactances were compared with the values determined by other methods.

THE DETERMINATION OF THE KIND OF PHASE-TO-PHASE SHORT CIRCUIT IN CURRENT LINE PROTECTION OF 6–35 KV

The methods of determining the kind of phase-to-phase short circuit (SC) on the lines of 6–35 kV for improvement the technical perfection of their current protections are surveyed. Preference is given to the method of determining damages according to the relative unbalance the operating currents. The possibility of using the phase currents or their differences for this purpose is demonstrated. The method of computational experiment was used to investigate the influence of the DC load line and transition resistance at the failure site on the relative asymmetry of the currents that ultimately determines the reliability of the establishment of the kind of SC. It is discovered that when the phase currents are used to determine the type of the failure higher sensitivity to remote two-phase SC is achieved. However, in this case, the accuracy of determining the type of failure is more affected by currents of the line load. Determination of failure with the use of differences of phase currents is less sensitive to remote two-phase SC. However, this provides less impact on the accuracy of determining the type of failure of load line currents. Transition resistance at the failure site shifts the relative unbalance of the currents to the area of twophase SC. It is established that despite the kind of a remote SC in parallel lines the proposed methods provide accurate determination of types of failure that simultaneously occurs on the monitored line. When failures are superpositioned, one of which is on one of the parallel lines near the common bus and the other second on the monitored bus, the kind of the SC, determined by any of the proposed methods may differ from the actual one. It depends on the types of resulting failures, the combinations of shutting phases, the steady-state current distribution in the network and other factors. The proposed methods make it possible to determine the kind of phase-to-phase SC, in the worst case, for a time not exceeding the period of industrial frequency.

针对两相短路故障的时间窗自动提取算法设计

本文针对输电线路两相短路故障，提出了一种基于工频分量单端故障测距原理的时间窗提取算法。此算法利用故障电流的差值对时间窗进行定位。首先利用PSCAD/EMTDC仿真软件搭建输电线路分布参数模型，对输电线路发生两相短路故障进行仿真建模，然后将仿真结果导入MATLAB，最后利用所提时间窗自动提取算法对故障点进行定位。经过对测距结果的分析，本文所提时间窗自动提取算法在输电线路发生两相短路故障后能有效对时间窗进行提取，可以为微机保护装置时间窗的快速准确选取提供参考。 This paper proposes a new time window automatic extraction algorithm of two phase short circuit fault based on power frequency component of the single-ended ranging principle. The time window automatic extraction algorithm is based on the differences of the phase current of fault phase to locate the time window. First, the transmission line distributed parameter model is built by using PSCAD/EMTDC simulation software to simulate two-phase short circuit fault. Then, the results of the two-phase short circuit fault simulation are used to the input of MATLAB. Finally, the algorithm proposed in this paper is used to locate the fault point. The result of the fault location verifies that the algorithm is feasible. The algorithm proposed in this paper can effectively extract the time window of two phase short circuit fault which can provide reference to the microcomputer protection device.

Design and Analysis of a kA-Class Superconducting Reactor

Abstract —This paper presents the designs of kiloampere-classreactors with high temperature superconducting (HTS) BSCCOtapes. The HTS solenoidal windings of the 100 A-class andkiloampere-class reactors consist of 34 coil layers and 136 coilturns in total. The structural design and performance evaluations,including critical current and ac loss calculations are discussedfor a single-phase grounding fault case and compared with a con-ventional copper reactor. The method to apply the HTS tapes andthe principal features of the HTS reactors have been theoreticallyidentified. Index Terms — AC loss, BSCCO, current limiting reactor, neu-tral grounding reactor, superconducting reactor. I. I NTRODUCTION R EACTORS ARE widely used in modern power systems,which provide functions such as limiting currents, com-pensation of power, and inductive connection to ground. Powerquality and reliability problems are normally caused by theabnormal operations of large-scale equipments and the short-circuit faults caused by the power system itself. High tempera-ture superconductors (HTSs) have been successfully applied inthe advanced reactor developments. As an example, a numberofreactor-basedsuperconductingfaultcurrentlimiters(SFCLs)including the saturated iron-core type [1], [2], transformer type[3], [4] reactor type [5], [6], and non-inductive type [7] aremadeavailabletoreducethefaultcurrentlevelsontransmissionand distribution networks.The power system faults mainly include three-phase shortcircuit, two-phase short circuit, two-phase grounding short cir-cuit and single-phase grounding short circuit. The single-phasegrounding faults, for example, account for about 91.23% of thetotal number of power system faults in the 6434 power trans-mission lines of 220 kV Chinese power grid in 2008. It meansthat single-phase grounding faults need to be solved urgently toimprove the whole power system quality and reliability [8].In the neutral indirectly grounded power systems, the single-phase grounding fault occurs most frequently. The three-phaseline voltages still keep symmetrical states and have negligibleimpact to the local power equipments. Therefore, the powersystem is allowed to continue running up to few hours before

Torsional Vibration of a Shafting System under Electrical Disturbances

Torsional vibration responses of a nonlinear shafting system are studied by a modified Riccati torsional transfer matrix combining with the Newmark-βmethod. Firstly, the system is modeled as a chain consisting of an elastic spring with concentrated mass points, from which a multi-segment lumped mass model is established. Secondly, accumulated errors are eliminated from the eigenfrequencies and responses of the system's torsional vibration by this newly developed procedure. The incremental transfer matrix method, combining the modified Riccati torsional transfer matrix with Newmark-βmethod, is further applied to solve the dynamical equations for the torsional vibration of the nonlinear shafting system. Lastly, the shafting system of a turbine-generator is employed as an illustrating example, and simulation analysis has been performed on the transient responses of the shaft's torsional vibrations during typical power network disturbances, such as three-phase short circuit, two-phase short circuit and asynchronous juxtaposition. The results validate the present method and are instructive for the design of a turbo-generator shaft.

Torsional Vibration of a Shafting System under Electrical Disturbances

Torsional vibration responses of a nonlinear shafting system are studied by a modified Riccati torsional transfer matrix combining with the Newmark-β method. Firstly, the system is modeled as a chain consisting of an elastic spring with concentrated mass points, from which a multi-segment lumped mass model is established. Secondly, accumulated errors are eliminated from the eigenfrequencies and responses of the system's torsional vibration by this newly developed procedure. The incremental transfer matrix method, combining the modified Riccati torsional transfer matrix with Newmark-β method, is further applied to solve the dynamical equations for the torsional vibration of the nonlinear shafting system. Lastly, the shafting system of a turbine-generator is employed as an illustrating example, and simulation analysis has been performed on the transient responses of the shaft's torsional vibrations during typical power network disturbances, such as three-phase short circuit, two-phase short circuit and asynchronous juxtaposition. The results validate the present method and are instructive for the design of a turbo-generator shaft.

Analysis on Torsional Fatigue Life of Turbo-Generator Shafts

Both low-cycle fatigue and high-cycle fatigue exist during torsional vibrations, but the impact of high-cycle fatigue has rarely been considered. In this paper, a torsional fatigue life analyzing method used for torsional vibration of turbo-generator shafts has been developed based on Manson-Coffin equation and high-cycle fatigue theory. The method has been used to estimate the torsional fatigue life in the most dangerous section of the shafts in a power plant. The cumulative torsional fatigue damage under two-phase short circuit simulation has been predicted.

Single-line-to-ground fault test of a 3-phase superconducting fault current limiting reactor

The current limiting behavior of a 3-phase superconducting fault current limiting reactor (SCFCLR) in a model power system at a single-line-to-ground (SLTG) fault is experimentally confirmed. A small arc gap is attached on one phase of the model transmission line. A single-line-to-ground fault is activated. The behavior of the grounding current and the arc is observed. It is shown that: (1) the fault current is limited to a very small value by the large zero-phase-sequence reactance of the SCFCLR, and the self-extinction of the fault arc is observed; (2) the power flow is not disturbed by a SLTG fault at all, and no power system disturbances are observed; and (3) the windings do not quench for a SLTG fault. A supplementary experiment for a two-phase short circuit fault was also carried out. >