Single-phase Short-circuit Fault Research Articles

A Novel Fault Location Method for a Cross-Bonded HV Cable System Based on Sheath Current Monitoring.

In order to improve the practice in the operation and maintenance of high voltage (HV) cables, this paper proposes a fault location method based on the monitoring of cable sheath currents for use in cross-bonded HV cable systems. This method first analyzes the power–frequency component of the sheath current, which can be acquired at cable terminals and cable link boxes, using a Fast Fourier Transform (FFT). The cable segment where a fault occurs can be localized by the phase difference between the sheath currents at the two ends of the cable segment, because current would flow in the opposite direction towards the two ends of the cable segment with fault. Conversely, in other healthy cable segments of the same circuit, sheath currents would flow in the same direction. The exact fault position can then be located via electromagnetic time reversal (EMTR) analysis of the fault transients of the sheath current. The sheath currents have been simulated and analyzed by assuming a single-phase short-circuit fault to occur in every cable segment of a selected cross-bonded high voltage cable circuit. The sheath current monitoring system has been implemented in a 110 kV cable circuit in China. Results indicate that the proposed method is feasible and effective in location of HV cable short circuit faults.

Second Order Sliding Mode Control of Three Phase Four Switch VSI Fed Fault Reconfigurable Sensor Less PMSM Drive

Short circuit switch faults in PMSM drives results in improper response of drive and reconfiguration of such a faulty drive requires manual interruption. Hence an online fault reconfiguration scheme is required for continuous and stable operation of drives. Single phase short circuit fault identification and reconfiguration system for three phase four switch inverter fed sensor less PMSM drive is proposed. Fault Reconfiguration system involves an additional leg with two switches and TRIACs connected in each phase of inverter and also in additional leg. Fault is detected based on over current flow in any phase of motor due to short circuit faults. Fault reconfiguration system involves opening of TRIAC in a faulty phase and closing of TRIAC in additional leg. This method does not require any additional changes in hardware to identify fault and the time taken for fault identification and reconfiguration is short such that the over current is suppressed within its first cycle. In addition to fault reconfiguration scheme, a second order sliding mode controller for speed control of PMSM motor is proposed. This controller converges faster and has finite reaching time and settling time even if system has non linearity including system parameters variation with time. To validate the performance of proposed speed controller and fault reconfiguration scheme for three phase four switch inverter fed sensor less PMSM drive is simulated in MATLAB/Simulink environment.

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.

Fault Analysis for 110 kV HTS Power Cables

It is very attractive to replace the traditional power cables into high-temperature superconducting (HTS) cables for electricity transmission to metropolitan areas with the advantages of high capacity and low losses. However, these advantages only present when the conductors are kept in certain low temperature range. When a fault occurs, the HTS cable may quench and the resistivity of the conductor will increase rapidly which will result in the reduction of transmission capacity, increase of the power loss and even electrical insulation breakdown. Therefore, it is necessary to investigate the level of over current and overvoltage. In this paper, an accurate model for a 1-km-long 110 kV HTS cable is given and a simple simulation model for HTS cable is built up using EMTP-ATP program. Single-phase short-circuit fault and electrical insulation breakdown fault are considered to investigate the overvoltage and over current level of the HTS cable. The simulation results may provide instructive guide for the protection systems for HTS cables.

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.

The Economic Operation of Common Coupling Groups of Distribution Transformer

Based on the method of symmetrical components of D, 11 and Y, o distribution transformer coupling two different effects of different magnetic circuit coupled to the three-phase system with a system-generated analysis and comparison. Analysis of the difference between the two groups of different connections on the transformer structure. Described in the single-phase short circuit fault clearing, 3n harmonic current suppression and affordability aspects of single-phase unbalanced load, D, ll coupling transformers are significantly better than Y,0 coupling transformer. This has necessarily important for the study of energy loss reduction.