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A procedure for generating customized wavelets for detecting the location of a fault along the length of a transmission line is proposed. Measuring the time-difference-of-arrival (TDOA) between two consecutive transient reflections or the TDOA between the two initial peaks of two synchronized voltage/current bus measurements provides an accurate fault location estimate. Highly accurate TDOA estimates can be obtained only when the processed fault waveform consists of short/peaked pulses that arrive on a bus with a small group delay. Our customization procedure enhances the “peakedness” and shortens the group delay of the transient waveform by optimizing a suitable peakedness metric. This approach yields more accurate estimates than the “classic” (Daubechies) wavelet-based techniques found in the literature. The proposed method is independent of the fault-type and can be used to reduce the required data sampling rate while maintaining reliable TDOA estimates. [ABSTRACT FROM PUBLISHER]

Flexible AC Transmission Systems (FACTS) technology is the most advanced tool for power flow control in electric network. Unified Power Flow Controller (UPFC) is the most versatile FACTS device for optimization and control of power flow in transmission system. It is a voltage source converter based FACTS controller for series and shunt compensation of the line which controls the real and reactive power independently. This paper deals with Adaptive Neuro Fuzzy Inference System (ANFIS) is used as the controlling technique for UPFC. The controller have been designed and tested for controlling the real and reactive power flow of UPFC. Computer simulation by MATLAB/SIMULINK has been used to verify proposed control strategies. [ABSTRACT FROM PUBLISHER]

Liquefied Natural Gas (LNG) Plants are conventionally supplied using onsite generation. This paper outlines alternative design concepts which utilize a public grid to partially or fully supply the process loads. The results obtained from the power system studies for such alternative design concepts as typically undertaken as part of the Front End Engineering Design (FEED) to ensure design requirements are met, are compared to the conventional islanded network configuration. The key differentiators in the results of the system analysis are outlined with a view to establish the merits of each design and to ensure the delivery of a reliable power system as the design process proceeds. [ABSTRACT FROM PUBLISHER]

The fields of application of adjustable speed drives fed by voltage source inverters is constantly increasing. For better exploitation of the system's capabilities all drive components are more and more operated near and even above their rated values. This leads to more strains for the drive. However, at the same time the demands for reliability are also increasing. To reach this requirement different strategies like fault tolerant design, fault detection and condition monitoring can be implemented. However, to implement such strategies a deep understanding of the effects that lead to problems or faults in the drive system is necessary. The fast switching of modern voltage source inverters leads to transient overvoltage stressing the machine's insulation system. A short literature study presenting the characteristic of and the parameters influencing the non-linear voltage distribution in the stator winding of inverter-fed machines will be presented. Furthermore the findings will be compared with experimental results on an induction machine with tapped windings. [ABSTRACT FROM PUBLISHER]

The paper is concerned with the analysis based on the Discrete Wavelet Transform (DWT) of (non)stationary regimes in power systems. Different techniques are employed to perform decompositions using trees with 10 levels for different signals in (non)stationary regimes. The abilities of different methods to detect faults and respectively to deal with severe asymmetries are discussed. Power indices are calculated with different methods. A class of original hybrid algorithms is described, analyzed and discussed, generalization being provided. These algorithms can be used in all regimes and provide the fast “perfect reconstruction” property. Considering the results and other important criteria (run time, memory consumptions), practical recommendations are made with respect to the selection of a proper reliable and fast DWT algorithm depending on the operating conditions. [ABSTRACT FROM PUBLISHER]

The power quality monitoring system (PQMS) at Con Edison integrates measurements from power quality monitors, digital protective relays, digital fault recorders, SCADA historians, phase angle sensors, battery monitoring systems, and smart meters. The PQMS is used for power quality event and trend analysis via desktop and web server applications. It also provides single-event and multi-event fault analysis. The PQMS serves a major role in automatic distribution fault notification and fault location. It also provides transmission feeder fault notification. The PQMS correlates all PQ monitor events, digital relay events, and DFR events with the Con Edison SCADA historian. It provides automatic single-event and multievent analysis of capacitor switching transients. The PQMS provides incipient fault detection functionality, notification, and location estimation. It includes statistical process control modules for assessing voltage and reactive power regulation. The PQMS also provides MAIFI calculations for overhead distribution feeders. [ABSTRACT FROM PUBLISHER]

A new principle of fault phase selection is presented. It is proposed to recognize the non-fault phase by comparing the initial direction fault traveling wave amplitudes and their time derivative polarities near their headers. The wavelet filter and its derived porous filter are employed to detect the amplitudes of the initial direction fault traveling wave in different way. The filter results can supply the modulus maximum of wavelet coefficients in different sample frequency, and can used to carry out the time derivative polarity of fault traveling wave near the singularity. At the fault point, the initial fault current in non-fault phase is zero, and it can be used as judging criterion for non-fault phase selector after being modified reasonably and strictly. The selector can carry out the correct result of the fault with large transition resistances and low initial fault voltages at the same time. The simulation and calculation results by ATP and MATLAB confirm sensitivity and reliability of the principle. [ABSTRACT FROM PUBLISHER]

The short circuit behavior of Type I (fixed speed) wind turbine-generators is analyzed in this paper to aid in the protection coordination of wind plants of this type. A simple network consisting of one wind turbine-generator is analyzed for two network faults: a three phase short circuit and a phase A to ground fault. Electromagnetic transient simulations and sequence network calculations are compared for the two fault scenarios. It is found that traditional sequence network calculations give accurate results for the short circuit currents in the balanced fault case, but are inaccurate for the un-faulted phases in the unbalanced fault case. The time-current behavior of the fundamental frequency component of the short circuit currents for both fault cases are described, and found to differ significantly in the unbalanced and balanced fault cases. [ABSTRACT FROM PUBLISHER]

Recent system instability events have interacted with both transmission and generation protection in ways not always envisioned by the protection engineer. This paper discusses what relay engineers need to know about power system stability, including the four basic types of power system instability: Voltage instability, Steady-state instability, Transient instability and Dynamic instability. The paper relates how these various forms of instability relate to generator and transmission system protection. The paper also discuss system schemes used to address instability including: Generator Fast Valving, Generator Tripping, Generator High-speed Excitation Systems, Independent Pole Circuit Breaker applications and various types of Special Protection Schemes (SPS).1 [ABSTRACT FROM PUBLISHER]

A method of power system transient signal analysis based on improved Prony algorithm and neural network is used here to improve the accuracy of analysis of the transient signal with harmonic and inter-harmonic. The model of the Prony algorithm has the excellent characteristic of exactly describing transient signal and directly acquiring the frequency of signal. The frequency components of the signal were estimated assumably using Prony algorithm to confirm the amount of nerve cells and the beginning parameter of neural network firstly. Next, each frequency was treated as weight to be adjusted to estimate frequency values and amplitudes of the base wave, harmonics and inter-harmonics. Matlab simulation results demonstrated that the algorithm achieved high accuracy and rapid convergence. [ABSTRACT FROM PUBLISHER]

The rotating part of a large steam turbinegenerator is typically composed of individual turbine rotors that support the turbine blades or a generator rotor that holds the generator windings. These individual parts are usually attached together by bolted couplings. Although this combined rotating part of the turbine-generator can be excited in torsion by oscillating torques applied to its various components, most of the torques that can damage the large steam turbine-driven machines that provide power to the grid is due to interaction with the electrical grid. Due to the increasing size of these turbine-generators, they can have between 20 to 30 torsional modes of vibration with frequencies in the range where they can be excited by the grid during normal operation. Since damping for torsional modes can be very low (in the order of 0.1 per cent of critical damping or less), vibratory response at resonance can exceed 500 times the response that would occur from an equivalent static load of the same magnitude. As a result, turbine-generators can be quite sensitive to torsional vibration stimulus from the electrical grid and they should not be allowed to be operated at near-resonance conditions. In addition the steam turbinegenerator must be capable of sustaining suddenly applied impulse torques that can be generated by electrical grid faults, mal-synchronization, turbine or generator trips, and switching of transmission lines. One way that torsional resonance can occur is if the turbine generator is allowed to operate with unbalanced load on the generator terminals while it has a torsional mode with a frequency close to twice the grid frequency. The unbalanced load can result in a steady oscillating negative sequence current torque at twice the grid frequency that can cause significant damage to the turbinegenerator if it has an excitable torsional mode with a frequency too close to that of the exciting torque. It is important to design the turbine generator to provide sufficient torsional frequency margin with respect to such steady oscillating torques at twice the grid frequency while also providing a sufficiently rugged design that can withstand the suddenly applied torques that occur due to transients, upsets, and faults that occur from time-to-time during operation. [ABSTRACT FROM PUBLISHER]

In 2009, DTE Energy — Detroit Edison began a pilot project to use power quality monitors to locate faults on numerous trunk lines and tie lines of its 24-kV and 41.57-kV systems. Fault measurements captured by the meters are downloaded automatically, integrated into a relational database, and processed for reactance calculations. The reactance calculations are combined with detailed subtransmission circuit models and geographic information system data to build estimated fault location tables and web-based map displays. The systems are integrated on the company intranet and used in realtime by numerous groups within Detroit Edison including system supervisors, field operations, and system planning. The algorithm used for waveform processing can distinguish between single-phase faults, multi-phase faults, subcycle faults, and feeder energizing magnetizing inrush. The system integrates the measurements from the power quality monitors with circuit breaker operations stored in the SCADA historian. This paper will present an overview of some of the parameters and practices for finding faults in place every day at Detroit Edison. [ABSTRACT FROM PUBLISHER]

Due to the integration of more renewable energy sources into transmission grids throughout the world, grid codes are being adapted to take into account the diversity and intermittent production of these types of power sources. These adaptations to the grid code affect new and existing plant connected to the grid and are putting new demands on the turbogenerators in many aspects of their electrical parameters and performance. The existing machine design codes (e.g. IEEE C50.13 and IEC60034) do not take into account these new operating demands and are in need of review. Additionally grid code legislators, system operators and plant owners need to be aware of the potential impact on new and existing plant when deciding on revised performance criteria. This paper discusses the major effects of changes in grid code requirements on generator machine design and the challenges associated with meeting these requirements. [ABSTRACT FROM PUBLISHER]

Vision of a fail proof smart grid can be fulfilled using modern control capabilities. To maximize performance on the “edge”, systems often evolve into a subtle mix of order and randomness (e.g., biology or astrophysics). Systems exploiting such “deterministic unpredictability” have been built (e.g., high performance aircraft). This paper proposes to expand the envelope of stable operations into the realm of “managed chaos” in order to realize an agile power grid that is more efficient and reliable with less redundancy in transmission capacity. This involves operation of the system with a string of local ephemeral equilibria created by changing control objectives, strategies and/or algorithms. The shallow potential wells around these equilibria keep the system prone to managed chaos, until reaching an acceptable final equilibrium. Overcoming grid stability problems as proposed would enable end-to-end direct transactions between energy producers and consumers with internet-like market reach, transparency and ease of execution. [ABSTRACT FROM PUBLISHER]

The paper first proves the existence of a non-linear, feedback loop due to the effect of the APF on the grid voltage for a multifunctional electric vehicle charging station. A linear, open loop model is derived based on DQ theory in discrete time domain. Based on this model, a linear, closed loop model is further developed with DQ theory in discrete time domain. Triangle hold theory instead of zero order hold theory is employed in the model for better representation. The developed linear, closed loop model is finally generalized to generalized power systems. Simulations are carried out to verify the developed models under transient conditions. The short-time (1–2 ms), transient stability of the grid is determined with the developed model. In contrast to existing stability analyses in the phasor domain, using DQ-theory can linearize the loop and simplify the loop model in discrete time domain. [ABSTRACT FROM PUBLISHER]

This paper considers the power sharing stability of a grid connected Micro-grid (MG) system with three Distributed Generation (DG) units via Power System Stabilizer (PSS). Various PSS structures are employed and compared in order to achieve the best transient response under different DG penetration levels. Particle Swarm Optimization (PSO) is used to tune to controller parameters. The optimal controller's parameters where found by minimizing an objective function that moved the unstable eigenvalues to the left-hand side of the complex s-plane. The PSO based PSS is designed for low and medium of the MG. The results proved the effectiveness of the PSO tuned PSS in stabilizing the power system for the selected operating points. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a technique cancel common mode signals of sinusoidally gated single photon avalanche diodes (SPADs). This approach enables the elimination of narrow-band filters that fix the frequency of conventional single photon detection with sine wave gating. [ABSTRACT FROM PUBLISHER]