Methodology for characterizing electric power system response and locating the energized capacitor banks using conventional power quality data

textA relatively small harmonic current with frequencies near or at the power system parallel resonant frequencies could excite the power system into a resonance condition. While a capacitor bank is not the root cause of the condition, it facilitates and helps cause the problem. This is because when the capacitor bank is energized, the system resonant frequency could shift closer to existing harmonic frequencies produced by nonlinear loads. Therefore, the objective of this dissertation is to quantify the power system characteristics corresponding to the parallel resonant frequencies and system damping. Additionally, since a capacitor bank actively facilitates the resonance condition, the relative or exact location of the involved bank must be determined. This dissertation first presents a practical and accurate methodology to estimate system parallel resonant frequencies by performing spectral analysis of the voltage and current transient data immediately after the capacitor bank switching. The proposed method is also robust in that the accuracy of the resulting estimates is not affected by prevalent harmonics in the system. This dissertation provides two efficient algorithms for estimating the system damping parameters using the Hilbert and analytic wavelet transforms. These algorithms take advantage of the principle of an asymptotic or weaklymodulated signal, for which the signal phase varies much more rapidly than the amplitude. The zero-input voltage response or free response of the capacitor bank energizing can be categorized into these asymptotic signals, and one can assign a unique time-varying amplitude with the system damping information and phase pair by building analytic signals. System model reduction theory also allows us to interpret or quantify this damping as an effective X/R ratio. This dissertation defines two fundamental signatures of shunt capacitor bank energizing. It demonstrates that these two signatures can be utilized to accurately determine the relative location of an energized capacitor bank whether it is upstream or downstream from the monitoring location. This dissertation also presents an efficient and accurate methodology for finding the exact location of an energized capacitor bank. Once a PQ monitor is found to be upstream from the capacitor bank by the relative location finding algorithm, the proposed algorithm can further determine the exact location of the switched capacitor bank by estimating the distance between the PQ monitor and the energized capacitor bank. Thus, one can pinpoint the energized capacitor bank causing the resonance.Electrical and Computer Engineerin

Diagnostic Applications for Micro-Synchrophasor Measurements

This report articulates and justifies the preliminary selection of diagnostic applications for data from micro-synchrophasors (µPMUs) in electric power distribution systems that will be further studied and developed within the scope of the three-year ARPA-e award titled Micro-synchrophasors for Distribution Systems

Advances and Technologies in High Voltage Power Systems Operation, Control, Protection and Security

The electrical demands in several countries around the world are increasing due to the huge energy requirements of prosperous economies and the human activities of modern life. In order to economically transfer electrical powers from the generation side to the demand side, these powers need to be transferred at high-voltage levels through suitable transmission systems and power substations. To this end, high-voltage transmission systems and power substations are in demand. Actually, they are at the heart of interconnected power systems, in which any faults might lead to unsuitable consequences, abnormal operation situations, security issues, and even power cuts and blackouts. In order to cope with the ever-increasing operation and control complexity and security in interconnected high-voltage power systems, new architectures, concepts, algorithms, and procedures are essential. This book aims to encourage researchers to address the technical issues and research gaps in high-voltage transmission systems and power substations in modern energy systems

Ultrasonic-Based Condition Assessment of Wooden Utility Poles

More than 300 million utility poles shoulder the utility grid in the United States. However, the ineffectiveness of the current inspection process causes roughly a third of utility poles removed from the service deemed suitable for reuse. Due to the utterly essential role of the power infrastructure, budget shrinkage, and the structural degradation of the modern distribution grid, this Ph.D. dissertation addresses the challenges by proposing a physics-based signal analysis method with a jointly developed ultrasonic UB1000 system c to enhance the objectivity in ultrasonic-based nondestructive evaluation (NDE). The proposed methodology has been deployed commercially in the field and featured in articles by the Missouri Public Utility Alliance and the Western Cooperative Electric. This dissertation proposes embedded waveguide as an ultrasonic radiation source. A systematic analytical model is developed based on the classical elastodynamic formulation to study the excitation and the propagation characteristics of the resulted elastic wave. Based on the steady-state assumption with a set of half-space boundary and interface loading conditions, the obtained closed-form displacement field yields the diffusive property of the shell region propagation as a function of the Poisson’s ratio. The diffusive property is discovered under the quasi-steady load condition, a reasonable model to describe the behavior of a narrow-band ultrasonic transducer. The estimated diffusive propagation is demonstrated through the numerical finite element method (FEM). This study developed the first high-fidelity numerical model of a wooden pole crosssectional region. It is capable of modeling a porous orthotropic medium under the cylindrical symmetry enabling high moisture content and/or incipient decay conditions to be simulated. Using a transient imposed boundary condition, the model uncovers different arrival wave modes resulted from propagating in various regions within the cross-section. By dissecting the waveform and isolating the corresponding arrival wave, it allows a direct examination of the wave energy content within the shell region, which is a critical area in the cross-section that dictates the overall strength of a wooden pole. By modifying the physical and the poroelastic properties of the medium to simulate the incipient decay and high moisture content, this study discovers a correlation between the selected features within the received waveform and the physical property of the medium (e.g., modulus of elasticity and the moisture saturation levels). The findings from both the numerical and analytical approaches motivate the proposed physics-based signal analysis to extract both the temporal and spectral information at the resonant frequency of the ultrasonic wave via the time and frequency (TF) transformation. A comparative study using the numerical results was performed to examine the Short Time Fourier Transformation (STFT) and Gabor Continuous wavelet transform (GCWT). Due to its superior temporal and spectral resolution, the GCWT is selected to analyze signals from different simulated conditions. The results produce a pronounced difference in the selected features in all the different simulated cases, suggesting a viable analysis approach for characterizing the medium. Based on the proposed physics-based signal analysis approach, this work develops and details a corresponding pole analysis algorithm. The experiments were carried out with specimens of different known Groundline(GL) conditions (healthy, decay and highmoisture) to examine the efficacy of the proposed waveguide design and the associated analysis algorithm. The collected signals are fed through the GCWT analysis algorithm to extracted the features sensitive to those conditions. The results suggest a high moisture content pole would have a typical energy attenuation of around 35% compared to a healthy pole with low moisture content, while the time when the peak energy occurs is relatively the same in both cases. In a decay wood specimen, the result suggests an 11% latency in peak energy time-of-flight (TOF), 50% energy reduction and a 50% increase in diffusivity by measuring the full width half maximum (FWHM) around the energy peak. A further refinement of the analysis places the peak energy TOF and energy reduction levels as the selected features on a feature space to assess fifteen poles with known categories. A clear decision boundary is discovered prompting a future research opportunity of using linear and/or non-linear classifiers to determine the wooden pole at the GL region

Data analytics applications to fault locations and overcurrent protection devices

Power quality (PQ) monitors installed in transmission and distribution systems record disturbance events occurring in the system, such as root mean square (RMS) variations and transients caused by short-circuit faults, transformer energizing, or capacitor switching around the clock, resulting in a large amount of data. Although the collected data contain valuable information about the system, they are often merely stored without any further analysis. Analysis of these data presents opportunities for improving the performance of power systems as well as for monitoring the health of the grid as a whole. The general objective of this proposal is to develop algorithms that make use of three phase voltage and current measurements recorded from the power quality monitors. Specifically, algorithms are developed for the analysis of (1) short circuit faults with their locations (fault analytics) and (2) overcurrent protection devices installed in the system (device analytics). The fault analytics module is used to identify fault events among other power quality events and estimates the location to the fault occurring in the system. The proposed method uses variable window size in calculating phasors and estimates a single fault location that is more accurate than the multiple locations estimated by the conventional approach using Fourier and cosine filters. The device analytics module aims to evaluate the overcurrent protection devices operating to isolate short-circuit faults from the system. This module identifies recloser and fuse operations and estimates the empirical inverse time-current characteristics of the devices. The results of the device analytics are used to evaluate device opening intervals and coordination and to further narrow down fault location because faults are located downstream from the clearing device. Finally, the dissertation presents a data analytics framework and an open power quality disturbance event schema. The schema is developed to promote the sharing of data recording PQ disturbance events and the metadata providing descriptive and quantitative analysis of the events.Electrical and Computer Engineerin

Characterization, Classification, and Genesis of Seismocardiographic Signals

Seismocardiographic (SCG) signals are the acoustic and vibration induced by cardiac activity measured non-invasively at the chest surface. These signals may offer a method for diagnosing and monitoring heart function. Successful classification of SCG signals in health and disease depends on accurate signal characterization and feature extraction. In this study, SCG signal features were extracted in the time, frequency, and time-frequency domains. Different methods for estimating time-frequency features of SCG were investigated. Results suggested that the polynomial chirplet transform outperformed wavelet and short time Fourier transforms. Many factors may contribute to increasing intrasubject SCG variability including subject posture and respiratory phase. In this study, the effect of respiration on SCG signal variability was investigated. Results suggested that SCG waveforms can vary with lung volume, respiratory flow direction, or a combination of these criteria. SCG events were classified into groups belonging to these different respiration phases using classifiers, including artificial neural networks, support vector machines, and random forest. Categorizing SCG events into different groups containing similar events allows more accurate estimation of SCG features. SCG feature points were also identified from simultaneous measurements of SCG and other well-known physiologic signals including electrocardiography, phonocardiography, and echocardiography. Future work may use this information to get more insights into the genesis of SCG