Browsing by Subject "Power system protection"
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Item Analyzing voltage sag direction using protective relays and deep-learning methods(2023-04-21) Patha, Lekhaj; Santoso, SuryaAs the electricity demand continues to grow, power systems are becoming more complex and interconnected, making the need for reliable protection systems more important than ever. Protection systems are designed to detect and isolate faults and other abnormal conditions, preventing them from cascading through the power grid and causing widespread outages. The primary challenge in protection is to detect the fault, the type of fault, and the location of the fault. Traditional relays effectively locate, detect, and isolate faults. Circuit breakers, fuses, and relays, these devices work together to ensure the power system remains stable and reliable, under various conditions including system failures. Smart Intelligent relays (SIRs) are designed to perform a broader range of functions, such as fault location, and power quality monitoring. Machine learning techniques are increasingly applied in power systems protection to enhance fault detection and classification accuracy and speed. ML algorithms can be used to analyze real-time data from sensors and other devices to detect and classify faults, including those that may be too small or subtle to be detected by traditional protection systems. The thesis aims to study methods of identifying the direction of voltage sags in the distribution circuits. Voltage sags arise from the presence of short-circuit faults involving single, double, and three phase-to-ground conditions. The direction of the fault is based on the direction of power flow before the occurrence of the event. A fault can be classified as a downstream fault from a monitoring location if the direction of power flow is towards the fault location before the occurrence of the event. Similarly, a fault can be classified as an upstream fault if the direction of power flow is against the fault location before the occurrence of the fault. The terms upstream and downstream are relative to the monitor location. A downstream fault for one monitor can be an upstream fault for a different monitor. This thesis studies the applications of protective relaying and deep learning techniques in identifying the direction of voltage sags using the real-time waveforms of voltage and current to estimate whether the fault is upstream or downstream from the monitored location(s). The fault data was generated using a time-domain power system modeling tool with variable fault impedances and multiple fault locations. Relay-based approaches have been studied, and a deep-learning technique has been developed with the data generated. The relay-based techniques were capable of identifying the fault direction in all the cases irrespective of the fault location and fault duration. ML algorithms can help analyze large amounts of data and detect patterns that may be difficult or impossible for traditional protection systems to identify.Item Data analytics applications to fault locations and overcurrent protection devices(2019-06-20) Min, Kyung Woo; Santoso, Surya; Baldick, Ross; Hallock, Gary; Arapostathis, Aristotle; Karadkar, UnmilPower 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.Item Model-based dynamic relaying for power system protection under uncertainty(2017-05) Lwin, Min Naing; Santoso, Surya; Baldick, Ross; Valvano, Jonathan; Ghosh, Joydeep; Bickel, EricSeveral major cascading outages have involved mis-operation or mis-coordination of protective relays during stressed system conditions that resulted in a vulnerable network. Such stressed conditions include concurrent high load demand, changes in circuit topology, equipment outages, and short-circuit faults. With levels of wind and photovoltaic (PV) generation projected to increase in the future, large-scale variable generation also presents an additional point of vulnerability to the existing protection system. In this work, a new framework is introduced that is built on model-based distributed relay intelligence. The framework integrates real-time measurements from adjacent buses and predictive circuit models embedded in relays. The data collected by the relay is input to circuit simulations in order to accurately predict possible fault conditions at the relay location. Settings can then be adapted in real-time based on prevailing system conditions. Several scenarios are evaluated to demonstrate the effectiveness of this approach. This work further develops a probabilistic formulation of optimal relay characteristics that adapts to the randomness and uncertainty introduced by renewable generation. In this framework, the calculation of relay operating times is formulated as a stochastic optimization problem. In addition, at the system level, a mixed-integer linear program is developed for protective device and switch allocation considering intentional islanding with distributed generation in distribution systems.Item Protection system lab experiments with overcurrent and differential relays(2020-05) Flint, Alison Ewing; Santoso, SuryaThis report presents the theory and application of two ubiquitous protection schemes, overcurrent protection and differential current protection, with the design of experiments and exercises for electrical engineering students. The objective of this undertaking is educational, so that students can learn, understand, and execute various operations pertaining to basic functions of relays. The result is a set of instructions for laboratory practices and exercises (lab manuals) which introduces relays in the context of the greater power system protection, and uses equipment modules to present relay functions.Item Time-domain modeling and validation of overcurrent/reclosing relay operation(2013-08) Lwin, Min Naing; Santoso, SuryaThe primary goal of this work is to develop a PSCAD/EMTDC simulation model which can emulate the reclosing capabilities of an actual reclosing relay. The first part of this work will demonstrate the capabilities of a commercially available, microprocessor-based reclosing relay, the SEL-551c. Next, a computer simulation model of this relay's reclosing capability will be developed in PSCAD/EMTDC and validated. The performance of the model will be compared to the performance of the SEL-551c. Because it is impractical to test the relay operation under fault conditions in a real distribution system, fault characteristics will be determined in PSCAD. Utilizing a test system for the SEL relay, we can show the accuracy of the PSCAD recloser model compared to the SEL-551c relay for similar fault scenarios. The validation is done by analyzing the data from the simulation and experiment. The results show that both the PSCAD recloser model and SEL-551c operate close to the expected theoretical values. The primary contribution of this work is the development of a PSCAD recloser model and validation with a real world reclosing relay. In previous works where recloser analysis was done in PSCAD, such as [14], recloser operation was manually accomplished. However, the recloser model developed in this work allows the user to enter any standard TCC equation that may be programmed into an actual relay and achieve similar results. The model is useful when analyzing larger distribution systems with multiple reclosers. Additionally, validating the PSCAD recloser model with a real world device provides confidence that the simulations provide reasonable and meaningful results.