Browsing by Subject "Protection"

Now showing 1 - 3 of 3
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    Fast Detection and Mitigation of Cascading Outages in the Power System
    (2012-02-14) Pang, Chengzong
    This dissertation studies the causes and mechanism of power system cascading outages and proposes the improved interactive scheme between system-wide and local levels of monitoring and control to quickly detect, classify and mitigate the cascading outages in power system. A novel method for evaluating the vulnerability of individual components as well as the whole power system, which is named as weighted vulnerability analysis, is developed. Betweenness centrality is used to measure the importance of each bus and transmission line in the modeled power system network, which is in turn used to determine the weights for the weighted vulnerability index. It features fast reaction time and achieves higher accuracy when dealing with the cascading outage detection, classification and mitigation over the traditional methods. The overload problem due to power flow redistribution after one line tripped is a critical factor contributing to the cascading outages. A parallel corridor searching method is proposed to quickly identify the most vulnerable components after tripping a transmission line. The power system topology model can be simplified into state graph after searching the domains for each generator, the commons for each bus, and links between the commons. The parallel corridor will be determined by searching the links and commons in system topology graph for the given state of power system operation. During stressed operating state, either stable or unstable power swing may have impacts on distance relay judgment and lead to relay misoperation, which will result in the power system lines being tripped and as a consequence power system operating state becoming even more stressful. At the local level, an enhanced fault detection tool during power system swing is developed to reduce the chance of relay misoperation. Comprehensive simulation studies have been implemented by using the IEEE 39-bus and 118-bus test systems. The results are promising because: The results from weighted vulnerability analysis could provide better system situational awareness and accurate information about the disturbance; The results form parallel corridor search method could identify the most vulnerable lines after power re-distribution, which will give operator time to take remedial actions; The results from new travelling wave and wavelet transform based fault detection could reduce the impact of relay misoperation.
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    Hydraulic performance of temporary construction traffic barriers
    (2010-05) Hudson, Cody Brent; Barrett, Michael E.; Charbeneau, Randall J.
    Temporary Concrete Traffic Barriers (TCTBs) are essential in order to protect the traveling public and highway construction crews from accidents due to driver misfortune or negligence. In order for TCTBs to be installed, however, they must be successfully crash tested. Barrier height and drainage open space are key characteristics that influence this crash test rating. This is because an increase in height will insure that a vehicle will not over-top the barrier and a decrease in drainage open space will result in greater barrier mass, which will in turn resist larger impact forces. The factors that increase the crash worthiness of a barrier, however, lead to poor hydraulic performance. This then becomes a concern if barriers are placed in areas where they may adversely impact the local floodplain elevation. The objective of this research is the development of a hydraulic rating curve that describes the relationship between upstream energy head and the flow rate passing the barrier. To accomplish this objective, a three parameter model with three unknown coefficient terms was utilized. The model was then fit to experimentally obtained data, and a rating curve was developed. In addition, the effects of downstream submergence and clogging of the drainage opening, with respect to the rating curve, was also analyzed. Finally, a method for using this information in the hydraulic modeling software HEC-RAS was developed.
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    Simulation-based assessment for construction helmets and clothing
    (2012-05) Long, James; Yang, Jingzhou; Ekwaro-Osire, Stephen; Tate, Derrick
    In recent years there has been a push for greater job safety in all industries. Personnel protective equipment or PPE has been developed to help mitigate the risk of injury to humans that might be exposed to hazardous situations. The human head is the most critical location for impact to occur on a work site. A hard enough impact to the head can cause serious injury or death. That is why industries have adopted the use of an industrial hard hat or helmet. The objective of this safety device is to reduce the risk of injury to the head. There has only been a few articles published that are focused on the risk of head injury when wearing an industrial helmet. A lack of understanding is left on the effectiveness of construction helmets when reducing injury. The scope of this study is to determine the threshold at which a human will sustain injury when wearing a helmet. Complex finite element, or FE, models were developed to study the impact on construction helmets. The FE model consists of two parts the helmet and the human model. The human model consists of a brain, enclosed by a skull and an outer layer of skin. The level and probability of injury to the head is determined using both the Head Injury Criterion (HIC) and tolerance limits set by Deck and Willinger. The HIC has been greatly used to assess the likelihood of head injury while in a vehicles. The tolerance levels proposed by Deck and Willinger are more suited for finite element models, but lack wide scale validation. Different cases of impact were studied using LSTC’s LS-DYNA. In this thesis a study was conducted that assesses the risk of injury for wearers of construction helmets or hard hats. Next a literature survey on clothing simulation was also completed. Cloth modeling and simulation has gained significant momentum in recent years due to advances in computational hardware and software. Cloth plays an important role not only in daily life, but also in special scenarios such as firefighter clothing, ballistic or bullet proof vest and space suits. There are special requirements such as the protective capability of the fabric and effects on mobility for the wearer of the particular fabric or garment. Traditional assessment of cloth is to develop prototypes first and conduct experiments to assess the garment. This is time consuming and expensive. Virtual cloth modeling and simulation provides a means to demonstrate and assess its performance before cloth is made. This study attempts to give a literature review to summarize the state-of-the-art of cloth modeling and simulation. After the literature survey several clothing simulations were completed using LS-Dyna. These simulations were able to test and predict some basic information. The testing showed that realistic draping and stress mapping for digital cloth can be achieved using LSTC’s LS-Dyna.