407 research outputs found

    Nuclear Magnetohydrodynamic EMP, Solar Storms, and Substorms

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    In addition to a fast electromagnetic pulse (EMP), a high altitude nuclear burst produces a relatively slow magnetohydrodynarnic EMP (MHD EMP), whose effects are like those from solar storm geomagnetically induced currents (SS GIC). The MHD EMP electric field E < 10^-1 V/m and lasts < 10^2 sec, whereas for solar storms E > 10^-2 V/m and lasts >10^3 sec. Although the solar storm electric field is lower than MHD EMP, the solar storm effects are generally greater due to their much longer duration. Substorms produce much smaller effects than SS GIC, but occur much more frequently. This paper describes the physics of such geomagnetic disturbances and analyzes their effects.Comment: 29 pages, 14 figures, 5 table

    Experiencing Physical Violence During Pregnancy: Prevalence and Correlates

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    Violence during pregnancy directly impacts the mental and physical health of pregnant women. We assessed the prevalence and correlates of physical violence around the time of pregnancy in a representative sample of 6,718 women in South Carolina. Physical violence, defined as being physically hurt by husband or partner or being involved in a physical fight was reported by 10.9% of recently pregnant women. These were correlates of violence: experiencing increased numbers of stressful life events, being unmarried, having increased parity, being on Medicaid, and having an unwanted pregnancy. Screening to identify violence in pregnancy in health care settings is vital to maternal and child health. However, identifying violence is not enough; community resources and clinic-based support are needed to help women deal with violence in their lives

    Breaker to Control Center Integration & Automation: Protection, Control, Operation & Optimization

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    Recent technological advances in protection, control and optimization are enabling a more automated power system. This paper proposes the use of these technologies towards an integrated and seamless infrastructure for protection, control and operation. This infrastructure is the basis for accommodating and providing robust solutions to new problems arising from the integration of renewables, namely more uncertainty and steeper ramp rates. At the lower level we propose a dynamic state estimation of a protection zone (EBP) for the purpose of providing protection for the zone. The estimation based protection (EBP) provides the real time dynamic model of the zone as well as the real time operating conditions. Since protection is ubiquitous, it can cover the full system. We assume that GPS synchronization of the EBP is available providing accurate time tags for the real time model and operating conditions. The real time model and operating conditions can extent from the “turbine to the toaster”. We propose a methodology for automatically constructing the power system state locally and centrally at the control center with distributed controls as well as centralized controls depending on the application. For example, the centralized \ system wide real time model is used to perform system optimization functions, and then send commands back through the same communication structure to specific power system components. Since protection is ubiquitous and the modern power system has several layers of communication infrastructure, the proposed approach is realizable with very small investment. The availability of the real time dynamic model and state locally and centrally enables the seamless integration of applications. Three applications are discussed in the paper: (a) setting-less protection, (b) voltage/var control and (c) feeder load flexibility scheduling. The proposed approach and infrastructure can form the basis for the next generation of Energy Management Systems.

    Optimal Reactive Power Dispatch Formulated as Quadratic OPF and Solved via CS-SLP

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    Increased penetration of inverter interfaced renewable energy resources creates challenges and opportunities for reactive power management in the modern electricity grid. Because of the multiplicity of new resources, new computational tools and optimization models are needed in formulating and solving the Optimal Reactive Power Dispatch Problem (ORPD). In this paper, we propose (1) an object-oriented ORPD formulation based on high-fidelity modeling of each device in the network, especially those with VAR/V control capability and (2) a two-step Convex Solution-Sequential Linear Programming algorithm. The proposed method introduces two innovations: (a) high fidelity quadratized models of each component of the power system with emphasis on those components that have VAR/V control capability; and (b) an object oriented convexification of the resulting quadratic OPF problem; the solution is obtained by first solving the convex problem using public solvers for convex problems and them removing the relaxation and solving the original OPF using SLP, starting from the solution of the relaxed (convex) problem

    Integrated Centralized Substation Protection

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    Substation cyber assets are mission critical for protection and control of substations. Managing and ensuring their secure operation is of paramount importance. A known vulnerability is hidden failures which are responsible for about 10% of mis-operations and their detrimental effects on system reliability. The paper presents an integrated centralized substation protection approach that is based on the recently developed setting-less relays which are integrated into a centralized substation protection scheme with the following features: (a) fast, dependable and secure protection of each substation protection zone by a settingless relay, (b) supervision of each settingless relay by validating relay input data by a substation wide state estimator, (c) self-healing against hidden failures by detecting and identifying compromised data and replacing them with estimated values, thus ensuring that the settingless relays will always operate on validated data. The paper provides a summary review of the settingless protective relay and introduces the Integrated Centralized Substation Protection Scheme (ICSP) which uses the data from all settingless relays in the substation to perform a substation wide state estimation. The state estimator uses a hypothesis testing algorithm to determine whether (a) data are valid with no faults or hidden failures, (b) data are valid and a fault exists in the system, or (c) some data are invalid due to hidden failures. In the last case, the state estimator uses the substation state and model to replace the compromised data with estimated values and thus enabling self-immunization against hidden failures. A byproduct of the method is the substation state estimate which is transmitted to the control center where it is used with the state from all substations to synthesize the system wide state estimate and model. Architectural issues are addressed as well as migration issues of existing systems into the proposed ICSP

    Physical Violence During Pregnancy: Maternal Complications and Birth Outcomes

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    Objective: To assess the association between physical violence during the 12 months before delivery and maternal complications and birth outcomes. Methods: We used population-based data from 6143 women who delivered live-born infants between 1993 and 1995 in South Carolina. Data on women\u27s physical violence during pregnancy were based on self-reports of partner-inflicted physical hurt and being involved in a physical fight. Outcome data included maternal antenatal hospitalizations, labor and delivery complications, low birth weights, and preterm births. Odds ratios and 95% confidence intervals were calculated to measure the associations between physical violence, maternal morbidity, and birth outcomes. Results: The prevalence of physical violence was 11.1%. Among women who experienced physical violence, 54% reported having been involved in physical fights only and 46% had been hurt by husbands or partners. In the latter group, 70% also reported having been involved in fighting. Compared with those not reporting physical violence, women who did were more likely to deliver by cesarean and be hospitalized before delivery for maternal complications such as kidney infection, premature labor, and trauma due to falls or blows to the abdomen. Conclusion: Physical violence during the 12 months before delivery is common and is associated with adverse maternal conditions. The findings support the need for research on how to screen for physical violence early in pregnancy and to prevent its consequences

    Autonomous Multi-Stage Flexible OPF for Active Distribution Systems with DERs

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    The variability of renewable resources creates challenges in the operation and control of power systems. One way to cope with this issue is to use the flexibility of customer resources in addition to utility resources to mitigate this variability. We present an approach that autonomously optimizes the available distributed energy resources (DERs) of the system to optimally balance generation and load and/or levelize the voltage profile. The method uses a dynamic state estimator which is continuously running on the system providing the real-time dynamic model of the system and operating condition. At user selected time intervals, the real-time model and operating condition is used to autonomously assemble a multi-stage optimal power flow in which customer energy resources are represented with their controls, allowing the use of customer flexibility to be part of the solution. Customer DERs may include photovoltaic rooftops with controllable inverters, batteries, thermostatically controlled loads, smart appliances, etc. The paper describes the autonomous formation of the Multi-Stage Flexible Optimal Power Flow and the solution of the problem, and presents sample results

    Breaker to Control Center Integrated Protection, Control and Operations Model

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    Technological advances in electric energy system data acquisition systems, time synchronization, and cyber assets used in power system substations, distribution systems, and control centers offer new opportunities to dramatically improve the practice of monitoring, protection, control, and operation of the system. We can make the computer based new technologies smarter and more intelligent to fully automate the basic protection and control functions. The challenges posed to the system from the continuous deployment of renewable resources that are typically inverter interface resources require monitoring of the system at much higher rates and development of protection and control systems that can respond in much faster rates than for conventional systems and they are immune to the characteristics of the new system, namely reduced fault currents and suppressed negative and zero sequence components of the fault currents. We propose a new system that provides validated data at fast rates (once per cycle), protective relays that are immune to the effects of inverter interfaced generation, detect anomalies, and enable the continuous operation of relays and other functions even in the presence of hidden failures in instrumentation. This system will be able to enable the operators to meet the challenges posed by the evolving power system and provides robust solutions to the new requirements

    Racial disparities in healthcare provider advice to quit smoking

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    African-American/Black smokers are less likely than White smokers to be told to quit smoking by healthcare providers. This preliminary study examined the predictors of being told to quit separately by race for the first time to potentially highlight the source of this racial disparity. A random, household sample of 1670 Black and White adults from a southeastern county of the United States completed a brief survey on their demographics, smoking, access to healthcare, health status, and receipt of healthcare provider advice to quit smoking. Analyses are based on the 512 Black and White smokers in that sample. The logistic regression for all smokers revealed that after controlling for demographic, healthcare, and health status variables, White smokers were 2.39 times more likely than Black smokers to have ever been told to quit smoking. The regression for Black smokers re- vealed that women and older people were more likely to be told to quit, and that healthcare and health status did not contribute. In the regression for White smokers, no predictor was statistically significant. These findings suggest that one possible reason that African-Americans receive cessation advice less often than Whites is that such advice varies with their age and gender, whereas for Whites this is not the case

    Disparities in Health Care Utilization by Smoking Status – NHANES 1999–2004

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    The objective of this study was to assess disparities in health care utilization, by smoking status, among adults in the United States. We used 1999–2004 National Health and Nutrition Examination Survey (NHANES) data from 15,332 adults. Multivariate logistic regressions were used to examine the relationship between smoking status (current, former, and never smoker), with health care utilization. After controlling for demographic characteristics, current smokers and former smokers who quit either <2 years or ≄10 years prior to the survey were more likely to have had inpatient admission in the past year than never smokers. Current smokers did not differ from never smokers on whether they had an outpatient visit in the past year. They were, however, more likely than never smokers to have ≄4 outpatient visits. Smokers who quit either <2 years ago or ≄10 years ago were more likely to have had an outpatient visit than never smokers. Former smokers were more likely than never smokers to have ≄4 outpatient visits regardless of when they quit. Our results show that cigarette smoking is associated with higher health care utilization for current and former smokers than for never smokers. Frequent hospitalization and outpatient visits translate into higher medical costs. Therefore, more efforts are needed to promote interventions that discourage smoking initiation and encourage cessation
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