Methods for Analysis and Quantification of Power System Resilience

This paper summarizes the report prepared by an IEEE PES Task Force. Resilience is a fairly new technical concept for power systems, and it is important to precisely delineate this concept for actual applications. As a critical infrastructure, power systems have to be prepared to survive rare but extreme incidents (natural catastrophes, extreme weather events, physical/cyber-attacks, equipment failure cascades, etc.) to guarantee power supply to the electricity-dependent economy and society. Thus, resilience needs to be integrated into planning and operational assessment to design and operate adequately resilient power systems. Quantification of resilience as a key performance indicator is important, together with costs and reliability. Quantification can analyze existing power systems and identify resilience improvements in future power systems. Given that a 100% resilient system is not economic (or even technically achievable), the degree of resilience should be transparent and comprehensible. Several gaps are identified to indicate further needs for research and development.Published versio

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Abstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Instruments to assess secondhand smoke exposure in large cohorts of never smokers: The smoke scales

© 2014 The Authors. Published by PLOS. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1371/journal.pone.0085809The objectives of this study were to: (i) to develop questionnaires that can identify never-smoking children and adults experiencing increased exposure to secondhand smoke (SHS+), (ii) to determine their validity against hair nicotine, and (iii) assess their reliability. A sample of 191 children (85 males; 106 females; 7-18 years) and 95 adult (23 males; 72 females; 18- 62 years) never-smokers consented to hair nicotine analysis and answered a large number of questions assessing all sources of SHS. A randomly-selected 30% answered the questions again after 20-30 days. Prevalence of SHS+ in children and adults was 0.52±0.07 and 0.67±0.10, respectively (p16.5 and >16, respectively. Significant Kappa agreement (p0.05). Area under the curve and McNemar's Chi-square showed no pair-wise differences in sensitivity and specificity at the cutoff point between the two different days for SS-C and SS-A (p>0.05). We conclude that the SS-C and the SS-A represent valid, reliable, practical, and inexpensive instruments to identify children and adult never-smokers exposed to increased SHS. Future research should aim to further increase the validity of the two questionnaires. © 2014 Misailidi et al.Published versio

Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

Funder: European Society of Intensive Care Medicine; doi: http://dx.doi.org/10.13039/501100013347Funder: Flemish Society for Critical Care NursesAbstract: Purpose: Intensive care unit (ICU) patients are particularly susceptible to developing pressure injuries. Epidemiologic data is however unavailable. We aimed to provide an international picture of the extent of pressure injuries and factors associated with ICU-acquired pressure injuries in adult ICU patients. Methods: International 1-day point-prevalence study; follow-up for outcome assessment until hospital discharge (maximum 12 weeks). Factors associated with ICU-acquired pressure injury and hospital mortality were assessed by generalised linear mixed-effects regression analysis. Results: Data from 13,254 patients in 1117 ICUs (90 countries) revealed 6747 pressure injuries; 3997 (59.2%) were ICU-acquired. Overall prevalence was 26.6% (95% confidence interval [CI] 25.9–27.3). ICU-acquired prevalence was 16.2% (95% CI 15.6–16.8). Sacrum (37%) and heels (19.5%) were most affected. Factors independently associated with ICU-acquired pressure injuries were older age, male sex, being underweight, emergency surgery, higher Simplified Acute Physiology Score II, Braden score 3 days, comorbidities (chronic obstructive pulmonary disease, immunodeficiency), organ support (renal replacement, mechanical ventilation on ICU admission), and being in a low or lower-middle income-economy. Gradually increasing associations with mortality were identified for increasing severity of pressure injury: stage I (odds ratio [OR] 1.5; 95% CI 1.2–1.8), stage II (OR 1.6; 95% CI 1.4–1.9), and stage III or worse (OR 2.8; 95% CI 2.3–3.3). Conclusion: Pressure injuries are common in adult ICU patients. ICU-acquired pressure injuries are associated with mainly intrinsic factors and mortality. Optimal care standards, increased awareness, appropriate resource allocation, and further research into optimal prevention are pivotal to tackle this important patient safety threat

Correction to: Prevalence, associated factors and outcomes of pressure injuries in adult intensive care unit patients: the DecubICUs study

The original version of this article unfortunately contained a mistake

Incorporating Mobile Energy Resources in Optimal Power Flow Models Considering Geographical and Road Network Data

<p>Mobile energy resources (MERs) are becoming an increasingly popular asset in modern power systems with several potential benefits. While the incorporation of MERs in optimal power flow (OPF) models can enhance both reliability and resilience of the system, they add additional levels of complexity to the optimization problem. To properly determine optimal dispatch of MERs, electrical power grid constraints must be incorporated with and associated to those posed by geography and road networks. In this paper, a mixed-integer programming (MIP) model is proposed which incorporates MER dispatch into OPF. The computational implementation using Python utilizes real-world geographical and road network data to provide an optimal dispatch of MERs in the OPF solution considering actual driving and dispatching times. The implemented model is demonstrated and validated using a 24-bus test system in Portugal. A day-ahead operation planning scenario is considered with overloading and loss of renewable generation, showcasing how load shedding can be mitigated through proper dispatch of MERs. Several scenarios are tested, including the definition of critical loads, varying individual MER capacities and numbers, and MER dispatch origins or depots. Finally, an N-1 contingency analysis is performed to study the effect the different MER dispatch scenarios on overall system reliability.</p&gt

Quantifying the Difference Between Resilience and Reliability in the Operation Planning of Mobile Resources for Power Distribution Grids

<p>Modern power grids have high levels of distributed energy resources, automation, and inherent flexibility. Those characteristics have been proven to be favorable from an environmental, social and economic perspective. Despite the increased versatility, modern grids are becoming more vulnerable to high-impact low-probability (HILP) threats, particularly for the distribution networks. On one hand, this is due to the increasing frequency and severity of weather events and natural disasters. On the other hand, it is aggravated by the increased complexity of smart grids. Resilience is broadly defined as the capability of a system to mitigate the effects of and recover from HILP events, which is often confused with reliability that is concerned with low-impact high-probability (LIHP) ones. In this paper, a distribution system in Portugal is simulated to showcase how the utilization of flexibility and mobile energy resources (MERs) should be considered differently relative to HILP vs LIHP threats.</p&gt

Integrating intermittent renewables via hydropower alone adversely impacts other sectors

&amp;lt;p&amp;gt;Large-scale integration of intermittent renewable sources in Africa, such as solar and wind, can accelerate the transition to low-carbon energy systems, which is critical to mitigate the impacts of climate change and increase electricity access. Hydropower can support this transition because its operational flexibility can be used, in a cost-effective manner, to counteract the variability and seasonality of intermittent renewables. However, using hydropower to provide energy system flexibility services can affect aquatic ecosystems and create intersectoral conflict. We use a multi-objective design framework to address this issue and demonstrate it on a national-scale case study for Ghana. This case study shows that available hydropower flexibility can be deployed to support expanding intermittent renewables by 38%. However, this would increase the sub-daily flow variability of the main national river (Volta) by up to 22 times compared to the historical baseload hydropower operation that does not support intermittent renewables. The increase in sub-daily flow variability is estimated to damage the river ecosystem and reduce national crop yield revenue by up to US$169 million per year. We propose an alternative approach that uses a diversified investment strategy, including intermittent renewables, bioenergy, and transmission network expansion in addition to existing hydropower, and show that such designs can maintain acceptable flow variability and agricultural performance while meeting future national energy service goals and reducing CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; emissions. The proposed framework can support governments and power system planners by designing efficient diversified energy investment portfolios and highlighting their sectoral and emission trade-offs.&amp;lt;/p&amp;gt;</jats:p

Risk of increased hydrological alteration due to penetration of intermittent renewable energy generation

&amp;lt;p&amp;gt;The penetration of intermittent renewable energy sources (RES) such as solar PV and wind is rapidly growing in many countries. Due to the RES intermittency, it is becoming increasingly difficult to manage the balance between energy generation and demand at any time. In this context, it is necessary to use other energy generation technologies, such as hydropower, a controllable renewable source that may already be available as a means to provide energy balance. Hydropower, through hydropeaking, is considered a flexible solution to this challenge as it can quickly help manage the fluctuations in the generation-demand balance due to the highly RES intermittency. Hydropeaking plants usually supply energy at maximum capacity during on-peak periods, whereas they run at low power output during off-peak periods. However, this operating scheme leads to heavy hydrological alteration downstream of the hydropower plants because of short-term fluctuations in turbined flows motivated by the integration of intermittent RES. In this work, an integrated and spatially distributed river-basin and energy system co-simulation model is used to evaluate the hydrological alteration produced by varying penetration levels of intermittent RES in Ghana's national power system. Results show that the spatial and temporal distribution of hydrological alteration, correlated with intermittent RES penetration levels, varies according to the hydropower plants' location within the power system and the intermittent renewable resources seasonality throughout the year.&amp;lt;/p&amp;gt;</jats:p

The value of incorporating technological uncertainty in adaptive infrastructure planning &amp;#8211; a conceptual example in hydropower investment

&amp;lt;p&amp;gt;In response to the increasing environmental concerns, there has been significant research and development of power generation technologies based on renewable energy sources (RES) such as solar, and hydrogen. On the one hand, the technologies are becoming more attractive by offering higher efficiencies and lifetimes, and lower costs. On the other hand, it has become challenging to cost-effectively plan and deploy RES technologies as their characteristics have become significantly more uncertain. This can have strong impacts on other established renewable generation technologies, such as hydropower, which might become less or more attractive depending on technological change. Furthermore, in the context of interlinked water-energy systems, RES impacts on hydropower can have cascading effects on water use. Accordingly, decision makers require improved planning strategies to &amp;amp;#8220;adapt&amp;amp;#8221; to technological change when making long-term planning and investment decisions.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This work explores how considering RES, namely solar and hydrogen, alongside their technological uncertainties related to installation costs and lifetimes, would impact hydropower investments in an adaptive plan. Based on a conceptual case study of a water-energy system, we demonstrate that hydropower investments could be delayed and/or reduced because of the possibility of efficiency improvements related to renewable energy technologies. Furthermore, we quantify the forgone financial value from not using adaptive approaches to design and plan infrastructure projects under technological uncertainty.&amp;lt;/p&amp;gt;</jats:p