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DOE OSTI2026

Evaluating Protection System Performance for a Real-World Weak Grid Area With High Inverter-Based Resources

This paper evaluates an existing protection scheme implemented in a real-world weak grid area with a high penetration of inverter-based resources (IBRs). The study aims to assess the reliability and adequacy of protection schemes originally designed for traditional synchronous machine systems and determine whether they can continue to operate reliably in systems with high levels of IBRs. Hardware relays are tested using a controller-hardware-in-the-loop setup. PSCAD electromagnetic transient simulation with an IBR original equipment manufacturer black-box model is used to perform fault studies and generate COMTRADE data, which are replayed by a realtime digital simulator (RTDS) to feed input to the hardware relays. Three scenarios are analyzed: normal operation, an N-1 contingency, and an IBR-only scenario. The evaluation results reveal the following: 1) the protection scheme remains reliable under normal conditions and N-1 contingencies and 2) in IBRonly scenarios, differential protection (87L) continues to operate reliably, whereas local protection elements, such as distance and directional elements, fail because of the lack of regulated negative sequence current contributed by IBRs. These findings provide utilities with valuable insights for improving their protection systems in high-IBRs.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2026

Evaluating Protection System Performance for a Real-World Weak Grid Area With High Inverter-Based Resources: Preprint

This paper evaluates an existing protection scheme implemented in a real-world weak grid area with a high penetration of inverter-based resources (IBRs). The study aims to assess the reliability and adequacy of protection schemes originally designed for traditional synchronous machine systems and determine whether they can continue to operate reliably in systems with high levels of IBRs. Hardware relays are tested using a controller-hardware-in-the-loop setup. PSCAD electromagnetic transient simulation with an IBR original equipment manufacturer black-box model is used to perform fault studies and generate COMTRADE data, which are replayed by a real-time digital simulator (RTDS) to feed input to the hardware relays. Three scenarios are analyzed: normal operation, an N-1 contingency, and an IBR-only scenario. The evaluation results reveal the following: 1) the protection scheme remains reliable under normal conditions and N-1 contingencies and 2) in IBR-only scenarios, differential protection (87L) continues to operate reliably, whereas local protection elements, such as distance and directional elements, fail because of the lack of regulated negative sequence current contributed by IBRs. These findings provide utilities with valuable insights for improving their protection systems in high-IBRs.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2020

High-Frequency Signature-Based Fault Detection for Future MV Distribution Grids

Increasing penetration levels of inverter based distributed energy resources (DERs) impact the legacy distribution system protection. Inverter based DERs provide approximately 1.2-2 pu fault current. In systems with high penetration of inverter based DERs, it is difficult for over-current based protection schemes to differentiate between normal loading conditions and a fault. Directional, distance, and adaptive forms of protection schemes are also affected by low fault currents. This paper analyzes fault generated traveling wave (TW) based high-frequency signatures in the distribution system. In order to simulate such signatures, frequency-dependent distributed parameter line modeling approach is used in this research work to represent distribution lines and underground cables. Modified IEEE 13-bus medium voltage test system is modeled in electromagnetic transient simulation tool and multiple transient scenarios are simulated in this test system. The results are analyzed to understand the high-frequency signatures that can be used to detect and locate faults under high penetration of DERs.

41 EE - Solar Energy Technologies Office (EE-4S)↗

DOE OSTI2020

High-Frequency Signature-Based Fault Detection for Future MV Distribution Grids

41 EE - Solar Energy Technologies Office (EE-4S)↗

DOE OSTI2022

Forecasting and modeling of the COVID-19 pandemic in the USA with a timed intervention model

We propose a novel Timed Intervention S, P, E, I, Q, R, D model for projecting the possible futures of the COVID-19 pandemic in the USA. The proposed model introduces a series of timed interventions that can account for the influence of real time changes in government policy and social norms. We consider three separate types of interventions: (i) Protective interventions: Where population moves from susceptible to protected corresponding to mask mandates, stay-at-home orders and/or social distancing. (ii) Release interventions: Where population moves from protected to susceptible corresponding to social distancing mandates and practices being lifted by policy or pandemic fatigue. (iii) Vaccination interventions: Where population moves from susceptible, protected, and exposed to recovered (meaning immune) corresponding to the mass immunization of the U.S. Population. By treating the pandemic with timed interventions, we are able to model the pandemic extremely effectively, as well as directly predicting the course of the pandemic under differing sets of intervention schedules. We show that without prompt effective protective/vaccination interventions the pandemic will be extended significantly and result in many millions of deaths in the U.S.

60 APPLIED LIFE SCIENCES↗

NASA NTRS2010

Optimal Codes for the Burst Erasure Channel

Deep space communications over noisy channels lead to certain packets that are not decodable. These packets leave gaps, or bursts of erasures, in the data stream. Burst erasure correcting codes overcome this problem. These are forward erasure correcting codes that allow one to recover the missing gaps of data. Much of the recent work on this topic concentrated on Low-Density Parity-Check (LDPC) codes. These are more complicated to encode and decode than Single Parity Check (SPC) codes or Reed-Solomon (RS) codes, and so far have not been able to achieve the theoretical limit for burst erasure protection. A block interleaved maximum distance separable (MDS) code (e.g., an SPC or RS code) offers near-optimal burst erasure protection, in the sense that no other scheme of equal total transmission length and code rate could improve the guaranteed correctible burst erasure length by more than one symbol. The optimality does not depend on the length of the code, i.e., a short MDS code block interleaved to a given length would perform as well as a longer MDS code interleaved to the same overall length. As a result, this approach offers lower decoding complexity with better burst erasure protection compared to other recent designs for the burst erasure channel (e.g., LDPC codes). A limitation of the design is its lack of robustness to channels that have impairments other than burst erasures (e.g., additive white Gaussian noise), making its application best suited for correcting data erasures in layers above the physical layer. The efficiency of a burst erasure code is the length of its burst erasure correction capability divided by the theoretical upper limit on this length. The inefficiency is one minus the efficiency. The illustration compares the inefficiency of interleaved RS codes to Quasi-Cyclic (QC) LDPC codes, Euclidean Geometry (EG) LDPC codes, extended Irregular Repeat Accumulate (eIRA) codes, array codes, and random LDPC codes previously proposed for burst erasure protection. As can be seen, the simple interleaved RS codes have substantially lower inefficiency over a wide range of transmission lengths.

Hamkins, Jon↗

NASA NTRS1997

Predictive Features of a Cockpit Traffic Display: A Workload Assessment

Eighteen pilots flew a series of traffic avoidance maneuvers in an experiment designed to assess the support offered and workload imposed by different levels of traffic display information in a free flight simulation. Three display prototypes were compared which differed in traffic information provided. A BASELINE (BL) display provided current and (2nd order) predicted information regarding ownship and current information of an intruder aircraft, represented on lateral and vertical displays in a coplanar suite. An INTRUDER PREDICTOR (IP) display, augmented the baseline display by providing lateral and vertical prediction of the intruder aircraft. A THREAT VECTOR (TV) display added to the IP display a vector that indicates the direction from ownship to the intruder at the predicted point of closest contact (POCC). The length of the vector corresponds to the radius of the protected zone, and the distance of the intersection of the vector with ownship predictor, corresponds to the time available till POCC or loss of separation. Pilots time shared the traffic avoidance task with a secondary task requiring them to monitor the top of the display for faint targets. This task simulated the visual demands of out-of-cockpit scanning, and hence was used to estimate the head-down time required by the different display formats. The results revealed that both display augmentations improved performance (safety) as assessed by predicted and actual loss of separation (i.e., penetration of the protected zone). Both enhancements also reduced workload, as assessed by the NASA TLX scale. The intruder predictor display produced these benefits with no substantial impact on the qualitative nature of the avoidance maneuvers that were selected. The threat vector produced the safety benefits by inducing a greater degree of (effective) lateral maneuvering, thus partially offsetting the benefits of reduced workload. The three displays did not differ in terms of their effect on performance of the monitoring task, used to infer head-down time, nor in the extent of vertical or airspeed maneuvering. The results are discussed in terms of their implications for 19 cognitive engineering design features.

Wickens, Christopher D.↗

DOE OSTI2021

Protection of Distribution Circuits with High Penetration of Solar PV: Distance, Learning, and Estimation-Based Methods

The results of DOE Solar Energy Technologies Office project 34233 are presented. The newest version of IEEE Standard 1547 enables photovoltaic inverters to ride through voltage disturbances, improving bulk system reliability, at the expense of removing undervoltage trip as a fast method of de facto fault detection in high PV adoption scenarios. The project explored new methods of fault detection that don't rely on communication systems and could be available quickly, including distance-based schemes, focused directional relays, and two different data-driven schemes. The schemes were evaluated with fast-phasor simulation, electromagnetic transient simulation, and field data collection at partner utilities Chattanooga Electric Power Board and Dominion Energy Virginia. Accomplishments and possible paths forward are summarized.

14 SOLAR ENERGY↗

NASA NTRS1991

Discussions on a long gap discharge to an EHV transmission tower by a rocket triggered lightning experiment

The triggered lightning experiments using a rocket have been carried out on a winter mountain in Japan since 1986. For the four years from 1986 to 1989, 39 rockets were launched and 19 of them triggered lightning strikes. The emphasis here is on the methodology for triggering lightning to the transmission system. Completed experiments are discussed. The failure of lightning protection and the striking distance are noted.

Nakamura, Koichi↗

NASA NTRS1992

Error control techniques for satellite and space communications

Worked performed during the reporting period is summarized. Construction of robustly good trellis codes for use with sequential decoding was developed. The robustly good trellis codes provide a much better trade off between free distance and distance profile. The unequal error protection capabilities of convolutional codes was studied. The problem of finding good large constraint length, low rate convolutional codes for deep space applications is investigated. A formula for computing the free distance of 1/n convolutional codes was discovered. Double memory (DM) codes, codes with two memory units per unit bit position, were studied; a search for optimal DM codes is being conducted. An algorithm for constructing convolutional codes from a given quasi-cyclic code was developed. Papers based on the above work are included in the appendix.

Costello, Daniel J., Jr.↗

DOE OSTI2023

Technical Justifications for Liquid Hydrogen Exposure Distances

The previous separation distances in the National Fire Protection Association (NFPA) Hydrogen Technologies Code (NFPA 2, 2020 Edition) for bulk liquid hydrogen systems lack a well-documented basis and can be onerous. This report describes the technical justifications for revisions of the bulk liquid hydrogen storage setback distances in NFPA 2, 2023 Edition. Distances are calculated based on a leak area that is 5% of the nominal pipe flow area. Models from the open source HyRAM+ toolkit are used to justify the leak size as well as calculate consequence-based separation distances from that leak size. Validation and verification of the numerical models is provided, as well as justification for the harm criteria used for the determination of the setback distances for each exposure type. This report also reviews mitigations that could result in setback distance reduction. The resulting updates to the liquid hydrogen separation distances are well-documented, retrievable, repeatable, revisable, independently verified, and use experimental results to verify the models.

08 HYDROGEN↗

DOE OSTI2024

Searching for Grid-Forming Technologies That Do Not Impact Protection Systems: A promising technology

The design of legacy-line protection elements has been guided by the behavior of synchronous machines during faults. Because of the significant field-winding inductance and rotating mass, the magnitude, angular frequency, and phase angle of the back-electromotive force (EMF) voltage waveforms of synchronous machines remain practically constant for several hundreds of milliseconds after a fault occurs. Furthermore this has facilitated the engineering of the memory-polarization technique in mho distance elements, which has been effective for machine-dominant power grids. However, this assumption is no longer held for inverter-based resources (IBRs) because of the lack of field winding and moment of inertia in power electronics devices. Notably, the negative-sequence directional overcurrent protection and the quadrilateral distance elements have been impacted by early IBRs with grid-following (GFL) controls because they did not inject negative-sequence currents during asymmetrical faults.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2022

Mineral Protection and Resource Limitations Combine to Explain Profile-Scale Soil Carbon Persistence

The fate of soil carbon (C) is largely controlled by microbial oxidation of organic matter (OM), which is constrained by a variety of mechanisms. OM association with soil minerals provides pronounced protection against microbial decomposition. However, factors such as climate, occlusion, and resource limitations also contribute to OM preservation. Here, we explore the factors explaining C distribution and age within an upland rainforest soil in Hawai'i, a site with abundant preferential flow paths (PFPs) and high short-range order (SRO) mineral content. We characterized lateral and vertical changes in Δ 14 C, SRO mineral content, C-functional group chemistry, and microbial community composition to elucidate the contributions of multiple protection mechanisms to OM preservation. Consistent with our expectation, SRO mineral content and Δ 14 C were strongly correlated (R 2 = 0.95), indicating strong mineral protection of OM throughout the profile. Surprisingly, distance from PFP was also a significant predictor of Δ 14 C and improved model fit, particularly in the shallow horizons (R 2 = 0.97). Elevated C/N ratios, decreased microbial abundance, and greater SRO mineral content suggest nitrogen limitations and enhanced mineral protection constrain OM turnover with distance from PFPs in deep, subsurface mineral horizons. Steady microbial abundance, increasing putative anaerobe abundance, and changes in C-functional group chemistry indicate oxygen limitations constrain OM turnover in the matrix of shallow mineral horizons. Given that oxygen and nutrient limitations contribute to OM preservation in this high SRO system—an exemplar of mineral protection—resource limitations may play an even more important role in OM preservation in other well-structured soils.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRSDate not supplied

Increased Treadmill Running and Lower-Body Resistance Training Intensity May Attenuate Aerobic Capacity Loss During Spaceflight

BACKGROUND: In-flight exercise training is the primary countermeasure to mitigate spaceflight-induced decrements in strength and aerobic capacity. Despite high-quality exercise capabilities and prescriptions aboard the International Space Station (ISS), most astronauts experience strength and aerobic capacity loss; however, significant individual variability exists. Recent findings suggest that greater in-flight running (i.e., distance per session) and lower-body resistance exercise intensity (i.e., load relative to body weight) help preserve strength. Whether similar variables contribute to the preservation of aerobic capacity during spaceflight is unknown. METHODS: A NASA database of exercise performance metrics was used to identify long-duration (≥ 90 days) ISS crew who completed pre- and post-flight aerobic capacity testing (VO2peak, cycle ergometry, n = 44). “Responders” (R) were classified as those that maintained or improved VO2peak (n = 13; 1.4 ± 3.3%), and “non-responders” (NR) were those with the most severe decrements (n = 13; -20.0 ± 3.4%) from pre- to post-flight. In-flight exercise records (cycling, treadmill, resistance exercise) were aggregated across flight weeks. Independent t-tests or Mann-Whitney U tests were used to compare training variables (i.e., frequency, time, intensity, volume) between R and NR. RESULTS: Consistent with the variables contributing to strength protection, in-flight running distance (R: 5.0 ± 0.7; NR: 4.2 ± 1.0 km/session, p = 0.020) and lower-body resistance exercise intensity (R: 110.9 ± 27.3; NR: 91.7 ± 16.5% body weight, p = 0.040) were greater in R than NR. Active running time was also greater in R than NR (R: 101.1 ± 20.4; NR: 82.3 ± 23.5 min/wk; p = 0.039). However, no group differences in cycling frequency, intensity, or time, as well as upper body or core resistance exercise intensity, volume, or frequency were observed. CONCLUSIONS: Although physiologically distinct stimuli, the exercise training variables contributing to the preservation of both strength and aerobic capacity during microgravity exposure appear to be consistent. Increased running time and distance, but not cycling, combined with higher-intensity lower-body resistance exercise, may help mitigate losses in both aerobic capacity and strength during long-duration spaceflight.

Alyssa N Varanoske↗

NASA NTRS1981

On the electrostatic charging of the cometary nucleus

The paper demonstrates that a water-dominated cometary nucleus is not shielded from solar UV radiation or solar wind by protective atmospheres beyond a heliocentric distance of 5 AU. It is also shown that submicron dust particles can be electrostatically levitated and blown off the cometary surface. An upper limit on the total mass that can be lost from the sunlit hemisphere is derived using two solar wind models, and the dust mantle erosion is estimated at 5-12 cm. It is noted that the erosion is comparable to the mass of dust blown off a typical medium bright comet by the viscous drag of the sublimating gases during perihelium passage between 3.0 and 0.5 AU, and it is therefore proposed, that the surface dust blow-off be included in the current balance equation.

Mendis, D. A.↗

DOE OSTI2024

Zone plate-based extreme ultraviolet mask microscope with through-pellicle imaging capability

Mirror-based and zone plate-based imaging systems are being used in actinic extreme ultraviolet (EUV) reticle review tools. With regard to zone plates, a short working distance is advantageous in terms of the required spectral bandwidth, manufacturability, and potential throughput and imaging performance. Zone plates therefore typically have a short working distance. The industry has adopted the use of an EUV pellicle to protect the photomask. Imaging photomask through-pellicle requires a working distance larger than 2.5 mm. A zone-plate-based EUV mask microscope with a 3-mm working distance has been commissioned at beamline 11.3.2 of the Advanced Light Source. Through-pellicle imaging at an exposure time of 2 s is demonstrated. The instrument achieves an image contrast of 95% on large features on a photomask with a tantalum-based absorber. Imaging down to 45-nm half pitch (mask scale) is demonstrated. A NILS of 2.55 is achieved on 60-nm half-pitch (mask scale) lines and spaces. These results demonstrate that zone-plate-based imaging systems can meet the requirements of an actinic EUV mask review tool in terms of imaging performance and throughput in an instrument compatible with EUV pellicles.

Extreme ultraviolet↗

DOE OSTI2021

National variability in Americans’ COVID-19 protective behaviors: Implications for vaccine roll-out

Protective behaviors such as mask wearing and physical distancing are critical to slow the spread of COVID-19, even in the context of vaccine scale-up. Understanding the variation in self-reported COVID-19 protective behaviors is critical to developing public health messaging. The purpose of the study is to provide nationally representative estimates of five self-reported COVID-19 protective behaviors and correlates of such behaviors. In this cross-sectional survey study of US adults, surveys were administered via internet and telephone. Adults were surveyed from April 30-May 4, 2020, a time of peaking COVID-19 incidence within the US. Participants were recruited from the probability-based AmeriSpeak® national panel. Brief surveys were completed by 994 adults, with 73.0% of respondents reported mask wearing, 82.7% reported physical distancing, 75.1% reported crowd avoidance, 89.8% reported increased hand-washing, and 7.7% reported having prior COVID-19 testing. Multivariate analysis (p critical value .05) indicates that women were more likely to report protective behaviors than men, as were those over age 60. Respondents who self-identified as having low incomes, histories of criminal justice involvement, and Republican Party affiliation, were less likely to report four protective behaviors, though Republicans and individuals with criminal justice histories were more likely to report having received COVID-19 testing. The majority of Americans engaged in COVID-19 protective behaviors, with low-income Americans, those with histories of criminal justice involvement, and self-identified Republicans less likely to engage in these preventive behaviors. Culturally competent public health messaging and interventions might focus on these latter groups to prevent future infections. These findings will remain highly relevant even with vaccines widely available, given the complementarities between vaccines and protective behaviors, as well as the many challenges in delivering vaccines.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2025

Strong-coupling quantum dot microscope

Here, we report the development and fabrication of a novel cryogenic instrument, a scanning quantum dot microscope (SQDM), capable of positioning a quantum dot to within tunneling range of a sample surface. The microscope is strong-coupling in the sense that electron wavefunctions in the quantum dot can directly overlap with electron wavefunctions in the sample, in contrast to probes based on electric-field coupling. The SQDM consists of a sharp glass probe with two asymmetric electrodes leading to an aluminum quantum dot at the apex. One electrode is capacitively coupled to the quantum dot, while the other lead is connected to the dot via a tunneling junction. A charge sensing circuit constructed from a high-electron-mobility transistor is attached to the capacitance lead to measure the charge state of the dot. The last key feature of the design is a tilted-apex geometry. This design feature, in conjunction with the capacitive sensing scheme, results in a robust quantum-dot probe capable of operating within angstrom distances of the sample surface while protecting the single tunnel junction responsible for electron transport onto the quantum dot. We demonstrate that our instrument can detect single-electron tunneling events and can also be operated as a standard scanning tunneling microscope capable of nanometer-scale resolution of the surface topography.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗