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Secondary or low-voltage (LV) networks are applied in many large cities throughout the U.S., and in some other countries. Various grounding schemes have been employed for the primary systems supplying these secondary networks. In this paper, characteristics of the different grounding schemes for the substation and primary feeders that supply the LV networks are reviewed. The impacts of primary system grounding on the ground fault currents, the unfaulted line-to-ground voltages, as well as the voltage sags in the LV network have been considered for the single line-to-ground fault on the primary. The differences between systems with network transformers having the delta- or grounded-wye-connected primary windings are discussed. The relationships between grounding characteristics and protection settings, including actual examples, have been documented. [ABSTRACT FROM AUTHOR]

Data centers are a significant and growing component of electricity demand in the United States. This paper presents a bottom-up model that can be used to estimate total data center electricity demand within a region as well as the potential electricity savings associated with energy efficiency improvements. The model is applied to estimate 2008 U.S. data center electricity demand and the technical potential for electricity savings associated with major measures for IT devices and infrastructure equipment. Results suggest that 2008 demand was approximately 69 billion kilowatt hours (1.8% of 2008 total U.S. electricity sales) and that it may be technically feasible to reduce this demand by up to 80% (to 13 billion kilowatt hours) through aggressive pursuit of energy efficiency measures. Measure-level savings estimates are provided, which shed light on the relative importance of different measures at the national level. Measures applied to servers are found to have the greatest contribution to potential savings. [ABSTRACT FROM PUBLISHER]

In the new open access environment, in pursuit of profit, power producers tend to operate closer to the security boundaries and consequently, the voltage instability, which is caused by insufficient reactive power support, threats system security and reliability. This paper presents a day-ahead reactive power market based on uniform auction price scheme considering voltage security. First, expected payment function (EPF), identified earlier in the literature to construct a bidding framework for synchronous generators, is modified. Then, the modified EPF is used as the objective function of optimal power flow problem to clear reactive power market. Finally, the OPF, including overload, voltage drop and voltage stability margin in its constraints, is solved by binary coded genetic algorithm. The validity of the proposed reactive power market is studied based on the IEEE 24-bus reliability test system. [ABSTRACT FROM AUTHOR]

The U.S. Navy is looking for methods to maximize the survivability of combat ships during battle conditions. A shipboard power distribution system is a stiff isolated power system that is vulnerable to voltage sags, which arise due to faults or pulsed loads, which can cause interruptions of critical loads. A series voltage injection type flywheel energy storage system (FESS) is used to mitigate voltage sags and maximize the survivability of the ship. The basic circuit consists of an energy storage system, power electronic interface, and a series injection transformer. In this case, the energy storage system consists of a flywheel coupled to an induction machine. The stored energy is used for sag correction for the critical load. Indirect field-oriented control (IDFOC) with space-vector pulsewidth modulation (SVPWM) is used to control the induction machine. Sinusoidal PWM is used for controlling the power system side converter. This paper presents the modeling, simulation, and analysis of a FESS with a power converter interface using PSCADIEMTDC. [ABSTRACT FROM AUTHOR]

Dynamic voltage scaling (DVS) is one of the most effective techniques for reducing energy consumption on battery-operated embedded systems. According to the granularity of units to which voltage scaling is applied, the DVS problem can be divided into two subproblems: (i) inter-task DVS problem and (ii) intra-task DVS problem. A lot of effective DVS techniques have addressed either one of the two subproblems, but none of them have attempted to solve both simultaneously. This paper examines the problem of combined inter- and intra-task DVS, called the combined DVS (CDVS) problem. We solve the CDVS problem in two embedded system domains: one is systems with a sleep state and the other without sleep state. For systems without sleep state, we propose a close-to-optimal algorithm for the CDVS problem. We show that the algorithm is optimal when the power is a quadratically increasing function of the system's clock speed or the applied voltage level. For systems with a sleep state, we propose a refinement algorithm that fine-tunes the solution to the CDVS problem without sleep state to further reduce energy consumption by exploiting sleep state. Experimental results show that our proposed CDVS algorithm without sleep state is able to reduce the energy consumption by 12.5% on average over the results by the method that sequentially performs two existing inter- and intra-task DVS techniques, which are both optimal under no sleep state. Furthermore, our CDVS algorithm with a sleep state can reduce the energy consumption by 7.1% on average over the results by the conventional representative method that utilizes sleep state, but does not consider intra- and inter-task DVS simultaneously. [ABSTRACT FROM PUBLISHER]

The use of high temperature superconducting (HTS) tapes in a flexible cryostat has been shown to provide great opportunities for the US Navy. The HTS tapes need to be fixed at the ends to provide an electrical connection. Since the ends are rigid but the tapes are contained in a changing environment there is a possibility that the tapes may become twisted and therefore damaged. Twisting is defined in this paper as the rotation of the tape along the length of the tape while the end has no attack-angle. The twisting length and angle of first generation (1G) BSCCO tapes is studied by measuring the voltage drop across the tapes in a liquid nitrogen bath when current is applied. [ABSTRACT FROM AUTHOR]

DEPFET detectors are silicon (Si) active pixel sensors designed and manufactured in the Max-Planck-Institut semiconductor lab. Their high spatial resolution and high energy resolution in X-rays make them attractive for particle tracking in colliders and for X-ray astronomy. This technology is foreseen for the Wide Field Imager of the International X-ray Observatory currently in study with ESA, NASA, and JAXA. New DEPFET matrixes with 256\,\times\,256 pixels of 75-\mum pitch have been produced, mounted on ceramic boards with dedicated front-end electronics and integrated in a new setup able to acquire large-format images and spectra. Excellent homogeneity has been observed. Energy resolution as low as 127 eV FWHM at 5.9 keV has been obtained including all single events of the matrix back illuminated at -45\,^\circC and read out at a 300-frames/s rate. This paper presents experimental methods and results. [ABSTRACT FROM AUTHOR]

The National Research Council (NRC) of Canada has recently established an alternating-current Josephson voltage standard (ACJVS) system based on the National Institute of Standards and Technology pulse-driven Josephson junction arrays. This paper describes the efforts undertaken at the NRC and the experience that was gained. An experimental method of measuring corrections for the voltage probe lead errors is described, and first results are reported. By introducing the ACJVS, the NRC will be able to reduce the uncertainties of the thermal transfer standard calibration by threefold on the 200-mV range and five- to tenfold on the 20-mV range, in comparison with thermal-converter- and micropotentiometer-based calibrations. [ABSTRACT FROM AUTHOR]

This paper describes a 10 V Josephson Voltage Standard (JVS) direct comparison between the National Institute of Standards and Technology (NIST) and the Instituto Nacional de Metrologia, Normalização e Qualidade Industrial (INMETRO) using automatic data acquisition. The results were in agreement to within 1.1 nV and the mean difference between the two JVSs at 10 V is 0.54 nV with a pooled combined standard uncertainty of 1.48 nV. Considering a recent JVS comparison between NIST and the Bureau International des Poids et Mesures (BIPM), the difference between INMETRO and the BIPM thus was found to be -0.26 nV with a standard uncertainty of 1.76 nV. INMETRO JVS improvements since the 2006 INMETRO-BIPM comparison are also described. [ABSTRACT FROM AUTHOR]

Type T thermocouples are commonly used in industrial measurement applications due to their accuracy relative to other thermocouple types, low cost, and the ready availability of measurement equipment. Type T thermocouples are very effective when used in differential measurements, as there is no cold junction compensation necessary for the connections to the measurement equipment. Type T's published accuracy specifications result in its frequent use in low-temperature applications. An examination of over 250 samples from a number of manufacturers has been completed for this investigation. Samples were compared to a standard platinum resistance thermometer (SPRT) at the LN2 boiling point along with four other standardized measurement points using a characterized ice point reference, low-thermal EMF scanner, and an 8.5 digit multimeter, and the data were compiled and analyzed. The test points were approximately −196 °C, −75 °C, 0 °C, + 100 °C, and + 200 °C. These data show an anomaly in the conformance to the reference functions where the reference functions meet at zero. Additionally, in the temperature region between −100 °C and −200 °C, a positive offset of up to 5.4 °C exists between the reference function equations published in the United States in ASTM E230-06 for the nitrogen point and the measured response of the actual wire. This paper also examines the historical and technological reasons for this anomaly in the US reference function. The study concludes that Type T thermocouples typically do not conform to the ASTM E230-06 published reference function describing their performance when used to measure temperature in the range of −100 °C to −200 °C. [ABSTRACT FROM AUTHOR]

Abstract: An energy efficiency and control analysis is given for application of a transparent electric curtain for dust mitigation on a solar panel. The electric curtain technique has been proposed by NASA as an effective active method for dust removal from solar panels in planetary and lunar exploration, and this method also has potential for mitigation of dust build-up on terrestrial solar panels in dry environments. Since energy expenditure rate required for electric curtain operation can be significantly higher than the energy capture rate from a solar panel, a control scheme for activation and deactivation of the electric curtain is necessary to achieve optimal net energy capture. The control method examined in the current paper is one in which the electric curtain is activated when the panel output voltage decreases to a fraction of the clean panel output voltage and deactived when the output voltage exceeds a second output voltage fraction . A combination of theoretical and computational approaches is used to determine how the energy efficiency changes with change in the threshold voltage ratios. A scaling analysis is developed that identifies a single key dimensionless parameter that influences the efficiency results. Optimal values of turn-on and turn-off voltage ratio are determined in terms of this parameter, and it is demonstrated that the efficiency decreases rapidly as the turn-off voltage ratio is raised above the optimal value. All of the efficiency predictions for a given mitigation velocity profile are collapsed onto a single curve with appropriate choice of the scaling parameters, which is then used to develop an optimal control criterion. [Copyright &y& Elsevier]

Blockchain technology is a secure and distributed information accounting, storage, and retrieval modality which has the ability to disrupt and revolutionize business practices. One such disruption resides in the capability of Blockchain to serve as a secure method for storing and sharing electronic medical records in new and innovative ways. Current medical record storage and transmission methods are proprietary and have interoperability and security problems. To that end, secure, effective, and interoperable electronic records options are highly prized. This article uses a grounded theory approach to qualitative analysis of electronic medical records users in the United States to develop a perspective from industry and scholarly practice on the suitability of Blockchain technologies for electronic medical records, security, and storage. [ABSTRACT FROM AUTHOR]

• We examine the emissions impact of battery storage across sensitivities and regions. • Existing studies focus on dispatch; we show how investment effects drive emissions. • Emissions impacts of storage vary based on policy and market assumptions. • Storage emissions reductions are more likely when wind and solar are lower cost. Battery storage technologies have attracted attention from policymakers for their potential to reduce electric sector emissions by enabling greater wind and solar penetration. Yet existing studies indicate that adding energy storage actually increases emissions. The difference may be explained by the absence in the previous literature of "investment effects" – changes in deployment of other generation technologies after storage is deployed. Our paper tests this hypothesis by evaluating battery-storage-induced emissions changes using a model that accounts for both long-run investment and dispatch effects simultaneously across regions in the United States, which can be used to separate the relative magnitudes of these two effects. Model results indicate that the investment effect dominates the dispatch effect under a range of sensitivities. We find that emissions may increase or decrease with battery storage, depending on policy and market assumptions, with reductions more likely in environments where wind and solar are more economically competitive relative to natural-gas-fired generation. These results suggest that existing studies that only account for operational impacts likely underestimate potential emissions changes from battery storage deployment. [ABSTRACT FROM AUTHOR]

Potential NASA optical missions such as the Space Interferometer Mission require actuators for precision positioning to accuracies of the order of nanometers. Commercially available multilayer piezoelectric stack actuators are being considered for driving these precision mirror positioning mechanisms. These mechanisms have potential mission operational requirements that exceed 5 years for one mission life. To test the feasibility of using these commercial actuators for these applications and to determine their reliability and the redundancy requirements, a life test study was undertaken. The nominal actuator requirements for the most critical actuators on the Space Interferometry Mission (SIM) in terms of number of cycles was estimated from the Modulation Optics Mechanism (MOM) and Pathlength control Optics Mechanism (POM) and these requirements were used to define the study. At a nominal drive frequency of 250 Hz, one mission life is calculated to be 40 billion cycles. In this study, a set of commercial PZT stacks configured in a potential flight actuator configuration (pre-stressed to 18 MPa and bonded in flexures) were tested for up to 100 billion cycles. Each test flexure allowed for two sets of primary and redundant stacks to be mechanically connected in series. The tests were controlled using an automated software control and data acquisition system that set up the test parameters and monitored the waveform of the stack electrical current and voltage. The samples were driven between 0 and 20 V at 2000 Hz to accelerate the life test and mimic the voltage amplitude that is expected to be applied to the stacks during operation. During the life test, 10 primary stacks were driven and 10 redundant stacks, mechanically in series with the driven stacks, were open-circuited. The stroke determined from a strain gauge, the temperature and humidity in the chamber, and the temperature of each individual stack were recorded. Other properties of the stacks, including the displacement from a capacitance gap sensor and impedance spectra were measured at specific intervals. The average degradation in the stroke over the life test was found to be small (≪3%) for the primary stacks and ≪4% for the redundant stacks. It was noted that about half of the stroke reduction occurred within the first 10 billion cycles. At the end of the life test, it was found that the actuator could recover about half of the lost stroke by applying a dc voltage of 100 V at room temperature. The data up to 100 billion cycles for these tests and the analysis of the experimental results are presented in this paper. [ABSTRACT FROM PUBLISHER]

Stochastic serial correlations are often ignored in the statistical uncertainty (Type A) analysis of measurement values. For repeated measurements, the standard deviation of the mean is often used to specify Type-A uncertainty, but it is frequently underestimated by assuming that it is given by the standard deviation divided by the square root of the number of measurements. Methods of time-series analysis such as the Allan variance (Avar) formalism give realistic estimates of Type-A uncertainty, but they require equal time intervals between successive measurements. This requirement is difficult to satisfy in comparisons of Josephson voltage standards (JVSs) because of the instability of the voltage steps and the small number of repeated measurements. A JVS comparison was made using a completely automatic compact JVS. The time intervals were uneven; thus, we studied the effect of their irregularity on the Avar by simulating data having the same noise model and uneven time intervals as the measured data. We found that, for this JVS comparison, the Avar is only slightly affected by uneven intervals. The noise was found to be a mixture of white and 1/f noise. The latter limits the Allan deviation to 0.64 nV after 14.3 h of measurement. The method of simulating data this way should be applicable to other complex measurement situations. [ABSTRACT FROM AUTHOR]

A direct comparison between two Josephson voltage standard (JVS) systems has been used in the Bureau International des Poids et Mesures key comparisons or regional supplementary comparisons to ensure the uniformity of the representation of the volt based on K{J - 90} with a relative uncertainty of a few parts in 10^10 at a nominal voltage of 10 V. Most direct JVS comparisons are manually operated. Hardware and protocol for an automatic direct JVS comparison have been developed to verify the performance of a JVS while retaining the same level of uncertainty attained by a manual comparison. The automatic JVS direct comparison significantly improves the efficiency of the data acquisition. A case study examining the offset related to the digital voltmeter polarity in an automatic direct JVS comparison is presented. [ABSTRACT FROM AUTHOR]

The National Institute of Standards and Technology has developed and implemented a new programmable Josephson voltage standard (PJVS) that operates at 10 V. This next-generation system is optimized for both dc metrology and stepwise-approximated ac voltage measurements for frequencies up to a few hundreds of hertz. The nonhysteretic Josephson junctions produce intrinsically stable voltages and are designed to operate in the 18–20 GHz frequency range. The most recent 10 V PJVS circuits have total output current ranges greater than 1 mA. [ABSTRACT FROM AUTHOR]

The National Institute of Standards and Technology has developed a quantum-voltage-noise-source-calibrated Johnson noise thermometer (JNT) to provide a new electronic measurement technique for determining the Boltzmann constant. Improvements in electronics and synthesized noise waveforms have led to reduced uncertainty in the measurement. Recent investigations have shown that some of the distortion in the present electronics arises in the differential stage of both the preamplifier and the analog-to-digital converter (ADC). The distortion can be reduced by compensating the direct current offset of the signal at the inputs to the differential stage. A four-channel cross correlation JNT with optimized preamplifiers and new ADCs is being assembled. The improvements are on track to reach the goal of an electronic measurement of the Boltzmann constant at a relative uncertainty of 6 \times 10^-6. [ABSTRACT FROM AUTHOR]

The US Domestic Agency is one of six parties supplying TF cable-in-conduit conductors (CICCs) for ITER. Previous tests have shown that measured performance of the TF CICCs can be much lower than expected from the strand properties at the projected uniaxial strain and that the cabling pattern may also be an important factor. Worst of all, voltage signals well below the expected critical surface could not be reliably interpreted or canceled, making test results very suspect. The TFUS1 sample was prepared to achieve multiple goals: 1) to ensure uniform current distribution and to eliminate parasitic voltage signals by improving joints, 2) to explore the potential benefits of a different cabling pattern for better support of strain-sensitive strands, and 3) to explore the source of voltage development in the cable through the use of innovative penetrating diagnostics. Test results of the first US-made samples are presented and discussed. [ABSTRACT FROM AUTHOR]

The article discusses the performance of medium voltage cables and the effects of changes made to production methods. The problem of early breakdown caused by water trees was studied and various techniques for increasing the life time of cables were investigated. French, American and German companies prefer water tight construction, an additive water tree retardant (WTR) package and a polymer WTR. Real cable failure data for European utilities are presented. Failure rates include cable failures related to electrical breakdown.

This patent pending technology relates, generally, to surge protection devices. More particularly, it relates to a surge protection device that relies on the capacitive properties of the Metal Oxide Varistor (MOV) as a part of an impedance network for failure identification. Unlike other designs that rely on thermal fusing to identify MOV operability, in this design the MO V is used as part of a capacitive network that would operate at a frequency other than 60Hz. During normal operation (no failure), every capacitive impedance, including the MOV, will exhibit a voltage drop across them. On the other hand when the MOV fails as an open circuit then the current in this network will be zero and as a result zero voltage drops will be across the capacitive impedances. The reason only open circuit failure will be detected is because MOVs initially fail as a short circuit but eventually they fail as open circuit, due to continuous conduction. [ABSTRACT FROM AUTHOR]