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Development of an Electrostatic Dust Detector for use in a Tokamak Reactor

Description: Initial results from a novel device to detect dust particles settling on remote surfaces are presented. Dust particle inventories are a concern in next-step fusion devices. The increase in duty cycle will lead to a scale-up in the amount of particles generated by plasma material interactions. These particles will be chemically and radiologically hazardous and it will be important to establish that the in-vessel particle inventory is within regulatory limits. The detection device consists of two interlocking combs of closely spaced conductive traces on a Teflon circuit board. When a DC bias is applied impinging dust creates a transient short circuit between the traces. The increase in bias current generates a signal pulse that is counted by standard nuclear counting electronics. We present data on the response of the device in air and vacuum to carbon particles.
Date: September 10, 2003
Creator: Bader, A.; C.H. Skinner, A.L. Roquemore & Langish, S.
Partner: UNT Libraries Government Documents Department

EEN-307, Irradiation of units at low temperature test

Description: EWR-ESE-144, Fifty MC-890 type final assemblies were subjected to irradiation at low temperature test in order to determine if irradiation would reduce the frequency of high voltage breakdowns. A control lot of a like number of units was subjected to low temperature test in the same manner except without irradiation.
Date: April 13, 1960
Creator: Guthrie, J.B.
Partner: UNT Libraries Government Documents Department

Blocking diodes and fuses in low-voltage PV systems

Description: Instructions and labels supplied with listed PV modules and the requirements of the National Electrical Code (NEC) dictate that a series fuse shall be used to protect the module against backfeed currents. Few of the hundreds of thousands of low-voltage (12, 24, and 48-volt) stand-alone photovoltaic (PV) power systems use series fuses on each module or string of modules. Tests and simulations at the Southwest Technology Development Institute (TDI) and at Sandia National Laboratories (SNL) have established that the absence of these fuses can pose significant fire and safety hazards even on 12-volt PV systems. If the system has sufficient backfeed voltage and current, it is possible that a ground fault in the wiring or inside a module can result in the destruction of a PV module.
Date: November 1, 1997
Creator: Wiles, J.C. & King, D.L.
Partner: UNT Libraries Government Documents Department

Summary of collaborative photovoltaic industry work to proactively improve codes and standards for photovoltaic power system applications

Description: Several important milestones in codes and standards pertaining to the design, installation and operation of photovoltaic (PV) systems have recently been completed with collaboration of participants from all sectors of the PV industry, utilities and the US Department of Energy`s National Photovoltaic Program. Codes and standards that have been proposed, written or modified include changes and additions for the 1999 National Electrical Code{reg_sign} (NEC{reg_sign}), standards for fire and personnel safety, system testing, component qualification, and utility interconnect. Project authorization requests with the Institute of Electrical and Electronic Engineers (IEEE) have resulted in standards for listing PV modules and balance-of-system components. Industry collaboration with Underwriter Laboratories, Inc. (UL), with the American Society for Testing and Materials (ASTM), and through critical input and review for international standards with the International Electrotechnical Commission (IEC) have resulted in domestic and international standards for PV. Work related to the codes and standards activities through the International Energy Agency (IEA) is also being supported by the PV industry and the US DOE. This paper will concentrate on and summarize the important new NEC proposals for PV systems and will also describe and show the bonds between the activities in other standards writing activities. The paper will also provide an analysis of changes and resulting impacts of selected proposed NEC changes on PV designs, installations and performance.
Date: August 1, 1997
Creator: Bower, W.I.
Partner: UNT Libraries Government Documents Department

Cable Hot Shorts and Circuit Analysis in Fire Risk Assessment

Description: Under existing methods of probabilistic risk assessment (PRA), the analysis of fire-induced circuit faults has typically been conducted on a simplistic basis. In particular, those hot-short methodologies that have been applied remain controversial in regards to the scope of the assessments, the underlying methods, and the assumptions employed. To address weaknesses in fire PRA methodologies, the USNRC has initiated a fire risk analysis research program that includes a task for improving the tools for performing circuit analysis. The objective of this task is to obtain a better understanding of the mechanisms linking fire-induced cable damage to potentially risk-significant failure modes of power, control, and instrumentation cables. This paper discusses the current status of the circuit analysis task.
Date: May 19, 1999
Creator: LaChance, Jeffrey; Nowlen, Steven P. & Wyant, Frank
Partner: UNT Libraries Government Documents Department

LDRD final report backside localization of open and shorted IC interconnections LDRD Project (FY98 and FY 99)

Description: Two new failure analysis techniques have been developed for backside and front side localization of open and shorted interconnections on ICs. These scanning optical microscopy techniques take advantage of the interactions between IC defects and localized heating using a focused infrared laser ({lambda} = 1,340 nm). Images are produced by monitoring the voltage changes across a constant current supply used to power the IC as the laser beam is scanned across the sample. The methods utilize the Seebeck Effect to localize open interconnections and Thermally-Induced Voltage Alteration (TIVA) to detect shorts. Initial investigations demonstrated the feasibility of TIVA and Seebeck Effect Imaging (SEI). Subsequent improvements have greatly increased the sensitivity of the TIVA/SEI system, reducing the acquisition times by more than 20X and localizing previously unobserved defects. The interaction physics describing the signal generation process and several examples demonstrating the localization of opens and shorts are described. Operational guidelines and limitations are also discussed. The system improvements, non-linear response of IC defects to heating, modeling of laser heating and examples using the improved system for failure analysis are presented.
Date: January 1, 2000
Creator: Cole, E.I. Jr.; Tangyunyong, P.; Benson, D.A. & Barton, D.L.
Partner: UNT Libraries Government Documents Department

Fast Diagnostic For Electrical Breakdowns In Vacuum

Description: The design of an inexpensive, small, high bandwidth diagnostic for the study of vacuum insulator flashover is described. The diagnostic is based on the principle of capacitive coupling and is commonly referred to as a D-dot probe due to its sensitivity to the changing of the electric displacement field. The principle challenge for the design proved to be meeting the required mechanical size for the application rather than bandwidth. An array of these probes was fabricated and used in an insulator test stand. Data from the test stand with detailed analysis is presented. A highlight of the application of the probes to the test stand was the ability to detect the charging of the insulator surface by UV illumination as a prelude to the insulator flashover. The abrupt change in the insulator's surface charge during the flashover was also detected.
Date: March 25, 2008
Creator: Houck, T L; Javedani, J B & Lahowe, D A
Partner: UNT Libraries Government Documents Department

Platform Li-Ion Battery Risk Assessment Tool: Cooperative Research and Development Final Report, CRADA Number CRD-01-406

Description: The pressure within a lithium-ion cell changes due to various chemical reactions. When a battery undergoes an unintended short circuit, the pressure changes are drastic - and often lead to uncontrolled failure of the cells. As part of work for others with Oceanit Laboratories Inc. for the NAVY STTR, NREL built Computational Fluid Dynamic (CFD) simulations that can identify potential weak spots in the battery during such events, as well as propose designs to control violent failure of batteries.
Date: July 1, 2012
Creator: Santhanagopalan, S.
Partner: UNT Libraries Government Documents Department

A review of the UK Geothermal Hot Dry Rock R&D Programme

Description: The UK Department of Energy's Geothermal Hot Dry Rock (HDR) Program was last reviewed in 1987/88, when a number of technical problems were identified. These related to the size of reservoir (heat exchanger), its thermal behavior (short circuits) and water losses. A program of work to address these problems was subsequently set up. This work has recently been reviewed. The main conclusions are: (1) a satisfactory procedure for creating a commercial-scale HDR reservoir has yet to be demonstrated; (2) there is a dearth of information on rock properties at the 6-7 km depths needed for a commercial reservoir; (3) a satisfactory method of sealing short circuits has not yet been demonstrated; (4) although it is difficult to determine accurately the economics of HDR because of these technical uncertainties, it is believed that electricity from a commercial HDR power station is unlikely to be competitive with conventional means of generation in the short to medium term; (5) despite the earlier promise of the technology, HDR has been shown over the past two years to be still at an early stage of development and it is unlikely to attract private sector funding in the short term; and (6) participation in a joint European program offers the opportunity of resolving some of the technical uncertainties.
Date: January 1, 1991
Creator: Symons, Geoff D. & Clarke, John H.
Partner: UNT Libraries Government Documents Department

Resistance of a water spark.

Description: The later time phase of electrical breakdown in water is investigated for the purpose of improving understanding of the discharge characteristics. One dimensional simulations in addition to a zero dimensional lumped model are used to study the spark discharge. The goal is to provide better electrical models for water switches used in the pulse compression section of pulsed power systems. It is found that temperatures in the discharge channel under representative drive conditions, and assuming small initial radii from earlier phases of development, reach levels that are as much as an order of magnitude larger than those used to model discharges in atmospheric gases. This increased temperature coupled with a more rapidly rising conductivity with temperature than in air result in a decreased resistance characteristic compared to preceding models. A simple modification is proposed for the existing model to enable the approximate calculation of channel temperature and incorporate the resulting conductivity increase into the electrical circuit for the discharge channel. Comparisons are made between the theoretical predictions and recent experiments at Sandia. Although present and past experiments indicated that preceding late time channel models overestimated channel resistance, the calculations in this report seem to underestimate the resistance relative to recent experiments. Some possible reasons for this discrepancy are discussed.
Date: November 1, 2005
Creator: Warne, Larry Kevin; Jorgenson, Roy Eberhardt & Lehr, Jane Marie
Partner: UNT Libraries Government Documents Department

An arc fault detection system

Description: An arc fault detection system for use on ungrounded or high-resistance-grounded power distribution systems is provided which can be retrofitted outside electrical switchboard circuits having limited space constraints. The system includes a differential current relay that senses a current differential between current flowing from secondary windings located in a current transformer coupled to a power supply side of a switchboard, and a total current induced in secondary windings coupled to a load side of the switchboard. When such a current differential is experienced, a current travels through a operating coil of the differential current relay, which in turn, opens an upstream circuit breaker located between the switchboard and a power supply to remove the supply of power to the switchboard.
Date: December 1, 1997
Creator: Jha, Kamal N.
Partner: UNT Libraries Government Documents Department

Radiation safety system (RSS) backbones: Design, engineering, fabrication and installation

Description: The Radiation Safety System (RSS) Backbones are part of an electrical/electronic/mechanical system insuring safe access and exclusion of personnel to areas at the Los Alamos Neutron Science Center (LANSCE) accelerator. The RSS Backbones control the safety fusible beam plugs which terminate transmission of accelerated ion beams in response to predefined conditions. Any beam or access fault of the backbone inputs will cause insertion of the beam plugs in the low energy beam transport. The Backbones serve the function of tying the beam plugs to the access control systems, beam spill monitoring systems and current-level limiting systems. In some ways the Backbones may be thought of as a spinal column with beam plugs at the head and nerve centers along the spinal column. The two Linac Backbone segments and experimental area segments form a continuous cable plant over 3,500 feet from beam plugs to the tip on the longest tail. The Backbones were installed in compliance with current safety standards, such as installation of the two segments in separate conduits or tray. Monitoring for ground-faults and input wiring verification was an added enhancement to the system. The system has the capability to be tested remotely.
Date: December 1, 1998
Creator: Wilmarth, J.E.; Sturrock, J.C. & Gallegos, F.R.
Partner: UNT Libraries Government Documents Department

Circuit bridging of digital equipment caused by smoke from a cable fire

Description: Advanced reactor systems are likely to use protection systems with digital electronics that ideally should be resistant to environmental hazards, including smoke from possible cable fires. Previous smoke tests have shown that digital safety systems can fail even at relatively low levels of smoke density and that short-term failures are likely to be caused by circuit bridging. Experiments were performed to examine these failures, with a focus on component packaging and protection schemes. Circuit bridging, which causes increased leakage currents and arcs, was gauged by measuring leakage currents among the leads of component packages. The resistance among circuit leads typically varies over a wide range, depending on the nature of the circuitry between the pins, bias conditions, circuit board material, etc. Resistance between leads can be as low as 20 k{Omega} and still be good, depending on the component. For these tests, the authors chose a printed circuit board and components that normally have an interlead resistance above 10{sup 12} {Omega}, but if the circuit is exposed to smoke, circuit bridging causes the resistance to fall below 10{sup 3} {Omega}. Plated-through-hole (PTH) and surface-mounted (SMT) packages were exposed to a series of different smoke environments using a mixture of environmentally qualified cables for fuel. Conformal coatings and enclosures were tested as circuit protection methods. High fuel levels, high humidity, and high flaming burns were the conditions most likely to cause circuit bridging. The inexpensive conformal coating that was tested - an acrylic spray - reduced leakage currents, but enclosure in a chassis with a fan did not. PTH packages were more resistant to smoke-induced circuit bridging than SMT packages. Active components failed most often in tests where the leakage currents were high, but failure did not always accompany high leakage currents.
Date: March 1, 1997
Creator: Tanaka, T.J. & Anderson, D.J.
Partner: UNT Libraries Government Documents Department

Statistical analysis of cavity RF faults

Description: During commissioning of the CEBAF accelerator, it was found that cavities could not be operated reliably at the gradients achieved for short periods during individual cavity commissioning. The principal hypothesis for the cause of about two-thirds the faults seen is charging of the cold ceramic RF window, which is 7.6 cm off the beam axis. Beginning in February, 1995, most RF systems faults were automatically logged. Simple statistical analysis of the accumulated fault data was first applied in July, 1995, with a substantial drop in fault rate recorded. The intent of the analysis was to predict the gradient for each cavity at which it would fault once every ten days, leading to a fault rate for the machine of about 33/day (330 cavities). This analysis method was pursued through July, 1996, with substantial benefit. Cavity gradients were increased thereafter to obtain information for an upgrade to 6 GeV, with concomitant fault rate increases. In late 1996 and early 1997, in situ helium discharge processing was employed in 88 cavities to reduce field emissions. The methods used for the analysis of 30,000+ faults recorded between February 1995 and December 1997 are presented. Comparisons of performance before and after helium processing are presented.
Date: September 1, 1998
Creator: Benesch, J.F.
Partner: UNT Libraries Government Documents Department

Breakdown in ZnO Varistors by High Power Electrical Pulses

Description: This report documents an investigation of irreversible electrical breakdown in ZnO varistors due to short pulses of high electric field and current density. For those varistors that suffer breakdown, there is a monotonic, pulse-by-pulse degradation in the switching electric field. The electrical and structural characteristics of varistors during and after breakdown are described qualitatively and quantitatively. Once breakdown is nucleated, the degradation typically follows a well-defined relationship between the number of post-initiation pulses and the degraded switching voltage. In some cases the degraded varistor has a remnant 20 {micro}m diameter hollow track showing strong evidence of once-molten ZnO. A model is developed for both electrical and thermal effects during high energy pulsing. The breakdown is assumed to start at one electrode and advance towards the other electrode as a thin filament of conductive material that grows incrementally with each successive pulse. The model is partially validated by experiments in which the varistor rod is cut at several different lengths from the electrode. Invariably one section of the cut varistor has a switching field that is not degraded while the other section(s) are heavily degraded. Based on the experiments and models of behavior during breakdown, some speculations about the nature of the nucleating mechanism are offered in the last section.
Date: July 1, 2001
Partner: UNT Libraries Government Documents Department

Backside localization of open and shorted IC interconnections

Description: A new failure analysis technique has been developed for backside and frontside localization of open and shorted interconnections on ICs. This scanning optical microscopy technique takes advantage of the interactions between IC defects and localized heating using a focused infrared laser ({lambda} = 1,340 nm). Images are produced by monitoring the voltage changes across a constant current supply used to power the IC as the laser beam is scanned across the sample. The method utilizes the Seebeck Effect to localize open interconnections and Thermally-Induced Voltage Alteration (TIVA) to detects shorts. The interaction physics describing the signal generation process and several examples demonstrating the localization of opens and shorts are described. Operational guidelines and limitations are also discussed.
Date: July 1, 1998
Creator: Cole, E.I. Jr.; Tangyunyong, P. & Barton, D.L.
Partner: UNT Libraries Government Documents Department

Thermal Modeling of TIVA Profiles of a Polysilcon-Metal Test Structure

Description: Thermal modeling and simulations were used to analyze the thermal profiles of a polysilicon-metal test structure generated by thermally-induced voltage alteration (TIVA), a new laser-based failure analysis technique to localize shorted interconnects. The results show that variations in TIVA thermal profiles are due mainly to preferential laser absorption in various locations in the test structure. Differences in oxide thickness also affect the local heat conduction and temperature distribution. Modeling results also show that local variation in heat conduction is less important than the absorbed laser power in determining the local temperatures since our test structure has feature sizes that are small compared to the length over which heat spreads.
Date: September 16, 1999
Creator: Benson, D.A.; Cole, E.I. Jr. & Tangyunyong, Paiboon
Partner: UNT Libraries Government Documents Department

Gate Drive For High Speed, High Power IGBTs

Description: A new gate drive for high-voltage, high-power IGBTs has been developed for the SLAC NLC (Next Linear Collider) Solid State Induction Modulator. This paper describes the design and implementation of a driver that allows an IGBT module rated at 800A/3300V to switch up to 3000A at 2200V in 3{micro}S with a rate of current rise of more than 10000A/{micro}S, while still being short circuit protected. Issues regarding fast turn on, high de-saturation voltage detection, and low short circuit peak current will be presented. A novel approach is also used to counter the effect of unequal current sharing between parallel chips inside most high-power IGBT modules. It effectively reduces the collector-emitter peak current, and thus protects the IGBT from being destroyed during soft short circuit conditions at high di/dt.
Date: June 18, 2007
Creator: Nguyen, M.N.; Cassel, R.L.; de Lamare, J.E.; Pappas, G.C. & /SLAC
Partner: UNT Libraries Government Documents Department

Grid FriendlyTM Device Model Development and Simulation

Description: In late 2007, the Bonneville Power Administration (BPA) contracted Pacific Northwest National Laboratory (PNNL) to complete a research project titled Grid-Responsive Demand-Side Control Using Grid Friendly Appliance Technologies [Hammerstrom 2009, DeSteese and Hammerstrom 2009]. Cosponsors included Portland General Electric (PGE) and Puget Sound Energy (PSE). The project focused on applications of the Grid Friendly Appliance (GFA) controller, which is an autonomous controller that was designed to advise devices like appliances concerning valuable demand-side grid services that should be conducted. The controller bases its advice on observations it makes from the ac voltage signal. Electric tank water heaters were selected to be controlled by the GFA controller in this project. Two autonomous responses are addressed herein. First, an under-voltage-responsive water heater is able to recognize sudden reductions in feeder circuit voltage at each water heater and may curtail any electric load that is being consumed by the water heater. These under-voltage events are usually induced by nearby electrical faults. An under-voltage response is necessarily specified by the set of voltage thresholds at which the responsive water heaters would respond. The set of voltages at which the curtailment would be released must also be specified. Additionally, any delays prior to the water heater load becoming curtailed or again released must be specified. For example, a delay may be intentionally imposed prior to curtailing water heater loads to avoid responses during the fault itself. Much longer and randomized delays should be imposed prior to the release of curtailments in order to re-establish diversity of the water heater loads and soften what could otherwise be an abrupt reintroduction of a large aggregated electrical load into the already stressed grid region.
Date: December 30, 2009
Creator: Lu, Ning; Hammerstrom, Donald J. & Patrick, Stasha N.
Partner: UNT Libraries Government Documents Department

Understanding and predicting metallic whisker growth and its effects on reliability : LDRD final report.

Description: Tin (Sn) whiskers are conductive Sn filaments that grow from Sn-plated surfaces, such as surface finishes on electronic packages. The phenomenon of Sn whiskering has become a concern in recent years due to requirements for lead (Pb)-free soldering and surface finishes in commercial electronics. Pure Sn finishes are more prone to whisker growth than their Sn-Pb counterparts and high profile failures due to whisker formation (causing short circuits) in space applications have been documented. At Sandia, Sn whiskers are of interest due to increased use of Pb-free commercial off-the-shelf (COTS) parts and possible future requirements for Pb-free solders and surface finishes in high-reliability microelectronics. Lead-free solders and surface finishes are currently being used or considered for several Sandia applications. Despite the long history of Sn whisker research and the recently renewed interest in this topic, a comprehensive understanding of whisker growth remains elusive. This report describes recent research on characterization of Sn whiskers with the aim of understanding the underlying whisker growth mechanism(s). The report is divided into four sections and an Appendix. In Section 1, the Sn plating process is summarized. Specifically, the Sn plating parameters that were successful in producing samples with whiskers will be reviewed. In Section 2, the scanning electron microscopy (SEM) of Sn whiskers and time-lapse SEM studies of whisker growth will be discussed. This discussion includes the characterization of straight as well as kinked whiskers. In Section 3, a detailed discussion is given of SEM/EBSD (electron backscatter diffraction) techniques developed to determine the crystallography of Sn whiskers. In Section 4, these SEM/EBSD methods are employed to determine the crystallography of Sn whiskers, with a statistically significant number of whiskers analyzed. This is the largest study of Sn whisker crystallography ever reported. This section includes a review of previous literature on Sn whisker crystallography. The ...
Date: January 1, 2012
Creator: Michael, Joseph Richard; Grant, Richard P.; Rodriguez, Mark Andrew; Pillars, Jamin; Susan, Donald Francis; McKenzie, Bonnie Beth et al.
Partner: UNT Libraries Government Documents Department

Restoration and testing of an HTS fault current controller

Description: A three-phase, 1200 A, 12.5 kV fault current controller using three HTS 4 mH coils, was built by industry and tested in 1999 at the Center Substation of Southern California Edison in Norwalk, CA. During the testing, it appeared that each of the three single-phase units had experienced a voltage breakdown, one externally and two internally. Los Alamos National Laboratory (LANL) was asked by DOE to restore the operation of the fault current controller provided the HTS coils had not been damaged during the initial substation tests. When the internally-failed coil vacuum vessels were opened it became evident that in these two vessels, a flashover had occurred at the high voltage bus section leading to the terminals of the superconducting coil. An investigation into the failure mechanism resulted in six possible causes for the flashover. Based on these causes, the high voltage bus was completely redesigned. Single-phase tests were successfully performed on the modified unit at a 13.7 kV LANL substation. This paper presents the postulated voltage flashover failure mechanisms, the new high voltage bus design which mitigates the failure mechanisms, the sequence of tests used to validate the new design, and finally, the results of variable load and short-circuit tests with the single-phase unit operating on the LANL 13.7 kV substation.
Date: January 1, 2002
Creator: Waynert, J. A. (Joseph A.); Boenig, H. (Heinrich E.); Mielke, C. H. (Charles H.); Willis, J. O. (Jeffrey O.) & Burley, B. L. (Burt L.)
Partner: UNT Libraries Government Documents Department

Measured responses of internal enclosures and cables due to burnthrough penetration of weapon cases by lightning

Description: The electrical effects of lightning penetration of the outer case of a weapon on internal structures, such as a firing set housing, and on samples of a flat, flexline detonator cable have been investigated experimentally. Maximum open-circuit voltages measured on either simulated structures (126 V) or the cable (46 V) located directly behind the point of penetration were well below any level that is foreseen to create a threat to nuclear safety. On the other hand, it was found that once full burnthrough of the barrier occurred, significant fractions of the incident continuing currents coupled to both the simulated internal structure (up to 300 A) or to the cable sample (69 A) when each was electrically connected internally to case ground. No occurrence was observed of the injection of large amplitude currents from return strokes occurring after barrier penetration. Under circumstances in which small volumes of trapped gases exist behind penetration sites, rapid heating of the gas by return strokes occurring after burnthrough has been shown to produced large mechanical impulses to the adjacent surfaces.
Date: August 1, 1994
Creator: Schnetzer, G. H.; Fisher, R. J. & Dinallo, M. A.
Partner: UNT Libraries Government Documents Department