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At least 19 records

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NASA NTRS1991

Voltages induced on a power distribution line by overhead cloud lightning

Voltages induced by overhead cloud lightning on a 448 m open circuited power distribution line and the corresponding north-south component of the lightning magnetic field were simultaneously measured at the NASA Kennedy Space Center during the summer of 1986. The incident electric field was calculated from the measured magnetic field. The electric field was then used as an input to the computer program, EMPLIN, that calculated the voltages at the two ends of the power line. EMPLIN models the frequency domain field/power coupling theory found, for example, in Ianoz et al. The direction of the source, which is also one of the inputs to EMPLIN, was crudely determined from a three station time delay technique. The authors found reasonably good agreement between calculated and measured waveforms.

Yacoub, Ziad↗

NASA NTRS1988

Measurements of induced voltages and currents in a distribution power line and associated atmospheric parameters

The frequency and intensity of thunderstorms around the Kennedy Space Center (KSC) has affected scheduled launch, landing, and other ground operations for many years. In order to protect against and provide safe working facilities, KSC has performed and hosted several studies on lightning phenomena. For the reasons mentioned above, KSC has established the Atmospheric Science Field Laboratory (ASFL). At these facilities KSC launches wire-towing rockets into thunderstorms to trigger natural lightning to the launch site. A program named Rocket Triggered Lightning Program (RTLP) is being conducted at the ASFL. This report calls for two of the experiments conducted in the summer 1988 Rocket Triggered Lightning Program. One experiment suspended an electric field mill over the launching areas from a balloon about 500 meters high to measure the space charges over the launching area. The other was to connect a waveform recorder to a nearby distribution power line to record currents and voltages wave forms induced by natural and triggered lightning.

Santiago-Perez, Julio↗

NASA NTRS2011

Circuit for Communication Over Power Lines

Many distributed systems share common sensors and instruments along with a common power line supplying current to the system. A communication technique and circuit has been developed that allows for the simple inclusion of an instrument, sensor, or actuator node within any system containing a common power bus. Wherever power is available, a node can be added, which can then draw power for itself, its associated sensors, and actuators from the power bus all while communicating with other nodes on the power bus. The technique modulates a DC power bus through capacitive coupling using on-off keying (OOK), and receives and demodulates the signal from the DC power bus through the same capacitive coupling. The circuit acts as serial modem for the physical power line communication. The circuit and technique can be made of commercially available components or included in an application specific integrated circuit (ASIC) design, which allows for the circuit to be included in current designs with additional circuitry or embedded into new designs. This device and technique moves computational, sensing, and actuation abilities closer to the source, and allows for the networking of multiple similar nodes to each other and to a central processor. This technique also allows for reconfigurable systems by adding or removing nodes at any time. It can do so using nothing more than the in situ power wiring of the system.

Krasowski, Michael J.↗

NASA NTRS1983

Innovation in Building Design

Thomas & Betts Corporation's Flat Conductor Cables, or FCC, were developed of necessity as aircraft and spacecraft became increasingly complex. In order to reduce size and weight of components, the use of thin flat wire instead of relatively thick and protrusive round cable, provided a dramatic reduction of the space occupied by the many miles of power distribution lines in an aerospace vehicle. Commercially, FCC offers cost savings in simplified building construction, reduced installation time and ease of alteration.

Source record↗

NASA NTRS1986

Transmission line design for a power distribution system at 20 kHz for aircraft

A low inductance, low characteristic impedance transmission line was designed for a 20 kHz power distribution system. Several different conductor configurations were considered: strip lines, interdigitated metal ribbons, and standard insulated wires in multiwire configurations (circular and rectangular cylindrical arrangements). The final design was a rectangular arrangement of multiple wires of the same gauge with alternating polarities from wire to wire. This offered the lowest inductance per unit length (on the order of several nanohenries/meter) and the lowest characteristic impedance (on the order of one Ohm). Standard multipin connectors with gold-plated elements were recommended with this transmission line, the junction boxes to be internally connected with flat metal ribbons for low inductance, and the line to be constructed in sections of suitable length. Computer programs for the calculation of inductance of multiwire lines and of capacitances of strip lines were developed.

Zelby, L. W.↗

NASA NTRS1977

Longitudinal variations of very-low-frequency chorus activity in the magnetosphere - Evidence of excitation by electrical power transmission lines

The distribution of VLF chorus in the high-altitude magnetosphere as detected by the Ogo 3 satellite was investigated. Chorus occurrence frequency over 4,668 samples of 5 min of broadband data was computed for Northern Hemisphere bins of 10 deg by 10 deg in dipole invariant latitude and longitude. Peaks in activity were noted over Alaska, the eastern U.S. and Canada, western Europe, and western Siberia, and were shown not to be the result of biased sampling. It is suggested that power line radiation of only about 1 W or less at a given harmonic frequency may be sufficient to stimulate the observed chorus activity and that such power levels can be expected in industrial areas or from large distribution networks. Preliminary results show that chorus starting frequencies are highly correlated with 60 Hz harmonics in the American sector and with 50 Hz harmonics in the European sector.

Luette, J. P.↗

NASA NTRS1984

Parametric analysis of hollow conductor parallel and coaxial transmission lines for high frequency space power distribution

A parametric analysis was performed of transmission cables for transmitting electrical power at high voltage (up to 1000 V) and high frequency (10 to 30 kHz) for high power (100 kW or more) space missions. Large diameter (5 to 30 mm) hollow conductors were considered in closely spaced coaxial configurations and in parallel lines. Formulas were derived to calculate inductance and resistance for these conductors. Curves of cable conductance, mass, inductance, capacitance, resistance, power loss, and temperature were plotted for various conductor diameters, conductor thickness, and alternating current frequencies. An example 5 mm diameter coaxial cable with 0.5 mm conductor thickness was calculated to transmit 100 kW at 1000 Vac, 50 m with a power loss of 1900 W, an inductance of 1.45 micron and a capacitance of 0.07 micron-F. The computer programs written for this analysis are listed in the appendix.

Jeffries, K. S.↗

NASA NTRS1990

Automatic Monitoring Of Complicated Systems

Collection of computer programs developed for expert computer system performing complicated, tedious, and repetitive portions of analysis of telemetry data from spacecraft. Provides nonstop, accurate surveillance of incoming data, also frees operators to concentrate their expertise on unexpected abnormal operating conditions. When unable to explain discrepancies with certainty resulting from data out of synchronization or other falso-alarm conditions, triggers alarm devices to request assistance from designated individuals. Concept useful in such terrestrial systems as production lines, power-distribution networks, chemical processes, large airplanes, and other assemblies of interdependent equipment.

Schwuttke, Ursula M.↗

NASA NTRSDate not supplied

The Effectiveness of Power Distribution Systems for Deployment on the Lunar Surface

Lunar habitation missions are currently being planned to have astronauts return to the moon by the mid 2020’s with a sustained lunar presence by the end of the decade. The various landed modules needed to support the missions are expected to be distributed around Shackleton Crater at distances ranging from 1 to 15 km and with power needs ranging from 10 kW to 50kW. Current plans call for a solar array to be installed on the rim of the crater that receives near-constant sunlight year around with a power distribution system that transfers power from the source to consumers. This paper details several power distribution systems: DC transmission lines, radio frequency power beaming, and optical power beaming. Sizing algorithms for each of these distributions systems along with their necessary subsystems were developed from literature and subject matter expertise input. Several experiments were then conducted to determine the performance of the systems along with their sensitivities to changes in assumptions for various sub-components. The defined Figures of Merit enable mission designers to select the best power distribution system for each possible power consumer mission scenario. The experimental results were analyzed and compiled into a set of figures that highlight the conditions for which a certain system outperforms the other.

Bradford Robertson↗

NASA NTRSDate not supplied

The Effectiveness of Power Distribution Systems for Deployment on the Lunar Surface

Bradford Robertson↗

NASA NTRS1984

Incoherent Scatter Radar Studies of the Mesosphere

All current incoherent backscatter radars can make mesospheric or D region measurements under at least some conditions. The conditions under which measurements are possible are derived and shown for each radar. Conditions examined include overall system sensitivity, electron and ion spectral line widths and power distributions, and time/height averaging effects. The radar equations is derived and calibrations of the radar system is discussed. Total power only and combined total power and ion line spectral measurements are described in terms of ease of use, applicability to various radars, and parameters of aerodynamic interest derivable from the measurements.

Mathews, J. D.↗

NASA NTRS1985

X-Band Strip-Line Power Divider/Combiner

Strip-line circuit for X-band signals both divides and combines microwave power for distributed amplifier. Strip-line pattern (foil pattern over insulating layer over ground plane) laid out so all eight distributed ports lie at electrical distances of odd integral multiples of half wavelength from main input/output port. Strip line used as power divider and as power combiner.

Conroy, B. L.↗

NASA NTRS1988

Power transmission studies for tethered SP-100

The tether and/or transmission line connecting the SP-100 to space station presents some unorthodox challenges in high voltage engineering, power transmission, and distribution. The line, which doubles as a structural element of this unusual spacecraft, will convey HVDC from SP-100 to the platform in low Earth orbit, and environment where the local plasma is sufficient to cause breakdown of exposed conductors at potentials of only a few hundred volts. Its anticipated several years operation, and continuously accumulating exposure to meteoroids and debris, raises an increasing likelihood that mechanical damage, including perforation, will be sustained in service. The present concept employs an array of gas insulated solid wall aluminum coaxial tubes; a conceptual design which showed basic feasibility of the SP-100 powered space station. Practical considerations of launch, deployment and assembly have lead to investigation of reel deployable, dielectric insulated coaxial cables. To be competitive, the dielectric would have to operate reliably in a radiation environment under electrical stresses exceeding 50 kV/cm. The SP-100 transmission line high voltage interfaces are also considered.

Bents, David J.↗

NASA NTRS1988

Power transmission studies for tethered SP-100

The tether and/or transmission line connecting the SP-100 to Space Station presents some unorthodox challenges in high voltage engineering, power transmission, and distribution. The line, which doubles as a structural element of this unusual spacecraft, will convey HVDC from SP-100 to the platform in low Earth orbit, and environment where the local plasma is sufficient to cause breakdown of exposed conductors at potentials of only a few hundred volts. Its anticipated several years operation, and continuously accumulating exposure to meteoroids and debris, raises an increasing likelihood that mechanical damage, including perforation, will be sustained in service. The present concept employs an array of gas insulated solid wall aluminum coaxial tubes; a conceptual design which showed basic feasibility of the SP-100 powered Space Station. Practical considerations of launch, deployment and assembly have led to investigation of reel deployable, dielectric insulated coaxial cables. To be competitive, the dielectric would have to operate reliably in a radiation environment under electrical stresses exceeding 50 kV/cm. The SP-100 transmission line high voltage interfaces are also considered.

Bents, David J.↗

NASA NTRS1995

Artificial neural network application for space station power system fault diagnosis

This study presents a methodology for fault diagnosis using a Two-Stage Artificial Neural Network Clustering Algorithm. Previously, SPICE models of a 5-bus DC power distribution system with assumed constant output power during contingencies from the DDCU were used to evaluate the ANN's fault diagnosis capabilities. This on-going study uses EMTP models of the components (distribution lines, SPDU, TPDU, loads) and power sources (DDCU) of Space Station Alpha's electrical Power Distribution System as a basis for the ANN fault diagnostic tool. The results from the two studies are contrasted. In the event of a major fault, ground controllers need the ability to identify the type of fault, isolate the fault to the orbital replaceable unit level and provide the necessary information for the power management expert system to optimally determine a degraded-mode load schedule. To accomplish these goals, the electrical power distribution system's architecture can be subdivided into three major classes: DC-DC converter to loads, DC Switching Unit (DCSU) to Main bus Switching Unit (MBSU), and Power Sources to DCSU. Each class which has its own electrical characteristics and operations, requires a unique fault analysis philosophy. This study identifies these philosophies as Riddles 1, 2 and 3 respectively. The results of the on-going study addresses Riddle-1. It is concluded in this study that the combination of the EMTP models of the DDCU, distribution cables and electrical loads yields a more accurate model of the behavior and in addition yielded more accurate fault diagnosis using ANN versus the results obtained with the SPICE models.

Momoh, James A.↗

NASA NTRS1980

Space platform utilities distribution study

Generic concepts for the installation of power data and thermal fluid distribution lines on large space platforms were discussed. Connections with central utility subsystem modules and pallet interfaces were also considered. Three system concept study platforms were used as basepoints for the detail development. The tradeoff of high voltage low voltage power distribution and the impact of fiber optics as a data distribution mechanism were analyzed. Thermal expansion and temperature control of utility lines and ducts were considered. Technology developments required for implementation of the generic distribution concepts were identified.

Lefever, A. E.↗

NASA NTRS1987

Space station electrical power distribution analysis using a load flow approach

The space station's electrical power system will evolve and grow in a manner much similar to the present terrestrial electrical power system utilities. The initial baseline reference configuration will contain more than 50 nodes or busses, inverters, transformers, overcurrent protection devices, distribution lines, solar arrays, and/or solar dynamic power generating sources. The system is designed to manage and distribute 75 KW of power single phase or three phase at 20 KHz, and grow to a level of 300 KW steady state, and must be capable of operating at a peak of 450 KW for 5 to 10 min. In order to plan far into the future and keep pace with load growth, a load flow power system analysis approach must be developed and utilized. This method is a well known energy assessment and management tool that is widely used throughout the Electrical Power Utility Industry. The results of a comprehensive evaluation and assessment of an Electrical Distribution System Analysis Program (EDSA) is discussed. Its potential use as an analysis and design tool for the 20 KHz space station electrical power system is addressed.

Emanuel, Ervin M.↗

NASA NTRS1981

The application of simulation modeling to the cost and performance ranking of solar thermal power plants

A computer simulation code was employed to evaluate several generic types of solar power systems (up to 10 MWe). Details of the simulation methodology, and the solar plant concepts are given along with cost and performance results. The Solar Energy Simulation computer code (SESII) was used, which optimizes the size of the collector field and energy storage subsystem for given engine-generator and energy-transport characteristics. Nine plant types were examined which employed combinations of different technology options, such as: distributed or central receivers with one- or two-axis tracking or no tracking; point- or line-focusing concentrator; central or distributed power conversion; Rankin, Brayton, or Stirling thermodynamic cycles; and thermal or electrical storage. Optimal cost curves were plotted as a function of levelized busbar energy cost and annualized plant capacity. Point-focusing distributed receiver systems were found to be most efficient (17-26 percent).

Rosenberg, L. S.↗