Nuclear Electromagnetic Pulse Research Articles

A multiconductor model for determining the response of power transmission and distribution lines to a high altitude electromagnetic pulse (HEMP)

A method for determining the response of a multiwire transmission or distribution line to a high altitude electromagnetic pulse excitation is discussed. An above ground multiconductor model is developed to take into account wire-to-wire coupling, the earth reflection and line propagation effects, as well as the effects of periodic grounding of shield or neutral conductors along the line. Sample numerical results are also presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Theoretical considerations for optimal positioning of peaking capacitor arms about a Marx generator parallel to a ground plane

The authors develop theoretical considerations useful in determining the electromagnetically optimal positions for a specified number of peaking-capacitor arms about a Marx generator parallel to a ground plane. It is shown that this can be determined by a conformal transformation. A parameter is defined and computed that is indicative of the effectiveness of the peaking-capacitor arms in shielding the Marx from the ground plane. The results of interest in connection with determining the hardness of systems to a nuclear electromagnetic pulse environment. >

Steep-Front Short-Duration Voltage Surge Tests of Power Line Filters and Transient Voltage Suppressors

Steep-front short-duration voltage surge tests were conducted on commercially available power-line filters and two types of transient voltage suppressors to determine their effectiveness for protection against nuclear electromagnetic pulse (EMP) induced power-line transients. The tested power line filters were single-phase industrial-type units in the 120/208 V and 277/480 V class rated at 100 or 200 A. It was found that the tested power-line filters provide from 38 to 54 dB of attenuation for steep front surges (20 to 40 ns rise time and 150 to 400 ns fall time to half-value waves for 2 to 20 kV peak voltage), and transient voltage suppressors add an additional 2 to 8 dB of attenuation. It was also found that while the tested power line filters provide good protection against EMP induced surges, degradation of the filter characteristics may occur and delayed failures of filter components are possible. Transient voltage suppressors reduce the EMP induced surge by 40% and thus provide some protection for the filter. >

The HEMP Response of an Overhead Power Distribution Line

The level of transient electrical surges in power system distribution lines plays an important role in determining the overall response of the electrical power network to a high altitude electromagnetic pulse (HEMP) produced by a nuclear explosion. A previous paper has discussed a multiconductor coupling model which permits the computation of the HEMP-induced voltage surges on above-ground lines, given a specified HEMP environment incident on the line. The use of this model with the Bell Laboratory HEMP waveform for performing a series of calculations of power system responses has resulted in line responses which are unreasonably large, and this has prompted EMP investigators to consider alternate, more physical, HEMP environments for such power system studies. Recently, the results of a parametric study of the HEMP-induced surges on a single conductor located 10 and 20 meters over the earth were reported, using a new HEMP environment. Peak line-to-earth voltages approaching 600 kV were observed for the 10 m line, and peak voltages exceeding 1 MV were noted for the 20 m line. For power transmission lines having a high basic insulation level (BIL), such surges may not be important. However, in power distribution systems, such overvoltages may pose serious problems to the insulators and load equipment, such as transformers, which are attached to the lines. Consequently, a study of the HEMP response of a realistic power distribution system shown in Figure 1 was undertaken, and its results are described in this paper.

Experimental Determination of the Effects of Steep Front-Short Duration Surges on 25 KVA Pole Mounted Distribution Transformers

Steep front-short duration (SFSD) surges have been implicated in the failure of distribution transformers. Researchers, through calculations and measurements, have determined that surges with rise times of less than 100 nanoseconds may occur from such causes as lightning, SF6 switching, and nuclear electromagnetic pulse. This paper documents a series of directly-injected, SFSD surge tests performed on standard, commercial distribution transformers. The tests were conducted at Maxwell Laboratories, San Diego, California in October, 1986. The objectives of the tests were to: 1) verify the insulation integrity of a small sample of pole-mounted distribution transformers of types commonly used by electric utilities, 2) subject these transformers to directly injected SFSD electrical surges, 3) determine the dielectric withstand capability of the transformers to such surges, and 4) complete the evaluation of transformer failure modes through disassembly of failed units at a transformer manufacturing facility. A series of SFSD impulse tests were conducted on 19, 25-kVA, 12470Y/7200-volt distribution transformers. The impulse test voltages at the terminals of the high voltage pulser were 400 kV, 500 kV, 800 kV, and 1000 kV open circuit with rise times of approximately 60 ns and decay times to half-crest value of approximately 2000 ns. The voltage was applied to the transformer under test through a 400-Ohm series resistor. This series resistor represented the distribution line surge impedance. These tests were conducted both with and without commercially available gapped silicon carbide surge arresters installed on the transformers.

Radiative reactions and coherence modeling in the high-altitude electromagnetic pulse.

A high-altitude nuclear electromagnetic pulse (EMP) with a peak field intensity of 5\ifmmode\times\else\texttimes\fi{}${10}^{4}$ V/m carries momentum that results in a retarding force on the average Compton electron (radiating coherently to produce the waveform) with magnitude near that of the geomagnetic force responsible for the coherent radiation. The retarding force results from a self-field effect. The Compton electron interaction with the self-generated magnetic field due to the other electrons accounts for the momentum density in the propagating wave; interaction with the self-generated electric field accounts for the energy-flux density in the propagating wave. Coherent addition of radiation is also quantitatively modeled.

Development of a New High Altitude Electromagnetic Pulse (Hemp) Environment and Resulting Overhead Line Responses

Being able to accurately determine the response of an electrical system which is excited by a high altitude nuclear electromagnetic pulse (EMP) requires a knowledge of the time history of the incident EMP field strength, as well as its angle of incidence and polarization. A commonly used, unclassified, description of this environment is provided by the ''Bell Laboratory waveform.'' Recent studies have shown, however, that this EMP waveform tends to overestimate the response of an above-ground transmission line by more than an order of magnitude. As a result, other unclassified high altitude EMP environments have been developed. This presentation discusses the development of two alternate unclassified EMP environment descriptions: one arising from a simple radiating dipole moment model, and the other resulting from curve-fitting the calculated fields from a computer code named CHAP. For both of these EMP models, the electric field at two earth observation points are compared. These fields are then coupled to an above-ground line and the resulting open-circuit voltage responses are compared. Using the CHAP EMP environment, a limited parametric study of the peak positive and negative open-circuit voltage is then performed and surface plots of these peak voltages are presented. 8 refs., 21 figs., 1more » tab.« less

EMP susceptibility insights from aircraft exposure to lightning

Examines the interactions of natural lightning and the nuclear electromagnetic pulse (EMP) with aircraft. The propositions that one can use normal exposure to lightning to provide information on EMP protection, and deliberate exposure to lightning to test EMP protection are evaluated. The rarity of encountering lightning, its random occurrence and variability (necessitating extensive onboard instrumentation), and its apparent deficiency in energy at the high frequencies make the use of lightning for an EMP surveillance or test impractical. >

Extrapolation of measured power system response data to high-altitude EMP excitation

Pulse injection measurements performed on an electrical generation plant in Sweden are reported. It is shown how these data may be used to calculate the high-altitude nuclear electromagnetic pulse (HEMP) response of the system when it is connected to the powergrid. It is found that the HEMP-induced current stages in overhead transmission lines are significantly attenuated as they propagate from the switch yard to the generator output terminals.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Differences between lightning and nuclear electromagnetic pulse interactions

Some important differences between the system interactions of electromagnetic transients from lightning (LEMP) and from high-altitude nuclear explosions (HEMP) are discussed. Interactions with small systems, such as aircraft, and large systems, such as electric power grids, are considered. Effects of factors like lightning channel attachment and the relatively local nature of the lightning excitation are contrasted with the broad-area effect of the HEMP interaction. It is concluded that although protective approaches and techniques for LEMP and HEMP are often similar, the two phenomena are sufficiently different that protection against one does not necessarily imply protection against the other.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Voltages Induced on Coaxial Cables or Multi-Wire Shielded Lines by a Disturbing Wave

ABSTRACT This paper presents an application of the transmission-line theory to determine the coupling of disturbing waves on coaxial or multiwire shielded cables. First the external problem is analyzed in the case of a line parallel to the ground and examples are given for an illumination either by the field radiated by a lightning stroke or due to a nuclear electromagnetic pulse. The influence of geometrical or electrical parameters such as the cable length, the angle of illumination and the ground conductivity are examined. Penetration of energy into the cable is studied for a coaxial cable. Then some experimental results on multi-wire shielded lines are presented in order to highlight the various mechanisms which can cause a differential voltage between each pair of the inner lines. Lastly, application of a simple numerical model shows the relative influence of dissymmetries either in the structure of the cable or in the load impedances connected at both ends.

A new sensor structure for the measurement of an electromagnetic pulse

Harry Diamond Laboratories (HDL), Woodbridge, VA, currently uses groundplane version electric- and magnetic-field sensors to measure the electric and magnetic fields produced during a simulated high-altitude electromagnetic pulse (HEMP). These sensors are also used for the measurement of such pulsed fields in the vicinity of metallic enclosures. A new sensor structure has been developed to measure the electric and magnetic fields accurately. The authors have recently fabricated and mounted a hollow metallic cylinder behind the sensor's 0.218-m (8 1/2 in) ground plane to house a fiber-optic transmitter, amplifiers, and other equipment necessary for data collection. The presence of this metallic cylinder increases (“enhances”) the amplitude of a signal when measured with this new sensor structure geometry (“sensor/cylinder”). The electric- and magnetic-field enhancements caused by the presence of this metallic cylinder were measured in both the frequency and time domains. The enhancement was also calculated numerically using a three-dimensional finite-difference code. To eliminate unwanted field coupling to the sensor's coaxial signal cable, the output of the sensor is transmitted through fiber-optic cables to remotely located recording equipment. In the frequency domain, the enhancements for both the electric and magnetic field were determined using a large transverse electromagnetic (TEM) cell. In the time domain, the enhancements were determined by comparing simulated HEMP fields measured with this sensor/cylinder to those measured with miniature electric- and magnetic-field sensors. The degree of enhancement of this sensor/cylinder will vary as a function of distance when the sensor/cylinder is placed next to a conducting object, such as a metallic shelter. These enhancements were also determined using miniature electric- and magnetic-field sensors.

Effect of the Fast Nuclear Electromagnetic Pulse on the Electric Power Grid Nationwide: A Different View

Effect of the Fast Nuclear Electromagnetic Pulse on the Electric Power Grid Nationwide: A Different View

Description of an Aircraft Lightning And Simulated Nuclear Electromagnetic Pulse (NEMP) Threat Based on Experimental Data

Most modern aircraft are designed to withstand a direct lightning strike. To accomplish this protection, the aircraft must have an external conductive path with a given skin thickness and a minimum amount of exposed areas and antennas that could allow energy coupling to the inside. Additionally, some modern military aircraft are also designed to operate in a nuclear electromagnetic pulse (NEMP) environment. This paper provides experimental lightning data and NEMP scalemodel data to characterize both phenomena. The lightning data were obtained by measuring the surface electromagnetic fields on a CV-580 research aircraft during an actual lightning strike. The aircraft was struck by lightning 48 times in central Florida between 1500- and 18 000-ft altitude during the summers of 1984 and 1985. One of these lightning events, for which an extensive set of data was available, has been analyzed. For this event, the maximum measured values were as follows: time rate of change of the surface magnetic flux density, 3750 T/s; total normal current density, 20 A/m2; peak current, 4.7 kA; and rate of rise of the current, 38 kA/ps. The NEMP data were obtained by measuring the surface electromagnetic fields during a simulated NEMP test in a 1:74 scale model of the same aircraft. During scale-model NEMP simulation, the maximum values measured were as follows: time rate of change of the surface magnetic flux density, 40 000 T/s; and total normal current density, 90 A/m2. The analyses of these results should provide new insights for combined lightning and NEMP protection.

URSI statement - Nuclear electromagnetic pulse [EMP] and associated effects

URSI statement - Nuclear electromagnetic pulse [EMP] and associated effects

Nuclear Electromagnetic Pulse (NEMP)—A Threat to Electronics

The paper generally reviews the basic physics, generation and mitigation techniques as applied to Electromagnetic Pulse (EMP) due to nuclear weapon explosion. EMP is generated due to all the three ...

Effect of the Fast Nuclear Electromagnetic Pulse on the Electric Power Grid Nationwide: A Different View

This paper primarily considers the potential effects of a single high-altitude nuclear burst on the U.S. power grid. A comparison is made between EMP and natural phenomena such as lightning. This paper concludes that EMP is no more harmful to the power grid than its counterparts in natuire. An upper limit of the electric field of the very fast, high-amplitude EMP is derived from first principles. The resulting values are significantly lower than the commonly presented values. Additional calculations show that the ionization produced by a nuclear burst severely attenuates the EMP.

In memorium: Peter H. Haas, 1921-1986

The entire nuclear weapons effects community suffered a major and tragic loss on June 19, 1986 when Peter H. Haas was killed in an automobile accident. Pete was a principal pioneer in the field of nuclear weapons effects beginning in the mid 1950s. As a member of the scientific staff of the Harry Diamond Laboratories (then known as the Diamond Ordnance Fuze Laboratory), he proposed and conducted some of the landmark experiments on nuclear electromagnetic pulse (EMP) and transient radiation effects on electronics (TREE). These experiments were conducted at the Nevada and Pacific Nuclear Test Sites under the sponsorship of the Armed Forces Special Weapons Project, the forerunner of the Defense Nuclear Agency (DNA). It was under his direction that some of the early neutron displacement effects research was done in pulsed nuclear reactors. He had the imagination and foresight to suggest that electronic circuitry might undergo severe changes in behavior when exposed to a nuclear radiation pulse, and this was the genesis of the discipline known as TREE. A brief biography of Peter H. Haas, 1921-1986 is given highlighting his professional achievements.

Nuclear Electromagnetic Pulse (EMP) and Associated Effects

Nuclear Electromagnetic Pulse (EMP) and Associated Effects

Electromagnetic Pulse and the Electric Power Network

This paper defines the nuclear electromagnetic pulse (EMP)-electric power system interaction problem. A description of high altitude EMP (HEMP) characteristics, source region EMP (SREMP) characteristics, and magnetohydrodynamics EMP (MHD-EMP) characteristics are presented. The results of initial calculations of EMP induced surges on electric power transmission and distribution lines are presented and compared with lightning induced surges. Potential EMP impacts on electric power systems are discussed, and an overview of the Department of Energy (DOE) EMP research program is presented.