Early-Time (E1) High-Altitude Electromagnetic Pulse Effects on Trip Coils

Nuclear electromagnetic pulse (NEMP) simulators are used to simulate the intense electromagnetic fields generated during a high altitude nuclear burst and in turn they are used for the hardening assurance of critical electronic systems. The guided wave (GW) NEMP simulator is like a transmission line, fed by a steep fronted high voltage pulse and terminated by a resistor on the other side. The resistive termination absorbs only the low frequencies of the pulse, while the high frequencies escape out from the simulator thereby acting as a high frequency radiator. These high frequency radiations could be a source of interference to the nearby sensitive installations, and hence it becomes imperative to study the leakage field radiation pattern of an NEMP simulator so that the direction and the intensity of the maximum radiated field can be ascertained. This study will be useful during the planning, and the commissioning of an NEMP simulator near critical infrastructures or adding a new critical infrastructure near an existing NEMP simulator. In this paper the leakage fields and their radiation pattern computed using Method of Moments (MoM) code and same has been validated by measurement results.

Distribution transformers may experience insulation breakdown or degradation when exposed to the influences of high‐altitude electromagnetic pulse (HEMP), thus posing significant threats and uncertainties to the safety and stable operations of power systems. Therefore, this study constructs a HEMP impact‐test platform for distribution transformers, evaluates and analyses the development patterns of partial discharge (PD) under the action of different amplitude conduction environments, decomposes and identifies the types of damage defects, proposes a quantitative classification method for the degree of HEMP damage to distribution transformers based on PD detection. And reveals the damage mechanism of distribution transformers exposed to HEMP at different damage levels. The results show that distribution transformers undergo insulation breakdown when subjected to the influences of HEMP and that performance degradation often occurs before breakdown. As the amplitude of the HEMP environment increases, the degree of transformer damage continues to deteriorate, and both the amount of PD and the repetition rate of discharges exhibit a step‐wise increase, with the increase in the repetition rate lagging behind that of the discharge amount. Based on the patterns of discharge quantity and repetition rate, transformer damage is categorised into three stages: undamaged, latent defect discharge, and severe defect discharge.

The high-altitude burst of a nuclear device over the continental United States can expose civilian electric utility systems to transient electromagnetic pulses (EMP). The electromagnetic fields experienced within one second after the burst have been collectively defined by the term high-altitude EMP (HEMP). The phenomena has been subdivided, for this report, into an early-time HEMP field followed by an intermediate-time HEMP field. This volume documents a preliminary research effort to: investigate the nature and coupling of the HEMP environments to electric power systems, define the construction of approximate system response models, and document the development of a methodology to assess equipment and system vulnerability.

The purpose of this report is to develop an engineering design package to protect the Federal Emergency Management Agency (FEMA) National Radio System (FNARS) facilities against the effects of high-altitude electromagnetic pulses (HEMPS). This report refers to the FEMA Federal Regional Center (FRC) in Bothell, Washington. It is highly probably that there will be a heavy dependence upon high-frequency (hf) radio communications for long-haul communications following a nuclear attack on the continental United States, should one occur. To maintain the viability of the FEMA hf radio network during such a situation, the FNARS facilities must take measures to protect against the effects of HEMP that are likely to be created in a nuclear confrontation. The equipment under stress has already been designed and built so that little opportunity exists for equipment design changes that could raise the threshold levels at which malfunctions occur. The solution must then be to reduce HEMP-induced stresses on the system by means of tailored retrofit hardening measures using commercial protection devices when available. If is the intent of this report to define the particular hardening measures that will minimize the susceptibility of the network components to HEMP effects. To the extent economically viable, protective actions have been recommended for implementation, along with necessary changes or additions, during the period of the FNARS upgrade program. This report addresses electromagnetic pulse (EMP) effects only, and disregards any condition in which radiation effects may be a factor. This report identifies the systems in the facility considered critical for emergency option. To identify the critical systems in the facility and the EMP coupling paths into these systems, an EMP survey of the facility was conducted. Results of the survey are presented along with recommendations for tailored retrofit hardening measures to be implemented to protect the facility from EMP.

Mechanical impedance of the femur: A preliminary report

This Letter proposes a mechanical impedance (MI) measurement technique using noncontact laser ultrasound. The ultrasound is generated by shooting a pulse laser beam onto a target structure, and its response is measured using a laser vibrometer. Once ultrasound propagation converges to structural vibration, MI is formed over the entire structure. Because noncontact lasers are utilized, this technique is applicable in harsh environments, free of electromagnetic interference, and able to perform wide-range scanning. The formation of MI and its feasibility for damage detection are verified through thermo-mechanical finite element analysis and lab-scale experiments.

The study of electromagnetic sensitivity of electronic modules is crucial for the selection of a component-level pulse current injection (PCI) waveform, which will determine whether a component-level PCI test is equivalent to a system-level pulse illumination test of the system to which the electronic module belongs. For electromagnetic sensitivity analysis, the equivalence between the injection waveform and a typical high-altitude electromagnetic pulse (HEMP) conducted disturbance waveform in a component-level PCI test is studied. Based on an RF low noise amplifier (LNA) test board, component-level PCI tests were performed using 20 ns/500 ns double exponential wave and square-wave pulse with multiple pulse-widths. The damage threshold was analyzed and determined by using vector norm and its internal damage was observed and validated by optical microscopic analysis. The conclusions are demonstrated as follows: first, during square-wave PCI tests of RF LNA, the electromagnetic sensitive parameter action is divided into three regions by pulse-width range, called ∞-norm, 2-norm and competitive failure-dominating regions; second, the electromagnetic damage effect of the RF LNA is mainly caused by the burning of its two cascaded transistors, forming a pulse energy transmission channel with short-circuit impedance from the input port to the ground; third, the 100 ns-width square waveform can be determined as the equivalent injection waveform of a HEMP conducted waveform, and the pulse peak value of injected current is determined as the electromagnetic sensitive parameter for square-wave PCI tests of the RF LNA. The conclusions verified the feasibility of establishing the equivalence between different pulse waveforms according to the electromagnetic sensitivity analysis based on the vector norm theory and effect mechanism analysis.

This report discusses the effects of the late-time high-altitude electromagnetic pulse (HEMP) on electrical transmission and distribution (T D) systems. This environment, known as the magnetohydrodynamic electromagnetic pulse (MHD-EMP), is a very slowly varying electric field induced in the earth's surface, similar to the field induced by a geomagnetic storm. It can result in the flow of a quasi-dc current in grounded power lines and in the subsequent magnetic saturation of transformers. This saturation, in turn, causes 6-Hz harmonic distortion and an increase in the reactive power required by generation facilities. This report analyzes and discusses these phenomena. The MHD-EMP environment is briefly discussed, and a simplified form of the earth-induced electric field is developed for use in a parametric study of transmission line responses. Various field coupling models are described, and calculated results for the responses of both transmission- and distribution-class power lines are presented. These calculated responses are compared with measurements of transformer operation under dc excitation to infer the MHD-EMP response of these power system components. It is found that the MHD-EMP environment would have a marked effect on a power system by inducing up to several hundreds of amperes of quasi-dc current on power lines. These currents will cause transformers to saturate which could result in excessive harmonic generation, voltage swings, and voltage suppression. The design of critical facilities which are required to operate during and after MHD-EMP events will have to be modified in order to mitigate the effects of these abnormal power system conditions.

The Effects of High-Altitude Electromagnetic Pulse (HEMP) on Telecommunications Assets

Petrophysical variation of coal treated by cyclic high-voltage electrical pulse for coalbed methane recovery

To more precisely measure the mechanical properties of the lung periphery in asthma, we have developed a forced oscillation technique that applies a broad-band flow signal through a wedged bronchoscope. We interpreted the data from four healthy and eight mildly asthmatic subjects in terms of an anatomically accurate computer model of the wedged segment. There was substantial overlap in impedance between the two groups, with resistance (R) showing minimal frequency dependence and elastance (E) showing positive and negative frequency dependence across subjects. After direct instillation of methacholine, R rose in both groups, but compared with healthy subjects, the asthmatic subjects displayed upward, parallel shifts in their dose-response curves. The baseline frequency-response patterns of E were enhanced after methacholine. Frequency dependencies of R and E were well reproduced in two normal subjects by a computational model that employed rigid airways connected to constant-phase tissue units but were better reproduced in the other two normal and three asthmatic subjects when the model employed heterogeneous, peripheral airway narrowing and compliant airways. To capture the frequency dependencies of R and E in the remaining five asthmatic subjects, the model was modified by increasing airway wall stiffness. These results indicate that the lung periphery of mildly asthmatic subjects is not well distinguished from that of healthy subjects by measurement of mechanical impedance at baseline, but group differences are seen after challenge with methacholine. Modeling of the response suggests that variable contributions of airway narrowing and wall compliance are operative in determining overall mechanical impedance of the lung periphery in humans with asthma, likely reflecting the functional consequences of airway inflammation and remodeling.

Characterization of Subcutaneous Edema by Mechanical Impedance Measurements

The resonance method was applied to measure shear mechanical properties of liquids, and it has thus been established that such low-viscosity liquids as water, cyclohexane, hexadecane, and dibutyl phthalate possess a shear elasticity of about 10 6 dyn/cm 2 at a frequency of shear oscillations of about 73.5 kHz. Now, according to the existing concepts on the nature of liquids, their shear elasticity should be observed only at a frequency of about 10 11 -10 12 Hz. The present work maintains a comparison with the known works on measurements of the shear mechanical impedance of liquids. It has been shown that the results obtained here agree satisfactorily with measurements of the shear mechanical impedance of low-viscosity liquids at a frequency of 40 MHz.

The ability to provide forced oscillatory excitation of the respiratory system can be useful in mechanical impedance measurements as well as high frequency ventilation (HFV). Experimental systems currently used for generating forced oscillations are limited in their ability to provide high amplitude flows or maintain the respiratory system at a constant mean pressure during excitation. This paper presents the design and implementation of a pneumatic pressure oscillator based on a proportional solenoid valve. The device is capable of providing forced oscillatory excitations to the respiratory system over a bandwidth suitable for mechanical impedance measurements and HVF. It delivers high amplitude flows (> 1.4 l/s) and utilizes a servo-control mechanism to maintain a load at a fixed mean pressure during simultaneous oscillation. Under open-loop conditions, the device exhibited a static hysteresis of approximately 7%, while its dynamic magnitude and phase responses were flat out to 10 Hz. Broad-band measurement of total harmonic distortion was approximately 19%. Under closed-loop conditions, the oscillator was able to maintain a mechanical test load at both positive and negative mean pressures during oscillatory excitations from 0.1 to 10.0 Hz. Impedance of the test load agreed closely with theoretical predictions. We conclude that this servo-controlled oscillator can be a useful tool for respiratory impedance measurements as well as HFV.

Errors in mechanical impedance data obtained with impedance heads