Farhad Rachidi-Haeri

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The formulation describing the electromagnetic field radiated by a lightning return stroke over a two-layered conducting ground is presented in this paper. The derivation of the Green's functions required to solve the problem is first discussed in detail, ...

In this paper, we present a methodology for estimating the protection levels of critical equipment against IEMI. We apply the method to a wireless communication infrastructure, but it can be applied to any critical infrastructure. The required protection l ...

We review in this paper simplified analytical expressions derived by Wait using the concept of attenuation function for the analysis of the propagation of lightning radiated electromagnetic fields over a horizontally stratified ground. Considerations regar ...

Materials exhibiting a gradient in permittivity are synthesized through the application of an external magnetic field to a suspension of Fe3O4@TiO2 nanoparticles in an epoxy matrix. It is shown how the application of the magnetic field not only induces the magnetophoretic motion of the particles, but causes also their alignment in high aspect ratio structures. The combination of these two effects gives rise to graded nanocomposites exhibiting gradients in permittivity that go beyond the ones predicted for n

Partial discharges (PDs) from inhomogeneities, potential sites for future faults, in cable defects, generate high-frequency pulses traveling along electric power networks. Online PD signal detection and location permits proactive maintenance, minimizing the impact of or, ideally, preventing outages, reducing the overall repair time and the customer minutes lost. PD monitoring techniques are commercially available, but their cost-effective implementation requires guarding large parts of a network at once. Th

Electromagnetic Time Reversal (EMTR) features the bounded phase property, a well-established and reliable method for fault location in two-conductor transmission lines. Under the EMTR-based framework for mismatched media, this property asserts that the phase of the overall forward and backward transfer function remains strictly confined at the true fault location. Extending this property to multi-conductor lines is challenging because the transfer function ceases to be a scalar and instead becomes a matrix.

An extension of the engineering return-stroke models for lightning strikes to tall structures that takes into account the presence of possible reflections at the return-stroke wavefront and the presence of an upward-connecting leader is presented. Based on the approach proposed by Shostak et al., closed-form, iterative solutions for the current distribution along the channel, and the strike object are derived. Simulation results for the magnetic fields are compared with experimental waveforms associated wit

We present in this paper experimental results obtained at the International Center for Lightning Research and Testing (ICLRT), Camp Blanding, Florida, where currents induced by triggered and natural lightning events were measured at one end of a shielded buried cable, both in the cable shield and in the inner conductor. The horizontal magnetic field was also measured. For the natural lightning events, the recorded waveforms are correlated with the data obtained by the U.S. National Lightning Detection Netwo

This paper presents an optimization of a virtual cathode oscillator (Vircator) with axial extraction using a novel evolutionary algorithm (EA) thought to reduce the number of evaluations. The EA was tested on a Vircator optimization with two objective func ...

By using the electromagnetic time reversal (EMTR) theory, the paper studies its properties in order to derive a new fault location method to be used in power networks. It is shown that, in the reversed-time stage, the current signal observed at the true fa ...

The ionosphere can be perturbed by solar and geomagnetic activity, earthquakes, thunderstorms, etc. In particular, electromagnetic pulses produced by thunderstorms can generate wave structures in the ionospheric plasma, which are known as atmospheric gravi ...

In this work, we present a novel technique to locate partial discharge (PD) sources based on the concept of time reversal. The localization of the PD sources is of interest for numerous applications, including the monitoring of power transformers, Gas Insu ...

In this paper, a new representation for the lightning channel base current is proposed in terms of the so-called Prony series, obtained by means of a modified time-domain variant of the well-known vector fitting technique. This method allows both to reprod ...

Vertical electric field waveforms of leader-return stroke sequences measured 500 m and 30 m from rocket-triggered lightning are presented. The 500-m data were recorded during the boreal summer of 1986, the 30-m data during the summer of 1991, both at the NASA Kennedy Space Center, Florida. The 40 leader-return stroke field waveforms at 500 m and the 8 waveforms at 30 m all appear as asymmetrical V-shaped pulses, the bottom of the V being associated with the transition from the leader to the return stroke. A

The article provides a new channel-based current function, which aims at faithfully reproducing the salient parameters of lightning currents. All the model parameters can be set in a fully analytical way, guaranteeing the possibility of changing them (acco ...

Electromagnetic time reversal (EMTR) has emerged as a promising technique to locate disturbances in power grids, thanks to its location accuracy and robustness against parameters uncertainties. Furthermore, in a reflective medium, like the one of a power n ...

We present a study focused on pulses superimposed on the initial continuous current of upward negative discharges. The study is based on experimental data consisting of correlated lightning current waveforms recorded at the instrumented Santis Tower in Swi ...

Interest in exploring the meteorological conditions favoring upward lightning from tall man-made structures has grown in recent years, largely due to the worldwide expansion of wind energy. To this end, instrumented towers existing around the world are the ...

The presence of an elevated strike object markedly affects both the measured lightning return stroke current and the radiated electromagnetic fields. The MTL and the TCS lightning return stroke models have been extended to take into account the presence of elevated strike objects. In this paper, we compare theoretical results obtained using these two models with a set of simultaneously recorded data consisting of the current measured at the top of the Peissenberg tower and the associated electric and magnet

Time reversal exploits the invariance of electromagnetic wave propagation in reciprocal and lossless media to localize radiating sources. Time-reversed measurements are back-propagated in a simulated domain and converge to the unknown source location. The ...

Farhad Rachidi-Haeri

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Lightning electromagnetic radiation over a stratified conducting ground: Formulation and numerical evaluation of the electromagnetic fields

Protection Strategy against IEMI for Wireless Communication Infrastructures

Validity of Simplified Approaches for the Evaluation of Lightning Electromagnetic Fields above a Horizontally Stratified Ground

Graded-permittivity polymer nanocomposites as superior dielectrics

Application of electromagnetic time reversal for online locating partial discharges in power networks

Fault Location in Multi-Conductor Transmission Lines Using Electromagnetic Time Reversal: The Extended Bounded Phase Property

Radiated Fields From Lightning Strikes to Tall Structures: Effect of Upward-Connecting Leader and Reflections at the Return Stroke Wavefront

Measurement of lightning-induced currents in an experimental coaxial buried cable

Optimization of a Vircator using a novel evolutionary algorithm designed to reducing the number of evaluations

Electromagnetic Time Reversal Applied to Fault Location: On the Properties of Back-Injected Signals

Ionospheric Variations Induced by Thunderstorms in the Central Region of Argentina during the RELAMPAGO–CACTI Campaign

Partial Discharge Localization Using Time Reversal: Application to Power Transformers

Prony Series Representation for the Lightning Channel Base Current

Characterization of vertical electric fields 500 m and 30 m from triggered lightning

A New Channel-Base Lightning Current Formula With Analytically Adjustable Parameters

A Full-Scale Experimental Validation of Electromagnetic Time Reversal Applied to Locate Disturbances in Overhead Power Distribution Lines

Fast Initial Continuous Current Pulses vs Return Stroke Pulses in Tower-initiated Lightning

Meteorological Aspects of Self-Initiated Upward Lightning at the Santis Tower (Switzerland)

Extension of two return stroke models to consider the influence of elevated strike objects on the lightning return stroke current and the radiated electromagnetic field: comparison with experimental results

Spatiotemporal energy‐density distribution of time‐reversed electromagnetic fields