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Ali, Mohammod

Publications and source records attributed to Ali, Mohammod.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Simulation Studies of Electromagnetic Energy Absorption by Hydride Materials

This paper investigates the key parameters that contribute to electromagnetic (EM) energy absorption and heating of hydride materials which could be used to release hydrogen for use as a fuel. Our simulation study using COMSOL focuses on EM energy absorption and resulting temperature rise in a thin circular slab of hydride material using resonant dipole and loop antennas. Presented results delineate the effects of conductivity, relative permeability, antenna type and slab size on temperature rise when the distance and amount of RF power are kept fixed.

Brown, Michael A.↗
DOE OSTI2023

A Reconfigurable Planar Capacitor Sensor for Thru the Jacket Dielectric Constant Measurement of Cable Insulation

Planar capacitor sensors have been proposed to measure the aging-related dielectric constant variation of the jacket or insulation materials of cables. Although capacitor sensors have been used to monitor the aging of cable insulation by removing the jacket, through the jacket measurement of cable insulation dielectric constant variation is difficult because once the sensor is placed on the jacket it would either measure the aging of the jacket or that of the jacket and insulation together. A reconfigurable sensor along with innovative cable-specific models could be used to determine the jacket and insulation aging using the same sensor. For the proposed novel reconfigurable sensor, the electric field penetration depth is changed by activating and deactivating PIN diode switches. In one instance, the sensor measures the dielectric constant variation of the jacket, while in the next, it measures the dielectric constant variation of both the jacket and the insulation. Here, by leveraging previously developed capacitance estimation models from large-scale finite element simulations for a specific cable, these two sets of measurement data are used to evaluate the aging-related dielectric constant variation of the insulation. Experimental data from aged cable specimens are presented to demonstrate the operation of the sensor.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Miniature Crack or Damage Detection on Cable Insulation and Jacket Using Conformal Surface Wave Reflectometry

This letter introduces the study and application of a conformal surface wave launcher array to detect miniature insulation and/or jacket damage on unshielded cables. Here simulation and experimental results are presented that demonstrate that with the proposed concept very small instances of damage at various distances along power cables can be detected. Effects of damage detection feasibility in the presence of other cables in proximity and for cables containing semiconducting screen are also presented.

42 ENGINEERING↗
DOE OSTI2022

Effect of Semiconducting Layer on Cable Insulation Damage Detection Using Surface Wave Reflectometry

This paper presents a study of the effect of the semiconducting layer present in medium and high voltage cables on surface wave propagation and its feasibility in detecting insulation damage on cables. Simulation studies were conducted using Ansys High Frequency Structure Simulator (HFSS). It was observed that attenuation increased with thicker semiconducting layer and higher conductivity of the layer. For instance, on a 24.4 mm diameter power cable, the electric field strength associated with a 1 GHz surface wave declines with distance and fades away after 30 m when a 2 mm thick semiconducting layer is present. More results as a function of semiconducting layer thickness, material conductivity and permittivity, distance of a damaged section, etc. will be presented.

reflectometry, unshielded power cable, semiconduct↗
DOE OSTI2022

Surface Wave Based Non-conductor-contact Reflectometry Method for Insulation and Jacket Damage Detection in Multi-Conductor Cables

This paper presents a non-conductor-contact surface wave reflectometry technique to locate insulation and jacket damage on multi-conductor cables at a distant location from the sensor. Simulation studies were conducted using Ansys high frequency structure simulator (HFSS). A GHz range surface wave launcher was employed such that maximum surface wave energies were confined in the insulation layer while minimizing attenuation. The wave launcher can potentially be mounted on the outer surface of live cables or cable conduits and requires no physical connection to the conductors. Multiple simulations involving a 4 GHz wave launcher and a three-conductor cable with an 8 mm outer diameter were carried out demonstrating the efficacy of the proposed method. Water leak and different types of insulation/jacket damage were simulated and detected.

reflectometry, multi-conductor cable, frequency do↗
DOE OSTI2022

Non-Conductor-Contact Surface Wave Reflectometry for Cable Insulation Damage Detection

Here, this paper presents a non-conductor-contact surface wave-based reflectometry technique to detect and locate missing or damaged insulation and/or jacket of electrical cables. The described sensor may be uniquely and practically implemented on live cables as a non-destructive evaluation (NDE) method since it may be applied to the outer insulation/jacket of a cable and requires no direct contact to the conductor. The innovation lies in a high-frequency surface wave launcher that can introduce broadband signals in the GHz frequencies that insure maximum electromagnetic (EM) energy localization within the insulation and/or jacket material. By further processing the reflection data in the frequency domain, the location and severity of insulation damage is detected. Simulated results of thin, thick, short, and long cables show the results expected from small, medium, and large damage regions. For example, the detection of 40 mm-long damage region at 40 m distance on a 50 m long cable (2.44 cm diameter) is demonstrated. Experimental results are presented that validate simulation findings.

Non Destructive Evaluation↗
DOE OSTI2021

Full-Wave and Circuit-Based Simulations of Cable Insulation Aging/Damage Using Time-Frequency Domain Reflectometry

This paper presents a combined full-wave and circuit-based simulation study to investigate the important topic of cable insulation aging and physical damage. The analysis employs the time-frequency domain reflectometry (TFDR) technique that combines the advantages of both time domain reflectometry (TDR) and frequency domain reflectometry (FDR) for improved location identification and feature resolution. Coaxial cable sections with a location containing insulation aging or physical damage are simulated using Ansys High Frequency Structure Simulator (HFSS). Simulated scattering (S) parameters are then imported into the Advanced Design System (ADS) solver for time domain simulation where a Gaussian windowed chirp signal or ‘chirplet’ is launched. Finally, continuous wavelet transform (CWT) is applied in MATLAB to perform time-frequency analysis of the reflected waveforms. The results reveal that a small change in the relative permittivity of the insulation or the presence of a small point of physical damage on the insulation is reflected as a considerable change in the CWT magnitude demonstrating the efficacy of the method.

cable aging, Non Destructive Examination, time-fre↗