Dissertation Announcement for Mojtaba Rostaghi — 10/14/2020 at 1:00 PM

September 24, 2020

Dear Faculty, Graduate and Undergraduate Students,

You are cordially invited to my Ph.D. dissertation defense.

Candidate: Mojtaba Rostaghi

Degree: Doctor of Philosophy, Electrical and Computer Engineering

Dissertation Title: Non-conventional sensors for measuring partial discharge under DC stress

Date and time: Wednesday, October 14, 2020, 01:00 PM to 3:00 PM

Venue: On-line Meeting – Details below


Dr. Chanyeop Park
Assistant Professor of Electrical and Computer Engineering
(Major Professor)

Dr. Masoud Karimi-Ghartemani
Associate Professor of Electrical and Computer Engineering
(Committee Member)

Dr. J. Patrick Donohoe
Professor of Electrical and Computer Engineering
(Committee Member)

Dr. Mehmet Kurum
Assistant Professor of Electrical and Computer Engineering
(Committee Member)

Abstract: “Partial discharge (PD) is a micro discharge that occurs in defected regions within the insulating media. These discharges are the main culprits that cause dielectric material aging. PD measurement is widely used for the assessment of insulating materials including solids, liquids, and gases for power applications. There are a variety of methods and sensors available for measuring PD that are sensitive to specific characteristics and operable over a wide range of frequencies. The goal of most PD measurement techniques is providing patterns that enable PD interpretation much easier for users. For example, in the case of AC applications, the phase-resolved partial discharge technique provides clearly identifiable patterns that are used for distinguishing various types of PD’s. However, the establishment of meaningful patterns for various types of PD’s in DC systems requires more sensitive and accurate measurements of individual PD pulses with noise rejection functionality due to the lack of the phase-resolved information.

Investigating of the transient phenomena such as individual PD pulses requires well-designed circuits with sufficiently large bandwidths. Waveshapes can be easily disturbed by background noises and deformed by frequency response of measuring circuits and data acquisition systems (DAQ). Noises are unwanted disturbances that could be suppressed by suitable filters or mathematical methods. Measurement circuits and DAQ systems consist of the transmission lines, sensors, connecting cables, connectors, DAQ hardware, and oscilloscopes. Therefore, matching the impedances of all components guarantees a reflection-free path for traveling signals and addresses most of the challenges relevant to transient phenomenon measurement.

In this dissertation, we proposed and designed an appropriate testbed equipped by high bandwidth transmission line and electromagnetic field sensors which is suitable for investigation of PD under DC stresses. We comprehensively used finite element analysis simulations through the COMSOL Multiphysics to find the real dimension and evaluate the frequency response of designed testbed, transmission line, and electromagnetic sensors. Furthermore, based on the new testbed, DC PD measurement was performed through the conventional and non-conventional sensors. In addition, an outstanding method for classification of DC PD defect was proposed regarding the characteristics of individual PD pulses.”

Thank you,

Mojtaba Rostaghi


Online Meeting Details:

Wednesday, Oct 14, 2020 1:00 pm | 2 hours | (UTC-05:00) Central Time (US & Canada)
Meeting number: 120 820 6355
Password: 1234

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