Electronic Theses and Dissertations

Identifier

4828

Date

2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Electrical and Computer Engr

Concentration

Power Systems

Committee Chair

Mohd. Hasan Ali

Committee Member

Russel Deaton

Committee Member

John Hochstein

Committee Member

Firouzeh Sabri

Abstract

Solar storms lead to geomagnetic disturbances (GMDs) which, in turn, drive geomagnetically induced currents (GICs) along transmission lines and through the grounded neutral of transformers. GICs cause half-cycle saturation in power transformers and increase their reactive power loss drastically. Consequently, due to a significant lack of power system reactive power support, voltage instability and potentially large-scale voltage collapse occur. Transformers may be overheated, and in the worst case, may be permanently damaged. There are few methods reported in the literature to mitigate the effects of GICs on power systems. However, those methods are extremely expensive and complex. This dissertation investigates new possible approaches, such as controlled variable grounding resistance and variable series reactance, to cope with the GICs, without interfering with the system’s normal operation and avoiding the complication associated with the existing methods. Also, this dissertation analyzes the effect GICs on distribution networks and renewable energy sources. Furthermore, an algorithm is developed in order to minimize the number of GIC blocking devices (BDs) installed and to optimize the critical placement points. The GIC study is divided into five stages; 1) Modeling of GIC and the power system, 2) Investigation of GIC effects on power transformers and harmonics, 3) GIC mitigation using controlled ground resistor, 4) GIC blocking using series variable reactance, and 5) Optimal placement and quantity minimization of GIC blocking devices. In order to demonstrate the effectiveness of the proposed new solutions, the GIC is tested on both transmission and distribution levels. Different voltage levels are considered, such as 765 KV, 500 KV, 138 KV and 25 KV. Simulation results were obtained and validated using the MATLAB/SIMULINK software. The experimental results confirm the effectiveness of the proposed solutions in blocking the GIC and limiting fault currents. Also, the performance of the proposed variable grounding resistance is better than that of the conventional fixed capacitor method. Moreover, the proposed algorithm for optimal placement of BDs works effectively.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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