JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD

Prerequisite

Electromagnetic Fields

Course Objectives:

• To know the phenomena of electric fields and field stress control around high voltage systems
• To understand the mechanism involved in non-destructive insulation and testing as well as over voltages in power systems.

Course Outcomes

After the completion of this course, the student will be able to

• select insulation materials in practice with the knowledge of requirements and compromises
• know different mechanisms that may lead to dielectric breakdown
• compute estimates of the electrical breakdown voltage from given models
• identify the fundamental physical mechanism behind given relaxation/permittivity curves

UNIT - I

Introduction: Electric stress and Electric strength, Breakdown mechanisms, Estimation and control of electric stress, Field sketching, high voltage measurements.

UNIT - II

Mechanisms Of Spark Breakdown In Gases: Basic process in gas breakdown-Primary process - secondary process, Mechanisms of breakdown - Townsend Mechanism, breakdown in electronegative gases, Time lags of spark breakdown, Breakdown Characteristics In Gases: Phenomenon in uniform fields, Phenomenon in non uniform fields, Surface flashover, dielectric recovery.

UNIT - III

Electrical Properties of High Vacuum: Pre-breakdown conduction, Factors affecting the breakdown voltage, Breakdown hypotheses, Vacuum breakdown criterion, Flashover across solid insulators. The Electrical Conduction and Strength of Pure Liquids: pure liquids, purification, test cells, natural conduction, induced conduction, process of conduction, breakdown phenomenon and electric strength of liquids, breakdown process.

UNIT - IV

Breakdown of Commercial Liquid and Liquid-Solid Dielectrics: breakdown due to gaseous inclusions, breakdown due to liquid globules, breakdown due to solid particles, deterioration due to internal discharges, electrochemical deterioration. Intrinsic and Related Forms of Breakdown in Solids: definition of intrinsic strength, theories of intrinsic strength, its measurements, comparison of theory with experiment, current problems in measurement of intrinsic strength.

UNIT - V

Thermal Breakdown Chemical and Electro Chemical Deterioration: thermal breakdown, chemical deterioration-oxidation, chemical stability, hydrolysis, leaching of chemically active substances, incompatibility of materials, electrochemical deterioration-nature, electrochemical effects in insulation with and without moisture.

TEXT BOOKS:

• 1. “High Voltage Engineering”, by M. S. Naidu, V. Kamaraju, Tata McGraw Hill Education, 2009.
• 2. “High Voltage Engineering”, by Farouk A.M. Rizk, Giao N. Trinh CRC Press Taylors, and Francis group.
• 3. “High Voltage and Electrical Insulation Engineering”, by Ravindra Arora and Wolfgang Mosch John Wiley & Sons, Inc.

REFERENCES:

• 1. “High Voltage Engineering Fundamentals”, by John Kuffel, Peter Kuffel second edition Newness, 2000.
• 2. “An introduction to high voltage engineering”, by Subir Ray, second edition PHI learning Pvt. Ltd., 2013.