Lecture 1 - Basics of High Voltage Engineering

High Voltage Engineering Lecture # 1

Basics of High Voltage

Arsalan A Rahim University of Engineering & Technology Lahore, Pakistan

Course Books • High Voltage and Electrical Insulation Engineering (June 2011 Edition) by Ravindra & Wolfgang (IEEE Press) • High Voltage Engineering Fundamentals (2nd Edition) by E.Kuffel, W.S.Zaengl, J.Kuffel • High Voltage Engineering by C.L. Wadhwa • High Voltage Engineering by M.S.Naidu (4th Edition)

Reference Books • Advances in High Voltage Engineering (IET) Edited by A.Haddad & D.Warne All books available for pdf Download at ep.nge.com.pk (Course Page)

Why High Voltage (Engineering)? It’s the knowledge of the behavior of dielectrics (insulator) — electrical insulation when subjected to high voltage No concept of a complete Insulator – Even a good Insulator can conduct under High Voltages

Result is to minimize the volume of the electrical insulation requirements and trouble-free life of high voltage apparatus. A totally different Domain (Engineering) when High Voltage are applied. Stray Capacitances & Inductances come into play.

HVAC & HVDC Transmission • Flexible AC Transmission System (FACTS) based on High Power GTO and IGBT’s • Examples of FACTS system include Fixed Series Capacitors (FSC) Thyristor Controlled Series Capacitor (TCSC) and STATCOMS • Link for FACTS devices http://www.siemens.com.pk/pt_ac.html • List of HVDC Projects http://en.wikipedia.org/wiki/List_of_HVDC_projects

Basic Definitions to Start With • • • • • • • • • •

Electron Proton Ion Ionization Electric Charge Space Charge Volume Charge Density ρv Electric Discharge Electric & Magnetic Field Electromagnetics

Di-Electric & Electric Material • What the difference between these ? • Electric Material – capable of developing (conducting) electric charge or current • Di-Electric Material – not capable of developing (conducting) electric charge or current but admits electrostatic and magnetic lines of force • Di-Electric Material Properties– Relative Permittivity εr , Type of Material & Amplitude of Voltage Applied

Electrical Breakdown • Failure of Electrical Insulation Properties (flow of current) of an Insulator or Di-electric

Local Breakdown

Global Breakdown

confined locally to a part of an Insulator

complete rupture or failure of insulator properties

(Partial Breakdown)

(Electrical Breakdown)

Corona: Partial Electrical Breakdown (discharge) • Stable Partial Breakdown (PB) in Gaseous Di-electrics • Types: Audible & Visible Corona

Streamer: Extension of Corona at Distance Shower of Discharge (Streamer Corona) Example: Discharge of Cloud (Lightning)

Aurora: • Luminous phenomenon consisting of streamers or Arches of Light at Polar Regions • Explained under “Faraday’s Glow” • Atoms in Ionosphere stuck by High Energy Electrons Coming from Sun (cosmic Radiation) • Aurora Australis (Southern Hemisphere) • Aurora Borealis (Northern Hemisphere)

Aurora:

Di-electric Property: Capacitance • Is the field between the plates of a Capacitor Uniform? • Permittivity of a Di-electric is Constant ?

Stray Capacitance • How to minimize it?

Electric Field • Electric Charge is considered static when there is no movement of charge • Field produced by Static charge or Direct Voltage is known as Electro-static field • Field produced by power frequency Alternating voltage is known as quasi-stationary Electric field • Electric Field Intensity

Dielectric Breakdown depends on • Composition of dielectric material, presence of impurities imperfections in the dielectric • Pressure • Humidity • Temperature • Electric field configuration (shape of the electrodes, their size and gap distance) • Electrode material • Duration • Magnitude and the waveform of the applied voltage

Today’s Text Covered from Chapter 1 of IEEE Press Book (Ravindra Book)

and Chapter 1 of Kuffel Book