High Voltage Engineering

(Advanced)

Arsalan A RahimUniversity of Engineering & Technology

Lahore, Pakistan

Lecture # 1

Basics of High Voltage

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

Reference Books• Advances in High Voltage Engineering (IET) Edited by

A.Haddad & D.Warne • High Voltage Engineering by C.L. Wadhwa• High Voltage Engineering by M.S.Naidu (4th Edition)

All books available for 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

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.

No concept of a complete Insulator – Even a good Insulator can conduct under High Voltages

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 Breakdownconfined locally to a

part of an Insulator(Partial Breakdown)

Global Breakdowncomplete rupture or failure of insulator

properties(Electrical Breakdown)

Corona:• Stable Partial Breakdown (PB) in

Gaseous Di-electrics

Partial Electrical Breakdown (discharge)

Streamer:Extension of Corona at Distance

Shower of Discharge (Streamer Corona)

• Types: Audible & Visible Corona

Example: Discharge of Cloud (Lightning)

Aurora:• Luminous phenomenon consisting of streamers

or Arches of Light at Polar Regions• Explained under “Faraday’s Glow”

• Aurora Australis (Southern Hemisphere)

• Aurora Borealis (Northern Hemisphere)

• Atoms in Ionosphere stuck by High Energy Electrons Coming from Sun (cosmic Radiation)

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 Field Intensity

• 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

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 + Uptil Article 2.3.1 from Chapter 2

of IEEE Press Book (Ravindra Book)

and

Chapter 1 of Kuffel Book