This document provides an overview of a lecture on high voltage engineering. It discusses various elements of high voltage power systems including transmission networks, insulation materials, generation of electricity using Faraday's law, substations, power lines, cables, transformers, circuit breakers, fuses, and surge arresters. The lecture covers breakdown mechanisms of gaseous dielectrics, materials used for insulation like air and sulfur hexafluoride gas, and components of high voltage systems like generators, transmission towers, conductors, and insulators.

1. EEE 465: High Voltage Engineering
Instructor: Nabil Shovon Ashraf, Ph.D.
Office Room to Contact: SAC 1047
Lecture 1
 In this introductory lecture, you will learn about
all the integral elements of a typical high voltage power
system transmission and distribution network
 For high voltage transmission and distribution power
network, proper insulation from breakdown of gaseous,
liquid and solid materials is unavoidable. Hence the
lecture will initiate the comprehensive study of
breakdown mechanism of first and foremost gaseous
dielectric and continue in lecture 2.

2. EEE 465: High Voltage Engineering
Figure 1: Schematic representation of a power network
Pay particular attention to the above power system
complete network that you would like to be
knowledgeable of. Substation and distribution stages
are arranged top-down and their respective step-up
and step-down voltage rating are also shown

3. EEE 465: High Voltage Engineering
To prevent current leakage or flashover, selection of proper
insulating material must be on the power system designer’s forte
 Air at atmospheric pressure has been an obvious choice as
an insulating material. Air can easily withstand 20 kV/cm. The
tripping point for flashover initiation is 30 kV/cm for air
 Sulphur hexaflouride gas (SF6) is used in metal clad gas
insulated system (GIS)

4. EEE 465: High Voltage Engineering
Figure: Principle of the generation of electricity, using Faraday’s Law
Generation of Electricity employed by major energy sources and
energy conversion obeys Faraday’s Law.
In the above figure, water, steam or wind energy causes rotation
of the turbine and generator rotor. When the magnetic poles on
the rotor move past the stator, electricity is induced in the stator
windings, producing three phase power

5. EEE 465: High Voltage Engineering
Viewgraphs of (1) hydro and fossil-fuel power stations & (2)
conventional and pebble bed modular reactors (PBMR)
Top figure: hydro-electric power station(left) and coal-fired power station (right)
Bottom figure: conventional pressurized water reactor (PWR)(left) and PBMR(right)

6. EEE 465: High Voltage Engineering
Generators: The rating of a typical large generator is between
500 and 900 MVA. The generator voltage is typically 24 kV with
an estimate of full load current 10-20 kA. The losses associated
with these high currents necessitate water-cooling of the stator
winding and the use of air-cooled bus ducts for the connections
between the generator and the generator transformer
(a) (b)
Figure: (a) Generator, stator windings and (b) detail of the winding insulation in the
stator slot

7. EEE 465: High Voltage Engineering
Substations: The substations are the nodes in the power system
where several lines and transformers are connected together.
Transmission substations serve as the interconnection nodes on
the main power transmission system
Figure: Single Line diagram of typical 132 kV substation

8. EEE 465: High Voltage Engineering
Substations: Conventional outdoor and indoor gas-insulated
substation (GIS) impart an alternative to efficient power
transmission and distribution. In GIS, compressed SF6 gas with
exceptional insulating properties facilitates the design of very
compact substations
Figure: Typical 132 KV substation. (a) outdoor and (b) indoor GIS

9. EEE 465: High Voltage Engineering
Power Lines and Cables: High voltage feeders in the form of
overhead power lines or underground cables interconnect high
voltage substations
(a) (b) (c)
Figure: Typical overhead high voltage lines: (a) 400 kV suspension tower
and (b) 400 kV double circuit strain tower (c) 22 kV woodpole distribution
line with fused cable connection

10. EEE 465: High Voltage Engineering
Power Lines: towers, conductors, metal ware and insulators.
Towers consist of steel lattice structures or wood or steel poles.
Conductors are aluminium core steel reinforced (ACSR). Where
the conductors are supported at the towers, insulators are used.
(a) (b) (c)
Figure: Examples of conductor power line components: (a) Detail of ACSR
conductor, (b) Pistol grip connection of a conductor to a strain insulator &
(c) Wind vibration dampers

11. EEE 465: High Voltage Engineering
Power Line Insulators: Traditionally the ceramic materials glass
and porcelain were the main insulator materials but now-a-days
various non ceramic insulator materials are available.
Figure: Insulator types

12. EEE 465: High Voltage Engineering
Underground power cables: Underground cables are buried in
trenches and correct installation is important from a safety point
of view. Heat dissipation is also important factor.
Figure: Various types of cable constructions and terminations

13. EEE 465: High Voltage Engineering
Bushings: It is sometimes required to take a high voltage
conductor through a wall or the tank of a transformer. In such
cases a bushing is required to support the high voltage
conductor and to provide the necessary insulation in the axial
and radial directions
Figure: (a) Normally straight
through epoxy line bushing and
(b) Capacitively graded paper and
oil bushing
Figure: Example of typical graded bushing

14. EEE 465: High Voltage Engineering
Power transformers: The power transformer transforms voltage
from one level to another and must be able to handle the full
power to be transformed, i.e., the copper windings must be able
to withstand the full load current and short term overcurrents and
the magnetic circuit and insulation must be able to cope with the
rated system voltage, allowing for overvoltages.
Figure: Power transformers

15. EEE 465: High Voltage Engineering
Instrument transformers: Current transformers (CT) and voltage
transformers (VT): In an operating power system, it is necessary
to know the system voltages and currents as accurately as
possible. Current transformers (CT’s), voltage transformers
(VT’s) and capacitive voltage transfomers (CVT’s) are used for
this purpose. A VT is a high impedance shunt device, similar to
normal power transformer whereas a CT is a low impedance
device in series with the power line circuit current

16. EEE 465: High Voltage Engineering
Voltage transformer: Voltage transformers are typically power
transformers with a rating of 110 kV: 110 V, a ratio of 1000:1 for
measuring, metering and protection purposes
Capacitive voltage transformers: These dividers divide the actual
high voltage level to a lower level before using a conventional
voltage transformer
Figure: (Left) a capacitive voltage transfor-mer

17. EEE 465: High Voltage Engineering
Line Traps: Power lines are provisioned to carry high frequency
signal 300 kHz in power line carrier applications. The high
voltage capacitors of the CVTs are used as coupling capacitors
and air cored inductors (line traps in this illustration) as part of
the filter circuits

18. EEE 465: High Voltage Engineering
Circuit breakers and fuses: The duty of circuit breakers and
fuses is to rapidly interrupt fault current.
Figure: Schematic representation of the interruption of the fault current by a
circuit breaker and associated protection relays

19. EEE 465: High Voltage Engineering
Air blast circuit breakers: In air blast circuit breakers,
compressed air at pressures as high as 1 Mpa is used to blow
out the arc as the contacts are separated. While the contacts are
open, full system voltage appears across the contact and the
required insulation is provided by the pressurized gas.

20. EEE 465: High Voltage Engineering
SF6 circuit breakers: In SF6 circuit breakers, the insulation and
arc quenching tasks are both performed by SF6 gas. SF6 is an
electronegative gas with superior insulation characteristics. The
gas also has the ability to assist arc quenching, due to its
thermal and electronegative properties. The circuit breakers are
usually spring operated.

21. EEE 465: High Voltage Engineering
Fuses are mainly used up to voltage 22 kV. High rupturing
capacity fuse elements are used. The fuses are often pole-mounted
as drop-out fuse link assemblies.

22. EEE 465: High Voltage Engineering
Isolators: When working on apparatus, such as circuit breakers,
it is necessary to disconnect the apparatus from the live system
and to apply visual earths. For this purpose isolators and
earthing switches are provided. Isolators are different from
circuit breakers in that they should be operated under no load
current and they have no arc quenching capacity.

23. EEE 465: High Voltage Engineering
Surge arresters and lightning arresters: The power system is
subject to transient overvoltages due to lightning and switching.
Lightning arresters, also called surge diverters, are applied to
limit the peak voltages to values that cannot damage the
equipment to limit overvoltages. Lightning arresters are usually
fitted with grading rings to ensure a more uniform voltage
distribution over the height of the arrester.