This document provides an overview of the High Voltage Engineering course code EE-4123. The summary includes:
1) The course covers topics such as high voltage DC circuits, high voltage AC circuits, impulse voltages, insulation testing, HVDC transmission, corona effects, high voltage measurement and testing, and overvoltage protection.
2) The objectives of the course are to teach students about different voltage levels, applications of high voltage, electrical insulation, dielectric materials, and breakdown mechanisms in solid, liquid, and gaseous dielectrics.
3) High voltage is defined as voltages above 11kV for power systems, with classifications of up to 100kV as high voltage, 100kV-400
High voltage technology & insulation testingZeeshan Akhtar
About HV Transmission, distribution, Voltage level classification, Insulation testing.
Part 1
What is High Voltage?
Why Needed
Levels of Voltages
Application of High Voltage
Electrical Insulation and Dielectrics
Part 2
Design & Test Issues for High Voltage
Aircraft Electric Power System
Introduction to the importance of HV in electric actuator systems
Basic review of HV design
Discussion of test methods
Summary
Part 3
Voltage Testing & Partial Discharge Measurement For Power Cable Accessories
Introduction
Ac Test After Installation
Acrf Test System
Schematic Diagram Of Test System
Arallel Operation Mode Of Test System
Artial Discharge Methods & Principle.
Iscussion & Conclusion.
Generation and transmission of electric energy – voltage stress –
testing voltages-AC to DC conversion – rectifier circuits – cascaded
circuits – voltage multiplier circuits – Cockroft-Walton circuits –
voltage regulation – ripple factor – Van de-Graaff generator.
High voltage technology & insulation testingZeeshan Akhtar
About HV Transmission, distribution, Voltage level classification, Insulation testing.
Part 1
What is High Voltage?
Why Needed
Levels of Voltages
Application of High Voltage
Electrical Insulation and Dielectrics
Part 2
Design & Test Issues for High Voltage
Aircraft Electric Power System
Introduction to the importance of HV in electric actuator systems
Basic review of HV design
Discussion of test methods
Summary
Part 3
Voltage Testing & Partial Discharge Measurement For Power Cable Accessories
Introduction
Ac Test After Installation
Acrf Test System
Schematic Diagram Of Test System
Arallel Operation Mode Of Test System
Artial Discharge Methods & Principle.
Iscussion & Conclusion.
Generation and transmission of electric energy – voltage stress –
testing voltages-AC to DC conversion – rectifier circuits – cascaded
circuits – voltage multiplier circuits – Cockroft-Walton circuits –
voltage regulation – ripple factor – Van de-Graaff generator.
This PPT was crate for my seminar presentation and upload for help and providing information about FAULT ANALYSIS IN HVDC & HVAC TRANSMISSION LINE and basic idea of HVDC System
Chaper 4 Unit 1 Basics of HVDC Transmission.pptonlystu007
Introduction in High voltage dc you are
HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end. HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end.
this shows how to generate High Voltage Dc from low input Ac a complex circuit may comprise of 8 stage Voltage Multiplier followed by a Voltage Doubler Circuit
Alternating current (AC) is the main driving force in the industries and residential areas, but for the long transmission line (more than 650 KM) AC transmission is more expensive than that of direct current (DC). Technically, AC transmission line control is more complicated because of the frequency. DC transmission does not have these limitations, which has led to build long HVDC transmission lines over the last 40 years. HVDC technology made possible to transfer bulk power over long distances.
A brief description about the components of the Distribution System. The components that are described below briefly are:-
1. Capacitor Voltage Transformer (CVT)
2. Current Transformer (CT)
3. Wave Trap
4. Isolators
5. Circuit Breakers
6. Surge arrester
7. Purpose of guard ring in suspension insulators
High Voltage Direct Current Transmission System ReportNadeem Khilji
The development of HVDC (High Voltage Direct Current) transmission system dates back to the 1930s when mercury arc rectifiers were invented. Since the 1960s, HVDC transmission system is now a mature technology and has played a vital part in both long distance transmission and in the interconnection of systems. Transmitting power at high voltage and in DC form instead of AC is a new technology proven to be economic and simple in operation which is HVDC transmission. HVDC transmission systems, when installed, often form the backbone of an electric power system. They combine high reliability with a long useful life. An HVDC link avoids some of the disadvantages and limitations of AC transmission. HVDC transmission refers to that the AC power generated at a power plant is transformed into DC power before its transmission. At the inverter (receiving side), it is then transformed back into its original AC power and then supplied to each household. Such power transmission method makes it possible to transmit electric power in an economic way.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
This PPT was crate for my seminar presentation and upload for help and providing information about FAULT ANALYSIS IN HVDC & HVAC TRANSMISSION LINE and basic idea of HVDC System
Chaper 4 Unit 1 Basics of HVDC Transmission.pptonlystu007
Introduction in High voltage dc you are
HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end. HVDC stands for High Voltage Direct Current. It's a technology used for transmitting electricity over long distances with lower energy losses compared to traditional AC (Alternating Current) transmission systems. HVDC systems are often used for interconnecting power grids, transmitting power from remote renewable energy sources, and improving grid stability. They involve converting AC to DC at the sending end, transmitting the power via cables or overhead lines, and then converting it back to AC at the receiving end.
this shows how to generate High Voltage Dc from low input Ac a complex circuit may comprise of 8 stage Voltage Multiplier followed by a Voltage Doubler Circuit
Alternating current (AC) is the main driving force in the industries and residential areas, but for the long transmission line (more than 650 KM) AC transmission is more expensive than that of direct current (DC). Technically, AC transmission line control is more complicated because of the frequency. DC transmission does not have these limitations, which has led to build long HVDC transmission lines over the last 40 years. HVDC technology made possible to transfer bulk power over long distances.
A brief description about the components of the Distribution System. The components that are described below briefly are:-
1. Capacitor Voltage Transformer (CVT)
2. Current Transformer (CT)
3. Wave Trap
4. Isolators
5. Circuit Breakers
6. Surge arrester
7. Purpose of guard ring in suspension insulators
High Voltage Direct Current Transmission System ReportNadeem Khilji
The development of HVDC (High Voltage Direct Current) transmission system dates back to the 1930s when mercury arc rectifiers were invented. Since the 1960s, HVDC transmission system is now a mature technology and has played a vital part in both long distance transmission and in the interconnection of systems. Transmitting power at high voltage and in DC form instead of AC is a new technology proven to be economic and simple in operation which is HVDC transmission. HVDC transmission systems, when installed, often form the backbone of an electric power system. They combine high reliability with a long useful life. An HVDC link avoids some of the disadvantages and limitations of AC transmission. HVDC transmission refers to that the AC power generated at a power plant is transformed into DC power before its transmission. At the inverter (receiving side), it is then transformed back into its original AC power and then supplied to each household. Such power transmission method makes it possible to transmit electric power in an economic way.
Democratizing Fuzzing at Scale by Abhishek Aryaabh.arya
Presented at NUS: Fuzzing and Software Security Summer School 2024
This keynote talks about the democratization of fuzzing at scale, highlighting the collaboration between open source communities, academia, and industry to advance the field of fuzzing. It delves into the history of fuzzing, the development of scalable fuzzing platforms, and the empowerment of community-driven research. The talk will further discuss recent advancements leveraging AI/ML and offer insights into the future evolution of the fuzzing landscape.
Immunizing Image Classifiers Against Localized Adversary Attacksgerogepatton
This paper addresses the vulnerability of deep learning models, particularly convolutional neural networks
(CNN)s, to adversarial attacks and presents a proactive training technique designed to counter them. We
introduce a novel volumization algorithm, which transforms 2D images into 3D volumetric representations.
When combined with 3D convolution and deep curriculum learning optimization (CLO), itsignificantly improves
the immunity of models against localized universal attacks by up to 40%. We evaluate our proposed approach
using contemporary CNN architectures and the modified Canadian Institute for Advanced Research (CIFAR-10
and CIFAR-100) and ImageNet Large Scale Visual Recognition Challenge (ILSVRC12) datasets, showcasing
accuracy improvements over previous techniques. The results indicate that the combination of the volumetric
input and curriculum learning holds significant promise for mitigating adversarial attacks without necessitating
adversary training.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Student information management system project report ii.pdfKamal Acharya
Our project explains about the student management. This project mainly explains the various actions related to student details. This project shows some ease in adding, editing and deleting the student details. It also provides a less time consuming process for viewing, adding, editing and deleting the marks of the students.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Quality defects in TMT Bars, Possible causes and Potential Solutions.PrashantGoswami42
Maintaining high-quality standards in the production of TMT bars is crucial for ensuring structural integrity in construction. Addressing common defects through careful monitoring, standardized processes, and advanced technology can significantly improve the quality of TMT bars. Continuous training and adherence to quality control measures will also play a pivotal role in minimizing these defects.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
1. Course code : EE-4123
High Voltage Engineering
Lecture _1: Introduction to High Voltage
Engineering
Presented by
Mst. Tajmun Nahar
Lecturer, Dept. of EEE, NUBTK
2. Course outline
Course No. EEE 4113
Course Title : High Voltage Engineering
High Voltage dc : Rectifier circuits, Voltage multipliers, Van-de-graff
generator.
High Voltage ac : Cascaded transformers and Tesla coils.
Impulse Voltage : Shapes, mathematical analysis, codes and
standards, single and multistage impulse generators, tripping and
control of impulse generators.
Insulation testing, HVDC transmisson, Merits and demerits over AC
transmission
Overvolatge protection
Flexible AC Transmission systems (FACTS)
3. Course outline
Course No. EEE 4113
Course Title : High Voltage Engineering
Control of voltage and Reactive Power.
Breakdown in gas, liquid and solid dielectric materials.
Corona: Power loss calculation, Coroma formation
voltages, corona breakdown of solid, liquid and gaseous
dielectric.
High Voltage measurement and testing.
Over voltage phenomena and insulation co-ordination.
Protection against Lightning and switching surges,
basic insulation level, surge diverters and arresters.
4. Objectives
In this course you will learn the following:
What is high voltage?
Why needed
Levels of voltages
Application of High Voltage
Electrical Insulation and Dielectrics
5. What is high voltage
A mobile phone is operated from a 4V
battery. It may be destroyed if anyone
attempts to operate it from a 12V car
battery.
Therefore 12V is quite a high voltage for a
mobile phone.
6. What is high voltage
High voltage is specially referred to
electrical power system.
At Kaptai we
generate at 11kV
or 21kV
Step up
transformer is
used to rise the
voltage to 132kV
or 230kV
Long transmission line used to
carry the power to Dhaka
Step down
transformer is
used to reduce
the voltage to
33kV
Step down
transformer is
used to reduce
the voltage to
11kV
Another Step down transformer
is used to reduce the voltage
further to 400V suitable for end
user.
Domestic users get electricity at
230Volt.
11kV
230kV
230kV
33kV
11kV
400V 230V
230kV
7. What is high voltage
Below 11kV : Low voltage
11kV – 100kV : HV (high Voltage)
100kV – 400kV : VHV (Very high voltage)
400kV and above : EHV ( Extra high voltage)
UHV : Ultra high voltage
8. Levels of high voltage:
World over the levels are classified as:
LOW VOLTAGE
HIGH VOLTAGE
VERY HIGH VOLTAGE
EXTRA VOLTAGE
ULTRA HIGH Voltages
However , the exact magnitude of these levels vary from
country to country. Hence this system of technical terms for
the voltage levels is inappropriate .
In most part of the world even 440 V is considered to be
high voltage since it is dangerous for the living being.
Hence it would be more appropriate to always mention
the level of voltage being referred without any set
nomenclature .
9. Why high voltage
Basically it is required for transmission lines to be
able to transmit more power over the same line.
Equation for
power is
P= V I Cos
Dhaka
I I
I
2I
Loss in
transmission line =
I2R
New Loss
in
transmissio
n line
(2I)2R=4I2
R
Therefore we conclude that it is not wise to
increase the line current to transmit more
power over a line, keeping the voltage same.
10. Why high voltage
Basically it is required for transmission lines to be
able to transmit more power over the same line.
Equation for
power is
P= V I Cos
Kaptai Dhaka
I
I
Loss in
transmission
line = I2R,
R is the resistance
of the line.
I
Generator
I
Transformer
V
2V
Therefore we see that if the
transmission line voltage is increased it
is capable of transmitting more power
without increasing the power loss in the
line.
11. Trends in voltage growth
Ac voltage
Unfortunately it is
a very old data.
Students are
requested to
update it.
In our country the
highest operating
voltage is 400kV.
We may realize our
position related to
the global trend.
12. Trends in voltage growth
Unfortunately
HVDC transmission
has been proven to
be less attractive to
the power system
engineers.
dc voltage
In our country we
do not have any
HVDC
transmission
system so far.
13. Fields of applications of HV
• Power system engineering
• Research laboratories
• Industries
• Nuclear research, particle
accelerators
• Electrostatic precipitators
• Automobile ignition coils
• Medical applications like X-ray
machine
Interested
students may find
new areas of
application of HV
14. What we learn in
High Voltage
Engineering
• Testing of HV equipments like
power transformers, bushings,
CB, insulators, cables etc.
• Usually tests are done at a
voltage much higher than the
operating voltage.
• Generation, measurement and
control of different types of HV.
15. What we learn in
High Voltage
Engineering
• Failure mechanism of HV equipments
caused by HV stress.
• Breakdown mechanism of different types
of insulating materials ( solid, liquid, gas,
vacuum) under different types of voltages
(ac, dc, li, si).
16. Few future prospects
of HV
• For cosmopolitan cities overhead
distribution lines are not allowed any
more. HV underground cables of
compact size is the solution.
• Compact all-in-one fix-and-forget type
GIS substations are required in near
future.
• HV has some residential and industrial
applications like water treatment plant,
insect killer/repeller, exhaust air
purifier etc.
17. ac High Voltage
Time
In
ms
Voltage
In
kV
100kV
power frequency
ac voltage
?
10 ms
?
Suppose it is said that the
voltage is 100kV.
Then this peak value is
=100 X 103 X 2 volt
140kV
In high voltage engineering,
we should always be careful
about the peak value of the ac
voltage, because this is the
maximum voltage in the
system and may be responsible
for initiating breakdown or
failure.
20. VOLTAGE LEVELS
Consumer
ac power frequency :
110 V, 220 V- single phase
440 V, 3.3 kV ,6.6 kV, 11 kV-three phase (3.3 & 6.6 kV are being phased out)
Besides these levels ,the Railway Traction at 25 kV , single phase is one of the
biggest consumer of power spread at any particular stretch to 40 km of track length
Generation : Three phase synchronous generators
440 V, 3.3 kV, 6.6 kV (small generators) , 11 kV (110 & 220 MW)
21.5 kV ( 500 MW), 33 kV (1000 MW)
[limitation due to machine insulation requirement]
Distribution :
Three phase
440 V, 3.3 kV, 6.6 kV, 11 kV, 33 kV, 66 kV
With the increase in power consumption density, the power distribution
voltage levels are at rise because the power handling capacity is proportional to
the square of the voltage level.
(In Germany 440 V , 3.0 kV 6.0 kV, 10 kV, 30 kV, 60 kV)
21. ac Transmission :
110 kV, 132 kV, 220 kV, 380 - 400 kV, 500 kV, 765 - 800 kV, 1000 kV and
1150 kV exist.
Work on 1500 kV is complete.
In three phase power system, the rated voltage is always given as line to line,
rms voltage .
d.c. transmission :
dc single pole and bipolar lines : ± 100 kV to ± 500 kV
22. Advance countries like US, Canada and Japan have their single phase
ac power consumption level at 110 V .Rest of the whole world
consumes single phase ac power at 220 V .
The only advantage of 110 V single phase consumer voltage is that it is
safer over 220 V. However, the disadvantages are many.
Disadvantages :
It requires double the magnitude of current to deliver the same amount
of power as at 220 V
Hence for the same magnitude of I2R losses to limit the conductor or
the insulation temperature to 70° C (for PVC) , the resistance of the
distribution cable should be 4 times lower. Therefore, the cable cross-section
area has to be increased four folds.
Four times more copper requirement, dumped in the building walls is an
expensive venture.
Due to higher magnitude of current, higher magnetic field in the
buildings . Not good for health.
With the installation of modern inexpensive protective devices (earth
fault relays), 220 V is equally safe as 110 V
23. Rated maximum temperature of cables:
It is important to understand the current and voltage carrying
capacities of a conductor separately. While the current carrying
capability is determined by the conductivity of the conductors, directly
proportional to the area of conductor cross-section, the voltage
bearing capacity depends upon the level of insulation provided to the
conductor .
The current carrying capability in turn is determined by maximum
permissible temperature of the insulation or that of the conductor.
The real power loss, I2R and the rate of cooling determine the
temperature rise of the conductor which should not be more than the
maximum permissible temperature of the type of insulation provided
on the conductor .
Hence, not only electrical but thermal and mechanical properties of
insulation are important in power system .
24. Electrical Insulation and Dielectrics
Gaseous Dielectrics:
Atmospheric air is the cheapest and most widely used dielectric .
Other gaseous dielectrics, used as compressed gas at higher pressures
than atmospheric in power system, are Nitrogen , Sulphurhexafluoride
SF6(an electro-negative gas) and it's mixtures with CO2 and N2 . SF6 is
very widely applied for Gas Insulated Systems (GIS), Circuit Breakers
and gas filled installations i.e. sub-stations and cables. It is being now
applied for power transformers also.
Vacuum as Dielectric :
Vacuum of the order of 10-5 Torr and lower provides an excellent
electrical insulation. Vacuum technology developed and applied for
circuit breakers in the last three decades is phenomenon .
25. Liquid Dielectrics:
Organic liquids, the mineral insulating oils and
impregnating compounds, natural and synthetic, of
required physical, chemical and electrical properties are
used very widely in transformers, capacitors, cables and
circuit breakers.
Ex: Polychlorinated biphenyls (PCBs)
Solid Dielectrics:
Very large in number .
Most widely used are : XLPE, PVC, ceramics, glass,
rubber, resins, reinforced plastics, polypropylene,
impregnated paper, wood, cotton, mica, pressboards,
Bakelite, Perspex, Ebonite, Teflon, etc.
Introduction of nano materials are in offing.
26. Recap
In this lecture you have learnt the following:
Levels of voltages for power consumption, distribution and transmission.
Electrical Insulation and Dielectrics in the power system.
Congratulations, you have finished Lecture 1.
A gas-insulated substation (GIS) uses a superior dielectric gas, SF6, at moderate pressure for phase-tophase and phase-to-ground insulation. The high voltage conductors, circuit breaker interrupters, switches, current transformers, and voltage transformers are in SF6 gas inside grounded metal enclosures. The atmospheric air insulation used in a conventional, air-insulated substation (AIS) requires meters of air insulation to do what SF6 can do in centimeters.
GIS can therefore be smaller than AIS by up to a factor of 10. A GIS is mostly used where space is expensive or not available. In a GIS the active parts are protected from the deterioration from exposure to atmospheric air, moisture, contamination, etc.
As a result, GIS is more reliable and requires less maintenance than AIS
Pentaerythritol tetra fatty acid natural and synthetic esters have emerged as an increasingly common mineral oil alternative
Silicone or fluorocarbon-based oils,
Polychlorinated biphenyls (PCBs)