ELECTRICAL POWER

1. ELECTRICAL POWER – 1
LEARNING OUTCOMES
After undergoing the subject, students will be able to:
 Distinguish and select suitable resource of energy required for a particular area and
environment
 Calculate effective cost generation
 Select suitable supporting structure, insulators, conductors and other accessories for
transmission lines and distribution lines
 Prepare layout plan for HT and LT lines/distribution system
 Prepare estimate for HT and LT (OH and underground cables) lines
 Operate and maintain indoor and outdoor substations
 Use various methods for improvement of power factor
CHAPTER-1
POWER GENERATION
1.1 Main resources of energy, conventional and non-conventional
Energy is one of the most important component of economic infrastructure. It is the basic
input required to sustain economic growth. There is direct relation between the level of economic
development and per capita energy consumption. Simply speaking more developed a country,
higher is the per capita consumption of energy and vice-versa. India’s per capita consumption of
energy is only one eighth of global average. This indicates that our country has low rate of per
capita consumption of energy as compared to developed countries.
Two Main Sources of Energy:
The sources of energy are of following types:
1. Conventional Sources of Energy:

2. These sources of energy are also called non renewable sources. These sources of energy are in
limited quantity except hydro-electric power.
2. Non-Conventional Sources of Energy:
Besides conventional sources of energy there are non-conventional sources of energy. These are
also called renewable sources of energy. Examples are Bio energy, solar energy, wind energy
and tidal energy. Govt. of India has established a separate department under the Ministry of
Energy called as the Department of Non-conventional Energy Sources for effective exploitation
of non-conventional energy.
1.2 Different types of power stations, thermal, hydro, gas, diesel and nuclear power
stations. Flow diagrams and details of their operation, comparison of the generating
stations on the basis of running cost, site, starting, maintenance etc.
Modern society cannot function without a reliable power system. We need energy for all our
activities, and we utilize this energy in various forms such as thermal, electrical, mechanical etc.
However, electrical energy can be considered as the most important of these since we can
generate, transmit, distribute, convert and utilize it efficiently and economically.
The generation aspect is at the foremost of the chain and it is realized with the help of power
plants. A set of equipments utilized to produce electrical power in large quantities (usually
hundreds - thousands of MW) is called a generating station or a power plant. Such a power plant
will convert one form of energy (nuclear, thermal, hydro, solar etc.) to electrical energy.
On the basis of this form of energy conversion, power plants are broadly classified as follows:
1. Thermal Power Station (Steam power plant)
2. Hydroelectric Power Station
3. Nuclear Power Station
There are other plants too, such as:
 Solar Power Plant
 Wind Power Plant
 Tidal Power Plant
 Geothermal Power Plant
 Diesel Power Plant
However, they represent only a small part of the global scheme in terms of capacity and
utilization.

3. Each of these power plants has its own set of features, requirements, advantages and
disadvantages. They can be compared on the basis of several parameters. The salient
points are given below:
Thermal Power Station
Principle of operation: It works on Modified Rankine Cycle.

4. Location: It is located at a site where coal, water and transportation facilities are available easily. It is
located near load centers.
Requirement of Space: Need a large space due to coal storage, turbine, boiler and other auxiliaries.
Efficiency: Overall efficiency is least compared to other plants. (30%-32%)
Fuel Used: Coal (mostly) or oil.
Cost of Fuel: High. Coal is heavy and has to be transported to the plant.
Hydroelectric Power Plant
Principle of operation: Potential energy of water is converted to Kinetic energy and used to rotate a
turbine.
Location: Located where a large amount of water can be collected easily in a reservoir by constructing a
dam. Usually in a hilly area at high altitude.
Requirement of Space: Very large space required. A dam is huge.
Maintenance Costs: Low.
Running Costs: Zero, because no fuel is needed.
Nuclear Power Plant
Principle of operation: Thermonuclear fission.
Requirement of Space: Requires minimum space compared to other plants of the same
capacity.
Efficiency: Higher than Thermal Power Station. About 55%
Start-up Power: 7% to 10% of unit capacity.
Starting time: Less than TPS. Can be started easily.
Standby Losses: Less.
1.3 Importance of non-conventional sources of energy in the present scenario. Brief
details of solar energy, bio-energy, wind energy.
Can you imagine a car that runs on water? Or one that runs on the power of
the Sun? Well, the truth is you might have to get used to such wacky
ideas. The planet is rapidly running out of conventional fuels, and non-
conventional sources of energy are becoming our future. And in order to
operate them let us learn more about non-conventional sources of energy.

5. Solar Energy
Solar energy is harnessed by converting solar energy directly into electrical energy in solar
plants. Photosynthesis process carries out this process of conversion of solar energy. In
photosynthesis, green plants absorb solar energy and convert it into chemical energy. Solar
energy is an essential energy of all non-conventional sources but its usage amount is very less. It
is the most important non-conventional source of energy and it gives non-polluting environment-
friendly output and is available in abundant.
Biomass energy
Biomass is the organic matter that originates from plants, animals, wood, sewage. These
substances burn to produce heat energy which then generates electricity. The chemical
composition of biomass varies in different species but generally, biomass consists of 25% of
lignin, 75% of carbohydrates or sugar. Biomass energy is also applicable for cooking, lighting,
and generation of electricity. The residue left after the removal of biogas is a good source of
manure. Biomass is an important energy source contributing to more than 14% of the global
energy supply.

6. Wind energy
Wind energy describes the process by which wind is used to generate electricity. As the wind
increases, power output increases up to the maximum output of the particular turbine. Wind
farms prefer areas, where winds are stronger and constant. These are generally located at high
altitudes. Wind turbines use wind to make electricity. There is no pollution because no fossil
fuels are burnt to generate electricity. One of India’s largest windmill farm is in Kanyakumari
which generates 380mW of electricity.
CHAPTER-2
Economics of Generation
2.1 Fixed and running cost, load estimation, load curves, demand factor, load factor,
diversity factor, power factor and their effect on cost of generation, simple
problems there on.
(1) Demand factor
 Demand Factor = Maximum demand of a system / Total connected load on the system
 Demand factor is always less than one.
 Example: if a residence having 6000W equipment connected has a maximum demand of
300W,Than demand factor = 6000W / 3300W = 55%.
 The lower the demand factor, the less system capacity required to serve the connected load.
 Feeder-circuit conductors should have an ampere sufficient to carry the load; the ampere of the
feeder-circuit need not always be equal to the total of all loads on all branch-circuits connected
to it.
Remember that the demand factor permits a feeder-circuit ampere to be less than 100% of the
sum of all branch-circuit loads connected to the feeder.
 Example: One Machine Shop has
Fluorescent fixtures=1 No, 5kw each, Receptacle outlets =1 No, 1500w each.
Lathe=1No, 10 Hp, Air Compressor=1 No, 20 Hp, Fire Pump=1 No, 15 Hp.
 After questioning the customer about the various loads, the information is further deciphered as
follows:
1. The shop lights are on only during the hours of 8 a.m. to 5 p.m.
2. The receptacle outlets are in the office only, and will have computers and other small
loads plugged into them.
3. The lathe is fully loaded for 5 minutes periods. The rest of the time is setup time. This
procedure repeats every 15 minutes.
4. The air compressor supplies air to air tools and cycles off and on about half the time.
5. The fire pump only runs for 30 minutes when tested which is once a month after hours.

7. Calculation:
 Lighting Demand Factor = Demand Interval Factor x Diversity Factor.
 = (15 minute run time/ 15 minutes) x 1.0 = 1.0
 Lighting Demand Load = 5 kW x 1.0 = 5 kW
 Receptacle Outlet Demand Factor = Demand Interval Factor x Diversity Factor
 = (15 minute run time / 15 minutes) x 0.1 = 0.1
 Receptacle Outlet Demand Load = 15 x 1500 watts x 0.1 = 2.25 kW
 Lathe Demand Factor = Demand Interval Factor x Diversity Factor.
 = (5 minute run time / 15 minutes) x 1.0 =0 .33
 Lathe Demand Load = 10 hp x .746 x .33 = 2.46 kW
 Air Compressor Demand Factor = Demand Interval Factor x Diversity Factor.
 = (7.5 minute run time / 15 minutes) x 1.0 = 0.5
 Air Compressor Demand Load = 20 hp x .746 x .5 = 7.46 kW
 Fire Pump Demand Factor = Demand Interval Factor x Diversity Factor.
 = (15 minute run time/ 15 minutes) x 0.0 = 0.0
 Fire Pump Demand Load = 15 hp x .746 x 0.0 = 0.0 kW
 Summary of Demand Loads :
Equipment kW D.F. Demand KW
Lighting 5 1 5
Receptacle Outlets 22.5 .1 2.25
Lathe 7.5 .33 2.46
Air Compressor 15 0.5 7.46
Fire Pump 11.25 0.0 0.0
TOTAL 61.25 Kw 1
2.2 Base load and peak load power stations, inter-connection of power stations and
its advantages, concept of regional and national grid.
What are Base Load and Peak Load?
Load, in electrical engineering, is the amount of current being drawn by all the components
(appliances, motors, machines, etc.).
Load is further categorised as base load and peak load depending upon the nature of the electrical
components connected. As you may be familiar, all electrical appliances at your home do not run
at all times.
 A toaster or microwave oven may be used for a few minutes,
 A television or computer may be used for a few hours
 Lighting in the house is only required during the evening and so on.

8. There are several appliances which keep running at all the times, no matter what. The
refrigerator, for example, has to be plugged in at all the times. Another such example are the
heating, ventilation and cooling systems in the house (HVAC system).
Peak Load and Base Load defined
Base load is the minimum level of electricity demand required over a period of 24 hours. It is
needed to provide power to components that keep running at all times (also referred as
continuous load).
Peak load is the time of high demand. These peaking demands are often for only shorter
durations. In mathematical terms, peak demand could be understood as the difference between
the base demand and the highest demand.
Now going back to the examples of household loads: microwave oven, toaster and television are
examples of peak demand, whereas refrigerator and HVAC systems are examples of base
demand.
A broader perspective of understanding these concepts
Now on a broader perspective, it could be assumed that the electrical grid is a big household.
Under normal circumstances, the power required by the electrical grid is fairly constant during
various period of the day.

9. This constant power, which is required at all times, is called the base loading. But during a
special event, like the final match of World Cup, the demand will be more, as a lot of people will
watch TV. This short, high demand period is considered to be a peak loading.
Base Load and Peak Load
Base Load and Peak Load power plants
Power plants are also categorised as base load and peak load power plants.
Base Load Power plants
Plants that are running continuously over extended periods of time are said to be base load power
plant.
The power from these plants is used to cater the base demand of the grid. A power plant may run
as a base load power plant due to various factors (long starting time requirement, fuel
requirements, etc.).
Examples of base load power plants are:
1. Nuclear power plant
2. Coal power plant
3. Hydroelectric plant
4. Geothermal plant
5. Biogas plant
6. Biomass plant
7. Solar thermal with storage
8. Ocean thermal energy conversion
Peak Load Power plants
To cater the demand peaks, peak load power plants are used. They are started up whenever there
is a spike in demand and stopped when the demand recedes.
Examples of gas load power plants are:
1. Gas plant
2. Solar power plants
3. Wind turbines
4. Diesel generators

10. CHAPTER-3
Transmission Systems
3.1 Layout of transmission system, selection of voltage for H.T and L.T lines, advantages of
high voltage for Transmission both AC and DC.
Low tension (LT) lines have low voltage (less than 1kV) and high current distribution
.(eg.230V/440V).The power supplying to our household applications are at LT . It is used to
transmit power at very small distances and uses thicker conductors.
High tension(HT) lines are using much higher voltages (11kV,33kV,66kV,110kV etc) .It is used
to transmit power to large distances by increasing voltage and decreasing current,so as to reduce
I^2 R losses. HT lines uses thinner conductors than LT line.
DC Transmission:Some times ago. The Electric power transmission was in DC due to
the following advantages.
Advantages of DC Transmission
Advantages:
There are two conductors used in DC transmission while three conductors required in
AC transmission.
There are no Inductance and Surges (High Voltage waves for very short time) in DC
transmission.
Due to absence of inductance, there are very low voltage drop in DC transmission lines
comparing with AC (if both Load and sending end voltage is same)
There is no concept of Skin effect in DC transmission. Therefore, small cross sectional
area conductor required.
A DC System has a less potential stress over AC system for same Voltage level.
Therefore, a DC line requires less insulation.
In DC System, There is no interference with communication system.

11. In DC Line, Corona losses are very low.
AC Transmission:
Nowadays, the generation, transmission and distribution mostly is in AC.
Advantages of AC Transmission System
Advantages:
AC Circuit breakers is cheap than DC Circuit breakers.
The repairing and maintenance of AC sub station is easy and inexpensive than DC
Substation.
The Level of AC voltage may be increased or decreased step up and Step down
transformers.
3.2 Comparison of different system: AC versus DC for power transmission, conductor
material and sizes from standard tables
The most crucial difference between the AC and the DC transmission line is that the AC
transmission line uses three conductors for power transmission whereas the DC transmission line
requires two conductors. The other differences between the AC and DC transmission lines are
explained below in the comparison chart.
The transmission line is a closed system through which the power is transfer from generating
station to the consumers. The transmission lined are categorised into three categories.
 Short Transmission Line – The length of the short transmission line is up to 80Km.
 Medium Transmission Line – The length of the medium transmission line lies between 80km to
200km.
 Long transmission Line – The length of long transmission line is greater than 150km.
The supports conductor, conductor, insulator, cross arms and clamp, fuses and isolating switches,
phases plates etc. are the main component of the transmission lines.
Comparison Chart
Basis for Comparison AC Transmission Line DC Transmission Line
Definition
The ac transmission line transmit
the alternating current.
The dc transmission line is used for
transmitting the direct current.
Number of Conductors Three Two
Inductance & surges Have Don’t Have
Voltage drop High Low
Skin Effect Occurs Absent
Need of Insulation More Less

12. Basis for Comparison AC Transmission Line DC Transmission Line
Interference Have Don’t Have
Corona Loss Occur Don’t occur
Dielectric Loss Have Don’t have
Synchronizing and
Stability Problem
No difficulties Difficulties
Cost Expensive Cheap
Length of conductors Small More
Repairing and
Maintenance
Easy and Inexpensive Difficult and Expensive
Transformer Requires Not Requires
AC Transmission Line
The ac transmission line is used for transmitting the bulk of the power generation end to the
consumer end. The power is generated in the generating station. The transmission line transmits
the power from generation to the consumer end. The power is transmitted from one end to
another with the help of step-up and step down transformer.

13. DC Transmission Line
In DC transmission line, the mercury arc rectifier converts the alternating current into the DC.
The DC transmission line transmits the bulk power over long distance. At the consumer ends the
thyratron converts the DC into the AC.
Key Differences Between AC and DC Transmission Line
1. The AC transmission line transmits the alternating current over a long distance. Whereas, the DC
transmission line is used for transmitting the DC over the long distance.
2. The AC transmission line uses three conductors for long power transmission. And the DC
transmission line uses two conductors for power transmission.
3. The AC transmission line has inductance and surges whereas the DC transmission line is free
from inductance and surges. The inductance and the surges are nothing but the wave of the
high voltage which occurs for short duration.
4. The high voltage drop occurs across the AC terminal lines when their end terminals voltage are
equal. The DC transmission line is free from inductance, and hence no voltage drop occurs
across the line.

14. 3.3 Constructional features of transmission lines: Types of supports, types of insulators,
Types of conductors, Selection of insulators, conductors, earth wire and their
accessories, Transposition of conductors and string efficiency of suspension type
insulators, Bundle Conductors
Types of Insulators in Transmission Lines:
The overhead line conductors should be supported on the poles or towers in such a way that currents
from conductors do not flow to earth through supports i.e., line conductors must be properly insulated
from supports. This is achieved by securing line conductors to supports with the help of insulators. The
insulators provide necessary insulation between line conductors and supports and thus prevent any
leakage current from conductors to earth. In general, Types of Insulators in Transmission Lines should
have the following desirable properties : High mechanical strength in order to withstand conductor load,
wind load etc. High electrical resistance of insulator material in order to avoid leakage currents to earth.
High relative permittivity of insulator material in order that dielectric strength is high. The insulator
material be non-porous, free from impurities and cracks otherwise the permittivity will be lowered. High
ratio of puncture strength to flashover.
Types of Insulators: The successful operation of an overhead Groo line depends to a considerable extent
upon cond the proper selection of insulators. There are several Types of Insulators in Transmission Lines
but the most commonly used are pin type, suspension type, strain insulator and shackle insulator.
1.Pin type insulators. The part section of a pin type insulator is shown in Fig.8.5 (i). As the name
suggests, the pin type insulator is secured to the cross-arm on the pole. There is a groove on the upper
end of the insulator for housing the conductor. The conductor passes through this groove and is bound
by the annealed wire of the same material as the conductor
2.Suspension type insulators. The cost of pin type insulator increases rapidly as the working voltage is
increased. Therefore, this type of insulator is not economical beyond 33 kV. For high voltages (>33 kV), it
is a usual practice to use suspension type insulators shown in Fig. 8.7. They consist of a number of
porcelain discs connected in series by metal links in the form of a string. The conductor is suspended at
the bottom end of this string while the other end of the string is secured to the cross arm of the tower.
Each unit or disc is designed for low voltage, say 11 kV. The number of discs in series would obviously

15. depend upon the working voltage. For instance, if the working voltage is 66 kV, then six discs in series
will be provided on the string. Types of Insulators in Transmission Lines.
3.Strain insulators. When there is a dead end of the line or there is corner or sharp curve, the line is
subjected to greater tension. In order to relieve the line of excessive tension, strain insulators me used
For low voltage lines (< 11 kV), shackle insulators are used as strain insulators. However, for high voltage
transmission lines, strain insulator consists of an assembly of suspension insulators as shown in Fig. 8.8.
The discs of strain insulators are used in the vertical plane. When the tension in lines is exceedingly high,
as at long river spans, two or more strings are used in parallel. Types of Insulators in Transmission Lines
4.Shackle insulators, In early days, the shackle insulators were used as strain insulators. But now a days,
they are used for low voltage distribution lines. Such insulators can be used either in a horizontal
position or in a vertical position. They can be directly fixed to the pole with a bolt or to the cross arm.
Fig. 8.9 shows a shackle insulator fixed to the pole. The conductor in the groove is fixed with a soft

16. binding wire.
3.4 Mechanical features of line: Importance of sag, calculation of sag, effects of wind and
ice related problems; Indian electricity rules pertaining to clearance
Sag is defined as the different in level between points of supports and the lowest point on the
conductor.
Here AOB is the transmission line conductor. Two supports are at point A and at point B. AB is the
horizontal line and from this horizontal line to point O, S is the sag when measured vertically.
Sag is mandatory in transmission line conductor suspension. The conductors are attached between two
supports with perfect value of sag. It is because of providing safety of the conductor from not to be
subjected to excessive tension. In order to permit safe tension in the conductor, conductors are not fully
stretched; rather they are allowed to have sag.
Sag calculation is classified on two conditions.

17. 1. When supports are at equal levels
2. When supports are not at equal levels
Now let us start discussion on two conditions.
Sag calculation for supports are at equal levels
Suppose, AOB is the conductor. A and B are points of supports. Point O is the lowest point and
the midpoint.
Let, L = length of the span, i.e. AB
w is the weight per unit length of the conductor
T is the tension in the conductor.
We have chosen any point on conductor, say point P.
The distance of point P from Lowest point O is x.
y is the height from point O to point P.
Equating two moments of two forces about point O as per the figure above we get,
Sag calculation for supports are at unequal levels

18. Suppose AOB is the conductor that has point O as the lowest point.
L is the Span of the conductor.
h is the difference in height level between two supports.
x1 is the distance of support at the lower level point A from O.
x2is the distance of support at the upper level point B from O.
T is the tension of the conductor.
w is the weight per unit length of the conductor.
Now,

19. So, having calculated the value of x1 and x2, we can easily find out the value of sag S1 and sag
S2.
The above formula are used to calculate sag when the conductor is in still air and ambient
temperature is normal. Hence the weight of the conductor is its own weight.
What is the Effect of Ice and Wind on Sag?
 The weight per unit length of the conductor is changed when wind blows at a certain force on
the conductor and ice accumulate around the conductor.
 Wind force acts on the conductor to change the conductor self weight per unit length
horizontally in the direction of the air flow.
 Ice loading acts on the conductor to change the conductor self weight per unit length vertically
downward.
 Considering wind force and ice loading both at a time, the conductor will have a resultant
weight per unit length.
 The resultant weight will create an angle with the ice loading down ward direction.
CHAPTER-4
Distribution System
4.1 Lay out of HT and LT distribution system, constructional feature of distribution lines
and their erection. LT feeders and service mains; Simple problems on AC radial
distribution system, determination of size of conductor
Lay out of HT and LT distribution system

20. HT Distribution panel
4.1 Constructional features of LT (400 V), HT (II kV) underground cables, advantages
and disadvantages of underground system with respect to overhead system .
What is Underground and Overhead Transmission?
The cables laid above the ground for transmission purpose is known as overhead transmission
lines while the cables laid below the ground (3-5 feet) for transmission purpose is known as
underground transmission lines. These lines are used for electric power transportation from one
place to the other.

21. Drawbacks or disadvantages of Underground Transmission
Following are the disadvantages of Underground Transmission:
➨Cost of underground cables (e.g. HVDC) are three times higher compare to overhead lines
(e.g. 400 KV).
➨Moreover laying or burying cost of underground lines are greater compare to overhead lines.
➨It is difficult to find and repair the wire breaks in case of failure of system. Moreover it takes
days or weeks to overcome the problem.
Advantages of Overhead Transmission
Following are the benefits or advantages of Overhead Transmission:
➨It is easy to repair and maintain.
➨They are not rectricted by landscape i.e. they can be easily installed over river or motorway or
hilly regions.
➨Chances of electrocution are less as they run high above the ground.
➨Cheaper to setup compare to underground transmission.
Disadvantages of Overhead Transmission
Following are the disadvantages of Overhead Transmission:
➨These lines visually pollute the areas where they are installed.
➨These lines suffer from problems such as terrorism, vandalism and lightning etc.
➨Sometimes these lines come in the way of birds and low flying aircrafts or drones which can
be dangerous.

22. 4.3 Losses in distribution system
Power is generated for the consumer utilization. From when power is generated it is transmitted
through transmission lines via grids & then distributed to the consumer. Power distribution is the
final and most crucial link in the electricity supply chain and most visible part of the electricity
sector, according to Power Grid Corporation of India Limited current distribution losses is about
30%. Distribution losses can be caused by theft of electricity, low metering levels and poor
financial health of utilities with low cost recovery, which generally causes power quality issues
and increase in the cost to electricity supply. Loss of power in distribution sector also causes
increase in cost to produce more power, and the global warming concerns. Distribution losses
can be classified into categories of Technical losses and Non-Technical losses. The technical
losses are most visible losses because it is related to material properties and its resistance to the
flow of current that is also dissipated as heat. The technical losses can be clearly classified as the
losses in power dissipated in distribution lines and transformers due to their internal resistance.
The deregulation and privatization are posing new challenges to the distribution systems. System
elements are going to be loaded up to their thermal limits, and wide-area power trading with fast
varying load patterns will contribute to an increasing congestion. About 30 to 40 % of total
investments in the electrical sector go to distribution systems, but nevertheless, they have not
received the technological impact in the same manner as the generation and transmission
systems. Nevertheless, there is an increasing trend to automate distribution systems to improve
their reliability, efficiency and service quality. Ideally, losses in an electric system should be
around 3 to 6%. In developed countries, it is not greater than 10%.However, in developing
countries, the percentage of active power losses is around 20%; therefore, utilities in the electric
sector are currently interested in reducing it in order to be more competitive, since the electricity
prices in deregulated markets are related to the system losses. In India, collective of all states, in
2008 the technical and nontechnical losses are accounted as 23% of the total input energy. To
manage a loss reduction program in a distribution system it is necessary to use effective and
efficient computational tools that allow quantifying the loss in each different network element
for system losses reduction.
4.4Faults in underground cables-determine fault location by Blavier Test, Murray Loop
Test, Varley Loop Test
Murray loop test is the most common and accurate method for locating earth faults and short-
circuit faults. However, to perform the Murray loop test, it is necessary that a sound (good) cable
runs along the faulty cable.This test employs the principle of Wheatstone bridge for fault
location.
To perform the Murray loop test, the alongside sound cable and the faulty cable are shorted
with a jumper conductor at the far end. The test side end is connected through a pair of resistors
to a voltage source. Also, a null detector or galvanometer is connected between the two
conductors at the test end. The circuit diagram is as shown in the image below.

23. CHAPTER-5
Substations:
5.1 Brief idea about substations; out door grid sub-station 220/132 KV, 66/33 KV outdoor
substations, pole mounted substations and indoor substation
Brief idea about substations; out door grid sub-station 220/132 KV.
Out door grid sub-station 220/132 KV
Outdoor Type Substation
Outdoor type substation are constructed in open air. Nearly all 132KV, 220KV,
400KV substation are outdoor type substation. Although now days special GIS
(Gas insulated substation) are constructed for extra high voltage system
which are generally situated under roof.

24. Indoor Substation
The substations are constructed under roof is called indoor type substation. Generally 11 KV and
sometime 33 KV substation are of this type.
Pole Mounted Substation
Pole mounted substation are mainly distribution substation constructed on two pole, four pole
and sometime six or more poles structures. In these type of substation fuse protected distribution
transformer are mounted on poles along with electrical isolator switches.
5.2 Layout of 33/11 kV/400V distribution substation and various auxiliaries and
equipment associated with it.

25. CHAPTER-6
Power Factor:
6.1 Concept of power factor
In AC circuits, the power factor is the ratio of the real power that is used to do work and
the apparent power that is supplied to the circuit. The power factor can get values in the
range from 0 to 1. When all the power is reactive power with no real power (usually
inductive load) - the power factor is 0.
6.2 Reasons and disadvantages of low power factor
Disadvantages of low power factor. ... At low power factor, the current is high which gives
rise to high copper losses in the system and therefore the efficiency of the system is
reduced. Higher current produced a large voltage drop in the apparatus. This results in the
poor voltage regulation.
6.3 Methods for improvement of power factor using capacitor banks, VAR `
Static Compensator (SVC)
A static VAR compensator is a set of electrical devices for providing
fast-acting reactive power on high-voltage electricity transmission
networks. SVCs are part of the Flexible AC transmission system device
family, regulating voltage, power factor, harmonics and stabilizing the
system. A static VAR compensator has no significant moving parts (other
than internal switchgear). Prior to the invention of the SVC, power
factor compensation was the preserve of large rotating machines such as
synchronous condensers or switched capacitor banks.
The SVC is an automated impedance matching device, designed to bring the system closer to
unity power factor. SVCs are used in two main situations:
 Connected to the power system, to regulate the transmission voltage ("Transmission SVC")
 Connected near large industrial loads, to improve power quality ("Industrial SVC")

26. In transmission applications, the SVC is used to regulate the grid voltage. If the power system's
reactive load is capacitive (leading), the SVC will use thyristor controlled reactors to consume
VARs from the system, lowering the system voltage. Under inductive (lagging) conditions, the
capacitor banks are automatically switched in, thus providing a higher system voltage. By
connecting the thyristor-controlled reactor, which is continuously variable, along with a
capacitor bank step, the net result is continuously variable leading or lagging power.