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220v gss working modelFinal report
1. i
A
PROJECT REPORT
ON
“220V GSS WORKING MODEL”
Submitted in partial Fulfillment of the requirements
For the award of the degree
BACHELOR OF ENGINEERING
Session 2017 - 18
Submitted To: Submitted By:
Prof. Sudanshu Gupta Giriraj Bairwa (13EKTEE032)
Mr.Surendera Choudhary
Deptt. Of electrical engg.
ELECTRICAL ENGG. DEPARTMENT
KAUTILYA INSTITUTE OF TECHNOLOGY &
ENGINEERING
RAJASTHAN TECHNICAL UNIVERSITY
2017
2. ii
CERTIFICATE
This is certify that the tilted “220v grid sub station working model” that
is being submitted by “GIRIRAJ BAIRWA” is in partial fulfillment of
the requirements of the award of BACHELOR OF ENGINEERING
DEGREE , is a record of bonafide work done under Mr. Sudanshu Gupta
guidance . The content of this report , in full or in parts , have neither been
taken from any other source nor have been submitted to any other institute
or University for award of degree and the same is certified.
Dr. K.C. Roy
(Head of electrical engineering dept.)
3. iii
ACKONWLEDGEMENT
This satisfaction and euphoria that accompany the successful completion of
any task Would be incomplete without the mentioning of the people whose
constant guidance and encouragement made it possible. We take pleasure in
presenting Before you, our project , which is result of studied blend of both
research and knowledge .
We exprees our earnest gratitude to our internal guide , “Associate Professor
Sudanshu Gupta” ,department of EE, our project guide Mr. Surender
Choudhary , for his constant Support , encouragement and guidance . we
are grateful for his coorperation and his Valiable suggestion .
Finally , we express our gratitude to all other member who are involved either
directly Or indirectily for the completion of this project .
4. iv
ABSTRACT
The present day electrical power system is AC. i.e. electric power is
generated, transmitted and distributed in the form of Alternating current. The
electric power is produce at the power station, which are located at favorable
places, generally quite away from the consumers. It is delivered to the
consumer through a large network of transmission and distribution. At many
place in the line of power system, it may be desirable and necessary to change
some characteristic (e.g. Voltage, ac to dc, frequency p.f. etc.) of electric
supply. This is accomplished by suitable apparatus called sub-station for
example, generation voltage (11KV or 66KV) at the power station is stepped
up to high voltage (Say 11KV to 33/220/440KV) for transmission of electric
power. Similarly near the consumer’s localities, the voltage may have to be
stepped down to utilization level. This job is again accomplished by suitable
apparatus called sub-station.
An power substation is a subsidiary station of an electricity
generation, transmission and distribution system where voltage is
transformed from high or medium to low or the reverse using transformers.
Electric power flows through several substations between generating plant
and consumer changing the voltage level in several stages.
A substation that has a step-up transformer increases the voltage with
decreasing current, while a step-down transformer decreases the voltage with
increasing the current for domestic and commercial distribution. The word
substation comes from the days before the distribution system became a grid.
At first substations were connected to only one power station where the
generator was housed and were subsidiaries of that power station.
5. v
DECLARATION
We , the undersigned , declare that the project entitled ‘22OV GRID SUB-
STATION WOKING MODEL’ , being submitted in partial fulfilment for
the award of bachelor of Engineering degree in Electrical engineering ,
Affiliated to Rajasthan Technical University ,is the work carried out by us.
Submitted By :
Giriraj Bairwa (13EKTEE032)
B.Tech (final year)
Batch – (2013-17)
6. vi
CONTENTS
CONTENTS PAGE NO.
1) Introduction To grid sub-station system 12
a. GSS System 13-14
b. Characterstics of GSS System 15
2) Block Diagram of 220KV GSS 16
3) Circuit Diagram Of 220V GSS Working model 17
4) Equipment Rating 18-19
Hardware Requirement
I. Pole
II. Bus – Bar
III. Relay
IV. Transformer
V. Circuit Breaker
VI. Current Transformer
VII. Potentional Transformer
VIII. C.T Circuit
IX. P.T Circuit
X. Load
XI. Control Room
7. vii
XII. L.E.D Display
XIII. Microcontroller
XIV. Ply-wood (6x4)
XV. Resistance
XVI. Capicator
XVII. Wire
XVIII. Input Supply (220v)
XIX. Glu-Gun
5) Transmission line Tower 20-22
6) Bus-Bar 23-24
7) Relay 25-26
8) Circuit Breaker 27-29
9) Transformer 30-33
10) Current Transformer 34-35
11) Potentional Transformer 36-37
12) Microcontroller 38
13) Isolater 39-40
11. xi
ABBREVIATIONS
S.No. Abbreviation Full form
1.
PT Power
Transformer
2.
CT Current
Transformer
3.
CB Circuit breaker
4.
PR Protective
Relay
5.
MCB Main Circuit
breaker
6.
GSS Grid Sub-
station
12. xii
CHAPTER-1
INTRODUCTION OF GRID SUB-STATION
Electrical power is generated, transmitted in the form of alternating current.
The electric power produced at the power stations is delivered to the
consumers through a large network of transmission & distribution. The
transmission network is inevitable long and high power line are necessary
to maintain a huge block of power source of generation to the load centers
to inter connected. Power house for increased reliability of supply greater.
The assembly of apparatus used to change some characteristics (e.g. voltage,
ac to dc ,frequency , power factor etc.) of electric supply keeping the power
constant is called a substation.
An electrical substation is a subsidiary station of an electricity generation,
transmission and distribution system where voltage is transformed from
high to low or the reverse using transformers. Electric power may flow
through several substations between generating plant and consumer, and
may be changed in voltage in several steps .
Other Defination “A substation is a part of an
electrical generation, transmission, and distribution system. Substations
transform voltage from high to low, or the reverse, or perform any of
several other important functions . Between the generating station and
consumer, electric power may flow through several substations at different
voltage levels. A substation may include transformers to change voltage
levels between high transmission voltages and lower distribution voltages,
or at the interconnection of two different transmission voltages.”
13. xiii
Fig1.1-working model of 220V GSS
Types of sub-station:-
Substations may be described by their voltage class, their applications
within the power system, the method used to insulate most connections, and
by the style and materials of the structures used.
1) Transmission substation
A transmission substation connects two or more transmission lines. The
simplest case is where all transmission lines have the same voltage.
2) Distribution substation
A distribution substation transfers power from the transmission system to
the distribution system of an area. It is uneconomical to directly connect
14. xiv
electricity consumers to the main transmission network, unless they use
large amounts of power, so the distribution station reduces voltage to a
level suitable for local distribution.
3) Collector substation
In distributed generation projects such as a wind farm, a collector
substation may be required. It resembles a distribution substation although
power flow is in the opposite direction, from many wind turbines up into
the transmission grid.
4) Converter substations
Converter substations may be associated with HVDC converter
plants, traction current, or interconnected non-synchronous networks.
These stations contain power electronic devices to change the frequency of
current, or else convert from alternating to direct current or the reverse.
5) Switching station
A switching station is a substation without transformers and operating only
at a single voltage level. Switching stations are sometimes used as collector
and distribution stations. Sometimes they are used for switching the current
to back-up lines or for parallelizing circuits in case of failure. An example
is the switching stations for the HVDC Inga–Shaba transmission line.
15. xv
Chacterstics of grid sub-station
Substations generally have switching, protection and control equipment,
and transformers. In a large substation, circuit breakers are used to interrupt
any short circuits or overload currents that may occur on the network.
Smaller distribution stations may use recloser circuit breakers or fuses for
protection of distribution circuits. Substations themselves do not usually
have generators, although a power plant may have a substation nearby.
Other devices such as capacitors and voltage regulators may also be located
at a substation.
A grounding (earthing) system must be designed. The total ground potential
rise, and the gradients in potential during a fault
(called touch and step potentials),[5] must be calculated to protect passers-
by during a short-circuit in the transmission system. Earth faults at a
substation can cause a ground potential rise. Currents flowing in the Earth's
surface during a fault can cause metal objects to have a significantly
different voltage than the ground under a person's feet; this touch potential
presents a hazard of electrocution. Where a substation has a metallic fence,
it must be properly grounded to protect people from this hazard.
Substations may be owned and operated by an electrical utility, or may be
owned by a large industrial or commercial customer. Generally substations
are unattended, relying on SCADA for remote supervision and control.
20. xx
CHAPTER-5
Transmission line Tower
Electrical Transmission Tower Types and Design
The main supporting unit of overhead transmission line is transmission
tower. Transmission towers have to carry the heavy transmission conductor
at a sufficient safe height from ground. In addition to that all towers have
to sustain all kinds of natural calamities. So transmission tower designing
is an important engineering job where all three basic engineering concepts,
civil, mechanical and electrical engineering concepts are equally applicable
.A power transmission tower consists of the following parts,
1. Peak of transmission tower
2. Cross arm of transmission tower
3. Boom of transmission tower
4. Cage of transmission tower
5. Transmission Tower Body
6. Leg of transmission tower
7. Stub/Anchor Bolt and Base plate assembly of transmission tower.
The main parts among these are shown in the pictures.
Peak of Transmission Tower
The portion above the top cross arm is called peak of transmission tower.
Generally earth shield wire connected to the tip of this peak.
Cross Arm of Transmission Tower
Cross arms of transmission tower hold the transmission conductor. The
dimension of cross arm depends on the level of transmission voltage,
configuration and minimum forming angle for stress distribution.
Cage of Transmission Tower
The portion between tower body and peak is known as cage of transmission
tower. This portion of the tower holds the cross arms.
Transmission Tower Body
The portion from bottom cross arms up to the ground level is called
transmission tower body. This portion of the tower plays a vital role for
maintaining required ground clearance of the bottom conductor of the
transmission line.
21. xxi
Types of pole :
1. Wooden poles : These are made of seasoned wood (sal or chir) and are
suitable for lines of moderate X-sectional area and of relatively shorter
spans, say upto 50 metres.Such supports are cheap, easily available, provide
insulating properties and, therefore, are widely used
for distribution purposes in rural areas as an economical proposition.The
wooden poles generally tend to rot below the ground level, causing
foundation failure.
Fig1.4:-Wooden pole
2. Steel poles : The steel poles are often used as a substitute for wooden
poles.They possess greater mechanical strength, longer life and permit
longer spans to be used.Such poles are generally used for distribution
purposes in the cities.This type of supports need to be galvanised or painted
in order to prolong its life.
The steel poles are of three types
(i) rail poles
(ii) tubular poles and
(iii) rolled steel joints.
3. RCC poles : The reinforced concrete poles have become very popular as
line supports in recent years.They have greater mechanical strength, longer
life and permit longer spans than steel poles.Moreover, they give good
outlook, require little maintenance and have good insulating
properties.Figure shows R.C.C. poles for single and double circuit.
22. xxii
Fig1.5:-RCC Pole
4. Steel towers : In practice, wooden, steel and reinforced concrete poles are
used for distribution purposes at low voltages, say upto 11 kV.However, for
long distance transmission at higher voltage, steel towers are invariably
employed.Steel towers have greater mechanical strength, longer life, can
withstand most severe climatic conditions and permit the use of longer
spans.
Fig1.6:-Steel pole
23. xxiii
CHAPTER-6
BUS BARS
Bus Bars are the common electrical component through which a large no
of feeders operating at same voltage have to be connected. If the bus bars
are of rigid type (Aluminum types) the structure height are low and
minimum clearance is required. While in case of strain type of bus bars
suitable ACSR conductor are strung/tensioned by tension insulators discs
according to system voltages. In the widely used strain type bus bars
stringing tension is about 500-900 Kg depending upon the size of conductor
use Here proper clearance would be achieved only if require tension is
achieved.
Loose bus bars would effect the clearances when it swings while over
tensioning may damage insulators. Clamps or even effect the supporting
structures in low temperature conditions . The clamping should be proper,
as loose clamp would spark under in full load condition damaging the bus
bars itself.
(6.1) Bus Bar Arangement May be of Following Type
Which is Being Adopted by RVPNL:-
(6.1.1) Single bus bar arrangement
(6.1.2) Double bus bar arrangement
(a) Main bus with transformer
(b) Main bus-I with main bus-II
(6.1.3) Double bus bar arrangement with auxiliary bus.
(6.1.1) Single bus Bar Arrangement:
This arrangement is simplest and cheapest. It suffers, however, from
major defects.
1. Maintenance without interruption is not possible
2. Extension of the substation without a shutdown is not possible
(6.1.2) Double Bus Bar Arrangement:
1. The load circuit may be divided in to two separate groups if needed
Operational consideration. Two supplies from different sources can be put.
2. Either bus bar may be taken out from maintenance of insulators.
3. The normal bus selection insulators can not be used for breaking load
currents. The arrangement does not permit breaker maintenance
without causing stoppage of supply.
24. xxiv
(6.1.3) Double Bus Bar Arrangements Contains Main Bus
With Auxilary Bus
The double bus bar arrangement provides facility to change over to either
bus to carry out maintenance on the other but provide no facility to carry
over breaker maintenance. The main and transfer bus works the other way
round. It provides facility for carrying out breaker maintenance but does
not permit bus maintenance. Whenever maintenance is required on any
breaker the circuit is changed over to the transfer bus and is controlled
through bus coupler breaker.
Fig. 1.7:-Bus-bar use in working model
25. xxv
CHAPTER-7
PROTECTIVE RELAYS
Relays must be able to evaluate a wide variety of parameters to establish
that corrective action is required. Obviously, a relay cannot prevent the
fault. Its primary purpose is to detect the fault and take the necessary action
to minimize the damage to the equipment or to the system. The most
common parameters which reflect the presence of a fault are the voltages
and currents at the terminals of the protected apparatus or at the appropriate
zone boundaries. The fundamental problem in power system protection is
to define the quantities that can differentiate between normal and abnormal
conditions. This problem is compounded by the fact that “normal” in the
present sense means outside the zone of protection. This aspect, which is of
the greatest significance in designing a secure relaying system, dominates
the design of all protection systems.
Fig1.7:-Relays
Fig1.8:-relay(12v)
26. xxvi
(7.1) Distance Relays:
Distance relays respond to the voltage and current, i.e., the impedance, at
the relay location. The impedance per mile is fairly constant so these relays
respond to the distance between the relay location and the fault location. As
the power systems become more complex and the fault current varies with
changes in generation and system configuration, directional over current
relays become difficult to apply and to set for all contingencies, whereas
the distance relay setting is constant for a wide variety of changes external
to the protected line.
(7.2) Types of Distance relay:-
(7.2.1) Impedance Relay:
The impedance relay has a circular characteristic centered. It is non
directional and is used primarily as a fault detector.
(7.2.2) Admittance Relay:
The admittance relay is the most commonly used distance relay. It is the
tripping relay in pilot schemes and as the backup relay in step distance
schemes. In the electromechanical design it is circular, and in the solid state
design, it can be shaped to correspond to the transmission line impedance.
(7.2.3) Reactance Relay:
The reactance relay is a straight-line characteristic that responds only to the
reactance of the protected line. It is non directional and is used to
supplement the admittance relay as a tripping relay to make the overall
protection independent of resistance. It is particularly useful on short lines
where the fault arc resistance is the same order of magnitude as the line
length.
27. xxvii
CHAPTER-8
CIRCUIT BREAKER
The function of relays and circuit breakers in the operation of a power
system. Prevent or limit damage during faults or overloads, and to minimize
their effect on the remainder of the system. This is accomplished by
dividing the system into protective zones separated by circuit breakers.
During a fault, the zone which includes the faulted apparatus is de-
energized and disconnected from the system. In addition to its protective
function, a circuit breaker is also used for circuit switching under normal
conditions.
Each having its protective relays for determining the existence of a fault in
that zone and having circuit breakers for disconnecting that zone from the
system. It is desirable to restrict the amount of system disconnected by a
given fault; as for example to a single transformer, line section, machine,
or bus section. However, economic considerations frequently limit the
number of circuit breakers to those required for normal operation and some
compromises result in the relay protection.
Circuit breakers at 220/110V side:-
C.B. at the side No. of circuit breakers
110V 7
Various types of circuit breakers:-
(1) SF6 Circuit Breaker
(2) Air Blast Circuit Breaker
(3) Oil Circuit Breaker
(4) Bulk Oil Circuit Breaker (MOCB)
(5) Minimum Oil Circuit Breaker
(1) SF6 Circuit Breaker:-
Sulphur hexafluoride has proved its-self as an excellent insulating and arc
quenching medium. It has been extensively used during the last 30 years in
circuit breakers, gas-insulated switchgear (GIS), high voltage capacitors,
bushings, and gas insulated transmission lines. In SF6 breakers the contacts
are surrounded by low pressure SF6 gas. At the moment the contacts are
opened, a small amount of gas is compressed and forced through the arc to
extinguish.
28. xxviii
Fig1.9:-Sf6 circuit breaker
(2) Air Blast Circuit Breaker:
The principle of arc interruption in air blast circuit breakers is to direct a
blast of air, at high pressure and velocity, to the arc. Fresh and dry air of the
air blast will replace the ionized hot gases within the arc zone and the arc
length is considerably increased. Consequently the arc may be interrupted
at the first natural current zero. In this type of breaker, the contacts are
surrounded by compressed air. When the contacts are opened the
compressed air is released in forced blast through the arc to the atmosphere
extinguishing the arc in the process.
(3) Oil Circuit Breaker:
Circuit breaking in oil has been adopted since the early stages of circuit
breakers manufacture. The oil in oil-filled breakers serves the purpose of
insulating the live parts from the earthed ones and provides an excellent
medium for arc interruption. Oil circuit breakers of the various types are
used in almost all voltage ranges and ratings. However, they are commonly
used at voltages below 115KV leaving the higher voltages for air blast and
SF6 breakers.
The advantages of using oil as an arc quenching medium are:
1. It absorbs the arc energy to decompose the oil into gases, which have
excellent cooling properties.
2. It acts as an insulator and permits smaller clearance between live conductors
and earthed components.
The disadvantages of oil as an arc quenching medium are:
1. Its inflammable and there is risk of fire
2. It may form an explosive mixture with air.
(4) Bulk oil Circuit breaker:
Bulk oil circuit breakers are widely used in power systems from the lowest
voltages up to115KV. However, they are still used in systems having
voltages up to 230KV.The contacts of bulk oil breakers may be of the plain-
29. xxix
break type, where the arc is freely interrupted in oil, or enclose within arc
controllers.
(5) Minimum oil Circuit Breaker:
Bulk oil circuit breakers have the disadvantage of using large quantity of
oil. With frequent breaking and making heavy currents the oil will
deteriorate and may lead to circuit breaker failure. This has led to the design
of minimum oil circuit breakers working on the same principles of arc
control as those used in bulk oil breakers. In this type of breakers the
interrupter chamber is separated from the other parts and arcing is confined
to a small volume of oil.
Advantages:
An air blast circuit breaker has the following advantages oil circuit breaker:
• The risk of fire is eliminated
• The arcing products are completely removed by the blast whereas the oil.
Fig1.10:-Circuit Breaker in Working Model of 220V GSS
30. xxx
CHAPTER-9
POWER TRANSFORMER
Power transformers are called auto transformers.
(9.1) Windings:
Winding shall be of electrolytic grade copper free from scales & burrs.
Windings shall be made in dust proof and conditioned atmosphere. Coils
shall be insulated that impulse and power frequency voltage stresses are
minimum. Coils assembly shall be suitably supported between adjacent
sections by insulating spacers and barriers. Bracing and other insulation
used in assembly of the winding shall be arranged to ensure a free
circulation of the oil and to reduce the hot spot of the winding. All windings
of the transformers having voltage less than 66 kV shall be fully insulated.
Tapping shall be so arranged as to preserve the magnetic balance of the
transformer at all voltage ratio. All leads from the windings to the terminal
board and bushing shall be rigidly supported to prevent injury from
vibration short circuit stresses.
Fig1.11:-Power Transformer in 220kv GSS
(9.2) Tanks and fittings:
Tank shall be of welded construction & fabricated from tested quality low
carbon steel of adequate thickness. After completion of welding, all joints
shall be subjected to dye penetration testing.
At least two adequately sized inspection openings one at each end of the
tank shall be provide for easy access to bushing & earth connections.
Turrets & other parts surrounding the conductor of individual phase shall
31. xxxi
be non-magnetic. The main tank body including tap changing compartment,
radiators shall be capable of withstanding full vacuum.
(9.3) Cooling Equipment:
Cooling equipment shall confirm to the requirement stipulated below.
(a.) Each radiator bank shall have its own cooling fans, shut off valves at the
top and bottom (80mm size) lifting lugs, top and bottom oil filling valves,
air release plug at the top, a drain and sampling valve and thermometer
pocket fitted with captive screw cap on the inlet and outlet.
(b.) Cooling fans shall not be directly mounted on radiator bank which may
cause undue vibration. These shall be located so as to prevent ingress of
rain water. Each fan shall be suitably protected by galvanized wire guard.
Fig1.12:-Radiator with fan
(9.4) Transformer Accessories:
(9.4.1) Buchholz Relay:
This has two Floats, one of them with surge catching baffle and gas
collecting space at top. This is mounted in the connecting pipe line between
conservator and main tank. This is the most dependable protection for a
given transformer.
Gas evolution at a slow rate that is associated with minor faults inside the
transformers gives rise to the operation or top float whose contacts are
wired for alarm..
32. xxxii
Fig1.13:- Buchholz Relay
(9.4.2) Temperature Indicators:
Most of the transformer (small transformers have only OTI) are provided
with indicators that displace oil temperature and winding temperature.
There are thermometers pockets provided in the tank top cover which hold
the sensing bulls in them.
This is done by adding the temperature rise due to the heat produced in a
heater coil (known as image coil) when a current proportional to that
flowing in windings is passed in it to that or top oil. For proper functioning
or OTI & WTI it is essential to keep the thermometers pocket clean and
filled with oil.
Fig1.14:-Micro switch type Winding and oil temperature indicator
33. xxxiii
(9.4.3) Silica Gel Breather:
Both transformer oil and cellulosic paper are highly hygroscopic. Paper
being more hygroscopic than the mineral oil The moisture, if not excluded
from the oil surface in conservator, thus will find its way finally into the
paper insulation and causes reduction insulation strength of transformer. To
minimize this conservator is allowed to breathe only through the silica gel
column, which absorbs the moisture in air before it enters the conservator
air surface.
Fig1.15:- silica Gel
(9.4.4)Conservator:
With the variation of temperature there is corresponding variation in the oil
volume. To account for this, an expansion vessel called conservator is
added to the transformer with a connecting pipe to the main tank. In smaller
transformers this vessel is open to atmosphere through dehydrating
breathers (to keep the air dry). In larger transformers, an air bag is mounted
inside the conservator with the inside of bag open to atmosphere through
the breathers and the outside surface of the bag in contact with the oil
surface.
34. xxxiv
CHAPTER-10
CURRENT TRANSFORMER
As you all know this is the device which provides the pre-decoded fraction
of the primary current passing through the line/bus main circuit . Now a day
mostly separate current transformer units are used instead of bushing
mounting CT’s on leveled structure they should be for oil level indication
and base should be earthed properly. Care should be taken so that there
should be no strain as the terminals. When connecting the jumpers, mostly
secondary connections is taken to three unction boxes where star delta
formation is connected for three phase and final leads taken to protection
metering scheme.
It can be used to supply information for measuring power flows and the
electrical inputs for the operation of protective relays associated with the
transmission and distribution circuit or for power transformer. These
current transformers have the primary winding connected in series with the
conductor carrying the current to be measured or controlled. The secondary
winding is thus insulated from the high voltage and can then be connected
to low voltage metering circuits.
Fig1.16:-current transformer in GSS
35. xxxv
Fig1.17:-current transformer in model of GSS
Fig1.18:-current transformer circuit in GSS working model
Current transformers are also used for street lighting circuits. Street lighting
requires a constant current to prevent flickering lights and a current
transformer is used to provide that constant current. In this case the current
transformer utilizes a moving secondary coil to vary the output so that a
constant current is obtained
36. xxxvi
CHAPTER-11
POTENTIAL TRANSFORMER
A potential transformer (PT) is used to transform the high voltage of a
power line to a lower value, which is in the range of an ac voltmeter or the
potential coil of an ac voltmeter. The voltage transformers are classified as
under:
• Capacitive voltage transformer or capacitive type
• Electromagnetic type.
Capacitive voltage transformer is being used more and more for voltage
measurement in high voltage transmission network, particularly for systems
voltage of 220KV and above where it becomes increasingly more
economical. It enables measurement of the line to earth voltage to be made
with simultaneous provision for carrier frequency coupling, which has
reached wide application in modern high voltage network for tale-metering
remote control and telephone communication purpose.
The capacitance type voltage transformers are of two type:
• Coupling Capacitor type
• Pushing Type
Fig1.19:-potential transformer
37. xxxvii
Fig1.20:- P.T use in working model 220V GSS
Fig1.21:-P.T circuit
The performance of CVT is affected by the supply frequency switching
transient and magnitude of connected Burdon. The CVT is more
economical than an electromagnetic voltage transformer when the nominal
supply voltage increases above 66KV. The carrier current equipment can
be connected via the capacitor of the CVT. There by there is no need of
separate coupling capacitor. The capacitor connected in series act like
potential dividers, provided, the current taken by burden is negligible
compared with current passing through the series connected capacitor.
38. xxxviii
CHAPTER-12
Microcontroller
A microcontroller (or MCU for microcontroller unit) is a
small computer on a single integrated circuit. In modern terminology, it is
a System on a chip A microcontroller contains one or
more CPUs (processor cores) along with memory and
programmable input/output peripherals. Program memory in the form
of Ferroelectric RAM, NOR flash or OTP ROM is also often included on
chip, as well as a small amount of RAM. Microcontrollers are designed for
embedded applications, in contrast to the microprocessors used in personal
computers or other general purpose applications consisting of various
discrete chips. Microcontrollers are used in automatically controlled
products and devices, such as automobile engine control systems,
implantable medical devices, remote controls, office machines, appliances,
power tools, toys and other embedded systems. By reducing the size and
cost compared to a design that uses a separate microprocessor, memory,
and input/output devices, microcontrollers make it economical to digitally
control even more devices and processes. Mixed signal microcontrollers
are common, integrating analog components needed to control non-digital
electronic systems.
Fig1.22:-microcontroller circuit (working model stater)-1.
Fig1.23:-microcontroller circuit
39. xxxix
CHAPTER-13
ISOLATER
“Isolator" is one, which can break and make an electric circuit in no load
condition. These are normally used in various circuits for the purposes of
Isolation of a certain portion when required for maintenance etc. Isolation
of a certain portion when required for maintenance etc. "Switching
Isolators" are capable of
• Interrupting transformer magnetized currents
• Interrupting line charging current
• Load transfer switching
Its main application is in connection with transformer feeder as this unit
makes it possible to switch out one transformer, while the other is still on
load. The most common type of isolators is the rotating center pots type in
which each phase has three insulator post, with the outer posts carrying
fixed contacts and connections while the center post having contact arm
which is arranged to move through 90` on its axis.
The following interlocks are provided with isolator:
(a) Bus 1 and2 isolators cannot be closed simultaneously.
(b) Isolator cannot operate unless the breaker is open.
(c) Only one bay can be taken on bypass bus.
(d) No isolator can operate corresponding earth switch is on breaker.
Now then decided by the relay . because in this working model fully relay
control based. Now then the relay control circuit is control to voltage limit
and current limit to flow in woking model of GSS.
41. xli
CHAPTER 14
CONTROL ROOM
Control panel contain meters, control switches and recorders located in the
control building, also called the dog house. These are used to control the
substation equipment to send power from one circuit to another or to open
or to shut down circuits when needed.
Fig1.26:- control room 220kv gss
Measuring Instrument Used:
(1) Energy Meter: To measure the energy transmitted energy meters
are fitted to the panel to different feeders the energy transmitted is recorded
after one hour regularly for it MWHr, meter is provided.
(2) Wattmeter’s: It is attached to each feeder to record the power
exported from GSS.
(3) Frequency Meter: To measure the frequency at each feeder there
is the provision of analog or digital frequency meter.
(4) Voltmeter: It is provided to measure the phase to phase voltage .It is
also available in both the analog and digital frequency meter.
(5) Ammeter: It is provided to measure the line current. It is also
available in both the forms analog as well as digital.
(6) Maximum Demand Indicator: There are also mounted the
control panel to record the average power over successive predetermined
period
42. xlii
CHAPTER-15
LOADS
An electrical load is an electrical component or portion of a circuit that
consumes electric power. This is opposed to a power source, such as a
battery or generator, which produces power. In electric power circuits
examples of loads are appliances and lights. The term may also refer to
the power consumed by a circuit.
Electrical Load Classification and Types:
The electrical loads can be classified into various categories according to
various factors as follows:
1- According To Load Nature-1
Resistive Electrical Loads.
Capacitive Electrical Loads.
Inductive Electrical Loads.
Combination Electrical Loads.
2- According To Load Nature-2
Linear Electrical Load.
None-Linear Electrical Load.
3- According To Load Function
Lighting Load.
Receptacles / General / Small Appliances Load.
Power Loads.
4- According To Load Consumer Category
Residential Electrical Loads (Dwelling Loads).
Commercial Electrical Loads.
Industrial Electrical Loads.
Municipal / Governmental Electrical Loads (Street Lighting, Power
Required For Water Supply and Drainage Purposes, Irrigation Loads And
Traction Loads).
5- According To Load Grouping
Individual Loads (Single Load).
Load Centers (Area Loads).
