1. Page 1
PROJECT REPORT ON
POWER DISTRIBUTION
AT
PGVCL RAJKOT CITY CIRCLE-3
NANA MAVA SUB-DIVISON
&
VISIT AT
GETCO 66/11 KV LAKHSMI NAGAR SUB-STATION RAJKOT
PREPARED BY:
VASA PRITEN
DOBARIYA PRIYESH
DHARMESH SAKARIYA
FACULTY OF TECHNOLOGY & ENGINEERING
DEPARTMENT OF ELECTRICAL ENGINEERING
2. Page 2
THANKING LETTER
TO
Mr. BAKSHI
DEPUTY ENGINEER
NANA MOVA SDO RAJKOT
We are very thankfulto PGVCL Nana Mava Sub divison for giving us a training & GETCO Laxmi
Nagar Sub divison for providing a visit and it was such a great opportunity here and given a
platformfor us to nourish our technicality rich with the great exposure . We also greet the all
the employees, Deputy Engineer ,Junior engineer including helpers and repairers for giving a
guidance and coretechnical knowledgewhich will be helpful for us to build and establish
strong career in this competitive field.
Thanking you
Vasa Priten
Priyesh Dobariya
Dharmesh Sakariya
SIGNED & CERTIFIED BY
MR K.H BAKSHI MR P.D PARMAR MR A.M SORATHIYA
DEPUTY ENGINEER JUNIORENGINEER JUNIORENGINEER
3. Page 3
BREIF OVER VIEW OF ELECTRICITY IN INDIA
The Gujarat Urja Vikas Nigam Limited (GUVNL) is an electrical services umbrella company in
the state of Gujarat, India. Itwas setup in May 1999 and is registered under the Companies
Act, 1956. TheCompany was created by the GujaratElectricity Board (GEB) as its wholly
owned subsidiary in the context of liberalization and as a part of efforts towards restructuring
of the power sector with the aim of improving efficiency in management and delivery of
services to consumers.As a partof Power Reform Process, theElectricity Act, 2003, was passed
by the Central Government and GujaratElectricity Industry (Re-organization & Regulation) Act,
2003, was passed by theGovernment of Gujaratto restructurethe Electricity Industrywith an
aim to improveefficiency in management and delivery of services to consumers.
Under the provisions of the said Acts Govt. of Gujaratframed the GujaratElectricity Industry
Re-organization & ComprehensiveTransfer Scheme, 2003, (theTransfer Scheme) vide
GovernmentNotification dated 24-10-2003 for transfer of assets/liabilities etc. of erstwhile
GEB to the successor entities.
Accordingly erstwhileGujaratElectricity Board (GEB) was reorganized effective from1 April
2005 into Seven Companies with functional responsibilities of Trading, Generation,
Transmission and Distribution etc.
The Companies incorporated are as under:
Gujarat Urja Vikas NigamLtd. (GUVNL) Holding Company
Gujarat State Electricity Corp. Ltd.(GSECL) Generation
Gujarat Energy Transmission Corp. Ltd.(GETCO) Transmission
Uttar Gujarat Vij Company Ltd. (UGVCL) Distribution
Dakshin Gujarat Vij Company Ltd. (DGVCL) Distribution
Madhya Gujarat Vij Company Ltd. (MGVCL) Distribution
PaschimGujarat Vij Company Ltd. (PGVCL) Distribution
4. Page 4
FUNCTIONS OF GUNVL
The Company was incorporated to take over the assets, liabilities and personnel of the GEB in accordance with
Schedule G of the Main Transfer Scheme Notification dated 24 October 2003. The Company has to carry out
the residual functions (including power trading) of the defunct GEB.
One of the functions of the Company includes coordination of the activities of its subsidiaries, business, and
works to determine their economic and financial objectives and targets and to review, control, guide and
direct their performance with a view to secure optimum utilization of all resources placed at their disposal
SUBSIDARIES COMPANIES
Gujarat State Electricity Corporation Limited (GSEC)
Gujarat Energy Transmission Corporation Limited (GETCO)
State Load Dispatch Center (SLDC)
Dakshin Gujarat Vij Company Limited (DGVCL)
Madhya Gujarat Vij Company Limited (MGVCL)
PaschimGujarat Vij Company Limited (PGVCL)
Uttar Gujarat Vij Company Limited (UGVCL)
Gujarat Energy Training and Research Institute (GETRI)
BROAD OVER VIEW TO ELECTRICAL POWER SYSTEM
The table below presents the electricity generation capacity, as well as availability to
India's end user and their demand
Of the 1.4 billion people of the world who haveno access to electricity in the world,
India accounts for over 300 million.
5. Page 5
800 million Indians usetraditional fuels – fuelwood, agriculturalwasteand biomass
cakes – for cooking and general heating needs
The five states with largestpower demand and availability, as of May 2011,
were Maharashtra, Andhra pradesh ,Tamil nadu, Uttar pradeshand gujarat
Problems
1) Governmentgiveaways such as free electricity for farmers, partly to curry political
favour, havedepleted the cash reserves of state-run electricity-distribution system.
2) Shortages of fuel: despite abundantreserves of coal, India is facing a severeshortageof
coal. The country isn't producing enough to feed its power plants. Some plants do not
have reservecoal supplies to last a day of operations.
3) The giant new offshorenaturalgas field has delivered less fuel than projected
4) hydroelectric power projects in India's mountainous north and northeastregions have
been slowed down by ecological, environmental and rehabilitation controversies,
coupled with public interest litigations.
5) The July 2012 blackout, affecting the north of the country, was the largestpower grid
failure in history by number of people affected.
Government measures
India's Ministry of Power launched Rajiv Gandhi Grameen Vidyutikaran Yojana as one of
its flagship programmein March 2005 with the objective of electrifying over one lakh
un-electrified villages and to provide free electricity connections to 2.34 crorerural
households
This free electricity programpromises energy access to India's ruralareas, but is in part
creating problems for India's electricity sector
CONCEPT OF ENERGY GENERATION, TRANSMISSION , DISTRIBUTION
6. Page 6
• The purposeof the electric transmission systemis the efficient interconnection of the
electric energy producing power plants or generating stations with the loads.
• Main Parts of Power System
• Four Main Parts:
• Generation System
• Transmission System
• Distribution System
• Consumer (LOAD)
Simplified Diagram of Power System
• One-Line Diagram of Generating Station
7. Page 7
POWER DISTRIBUTION & POWER LOSS REDUCTION METHODS
CONTENTS
• Power Distribution System
• Equipment in Power Distribution
• Losses in the System
• Methods of Reducing Losses
Classification of Power Distribution
1. According to type of current
a. DC Distribution
b. AC Distribution
2. According to construction
a. Over head distribution system
b. Underground distribution system
3. According to service
a. General lighting and power
b. Industrial power
c. Street Lighting
4. According to number of wires
a. Two wire
b. Three wire
c. Four wire
5. According to scheme of connections
a. Radial system
b. Ring system
c. Inter connected system
CONNECTION SCHEMES OF DISTRIBUTION SYSTEM
8. Page 8
1. Radial system: In this systemfeeders radiate from single sub station and feed the distribution at one
end only.
2. Ring system: In this system each consumer is supplied via two feeders. The arrangement is similar to
two feeders in parallel on different routes.
3. Inter connected system: In this system the feeder ring is energized by two or more generating stations
or sub stations
POWER DISTRIBUTION ATNFC
1. 132kVMAIN RECEIVING STATION
i. 132kV is step down to 33kV or 11kV over two 3 windings transformer of capacity 20/31.5MVA
132kV/33kV/11kV.
ii. The two feeders at 132kV are of 100% capacity
iii. An ON LOAD TAP CHANGER (OLTC) which is controlled by automatic voltage regulator to
provide a constant secondary voltage of 11kV irrespective of primary incoming feeder voltage
in a range of 138.6kV to 99kV.
2. 66 kV DISTRIBUTION SYSTEM
i. 66kV is step down to 11kV by two 15/20MVA, 66KV/11 transformer.
ii. The step down secondary voltage is connected to the switch board through a closed
type bus duct 11kV switch board as 20 bulk oil circuit breaker to feed the 1250kVA,
11kV/433V transformer.
3. 11kVDISTRIBUTION SYSTEM
i. 11kV supply from 20/31.5MVA transformer is drawn to the switch panel through XLPE
cables.
ii. SF6 gas circuit breaker
CAPTIVE POWER GENERATION PLANT (CPGP)
• Maximum demand of NFC made with APTRANSCO is 10MVA.
• Total capacity of 7.5MVA, consisting of 3 DG sets, each of 2.5MVA capacity.
• DG sets are connected to an 11kV bus of the power plant which is linked with the 11kV with board of
MSDS-1 over to full capacity feeders.
• Every production unit is provided with a diesel generator set of capacity 40kVA or 180kVA or 500kVA
according to their emergency demand.
9. Page 9
EQUIPMENT IN POWER DISTRIBUTION
• Bus bars: Bus bars or buses are conductors to which several local feeders or sources are connected.
• Outdoor Bus bars
• Indoor Bus bar
• Compound Immersed Bus bar
• Various types of bus bar arrangements:
Single Bus bar Arrangement
Duplicate Bus bar Arrangement
Sectionalization of Bus bar
Ring Bus
• Circuit breakers: Circuit breaker requires the separation of contacts in a presence of a dielectric
medium which serves two functions as
1. It extinguishes arc between two contacts.
2. Provides adequate insulation between the contacts and from each contact to earth.
Classification of Circuit Breaker:
1. Air Circuit Breakers
2. Oil Circuit Breakers
3. SF6 Circuit Breakers
• Surge Arresters:
Surge arresters are used to protect the apparatus insulation from lightning surges and switching
surges.
Surge arresters are usually connected between phase and ground in distribution system;
near the terminals of the large medium voltage machines and in HV, EHV, HVDC substations.
Two types of Surge Arresters:
1. Gapping Silicon Carbide Surge Arresters
2. Zinc Oxide Gapless Arresters.
EQUIPMENT IN POWER DISTRIBUTION
10. Page 10
S.No Equipment Functions
1 Bus bars Incomingandoutgoingcircuitsare connectedtob
2. Lighteningarrestors To discharge lightningovervoltagesandswitching
3. Shuntreactor inE.H.V substations To provide reactive powercompensationduringl
4. Seriesreactors To reduce the short circuitcurrentsor startingcur
5. Neutral GroundingResistor To limitthe earthfaultcurrents.
6. CouplingCapacitor To provide connectionbetweenhighvoltageline
equipment.
LOSSES IN THE POWER DISTRIBUTION
• Distribution Line Losses
• Transformer Losses:
i. Core Losses
ii. Copper Losses
iii. Dielectric Losses
iv. Stray Magnetic Losses:
• Losses due to Harmonics
• Losses due to low power factor
• Miscellaneous losses
IMPROVEMENTS IN POWER DISTRIBUTION IN AN INDUSTRY
• Energy Management System
11. Page 11
• Power Factor Correction
• High Efficiency Transformers
i. Dry Type Transformer
ii. Amorphous Core Type Transformer
• Lighting
Energy Management System
Industrial Energy Management systems are key factors in energy cost conservation.
i. Monitoring and reports
ii. Load shedding
iii. Load forecasting
Monitoring and Report
i. Monitoring and reports also reveal at what times there were particularly high loads.
ii. From here strategies can be developed to avoid such critical situations.
12. Page 12
iii. Load Shedding
iv. Load shedding modules in an energy management systemoffer the possibility of specifying a "turn-off
strategy" which states precisely which consumers may be turned off at all and in which order.
Industrial load forecasting:
• Load forecasting gives you a preview of your company’s load curve, it stores knowledge about the
production processes’ behavior in typical production situations from several hours to several days
ahead.
o Forecasting can be done in three modes:
i. Assistance Mode
ii. Semi-automatic Mode
iii. Automatic Mode
• DRY TYPE TRANSFORMER
• Rating ranges from 100 to 20000 KVA
13. Page 13
• They make use of flame-retardant inorganic insulating materials which free these transformers from all
restrictions that apply to oil-filled electrical equipment, such as oil-collecting pits, fire walls, fire
extinguishing equipment, etc.
• Dry Type Transformers are installed wherever oil-filled units cannot be used
• Their efficiency is rated at 99.02%
AMORPHOUS TRANSFORMERS
• Amorphous Transformer has become well known after "Super amorphous transformer" produced by
Hitachi Ltd.,
• Amorphous transformer uses amorphous alloy in the core.
• Core material is an alloy of Fe,B,Si.
• Low iron loss, High permeability, Low stress sensitivity
POWER FACTOR CORRECTION
i. The input power factor is the real power divided by the apparent power
ii. BENEFITS
a. Released System Capacity
b. Reduced Power Losses
c. Voltage Improvement
14. Page 14
ELECTRICITY THEFT
A MAJOR ISSUE IN POWER INDUSTRY
CONTENTS
• Introduction
• India’s generationcapacity
• India’s consumptioncapacity
• Deficit
• Electricity theft
• Major causes of electricity theft
• Measures tocontrol theft
• Conclusion
INTRODUCTION
• Many developing countries confront widespread theft of electricity from government owned power
utilities.
• In India electricity theft leads to annual losses estimated at US$4.5 billion, about 1.5 percent of GDP.
• Who are the losers??
• Honest consumers, poor people, and those without connections, who bear the burden of high tariffs,
system inefficiencies, and inadequate and unreliable power supply.
• India is the seventh-largest country by area, the second-most populous country with over 1.2 billion
people, and the most populous democracy in the world.
• Who are the losers? Honest consumers, poor people, and those without connections, who bear the
burden of high tariffs, system inefficiencies, and inadequate and unreliable power supply.
While 80% of Indian villages are electrified, only 44% of rural households have access to power.
DEFICIT
India has been facing growing shortages over the past five years
1. During the year 2007-08
peak deficit:8,000 MW (16.5%)
average energy shortage:73 Billion kWh (10%).
2. During the year 2008-09
peak deficit 13,000 MW (12%)
average energy shortage: 86 Billion kWh (11%).
3. During the year 2009-10
peak deficit:5,157 MW (12.7%) average energy shortage:84 Billion kWh (10.1%).
15. Page 15
ELECTRICITY THEFT
WHAT IS ELECTRICITY THEFT….???
• Itis the useof electrical power without a contract with a supplier with total or partial
bypassing metering system
OR
• Interfering this systemin the way to adulterate its measurements.
MAJOR CAUSES OF ELECTRICITY THEFT
• Absence of accountability.
• Inadequate and ineffective enforcement of law.
• Political protection to employees and influential customers.
• Customer attitude: “Immoral to steal from neighbor but legitimate to steal from state’’.
WHERE DOES ELECTRICITY THEFT OCCUR MOST COMMONLY ?
16. Page 16
ELECTRICITY THEFT METHODS
Meters:
• Tampering with meters and seals
• By-passing the meters
• Damaging or removing meters
Wires/ Cables:
• Illegal tapping to bare wires or underground cables
Transformers:
• Illegal terminal taps of overhead lines on the low side of the transformer
Billing irregularities made by meter readers.
Unpaid bills by individuals, government institutions and “untouchable” VIPs.
FEW OTHER WAYS FOR POWER THEFT
• Use of single phase supply from three phase supply.
• Disconnected neutral from both the ends.
• Used earth/separate neutral for return circuit.
• Connecting phase voltage to neutral of used single phase supply. Potential difference w.r.t. neutral of
used single phase supply is zero. Hence power product of voltage and current, will be zero.
• Isolating neutral from both ends.
THEFT OCCURS WHEN:
• An illegal consumer(not a registered customer) steals directly from the distribution lines or from
another legal customer.
• A legal customer(registered customer) steals either bypassing the meter (connecting around the
meter to a live cable on the company side of the meter) or tampering with the meter to make it read
less or no consumption.
• There is a collusion between the customer and a company employee to reduce the amount paid to
the company (with lower side payments to the employee in return).
20. Page 20
HOW CAN ELECTRICITY THEFT BE REDUCED
NON TECHNICAL SOLUTIONS
Financial rewards:
Utility companies encourage consumers to report electricity theft
Periodic checks:
Electricity theft frequently takes place after service has been disconnected. Some utility companies
periodically check disconnected meters if the customer has not contacted them to reconnect service.
Enforcement of law: Fines should be imposed by the government for stealing electricity.
• Taps, makes or causes to be made any connection with overhead, underground or under water lines or
cables, or service wires, or service facilities of a licensee;
• Tampers a meter, installs or uses a tampered meter, current reversing transformer, loop connection or
any other device or method which interferes with accurate or proper registration, calibration or
metering of electric current or otherwise results in a manner whereby electricity is stolen or wasted.
• Damages or destroys an electric meter, apparatus, equipment, or wire or causes or allows any of them
to be so damaged or destroyed as to interfere with the proper or accurate metering of electricity, so as
to abstract or consume or use electricity shall be punishable with imprisonment for a term which may
extend to three years or with fine or with both.
TECHNICAL SOLUTIONS
Electronic tamper detection meter
Pre payment meters
Plastic meter encasements
Anti theft cable
Using GSM
Using PLCs
21. Page 21
Electronic Tamper Detection Meters
Automatic detection of :
•
• Meter tamper
• Meter Bypass
• Meter disconnection
Pre-Payments Meters
• Credit added to the meter on the keypad.
• Credit is purchased on the recharegable token and entered to the meter with disconnection
ability
Plastic meter encasements
Hard plastic encasements are a type of meter seal. These transparent plastic covers serve as a warning.
22. Page 22
• Anti theft cable
DISTRBUTION SYSTEM FAULT MANAGEMENT
AGENDA
Introduction.
Currently Existing System.
New Fault Management System.
Advantages, Applications, Improvements.
DISTRIBUTION SYSTEM.
Distribution systemis that part of the power systemwhich distributes power from distribution
substation to local use .
Generally the higher voltage for distribution is 11000v and the lower voltages are 400 v and 220v.
7
General
layoutof
distribution
system
33KV
Substation
11KV
Distribution
Transformer
11KV
Distribution
Substation
0.4KV
23. Page 23
TRANSFORMERSwitch(OPEN)
SUBSTATIONBUS
SWITCH
(CLOSED)
STATIONCIRCUIT
BREAKER
OPENLOOPSYSTEM
HRCFUSE
Load
8
TYPICALDISTRIBUTIONSYSTEM
TYPES OF FAULTS IN DISTRIBUTION SYSTEM
• LINE TO LINE FAULT .
• LINE TO GROUND FAULT .
• 3 PHASE FAULTS.
• OVER CURRENT FAULTS
LINE TO LINEFAULT.
It’s The Fault Which Occurs Between Any Of The 2 Lines .
At This Fault The Voltage Across Two Lines Will Be Zero, And Current Is Maximum.
V=0,I=∞
LINE TO GROUND FAULT
IT IS THE FAULT OCCURS BETWEEN ANY LINE TO GROUND.
AT THIS FAULT THE VOLTAGE ACROSS LINE TO GROUND IS ZERO, AND CURRENT IS MAXIMUM.
V=0,I=∞
THREE PHASEFAULTS
Over Current Faults
In Overcurrent Faults The Current Is Maximum ,That Is More Than Rated Value.
24. Page 24
OVERVIEW OF CURRENT FAULT MANGEMENT SYSTEM
DIFFICULTIES IN CURRENTLY EXISTING SYSTEM
• Fault Identification takes too much time.
• At the time of raining it is too difficult find and correct faults.
• With the human error fatal accidents are common .
• L.V. distribution faults(after the secondary of distribution transformer) are cannot be identified from
existing relays, faults like conductor down, overloading, short circuiting of conductors etc. which
unexpected and very difficult identify.
OBJECTIVE OF FAULT MANAGEMENT SYSTEM
To improvereliability and quality of serviceof distribution systemby
Reducing frequency and duration of power interruptionsto targets
consistent with best internationalpractice
To operate efficiently and safely by
Minimizing power losses
Applying manpowerresourceseffectively
25. Page 25
METHOD INVOLVED
It will be consisting of control room with a signal indicating systemit may be a computer monitor or big
screen
Which will be indicating the status of all section voltage and current with alarm for any abnormal
conditions .
After I identifying the fault feeder all loads are removed from the network and network will be charged
idly with full voltage and limiting current through a current limiter which may be a saturable reactor so
it limits the fault currents.
After charging the line idly , all sections current and voltage status will be absorbed and faulty section
is identified.
after identifying faulty section, it will be isolated from the healthy one from remotely .
After clearing the fault the section will be closed.
Fault cleared successfully.
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APPLICATIONS
Fault Location, Isolation, and ServiceRestoration
◦ Can detect and locate fault, isolate the faulty section, restore power to “healthy”
feeder segments
Load Shedding
◦ Can shed one feeder section if necessary
Cold Load Pickup
◦ Can pick up feeder load one section at a time
Feeder Reconfiguration
◦ Can balance load between feedersand reduce losses
“Intelligent” Substation Bus Transfer
◦ Can transfer load to another substation following transformerfailure
. DIFFERENT PROVISIONS FOR THEFT OF ELECTRICITY IN EA, 2003 & COMMENTS
2.1 Focus on revenue realization rather than criminal proceedings.
(Sections 126, 135)
The real focus after the identification of the activity of electricity theft by any class of consumer is on the
collection of revenue which is chargeable to the offender according to the financial gain incurred by him
brought out by the assessment of the assessment officer. There are very low measures for severe
punishments so that it is ensured that the same crime does not take place again. The tempting condition
behind collection of revenue as a fine at the first place may be because of the poor financial condition of the
distribution utilities. There is no act of imprisonment to a consumer with a load of less than 10 kilowatts.
These are mainly the retail customers and many cases have been found with these customersleading to a huge
loss to the utilities. Theft by these consumers is majorly done by tapping an electric cable/pole or by
tampering of meters. Also, to the consumers above the load of 10 kilowatt imprisonment clause is only after
the repeated offence.
2.2 Penalties linked to the connected load and quantum of energy and financial gain
involved in theft.
30. Page 30
(Section135)
For the case where the load abstracted, consumed or used/attempted does not exceed 10 kilowatt, the fine
imposed on first conviction will not be less than three times the financial gain realized due to such an activity.
For second conviction the fine has not to be less than six times the financial gain realized out of such activity.
For the case where the load abstracted, consumed or used/attempted exceeds 10 kilowatt, the fine imposed
on first conviction is not less than three times the financial gain derived from such activity. Upon second
conviction the consumer can be imprisoned for a period not less than six months and which may extend to
five years along with the penalty of six times the financial gain realized. Here, if the period of theft/pilferage
cannot be ascertained it is taken to be 12 months from the date of noticing the theft. There is no proper
method to reach to the actual
(Section126)
The officer in-charge, if by inspection of any place or equipments comes to the conclusion that there is some
unauthorized use of electricity, he can provisionally access to the best of his judgment the electricity charges
payable by the person benefited by such use. An order of provisional assessment shall be served on the
person who owes the premise. The person may accept the assessment and deposit the assessed amount with
the licensee within seven days of the assessment order. After assessment if the person is found guilty the
assessment has to be done for the entire period for which the activity has been carried out. In cases where
this cannot be ascertained the period of theft is takes as twelve months from the date of first inspection and
this assessment shall be at the rate twice the tariff rates applicable for the particular class of consumer.
31. Page 31
AN OVERVIEW OF TRANSMISSION SUBSTATION LAYOUT AND ITS EQUIPMENTS
“SUBSTATION LAYOUT”
• Single line diagram
Substation Switchyard Accessories
• Lightning Arrestor
• CVT
• Earthing switch
• Wave trap
• Isolator
• Current transformer
• Circuit Breaker
• Power Transformer
• Current transformer
• Reactors and capacitors
• Other Switchyard Equipments
• PLCC
• SCADA
32. Page 32
SWITCHYARD LAYOUTING
CLASSIFICATION OF SUBSTATIONS
• Based on working
I. Generating substation (step up s/s)
II. Grid substation
III. Switching substation
IV. Secondary substation -- a) sub transmission voltage
b) primary distribution
c) distribution substation
• Based on structure
I. Outdoor conventional air insulated substation (AIS)
II. Indoor substation
III. Compressed air insulated
IV. G I S
LIGHTNING ARRESTORS
A lightning arrester is a device used on electrical power systems to protect the insulation on the
system from the damaging effect of lightning.
Metal oxide varistors (MOVs) have been used for power systemprotection since the mid 1970s.
The typical lightning arrester also known as surge arrester has a high voltage terminal and a ground
terminal.
Current from the surge is diverted around the protected insulation in most cases to earth.
33. Page 33
CVT
Capacitor Voltage Transformer (CVT), Capacitance Coupled Voltage Transformer(CCVT)
o To step down extra high voltage signals and provide a low voltage .For measurement or to operate
a protective relay
EARTHING SWITCH
• Earth Switch is used to discharge the voltage on the circuit to the earth for safety.
• Earth switch is mounted on the frame of the isolators.
• It is located for each incomer transmission line and each side of the busbar section.
34. Page 34
LINE TRAP (WAVE TRAP)
Connected in series with the power (transmission) line.
It blocks the high frequency carrier waves (24 KHz to 500 KHz) and let power waves (50 Hz - 60 Hz) to
pass through.
It is basically an inductor of rating in Milli henry (approx 1 milli Henry for 220 KV 1250 Amp.).
It has three main components:-
1. Main coil.
2. Tuning Device.
3. Lightning Arrestor.
ISOLATOR
35. Page 35
• Disconnector or Isolator switch is used to makesure that an electrical circuit can be
completely de-energised for service or maintenance.
• Isolator is an off-load device.
• Types of Isolators are
1. Central rotating, horizontal swing
2. Centre-Break
3. Vertical swing
4. Pantograph type
CURRENT TRANSFORMER
Current transformers are used for Stepping down current for measurement, protection and control.
Current transformers are of two types
1. Protective CT
2. Measuring CT
CIRCUIT BREAKERS
36. Page 36
A Circuit breaker is an automatically operated electrical switch designed to protect an electrical
circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition
and, by interrupting continuity, to immediately discontinue electrical flow.
All circuit breakers have common features in their operation, although details vary substantially
depending on the voltage class, current rating and type of the circuit breaker.
Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit.
Small circuit breakers may be manually operated; larger units have solenoids to trip the mechanism,
and electric motors to restore energy to the springs.
HIGH-VOLTAGE BREAKERS ARE BROADLY CLASSIFIED BY THE MEDIUM USED TO EXTINGUISH THE ARC
• Bulk oil
• Minimum oil
• Air blast
• Vacuum
• SF6
BUSBARS
Busbars receive power from incoming circuits and deliver power to outgoing circuits
REACTORS
The majority of the load in a typical AC power system is inductive; the current lags behind the voltage. Since
the voltage and current are out-of-phase, this leads to the emergence of an "imaginary" form of power known
as reactive power. Reactive power does no measurable work but is transmitted back and forth between the
reactive power source and load every cycle. This reactive power can be provided by the generators
themselves, through the adjustment of generator excitation, but it is often cheaper to provide it through
capacitors, hence capacitors are often placed near inductive loads to reduce current demand on the power
37. Page 37
system (i.e, increase the power factor), which may never exceed 1.0, and which represents a purely resistive
load. Power factor correction may be applied at a central substation, through the use of so-called
"synchronous condensers" (synchronous machines which act as condensers which are variable in VAR value,
through the adjustment of machine excitation) or adjacent to large loads, through the use of so-called "static
condensers" (condensers which are fixed in VAR value).
Reactors consume reactive power and are used to regulate voltage on long transmission lines. In light load
conditions, where the loading on transmission lines is well below the surge impedance loading, the efficiency
of the power systemmay actually be improved by switching in reactors. Reactors installed in series in a power
system also limit rushes of current flow, small reactors are therefore almost always installed in series with
capacitors to limit the current rush associated with switching in a capacitor. Series reactors can also be used to
limit fault currents.
Capacitors and reactors are switched by circuit breakers, which results in moderately large steps in reactive
power. A solution comes in the form of static VAR compensators and static synchronous compensators.
Briefly, static VAR compensators work by switching in capacitors using thyristors as opposed to circuit
breakers allowing capacitors to be switched-in and switched-out within a single cycle. This provides a far more
refined response than circuit breaker switched capacitors. Static synchronous compensators take a step
further by achieving reactive power adjustments using only power electronics.
SHUNT REACTORS
• Shunt Reactors are used for long EHV transmission lines to control voltage during low – load period.
• Shunt reactors is also used to compensate shunt capacitance of transmission line during low load
periods.
• Usually Shunt reactors are unswitched.
38. Page 38
SHUNT CAPACITORS
• Shunt capacitors are used for compensating reactive power of LPF.
• They are used for improving the power factor. It is also used for voltage control during heavy lagging
power factor loads.
• They are located at the receiving stations and distribution substations.
• They are switched on during heavy loads and switched off during low loads.
NEUTRAL GROUNDING EQUIPMENT
• Neutral Grounding Equipment are Resistors and reactors.
• They are used to limit the short circuit current during ground fault.
• They are connected between neutral point and ground.
WHAT IS SCADA ?
• SCADA stands for Supervisory Control And Data Acquisition.
• It is not a full control system, but rather focuses on the supervisory level.
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• It is a purely software package that is positioned on top of hardware to which it is interfaced. ( via
Programmable Logic Controllers(PLCs)) .
The SCADA systems are arranged to perform the following tasks.
• Data Collection (Data Acquisition)
• Data transmission (telemetry)
• Scanning, Indication, Monitoring, Logging.
• Control and indication.
• Ensure sequential events.
• Data presentation, display, reporting
• Execution of operating, commands: on/off,raise/lower.
• Network supervision, alarms and report any uncommon
change of state.
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