Switchyards and SCADA systems are important components of power generation and distribution. A switchyard stabilizes the link between generation and transmission by controlling voltage, current, and power distribution. It includes components like transformers, bus bars, circuit breakers, and isolators. SCADA systems monitor and control equipment remotely using sensors, PLCs, and a control unit interface. They allow operators to detect issues and respond quickly from a central location. Together, switchyards and SCADA improve efficiency and safety in power systems.

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A comprehensive report on
switchyArd And scAdA
Submitted by
PALLAV PRINCE
KIIT University
Bhubaneswar, Odisha
Under the guidance of
Mr. A. N. Srivastava
Mr. A. K. Chuhan
Mr. Kamlesh Kumar
Contents
• Switchyard
• Working of switchyard
• Components of switchyard
• SCADA
• Working of SCADA
• Single line diagram
• Control unit
• References

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 Switchyard
• Switchyard is the one of the most important sections of a power station
• It stabilises a link between power generation unit and power transmission unit
• It is normally interconnected to all power grids and generation plants
 Working
• It transmits and receives the signal to/from grid control unit with the help of
microcontrollers
• It is used for protection from short circuit, overloading, and under-loading
condition, by accidently or due to bad weather
• The main function of a switchyard is to control the voltage and current and to
distribute the power among sub-grids
• It is also used for synchronizing the generating power and field power
Switchyard: NTPC Kanti
 NTPC Kanti distributes power to the sub-grids as
UNIT (KV) LOCATION
220 Darbhanga, Begusarai, Gopalganj (1,2), and KAFAN (1,2)
132 Motihari, Muzaffarpur (1,2), Samastipur (1,2), and SKMCH (1,2)

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Components of a Switchyard
i. Voltage Transformers
ii. Current transformer
iii. Bus bar
iv. Lightening arrestor
v. Isolator
vi. Circuit breaker
vii. Wave trapper
viii. Earth switch
ix. Transmission tower
Transformer
• Electrical machine which transforms the voltage from high voltage to Low voltage level
and vice-versa whereas maintains the same frequency and power at input and output
terminals
• It consists of core, primary winding, secondary winding for power transfer and oil for
cooling purpose
Voltage Transformer
• To step-down (step-up) the high voltage to low voltage (low voltage to high voltage)
Current Transformer
• It measures current and auto adjust it to the required level
• It is a type of Auto-transformer

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Generation transformer (GT)
Quantity Value
Kilo volt no
load
HV 230
LV 11
Line Amperes HV 351.4
LV 7348.31
Phase 3
Frequency 50 Hz
Vector symbol Ynd11
Oil
temperature
50 °C
Winding
temperature
55 °C
Table: Name plate of GT
Voltage Transformer Current Transformer

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Bus Bar
Conductors to which a number of circuits are connected
Quantity Value Unit
Type of switchgear Metal clad
Rated voltage 6 KV
Power freq. withstand voltage 25 Hz
Peak impulse withstand voltage 60 KVP
Rated continuous current 3150/1600 A
Rate short circuit current for 1 Sec 40 KA
Material of bus bar Copper
Max temperature 95 °C
Control power supply 220 V DC
Protection Class IP4 1
Table: Bus bar details used at NTPC Kanti
Lightning arrestors
• It is protecting device used to protect from high current flow in circuit due to
lighting
• It discharge high voltage to ground
• It is connected in all RYB-phase of supply
Indicator of arrestor Photo: Lightning arrestors of NTPC Kanti
Quantity Value
Rating 216KV, 10A
Type IMAS
Max cont. operating voltage 156 KV rms
Pressure relief current 40 KA
Frequency 50 Hz
L.D. discharge class 3
Name plate of arrestor

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Isolator
• Isolator is a circuit breaker and circuit maker
• It is used to open and close the bus connections
• It helps to insure circuit connection from distance
• It can operate manually or with the help of command from control room
Photo: Isolator
Circuit Breaker
 The protecting device to breaks the physical connections under fault conditions
 Main parts of circuit breaker
 Fixed Contact
 Movable Contact
 Operating Mechanism
 Arc extinguishing medium
 Working
 When faults occurs high current may flow through circuits which is detected by
microcontrollers and hence send controlling signals to the “Relay”
 Relay becomes activated and send command to the circuit breaker
 Tripping coil of breaker gets activated and it trips or disconnects the connections
 An arc may produce between the contacts and it is extinguished by the arc
extinguisher

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Arcing
• High current flows through contact at the time of fault
• On sudden break of contact the charge density increases between contact areas
• Due to charge density heat generates and arc medium gets ionised
• Ionised medium makes an instant connection between contact areas and arc
produces
• Arc is extinguished by arc extinguisher present in the circuit breaker
 Types of arc extinguisher
• Air
• Oil And
• Sulphur Hexafluoride (SF6) Circuit Breakers
Types of Circuit Breaker
 Miniature Circuit Breakers
 Vacuum Circuit Breakers
 SF Circuit Breakers
 Air Blast Circuit Breakers
 Oil Circuit Breakers
Only and Vacuum Circuit Breakers are used at NTPC Kanti

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Miniature Circuit Breakers (MCB)
Advantages
1. It is more sensitive than fuse
2. It can be operate up to 100
Amp current
3. Less maintenance and
4. Low cost
Disadvantage
Not fully Automatic
Vacuum Circuit Breakers
Advantages
1. No need of oil or gases
2. Highly sensitive and self operating
Device
3. Programmable and compact circuit
4. It can be use for high voltage
5. Low maintenance
Disadvantages
1. Bulky size
2. Loss of vacuum due to small damage
Vacuum chamber of VCB

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Rating of VCB (NTPC Kanti)
Quantity Value
Type MHVCB
Rated voltage 7.2 KV
Rated Current 2750 A
Frequency 50 Hz
Short circuit breaking current 40 KA
Short circuit duration 1 Sec
Photo: Front panel of Vacuum circuit breaker
Circuit Breakers
• sulphur hexafluoride (SF ) gas is used in breaker medium
• High pressure of gas extinguishes the arc produced in circuit and it also keeps
the breaker cool
Advantages
1. Highly sensitive
2. Gas provide the insulation between contacts
3. It is used for high voltage
4. It has indicators to indicate pressure of gas
5. It can be used in outdoor
Disadvantages
1. High maintenance cost
2. Leakage of gas due to damage

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 Circuit Breaker (NTPC Kanti)
Quantity Value
Type SF
cont. current for incomer 3150/1250 A
Cont. current for feeder 630 A
Short circuit breaking current 40 KA (rms)
Duty cycle O-3sec-CO-3min
CB opening time 70
CB closing time 72
Type of operating mechanism Motor operated spring
charged
Power supply 220 V Dc
No of trip coil 2
Emergency mechanical trip Provided
Air Blast Circuit Breakers (ABCB)
 Advantages
1. It is commonly used in day to day
life
2. Needs no oil or gas
3. It is used at atmospheric pressure
 Disadvantages
1. It can not be used for high voltage
2. Oil circuit breaker is more
advantageous than ABCB

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Oil Circuit Breakers
The mineral oil is used in oil circuit breaker. It is better insulating medium
than air. Highly compressed gas bubbles extinguish the arc.
 Types of oil circuit breaker
1. Bulk Oil Circuit Breaker (BOCB)
2. Minimum Oil Circuit Breaker (MOCB)
 Advantages
1. It is more sensitive
2. Widely used all over the country
 Disadvantages
1. Needs high maintenance
2. Leakage of oil due to damage
Relay
• It is an important device of a switchyard
• Relay is an electrical switching device
• It works on electromagnetic principle
• It is connected between circuit breaker and microcontrollers
• It is highly sensitive and self operating device
• It can operate manually as well as automatically
• Circuit breaker is tripped on activation of relay
• Needs low maintenance

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SCADA
• SCADA stands for “Supervisory Control and Data Acquisition”
• Supervisory - It means to monitor the data remotely
• Control – It means to control the data remotely
• Data Acquisition - It means to store the data to the system
• SCADA is widely used in industries
Working
• SCADA controls and monitor the devices and machines like motors, generators,
circuit breakers, oil tank level, gas leakage, etc. with the help of HMI (Human-
Machine-Interface) technology.
• Sensor detects the physical parameters from the machines and sents data to PLCs
(Programmable Logical Controls) which interface the data to the SCADA system
• Hence, command sent from control unit to the device and machines are remotely
controlled
Single Line Diagram (SLD) of NTPC Kanti

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 Control unit: NTPC Kanti
• The control unit having
o SCADA display
o SCADA software installed systems
o Relay and microprocessor devices
o Controlling and protection panels of different units and areas
SCADA Display, NTPC Kanti

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Relay and microprocessor devices
Relay box Microprocessor device
Controlling and protection panel
Internal view of panel

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Application of SCADA
 It is used
• To insure the correct working of machines in industry
• To remotely activate or deactivate the controllers to avoid hazards
• To control speed of motors, turbines, etc.
• To detect the leakages of gas, oil, or other fluid
Disadvantage
1. Requires local area networking
2. On slightly mistake in operation it invites hazards
3. Requires power supply to each and every controllers continuously
Advantages
1. Fault response time is very short
2. Isolate and precisely locate the faults
3. It can operate remotely
4. Less number of human source required
5. Display all the information separately on screen

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• Wikipedia
• Google Images
• Other web page: http://time-i.com/html/advantages.html
http://www.electrical4u.com/air-circuit-breaker-air-blast-circuit-breaker/
http://hubpages.com/technology/Vacuum-Circuit-Breakers-Advantages-Disadvantages
References