session-1_fundamentals of power system protection
TRANSCRIPT
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Co-ordinator
P.Raja, M.Tech.,
Assistant Professor
Dept. of Electrical and Electronics Engineering
NIT, Trichy - 15
Short-term course on
Power System Protection Issues withDistributed Generators
3rd4th August 2012
Department of Electrical & Electronics Engineering
NIT Trichy
Welcomes You all
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Session 1
Fundamentals of Power System Protection
P.Raja, M.Tech.,
Assistant Professor
Dept. of Electrical and Electronics Engineering
NIT, Trichy - 15
Short-term course on
Power System Protection Issues with
Distributed Generators3rd4th August 2012
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BASIC PROTECTION RELAYING
Session I
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What is Protection? - General
The act of protecting something / somebody
Necessary when there is something wrong /
abnormal condition
Avoid the process of expansion should notallow the wrong / abnormal condition to spoil
something is good
In our discussion Protection of Power system
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Need for Protection Analogy Rain Umbrella
Sensing
Processing & Signaling
Action
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Discussion on
Need for Protection
Abnormal conditions of Electric Power
System
Components of Basic Protection system
Fault Statistics
Relaying schemes Different discrimination
Methodology of implementation
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Discussion on
Expected quality of a Relay
Basic operation of a Relay
Concepts of Over current relay
Directional over current relay
Differential protection
Distance relay
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Components of Power Systems
Generator
Bus Bar
Transformer
Transmission Line
Loads
Generator
Transformer
Transmission Line
Transformer
Bus Bar
RainCurrent
Voltage
Frequency
Voltage
Frequency
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Fault conditions
Insulation Failure in any component
Open conductor fault
Line faults
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Abnormal Conditions
Abnormal changes in
Current (Increment / Decrement)
Voltage (Increment / Decrement)
Frequency (Increment / Decrement)
Who causes the abnormality..?!
Fault
Basic Circuit concept Short circuit
Increase in current & Decrease in Voltage
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What is Protection?
The function of protective equipment is not
the preventive one its imply
Takes action only after a fault has
occurred
Its the ambulance at the foot of the cliff
rather than the fence at the top
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Fundamental Principles
The essential and discriminative removal
of an abnormality from a power system
To minimize loss of supply and damage
Two Basic requirements of the system
Must be provided with sufficient number of
CBs
Appropriate action of controlling and
disconnecting equipments and there by
remove the abnormal conditions
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Fault Statistic Probability of
Faults Overhead lines 50 %
CTs, PTs & control equipment 12%
Switch gear 12 %
Transformers 10%
Underground cables 9% Generators 7%
GeneratorTransmission LineBus Bar
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Overhead Line Protection
(Probability of Occurrence)
Line Ground (LG) 85% (least severe)
Line Line (LL) 8%
Line Line Ground (LLG) 5% Line Line Line (LLL) 2% (Most Severe)
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Methods of Discrimination
Generator
Transformer
Transmission Line
Transformer
Bus Bar
VoltageFrequency
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Methods of discrimination
By current magnitude
By time
By current with time
By time and direction
By distance measurement
By distance with time By current balance
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Methods of discrimination
By Opposed voltage protection
By Phase comparison
Distance protection with signaling channel
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The Mediator!?
Generator
Transformer
Transmission Line
Transformer
Bus Bar
Voltage
Frequency
Relay
SensingCB
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1900 1920 1940 1960 1980 2000 2005
OC
Differential
Directional
Electromechanical
Distance
Digital
DistanceTravelling
Wave
Adaptive
ANN
Wavelet
Wide area
Hybrid
Static
DigitalP based
Numerical
Network Based
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Components of Power System
Protection
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Instrumentation Transformers
CT
Characteristics
PT
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Expected qualities of Protective
Relay
Sensitivity
Selectivity
Speed
Simplicity
Reliability
Economics
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Relaying Over current
Sensing Current Current Transformer
Relaying Electromechanical Attraction
Induction
Comparison
Pick up value
Discrimination by level of current
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Over current relay
Disadvantage of only current
discrimination
Transmission system
Zonal protection
Primary and Back up protection
Importance of timing
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Over current Relay with Time
B1 B2B3
B4
R1 R2 R3 R4 R5 R6 R7 R8
R9
B1 B2B3
B4
R1 R2 R3 R4 R5 R6 R7 R8
R9
Primary Relay
Back up Relay
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Parameters
Pick up value Minimum operating value required to operate
the relay
How do you select? Plug setting multiplier (PSM)
PSM=Fault current at the relay coil/Pick up
current Pick up current = Rated secondary of the CT
x Current setting
Time multiplier setting
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Over current relay with timing
Inverse time over current relay A - IDMT
B - Very inverse
C - Extremely inverse
1
)(14.002.0
PSM
TMStop
1
)(5.13
PSM
TMS
top
1
)(802
PSM
TMStop
A
B
C
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Over current relay with Directional Element
Simple necessity of Directional element inOver current relay
G
A B
D C
Parallel Feeder
Ring Main system
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Implementation of Electro-Mechanical Relay
Fuse
Attraction Based
Induction based
Shaded pole
Watt-hour
structure
Induction cupstructure
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Shaded-Pole Structure
Derivation of Torque
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Watt-hour structure
E core
U core
Can be used fordirectional
operation
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Differential/ unit relay
Sensing two end currents
Find the difference
If the difference > set value Relay operates
Zonal ProtectionEnd 1 End 2
Pilot wire
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Applications of Differential Relay
Unit Protection
Apparatus of smaller distance
Transformer
Alternator
Motor
Transmission Line*
Di d t f O t l
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Disadvantage of Over current relayB1
R1B2
F1 F2 F3
Distance
From
Relay location
Fault Current
LG
LLG
LLLG
Ipu
Reach of LG
Reach of LLG
Reach of LLLG
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Distant Relays
Simple over current relay
Over reach or Under reach problemB1
R1
Fault Current at
Location
Voltage at
location
Compare Desired response
F3 IR3 VR3 |VR3|>|IR3||Zset| Restrain
F2 IR2 VR2 |VR2|>|IR2||Zset| Verge of Operation
F1 IR1 VR1 |VR1|>|IR1||Zset| Trip
B2
F1 F2 F3
ZL1
ZL2
ZL3
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Distance Relay
Simple Impedance Relay See saw
Reactance Relay
Mho Relay
General Torque Equation
43
2
2
2
1 )cos( kIVkVkIkT RRRR
Will be continued in Transmission Line protection
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Thank you
Questions if any?!