Line Protection AVSRamesh 28 Sep 2006
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Transcript of Line Protection AVSRamesh 28 Sep 2006
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Protective RelaysAVS RameshDy.Manager (Operation Services)POWERGRID
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One and Half Breaker Scheme
Ckt-1 Ckt-2
Bus-1
Bus-2
21
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Distance Protection
Distance Protection schemes shall have
Three independent zones
Separate measurements for all Phase to Phase &Phase to ground faults.
Single and three pole tripping capability.
Directional characteristics for Zone-1, Zone-2 and
Zone-3. Capability of operation for close up three phase and
switch on to faults.
Adjustable characteristic angle to match line angle.
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Distance ProtectionDistance Protection schemes shall have
Accuracy of better than or equal to 5% of set value for
reach measurement in Zone-1 & Better than equal to10% of set value for Zone-2 & Zone-3.
Accuracy of better than or equal to 5% of set value
for time measurement of Zone-2 & Zone-3.
Power Swing detection feature for selective blocking,
as required.
Suitable fuse failure protection to monitor all types of
fuse failure and block the protection.
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Distance Protection - Setting criteria
Reach Setting:
Zone-1 : To cover 80-85% of protected line section.
Zone-2 : To cover minimum 150% of length ofprincipal line section.
Zone-3 : To cover 120% of principal section plusadjacent longest section.
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Zone-1Zone-2
Zone-3
A B C85%
150%
ZAB + 120%
Distance Protection - Setting criteria
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Time setting:
Zone-1 : Instantaneous Zone-2 : 0.3 sec,0.5 sec
(For short line followed by long line)
Zone-3 : 1.0 sec.
Distance Protection - Setting criteria
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Power Swing
LoadArea
X
R
Z1
Z2
Z3
RecoverableSwing
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Phase Comparison Protection
Current Phase comparison type
Suitable for operation without PLCC
High sensitivity for all types of faults
Capable of single and three pole tripping
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Phase Comparison Relay(Through fault)
A B
A
B
A+B
B
A
A+BNo Trip No Trip
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Phase Comparison Relay(In-Zone fault)
A B
A
B
A+B
B
A
A+BTrip Trip
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Phase Comparison Protection shall be
Un-Affected by :
Heavy load transfer Power swings
CT saturation
CT Phase errors Propagation delays
Capacitance current
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Technology comparison for Protective Relays
Sl.No.
Subject Electro-mechanical
Static/Electronic
Numerical
1. MeasuringElements/Hardware
Induction disc,Electromagnets, Induction cup,Balance beam
Discrete R, L, C,Transistors,
Analogue ICs,Comparators
Microprocessors, Digital ICs,Digital SignalProcessors
2. Construction
size
Bulky Modular,
Compact
Most compact
3. Parametersetting
Plug setting,Dial setting
Thumb wheel,Potentiometers,Dual In Lineswitches
Keypad forNumericalvalues
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Technology comparison for Protective Relays
continued
Sl.
No.
Subject Electro-
mechanical
Static/
Electronic
Numerical
4. CT Loading/
burden
8-10 VA 1 VA < 0.5 VA
5. Self
monitoring
No Yes
.Hardware
partially
.Powersupply
Yes
.Hardware
.Power supply
.Output relays
.Software
.CT, PT,Ckts
6. Temperature
stability
Yes No Yes
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Technology comparison for Protective
Relays continued
Sl.
No.
Subject Electro-
mechanical
Static/
Electronic
Numerical
7. Vibration
proof
No Yes Yes
8. Harmonic
immunity
No Possible through
analog
filtering
Yes, digital
filtering
incorporated
9. Calibration Frequently
required as
settings drift
due to ageing
Required as
settings drift
due to ageing
Not required as
settings are
stored in memory
in digital format
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Technology comparison for Protective
Relays continued
Sl.No.
Subject Electro-mechanical
Static/Electronic
Numerical
10. Auxilliarysupply
Required Required Required
11. Electromagnetic/electrostatic
/HF
disturbance
Immune Susceptible Immune
12. Multiplecharacteristics
Not possible Not possible Possible
13. Integratedprotective
functions
Not possible Not possible Possible
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Technology comparison for ProtectiveRelays continued
Sl.No.
Subject Electro-mechanical
Static/Electronic
Numerical
14. Range of settings Limited Wide Wide
15. Operational valueindication
Not possible Possible Possible
16. Fault disturbancerecording
Not possible Not possible Possible
17. Digitalcommunicationport
Not possible Not available Available
18. Commissioningsupport from relay
No No Yes
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Analog filter
Sample & Hold
Multiplexer
Signal Input
A/D converter
Digital Filter Protn. algorithm
Relay logic
Trip /alarm
Numerical Distance Relay
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Numeric Protection Sample and hold amplifier
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Numeric Protection
Signal Sampling principle
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Numeric Protection
Typical numeric relay hardware
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Numeric Protection
Distance relay model ofTransmission Line
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Numeric Protection
Impedance measuring algorithm
Vr = Rir + L (dir /dt) -------------- (1)
where
R = Series ResistanceL = Inductance
vr = Relaying voltage
ir = Relaying current
The current derivative of equation (1) can be written as
Vr = Rir + L ir where ir = (dir/dt)
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Numeric Protection
Impedance measuring algorithm ..contd.
To solve for two unknowns, two equations are required..
Hence two sets of relay voltages, currents and currentderivatives are utilised.
Vr1 = Rir1 + L ir1Vr2 = Rir2 + L ir2
Combining the above two equations,
R = (Vr1ir2 - Vr2 ir1)/(ir1ir2 - ir2 ir1)
L = (Vr2 ir1 - Vr1ir2 ) / (ir1ir2 - ir2 ir1 )
For convenience, let D = (ir1ir2 - ir2 ir1 )
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Numeric Protection
Impedance measuring algorithm ..contd
The apparent resistance and reactance presented to the relaymay be calculated as follows:
R x D = (Vr1ir2 - Vr2 ir1) and
X x D = LD = (Vr2 ir - Vr1ir2 )
where is power system frequency and X is reactance
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Numeric Protection Impedance measuring
algorithm ..Time spaced solution
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Numeric Protection Impedance
measuring algorithm ..current derivative
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Numeric Protection Quadrilateral
characteristic and counting strategy
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Auto Reclosing scheme Single Phase and /or three Phase reclosing facilities
Continuously variable single phase and three phasedead time.
Continuously variable reclaim time
Facility of selecting single phase / three phase /Single & three phase auto reclosure/ Non-autoreclosure modes.
Facility for selecting check synchronising or dead linecharging features.
Sequential reclosing facility of breakers in multiplebreaker arrangement.
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Auto Reclosing scheme Setting criteria of auto reclosure
Dead time : 1 sec
Reclaim time : 25 Sec
Protections which shall start autoreclosing
Main-I Protection
Main-II Protection
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Y Y
B B
R R
Y Y
B B
R R
Y Y
B B
R R
I II
III
Auto Reclosure Sequence
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Auto Reclosing scheme Protections which block auto reclosing:
LBB
Line reactor Protection Over Voltage Protection
Bus Bar Protection
Zone-2/3 of distance Protection
Circuit breaker problem
Carrier fail
Receipt of DirectTrip signal.
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Over Voltage Protection Two stages
High drop off to pick up ratio.
Adjustable setting range for voltage and time.
Low set stage and shall monitor any onePhase Phase voltage and shall have
associated timer. High set stage shall monitor all three voltage
and shall have associated timer.
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59
Vn
1.1 Vn
CVT
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Over Voltage Protection Over Voltage Protection shall be
connected to:
Trip connected line breaker(s)
Start LBB
Block auto reclose
Send direct trip command
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Over Voltage Protection-Settings
Low set stage at110% with typical timedelay of 5 seconds.
High set stage at150% with time delayof100mSec
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Transformer Protection Transformer differential protection
Restricted earth fault protection
Over fluxing protection
Back up directional Over current &Earth fault protection on HV side
Back up directional Over current &Earth fault protection on IV side
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Transformer Differential Protection
R
Y
B
RYB
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Transformer Protection Protections & Monitors built-in to transformer
Buchholz relay
Winding temperature Oil temperature
Oil level
Pressure relief
Fire protection
Protection of tertiary winding
Over load alarm
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Differential Protection Triple pole feature with individual phase
indication
Unrestrained instantaneous high set O/C unitswhich should not operate during in rush.
Adjustable for multi bias setting
Second harmonic or other inrush proof feature.
One bias winding per phase and per CT input
An adjustable operating current
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Bias
1.0 2.0 3.0 4.0
0.2
1.0
2.0
3.0
Through Bias Current
Operate
Not-Operate
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Restricted earth fault protection
64
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Over Fluxing Protection Phase to Phase connected
Operating on the principle of measurement of
voltage to frequency ratio. Provided with inverse time characteristics
compatible with transformer over fluxing.
Provided with independent alarm with a
definite time delay at value of V/F between100% to 130% of rated value.
Having high reset ratio of 98% or better.
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51
51
220KV
400/220 KVTransformer
A
B
Back-Up Over currentprotection
400KV
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Over Load alarm Single Pole feature
Definite time over current feature
Continuously variable current range of50-200% of rated current andcontinuously variable timer setting
range of1
to10
Secs. Drop off to Pick up ratio of 95% or
better.
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Reactor Protection Differential Protection
Restricted earth fault Protection
Reactor Back-up protection Buchholz relay
Winding temperature
Oil Temperature
Pressure relief
Oil Level
Fire Protection
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R
Y
B B
Y
R
Shunt Reactor
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R
Y
B B
Y
R
Single line to Ground Fault
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Differential Protection -
Reactor Operating current sensitivity of atleast
10% of nominal current
Tuned to system frequency Suitable non-linear resistors to limit peak
voltage during in-zone faults
High or low impedance principle
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Differential Protection -
Reactor
Operating current sensitivity of atleast
10% of nominal current
Tuned to system frequency
Suitable non-linear resistors to limit peak
voltage during in-zone faults
High or low impedance principle
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Backup Protection-Reactor Either Impedance type or definite time O/C & E/F
type
Impedance type reactor back up Protection shall be
Triple Pole type
Single step Polarised MHO or impedance distancerelay
Having characteristic angle between 60 80
degree. Provided with adjustable definite time delay relay
Provided with suitable range for covering 60% ofreactor impedance.
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Bus Bar Protection
87
Ckt-1Ckt-2
87Main Zone
Check Zone
RYB
N
RY
B
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Bus Bar Protection 3 Phase type and operate selectively for each
bus bar section
Operating on differential principle and shallprovide independent zones of protection foreach bus.
Provided with Zone indication
Stable for through fault condition Provided with continuous supervision for CT
secondaries.
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Local Breaker Backup
protection Short operation and drop-off times
Three phase current elements with facility
for phase wise initiation Current setting range such that the relay can
be set at minimum 200mA (for line) and 50mA (for generator) for 1Amp CT secondary
Associated timer with adjustable setting.
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Distance to Fault locator Shall be electronic or microprocessor
based
On line type
Shall be suitable for CB operation of2cycles
Built-in display(KM)
3% accuracy for all type of faults
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Distance to Fault locator Accuracy shall not be affected by Remote end
infeed
Dc component in fault current Arc resistance
CVT transients
Mutual compensation facility
Based on traveling wave generated by fault
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Event Logger To record the state of switchyard
equipments and relays.
To record the occurrence of alarms.
To record changes in digital inputs
To record switching of primary plant
within sub-station.
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Event Logger Time synchronised with GPS clock
Permissible drift +/- 0.5seconds/day
Print out of current alarm and plant status available on request.
To entry of date and time from key board.
Programmability at site. Shall record 40 changes in 10mSec interval.
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Disturbance Recorder To understand behavior of the Power
network before or after any
disturbance.
Useful info in planning of newinstallations.
For further improvement in theequipment
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Disturbance Recorder-Functions Records instantaneous values of V, I, In and open delta
voltage.
Status of relay contacts and CB during disturbance. Requirement
Recoding capacity-8 analog + 16 digital.
Memory 5 sec
Min. Pre fault 160mSec Post Fault 2sec- min , not less than 5sec.
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Disturbance Recorder-TriggersAny digital signal triggering.
Analog triggering by threshold levels.
Trigger selection of over/under levelsshould be possible.
Time tagging:
Built-in real time clock. Drift of the clock shall not be more than
0.5sec per day.
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Disturbance Recorder Sampling rate : 1 Khz
Recording : 5Hz to 250Hz.
Special requirement: Sync. With GPS
16Analog + 32 digital for D/C lines
DR + FL
If DR is part of Numerical Protection,externalbinary input should be possible.
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