power swing
TRANSCRIPT
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Brief Introduction for Power Swing Detection Methods & Testing
Kamin DaveApplication Engineer (Protective Relaying)
DOBLE ENGINEERING COMPANYDoble Conference - 2007
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Basic definitions:
Power Swing: A variation in three phase power flow which occurs when the generator rotor angles are advancing or retarding relative to each other in response to changes in load magnitude and direction, line switching, loss of generation, faults, and other system disturbances.
Pole Slip: A condition whereby a generator, or group of generators, terminal voltage angles (or phases) go past 180 degrees with respect to the rest of the connected power system.
Stable Power Swing: A power swing is considered stable if the generators do not slip poles and the system reaches a new state of equilibrium, i.e. an acceptable operating condition.
Unstable Power Swing: A power swing that will result in a generator or group of generators experiencing pole slipping for which some corrective action must be taken.
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power swing due to;Power system faults (System more affected on 3-ph fault, so power gain is very less)Sudden changes to electrical power due to rejection of load or generatorsThese type of disturbances causes oscillation in machine rotor angles (Load Angle = 900 or 1200) & can result in sever power flow swings. Power swings are variations in power flow that occur when the internal voltages of generators at different network locations of the power system slip relative to each other.
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Vector diagram: two machines
ΙL ⋅ ZS1 ΙL ⋅ ZL ΙL ⋅ ZS2
E2 = E'2E1UA UB
U'B
U'A
Ι 'L ΙL
ϑ' ϑE'1
E1 E2ZS1 ZS2ZL
UAUB
Two Machine Problem
If the Load angle becomes too large, the system stability can be lost
Pmax = {(E1*E2)/X}*SIN(theta)
Figure:-1
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power diagram:
If the Load angle becomes too large, the system stability can be lost
Pmax = {(E1*E2)/X}*SIN(theta)
Figure:-1A
Critical Angle
Rotor Angle
Stability limit
Power Diagram
0
50
100
150
200
250
300
0 50 100 150 200
Angle in Degree
Pow
er
Stability region
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power swing detection methods:Conventional “Rate of Change of Impedance” (Dz/Dt) Methods:Concentric characteristic schemes.Continuous Impedance calculation schemes.Blinder Schemes:1) Single Blinder2) Double Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Conventional PSB detection methods:It measures the Positive sequence impedanceDuring a system swing, the measured impedance moves slowly on the impedance plane, and the rate of impedance change is determined by the slip frequencyo f a n e q u i v a l e n t t w o - s o u r c e s y s t e mTravel Time (Delta-t) from one point to next point is to differentiate between fault & swing. Travel time is more than set value then, distance relay sense as swing. Travel time less than set value then, it sense as fault
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Conventional PSB detection methods:Concentric circle characteristic schemes:It is simplest method to detect “rate of change of impedance”Two impedance zones. Inner zone & outer zoneFigure-3 shows, Relay indicates PSB when transition time of impedance from outer zone to inner zone is more than set value (impedance locus move slowly).PSB: Blocks the zones when swing is stable (Figure:-3)OST: Trip zones when swing is un stable (Figure-4)Major drawback of this characteristic is load encroachment.
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Figure:-3
Swing Locus
∆t = time for transition of Z from outer to inner zone
∆t
Stable Swing
Set “Zin” & “Zout” on line angle
Concentric characteristic scheme: MHO Circle
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Figure:-4
∆t = time for transition of Z from outer to inner zone
∆t Un stable Swing
Concentric characteristic scheme: MHO Circle
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Figure:-5
∆t = time for transition of Z from outer to inner zone
∆t •R & X reach are dependent on Z value
•Difficult to set on Load Encroachment
Set “Zin” & “Zout” on line angle
Load
Concentric characteristic scheme: MHO Circle
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Concentric characteristic scheme: Lens
Load
Avoid mal operation during load encroachment
Figure:-6
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Conventional PSB detection methods:
Concentric characteristic schemes:Polygon Characteristic concept is much more better than concentric circle characteristic.Rset & Xset for out zone can able to set independently.Rset of outer zone can not reach in to Load region
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Concentric characteristic scheme: PolygonCharacteristic in relay type REL511
56
1
34
X
RZload
ZS1
ZS1
ZL2
2
0ϑ0
Dz1/Dt1Dz2/Dt2
Dz3/Dt3
Dz4/Dt4
Inner boundary = Zin Outer boundary = Zout
Polygon Characteristic for Power swing detection: Set R & X reach independently
Figure:-7
Set “R” reach
Set “X” reach
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
∆Z
∆t = time for transition of Z from outer to inner zoneR reach reduce for Load encroachment
Concentric characteristic scheme: PolygonCharacteristic in relay type 7SA610
Polygon Characteristic: Set “R” reach according to Load Encroachment
Figure:-8
Load Angle = 120o or 90o
Angle = 45o
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
E1 = E2
E1 > E2
E1 < E2
X
R
ZS2
B
ZL
A
ZS1
ZLoad
ϑϑ' load point
Figure:-9
Concentric characteristic scheme: PolygonCharacteristic in relay type 7SA610
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
∆t = time for transition of Z from outer to inner zone
Concentric characteristic scheme: Quadrilateral
Quadrilateral Characteristic: Set “R” reach according to Load Encroachment
Figure:-10
Load
Line Angle
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Concentric characteristic scheme: PolygonCharacteristic in relay type RELZ 100
Stable Swing
Unstable Swing
Quad + Polygon
Zone 3 limit
Zout boundary
• Timer unit count to starts travel time when Power swing locus crosses Zout boundary • Travel time (Delta T) more than set time, relay detect as a Power swing
Figure:-11
Z1(t1)Z2(t2)
Z3(t3)
Z4(t4)
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Concentric characteristic scheme: PolygonCharacteristic in relay type P442
Line Angle
Figure:-12
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Continuous Impedance calculation for PSB detection methods:
Scheme determine Power swing condition based on a continuous impedance calculation. i.e for each 2ms or 5ms step an impedance calculation is performed & compared with the impedance calculation of previous 2ms or 5ms.This step value is depend on sampling freq. rate.The next impedance that should be calculated 2ms or 5ms later is predicted based on impedance difference of the previous measured impedances.Not required any delta impedance settingsRequire delta time settingsDrawback is; if prediction is correct, then only distance prot. consider as a traveling impedance & a power swing condition is detected. For security reason additional predictive calculation is required
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Figure:-13
Continuous Impedance calculation for PSB detection methods:
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Continuous Power calculation for PSB detection methods: Polygon characteristic in relay type P437
Stable Swing
Unstable Swing
R-R
-X
X
Zpos(t)
Setting Parameters:•Rset•Xset•Line Angle
Detect as Fault:Zpos(t1) = 0 ms Zpos(t2) < 40 ms
Detect as Swing:Zpos(t1) = 0 ms Zpos(t2) > 40 ms
Figure:-14
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Relay measures the rate of change of Positive sequence Apparent Power:
Delta-SPOS = (SPOS2 – SPOS1) / (SPOS2)
Let,SPOS1 = Positive sequence Apparent Power at time (t1)SPOS2 = Positive sequence Apparent Power at time (t1 + 40 ms)
Continuous Power calculation for PSB detection methods: Polygon characteristic in relay type P437
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Pole slip detection method: Relay type REM54
• Scheme is applicable for Out of Step tripping of Generator • Pole slip detection = OMHO characteristic + Counter• Counter count number of operation• Reset time required to set properly other wise it will detect loss of field function• Normally counter setting is 3 or 4
XS
X’d / 21
2
Offset mho characteristic
Counter
-X
X R-R
Operating Region
Counter Reset
Figure:-15
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Apparatus Maintenance and Power Management for Energy Delivery
Pole slip detection method: Relay type REG 316
Pole-Slip Characteristic
-7
-5
-3
-1
1
3
5
7
-7 -5 -3 -1 1 3 5 7
R in Ohm
X in
Ohm
ZB
ZC
ZAWarning Angle
Tripping Angle
Figure:-16
Trip When Load angle isMore than Trip Angle
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
System Load angle is more than set value with calculated slip freq., relay will detect pole slip (Power swing)Relay calculating Freq slip based on T-Slip time (say 55 ms)Tripping Angle setting should be based on critical angle of machineWithout system study, recommended angle setting is 120o
Pole slip detection method: Relay type REG 316
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Blinder Schemes: Single BlinderBlinder schemes:Single Blinder (one pair) scheme (Figure:-17):One sets of blinders: Resistive reach inner (RRI) & Resistive reach outer (RRO)It can be used to restrict tripping of the distance relay for loads outside of the blinders.
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
DR/DT schemes:Single Blinder scheme (Figure:-17):One sets of blinders: It can be used to restrict tripping of the distance relay for loads outside of the blinders.If travel time is more than set time & it crosses blinder-1, a power swing situation is detected further it crosses blinder-2 then it gives a tripping. Scheme is more suitable for out of step protection for generators.Correct settings of blinder-2 & RRR are very difficult to set, again it’s require high skilled expert to do grid analysis & effect on machines.
Blinder Schemes: Single Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
DR/DT scheme:How to set timer?T = {(Critical load angle – Rotor angle)*Fn}/{(360)*(slip frequency)}
Where;Critical load angle = 150 degreeRotor angle = 90 degreeFn = 50Hzslip freq. = 4Hz
T = {(150 – 90)*(50)} / {(360)*(4)}= 2.0833 Cycles
T = 2.0833 * 20 = 41.66ms
Blinder Schemes: Single Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Blinder-1Blinder-2
Figure:-17
Single Blinder
Un stable swingStable swing
RRR
RRR = Reverse Resistive Reach in Ohms
OST-REGION
OST = Out of Step trip
Relay Type: ZTO 11
Blinder Schemes: Single Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Blinder-1Blinder-2
Single Blinder
Un stable swingStable swing
MHO supervising unit
Mho supervising unit will restrict mal-operation of relay
Rset is not adjustable in forwarddirection
Blinder Schemes: Single Blinder
Figure:-18
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
CEB + CEH Relays
X’d
XT+XS
Blinder 1
Line Angle
MHO supervising control
Blinder Schemes: Single Blinder
Load Angle = 90o or 120o
Swing Centre = {X’d + (XT + XS)} / 2
Figure:-19
Swing Locus
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Blinder schemes:Double Blinder (Two Pair) scheme (Figure:-20):Two sets of blinders: Resistive reach inner (RRI) & Resistive reach outer (RRO)Time Counter starts when the impedance vector crosses outer limit (RRO) & stops when it crosses inner limit (RRI)If travel time is more than set time, power swing situation is detectedScheme is applicable for independent of the distance zonesCorrect setting for Blinders are very difficult & it requires good expert who can able to do power grid analysis.
Blinder Schemes: Double Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Blinder-1Blinder-2
Figure:-20
Double Blinders
Blinder-1Blinder-2
Blinder Schemes: Double Blinder
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Testing methods with F6150:
Asynchronous method by using Doble advance transient creatorDz/Dt simulation by using State simulation module
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Asynchronous method by using doble advance transient creatorTwo machines
Power Swing Testing: Asynchronous method
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: Asynchronous method
Select “Swing”
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: Asynchronous method
Source-1 parametersSource-2 parameters
Slip freq. = 2Hz
Line parameters
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: Asynchronous method
Save datc file
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Asynchronous method: Power swing Waveform
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: Asynchronous method
Save comtrade file for test
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: Dz/Dt Method
Dz/Dt simulation by using State simulation moduleTotal 25 nos. of statesEach state having independent magnitude, phase angle & frequency controlledIndividual time setting for each stateEach state having option to enter individual value for “L/R” constantPhasor diagram for each state to show voltage & current vectors
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Blocking Testing: REL100
Figure: 11 shows relay characteristicModule Type: State SimulationTest Sequence:
Load condition: State 1Apply 3-phase Fault in PSB locus(Z1): State 2Apply 3-phase Fault in Zone 3: State 3Travelling time between State 2 & State 3 should be more than time out setting of relay (Say: 70 ms if relay setting = 50ms)Remove fault: State 4
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
State Simulation
Travel TimeZ1 Z2 Z3
Phasor
State: 2 State: 3 State: 4
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Apparatus Maintenance and Power Management for Energy Delivery
Excel Spread sheet Control:
Micro Soft Excel Spread sheet for Custom ApplicationEasy to useState Simulation up to 20 statesEasy to simulate any Power System EventsMore flexibility to calculate numerical functionsInterface with F6150 via serial communicationEngineers’ choice
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
REL100: PSB Testing
REL100:Relay settings:ZONE-3:Rin = 7.97 Ohms, Xin = 43.97 OhmsPSB settings (Polygon char.):Rout = 7.97*1.2 = 9.56 OhmsXout = 43.97*1.2 = 52.76 Ohms
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
PSB settings
Power Swing Testing: REL100
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Power Swing Testing: REL100
State: 1/2/3/4/5
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Apparatus Maintenance and Power Management for Energy Delivery
Plot “Dz/Dt” locus
PSB Polygon
Power Swing Testing: REL100
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Run Test
Select Com Port
Auxiliary DC
Assign Trigger
Power Swing Testing: REL100
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
REL521: PSB Testing
Dz/Dt simulation by using State simulation moduleREL521:PSB settings:Inner zone settings (Polygon char.):RIN = 3.0 Ohms, XIN = 3.0 OhmsOuter zone settings:KR = 125%, KX = 125%RIN = 3*1.25 = 3.75 OhmsXIN = 3.*1.25 = 3.75 Ohms
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
REL521: PSB Testing
PSB settings
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Enter values in states
Enter travel time in states
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
REL521: PSB Testing
Dz/Dt locusZin Zout
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Pole Slip Relay Testing with F6150 & Excel Spread sheet control
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Basic definitions: Pole Slip
Pole Slip: A condition whereby a generator, or group of generators, terminal voltage angles (or phases) go past 180 degrees with respect to the rest of the connected power system.High level Transient torque develop in machine shaft can break the shaftHigh Stator Iron flux can over heat generator stator coreProtection is also known as a out of step Protection of machineProtection is applicable for synchronous machines
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Basic definitions: Pole Slip
X’d = 25%
XT + Xs = 18%
90o
90o
Electrical Centre
Theta
Theta = Line Angle
Rotor Angle
Xs
XTX’d
G
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Relay Details:MAKE : GEC ALSTHOMMODEL : ZTO 11
Relay Settings:K1 = 1K2 = 1K3 = 8R = K1*K2*k3 = 8 OhmsBlinder 1 = 65 DegreeBlinder 2 = 65 DegreeTime = 55ms
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Relay Characteristic: Blinder Scheme
R R
X
-X
-R
Traveling Time (Dt) should be more than 55 ms from one point to next point
Power swing Locus
65o 65o
Blin
der 1
Blin
der 2
A
A’’
B
B’’
ZTO 11
Ope
ratin
g Re
gion
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Relay Characteristic: Blinder Scheme
R R
X
-X
-R
Traveling Time (Dt) should be more than 55 ms from one point to next point
Power swing Locus
65o 65o
Blin
der 1
Blin
der 2
A
A’’
B
B’’
Optional Scheme:ZTO 11 + YTGM15
Mho Characteristic to reduce the mal operation of relay
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
Pole Slip Protection: ZTO11
Four ElementsOver current starterBlinder 1 Unit (A-Unit)Timer Unit (T-Unit)Blinder 2 Unit (B-Unit)
Alarm: Operation of A & T units with O/C starterFault condition: Operation of A & B units with O/C starterPole Slip condition: Operation of A, T & B units in sequence with O/C starter
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
ZTO11: Stable Swing
Enter Time out Time more thanSet value
Swing Locus
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
ZTO11: Pole Slip Condition
Enter Time out Time more thanSet value
Swing Locus
VTest & ITest values set for Test
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
ZTO11: Fault Condition
Enter Time out Time less than set value
Swing Locus
VTest & ITest values set for Test
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
ZTO11: Reverse Resistive Reach Test
Enter Time out Time less than set value
Swing Locus
Knowledge Is PowerSM
Apparatus Maintenance and Power Management for Energy Delivery
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