auto synch considerations methods
TRANSCRIPT
Providing Security Against Faulty Synchronization and
Attendant Damage
Providing Security Against Faulty Synchronization and
Attendant Damage
25
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As protection practitioners, we spend the majority of our time designing protection systems to trip
Designing a protection system to close requires careful attention to security
You want to provide security against improper closure of two electrical sources
What defines proper closure?
Introduction
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Protect against harmful effects of closing two ac electrical sources with excessive:
- Phase Angle Difference (Ø)- Slip Frequency (ΔF or S)- High or Low Voltage (UVL, LVL)- Voltage Difference (ΔV)
Synchronizing is Used in Generator Synchronizing and System Line Restoration Applications
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Introduction
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Φ
ΔV
f1
f2
Phase Angle in 1cycle
Asynchronous Sine Waves
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Phasor RepresentationSynchronizing
VA
VBVC
VA
Phase Difference 0º
P = E1 E2---------------------------------------------------------------
Zsin 0º
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Phase Difference 80ºVA
VBVC
VA
P = E1 E2---------------------------------------------------------------
Zsin 80º
Phasor Representation
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Phase Difference 160ºVA
VBVC
VA
P = E1 E2---------------------------------------------------------------
Zsin 160º
Phasor Representation
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Synchroscope Display of Phase Angle
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Schematic of a Model SystemSynchronizing
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Effects of Synchronizing ErrorsExcessive Phase Angle – Machine IssuesExcessive Phase Angle - Closing at a static angle as low as 15 degrees can cause as large a power swing as closing at 0 degrees with an excessive slip frequency of 0.5 Hz (2-second scope). Tends to sharply “bump” the generatorMechanical shock can cause extensive damage to the rotorThough mechanical damage may not be significant cumulative fatigue damage on the shaft will ultimately reduce the life expectancy of the generatorThis cumulative fatigue damage on the shaft is often expressed as a loss-of-life value.High stator currents cause deformation of generator-end-turns and eventual winding failureFaulty synchronizing subjects the windings of the power transformer to stress
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Effects of Synchronizing ErrorsExcessive Phase Angle – System IssuesCauses Instantaneous Power and VAr FlowsMay cause transient high voltageMay cause stability issue
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VA
VA
VB VB
VCVC
ZB
ZA
ZC
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90O 180O0O
1 PU
Even a small angle (12 degrees) can causelarge instantaneous power flows
P= E1 * E2 (sin0) Z
Even a small angle (12 degrees) can causelarge instantaneous power flows
Phase Angle Difference: Power Flows
A 12 degree close hard-loads a machine to 30% of full-load shock !
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Excessive Frequency Difference
Known as “hard loading”
Causes power flows- Power out if slip is positive- Power in if slip is negative
Cumulative mechanical stress on rotating machinery
Excessive frequency difference errors can cause a disturbance when the power swing exceeds stability limits
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Excessive Voltage Difference
If the generator voltage is higher than the system voltage, the generator will supply Vars
May cause transient high voltage
If the generator voltage is lower than the system voltage, the generator will sink Vars
May trigger system instability as excitation systems react and cause power oscillations
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The Cost of Faulty Synchronization
Machine repair costs
Down Time
Lost Revenue
Lost of Interest on Investment
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Faulty Generator Synchronizing
Synchronization of Generator 5-AT
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Faulty Generator Synchronizing
Synchronization of Generator 6 at Avon
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[1] Robert W. Beckwith, "Calculations of Circuit Breaker Closing Criteria for Synchronizing a Generator." Beckwith Electric Company, August 1979.
[2] I. M. Canay, H. J. Rohrer, K. E. Schnirel, "Effect of Electrical Disturbances, Grid Recovery Voltage and Generator Inertia on Maximization of Mechanical Torques in Large Turbogenerator Sets." IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No.4, July/August 1980, pp. 1357-1370.
[3] H. H. Chen, G. E. Jablonka, J. V. Mitsche, J.B. Lewis, "Turbine-Generator Loss-of-Life Analysis Following a Faulty Synchronization Incident." American Power Conference, Chicago, Illinois, April 21-23, 1980.
[4] R. D. Dunlop, A. C. Parikn, "Verification of Synchronous Machine Modeling in Stability Studies: Comparative Tests of Digital and physical Scale Model Power System Simulations. IEEE Transactions on Power Apparatus and Systems, Vol. PAS -98, No.2, March/April 1979, pp. 369-378.
[5] D. R. Green, et al, "IEEE Screening Guide for Planned Steady-State Switching Operations to Minimize Harmful Effects on Steam Turbine-Generators." IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No.4, July/August 1980, pp. 1519-1521.
References
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[6] T. J. Hammons, "Stressing of Large Turbine-Generators at Shaft Couplings and LP Turbine Final-Stage Blade Roots Following Clearance of Grid System Faults and Faulty Synchronization." IEEE Transactions on Power Apparatus and Systems, Vol. PAS -99, No.4, July/ August 1980, pp. 1652-1662.
[7] M. C. Jackson, S. D. Umans, "Turbine-Generator Shaft Torques and Fatigue: Part III -Refinements to Fatigue Model and Test Results IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No.3, May/ June 1980, pp. 1259-1268.
[8] John S. Joyce, Dietrich Lambrecht, "Status of Evaluating the Fatigue of Large Steam Turbine-Generators Caused by Electrical Disturbances." IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No. 1, Jan./Feb. 1980, pp. 111-119.
[9] John S. Joyce, Tadeusz Kulig, Dietrich Lambrecht, “The Impact of High-Speed Reclosure of Single and Multi- Phase System Faults on Turbine-Generator Shaft Torsional Fatigue”. IEEE Transactions on Power Apparatus and Systems, Vol. PAS- 99, No. 1, Jan./Feb. 1980, pp. 279-291.
[10] J. V. Mitsche, P. A. Rusche, “Shaft Torsional Stress Due to Asynchronous Faulty Synchronization.” IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No.5, Sept./act. 1980, pp. 1864-1870.
References
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[11] D. G. Ramey, G. C. Kung, “Important Parameters in Considering Transient Torques on Turbine-Generator Shaft Systems.” IEEE Transactions on Power Apparatus and Systems, Vol. PAS-99, No. 1, Jan./Feb. 1980, pp. 311-317.
[12] P. A. Rusche, P. C. Krause, W. C. Hollopeter, “Results of an Investigation into the Torsional Shaft Failure of a 21 MW Combustion Turbine.” IEEE Publication No. CH1523-4/80/1172.
[13] Jan Stein, Horst Fick, “The Torsional Stress Analyzer for Continuously Monitoring Turbine-Generators.” IEEE Transactions on Power Apparatus and Systems, Vol.. PAS-99, No.2, March/April 1980, pp. 703-710.
[14] United States Department of the Interior, Bureau of Reclamation, Denver, Colorado, “Power O and M Bulletin.” No.27, June 1957.
References
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Sync Check (25SC, 25SC+)
Automatic Synchronizer (25A)
Speed (Frequency) Matching (15)
Voltage Matching (90)
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Synchronizing Elements
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√−−−−−−GEN VOLTAGE RAISE/LOWER
√−−−−−−GEN SPEED RAISE/LOWER
−−−−√√DEAD LINE/BUS CLOSE
−−√√√VOLTAGE DIFFERENCE (ΔV) LIMIT
−−√√√LOWER VOLTAGE LIMIT (LVL)
−−√√√UPPER VOLTAGE LIMIT (UVL)
−−√−−BREAKER CLOSING TIME (TBC)
−−√√−−FREQUENCY DIFFERENCE (ΔF) LIMIT
−−−−√√PHASE ANGLE TIME DELAY (TSC)
−−AUTO√√PHASE ANGLE (Φ) LIMIT
15/9025A25SC+25SCDEVICE NUMBER
GEN CONTROL
AUTO SYNC
SYNC CHECK PLUS
SYNC CHECKDEVICE
Synchronizing Elements
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Sync Check Logic
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Classic sync check relays use phase angle/time
- This is done so an inferred slip limit can be realized
Modern sync check relays use phase angle/slip
- Using slip frequency directly is better than using time
- Do not have to widen the angle setting- Do not have to have a deliberate delay
Affords faster restoration on tie line applicationsAffords tighter angle settings for generator applications
Sync Check Plus
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Slip Frequency Limit OK
Sync Check Plus Logic
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Auto Sync, Sync Check & Sync Check + with Rotating Phase Angle
25A
25SC Start Φ3
25SC+Close Φ3
25SC Close ΦT
Φ = 360 S T
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Generation
- Used to supervise an operator or automatic synchronizing relay
Tie Line
- Used to verify static phase angle or extremely low slip between systems
- Used to supervise a SCADA or automatic synchronizing relay
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Sync Check Plus Applications
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Used to connect two electrical systems that are separated
Have the ability to calculate an advance time to close a breaker that takes into account the slip frequency between the two systems
Φ = 360 S T
Applications- Connect a generator to the grid- Tie systems when one is islanded
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Automatic Synchronizing Relays
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Generator
Generator Synchronizing
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Generator Synchronizing DC Control
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Auto SyncMaximum Advance Angle Calculation
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Sync Check PlusPhase Angle Limit Calculation
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Electromechanical Sync Check in Series with Operator
**** WARNING ****Close Characteristic
- Time Delay Cannot Be Adjusted to Zero- Phase Angle Setting Varies with Applied Voltage
Blocking Characteristic
- Once Made Up, Opens at Large Angles Exiting Zero Degrees ! ! !
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Electromechanical Sync Check in Series with Operator
Causes a Late Close !
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Electromechanical Sync Check in Series with Operator
Synchronism-Check Relay TestGeneral Electric Type IJS52
The purpose of this test was to determine the blocking characteristics of the IJS Relay set for 20° and minimum time delay. Tests were run for the following conditions:
With the initial phase angle at 0° and both inputs at 60Hz, increase the line frequency to create a slip frequency (ΔF) and measure the blocking time and blocking angle.
TEST DATA
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Manually Supervised Automatic
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Classical Method
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25A
52CS
ClosingCircuit
Autosync
Auto Sync in Series with Operator
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Auto Sync in Series with Operator
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25A
52CS
ClosingCircuit
OperatorWindow
Autosync
“Operator Window” Concept
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Operator Window
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25A
25
52CS
ClosingCircuit
OperatorWindow
Autosync
SyncCheck
Operator Window with Backup Sync Check
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Auto Sync with Operator Window and Backup Sync Check: Failure AnalysisFailed Sync Check Relay &Improper Operator Action
52CS
25A
25SC
LEGEND:
25A – Autosynchronizer25SC – Sync Check Relay
– Circuit Breaker Control Switch52CS
Denotes Elements Failed Closed
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Auto Sync with Operator Window and Backup Sync Check: Failure AnalysisFailed Autosynchronizer &Improper Operator Action
52CS
25A
25SC
LEGEND:
25A – Autosynchronizer25SC – Sync Check Relay
– Circuit Breaker Control Switch52CS
Denotes Elements Failed Closed
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Auto Sync with Operator Window and Backup Sync Check: Failure AnalysisFailed Autosynchronizer &Sync Check Relay
52CS
25A
25SC
LEGEND:
25A – Autosynchronizer25SC – Sync Check Relay
– Circuit Breaker Control Switch52CS
Denotes Elements Failed Closed
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Auto Sync / Sync Check in Parallel with Backup Sync Check
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Ring Bus
1 2
4 3
G Line
Line
Line
1 2
4 3
G Line
Line
Line1 2
4 3
G Line
Line
Line
(a) Circuit breakers 1 and 4 are open; generator is ready for sync.
(b) Circuit breaker 1 closes on rotating phase angle. The autosync closes the breaker.
(c) Circuit breaker 4 is closed on the static angle. The sync check relay closes the breaker.
NOTE: All lines are energized and tied.
Closed Breaker
Open Breaker
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(a) Circuit breakers 1, 2, 3, 5 and 8 are open;circuit breakers 4, 6, 7 and 9 are closed.
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(b) Circuit breaker 5 ties buses 1 and 2 on a rotating or static phase angle, or hot/dead depending on line conditions.
Closed
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(c) Circuit breaker 8 closed on the static phase angle.
Closed
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(d) Circuit breaker 1 closed on therotating phase angle.
Closed
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(e) Circuit breaker 3 closed on therotating phase angle.
Closed
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Breaker and 1/2
7
8
G
Line
9
4
5
6
1
2
3
G
Bus 1
Bus 2
Closed Breaker
Open Breaker
LineLine
Line
(f) Circuit breaker 2 closed on the static angle.Station is synchronized.
Closed
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Generation- Speed matching is required to bring a generator’s
frequency equal to the grid frequency
- Voltage matching is required to bring a generator’s voltage equal to the grid voltage
Speed & Voltage Matching Relays
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Supervise and control generation coming onto bus (system)
- Control generator so ideal synchronizing conditions occur
Speed matchVoltage match
- Properly close the breaker
Application: Generation
Synchronizing
Difficulties are often encountered that affect operators and speed matching relays
- High inertia of turbine-generator causes response lags- Governor control systems take time to physically
move, causing a response lag
The speed matching algorithm has to take the lags into account or control overshoot will result
Speed Matching
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Proportional Pulse Frequency : Ideal Response
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Proportional Pulse Frequency : Actual Response
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Proportional Pulse Width: Ideal Response
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Proportional Pulse Width: Actual Response
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Proportional Pulse Width: Real World
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Supervise connection of two electrical systems
- Synchronous Tie: Systems are connected together at some other location
- Asynchronous Tie: Systems are not connected anywhere
This is sometimes referred to as connected islanded systems together
Application: System Restoration
Synchronizing
25
SystemA System
B
Synchronous Tie
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25
SystemA System
B
Asynchronous Tie
Synchronizing
Tie Line
System Restoration Synchronizing
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Provisions to Jump Sync Check Angle Under Certain System Conditions
Auto Sync: Max ΔF Limit
Sync Check: Angle Limit, Low ΔF Limit
System Restoration Synchronizing DC Control
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System Restoration: Element Applications
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Providing Security Against Faulty Synchronization and
Attendant Damage
Providing Security Against Faulty Synchronization and
Attendant Damage
25Questions ?
Questions ?
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©2008 Beckwith Electric Co., Inc.