Auto synch considerations methods

Providing Security Against Faulty Synchronization and

Attendant Damage


Attendant Damage

25

SynchronizingSynchronizing

Synchronizing

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

Synchronizing

Synchronizing

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

Synchronizing

Introduction


Φ

ΔV

f1

f2

Phase Angle in 1cycle

Asynchronous Sine Waves

Synchronizing

Phasor RepresentationSynchronizing

VA

VBVC

VA

Phase Difference 0º

P = E1 E2---------------------------------------------------------------

Zsin 0º


Phase Difference 80ºVA

VBVC

VA

P = E1 E2---------------------------------------------------------------

Zsin 80º

Phasor Representation


Phase Difference 160ºVA

VBVC

VA

P = E1 E2---------------------------------------------------------------

Zsin 160º

Phasor Representation


Synchroscope Display of Phase Angle

Synchronizing

Schematic of a Model SystemSynchronizing

Synchronizing

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

Synchronizing

Synchronizing

Effects of Synchronizing ErrorsExcessive Phase Angle – System IssuesCauses Instantaneous Power and VAr FlowsMay cause transient high voltageMay cause stability issue

Synchronizing

VA

VA

VB VB

VCVC

ZB

ZA

ZC

Synchronizing

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 !

Synchronizing

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

Synchronizing

Synchronizing

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

Synchronizing

Synchronizing

The Cost of Faulty Synchronization

Machine repair costs

Down Time

Lost Revenue

Lost of Interest on Investment

Synchronizing

Synchronizing

Faulty Generator Synchronizing

Synchronization of Generator 5-AT

Synchronizing

Faulty Generator Synchronizing

Synchronization of Generator 6 at Avon


[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


[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


[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

Synchronizing

Sync Check (25SC, 25SC+)

Automatic Synchronizer (25A)

Speed (Frequency) Matching (15)

Voltage Matching (90)

Synchronizing

Synchronizing Elements

Synchronizing

√−−−−−−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

Synchronizing

Sync Check Logic

Synchronizing

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

Synchronizing

Slip Frequency Limit OK

Sync Check Plus Logic

Synchronizing

Auto Sync, Sync Check & Sync Check + with Rotating Phase Angle

25A

25SC Start Φ3

25SC+Close Φ3

25SC Close ΦT

Φ = 360 S T

Synchronizing

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

Synchronizing

Sync Check Plus Applications

Synchronizing

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

Synchronizing

Automatic Synchronizing Relays

Synchronizing

Generator

Generator Synchronizing

Synchronizing

Generator Synchronizing DC Control

Synchronizing

Auto SyncMaximum Advance Angle Calculation

Synchronizing

Sync Check PlusPhase Angle Limit Calculation

Synchronizing

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 ! ! !

Synchronizing


Causes a Late Close !

Synchronizing


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

Synchronizing

Manually Supervised Automatic

Synchronizing

Synchronizing

Classical Method

Synchronizing

25A

52CS

ClosingCircuit

Autosync

Auto Sync in Series with Operator

Synchronizing

Auto Sync in Series with Operator

Synchronizing

25A

52CS

ClosingCircuit

OperatorWindow

Autosync

“Operator Window” Concept

Synchronizing

Operator Window

Synchronizing

25A

25

52CS

ClosingCircuit

OperatorWindow

Autosync

SyncCheck

Operator Window with Backup Sync Check

Synchronizing

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

Synchronizing

Auto Sync with Operator Window and Backup Sync Check: Failure AnalysisFailed Autosynchronizer &Improper Operator Action

52CS

25A

25SC

LEGEND:




Synchronizing

Auto Sync with Operator Window and Backup Sync Check: Failure AnalysisFailed Autosynchronizer &Sync Check Relay

52CS

25A

25SC

LEGEND:




Synchronizing

Auto Sync / Sync Check in Parallel with Backup Sync Check

Synchronizing

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

Synchronizing

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.

Synchronizing

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

Synchronizing

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

Synchronizing

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

Synchronizing

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

Synchronizing

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

Synchronizing

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

Synchronizing

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

Synchronizing

Proportional Pulse Frequency : Ideal Response

Synchronizing

Proportional Pulse Frequency : Actual Response

Synchronizing

Proportional Pulse Width: Ideal Response

Synchronizing

Proportional Pulse Width: Actual Response

Synchronizing

Proportional Pulse Width: Real World

Synchronizing

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

Synchronizing

25

SystemA System

B

Asynchronous Tie

Synchronizing

Tie Line

System Restoration Synchronizing

Synchronizing

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

Synchronizing

System Restoration: Element Applications

Auto synch considerations methods

Engineering

Transcript of Auto synch considerations methods