Industrial Thompson Fundamentals and Advancements in Generator Synchronizing Systems

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Fundamentals and Advancements inGenerator Synchronizing Systems

Michael J. ThompsonSchweitzer Engineering Laboratories, Inc.



Outline

• Consequences offaulty synchronization

• Components of

synchronizingsystems

• Fundamentals of

system design

• Advances



Consequences of Faulty

Synchronization

• Damage to generator and prime mover

♦ Mechanical (rapid acceleration / deceleration)

♦ Damaged windings (due to high current)

• Standards for generators

♦ Slip, ±0.067 Hz

♦ Voltage, +5%

♦ Angle, ±10°



OOP 3PH T S GI > I when (X + X ) < X"

G SOOP

G T S

V VI

X" X X

+=

+ +

G3PH

G

VI

X"=

VG

X"G

3PH Fault

+

–

VS

X"G

VG

XT XS

Close Breaker Out of Phase

+

– +

–

Current Can Exceed Three-Phase

(3PH) Short Circuit



Consequences of Faulty

Synchronization

• System disturbances

♦ Power oscillations

♦ Voltage depression

• Relay operation

♦ Reverse power

♦ Loss of field



IEEE Standards and Guides

• IEEE C50.12, Standard for Salient-PoleGenerators

• IEEE C50.13, Standard for Cylindrical-

Rotor Generators

• IEEE 67, Guide for Operation and

Maintenance of Turbine Generators

• No guide for prime mover



Synchronizing System Components

• Control functions♦ Control governor to match frequency

♦ Control exciter to match voltage

♦ Cause breaker to close at 0°

• Automatic and / or manual controls?

♦ All functions automatic or manual♦ Mix of both

♦ Both available and used as required



Permissive Devices

• Synchronism check

• Voltage elements

• Operator control



Manual Systems

• Require an operator in the control loop• Operator indications typically include

♦ Two light bulbs (composite measurement of all

three parameters)

♦ Synchroscope (angle, rpm gives slip)

♦ Voltmeters (voltage difference)

Incoming (generator)

Running (bus)



Automatic Systems

• Slip-compensated advanced angle closeCalculate angle using measured slip multiplied

by mechanism delay

• More precise and consistent than operator



Automatic Systems

• Generator control♦ Raise and lower pulses

♦ Proportional pulse width characteristic

• Islanding systems with multiple generators

♦ Synchronizer sends slip and voltage difference

to automatic generation control (AGC)

♦ AGC matches

♦ Synchronizer does slip-compensated

advanced angle close



Visualization

• Critical for manual systems

• Optional for automatic systems



Synchronism-Check Relays

• Traditional♦ Window and delay surrogate for slip

♦ Late close possible in slipping applications

• Microprocessor-based

♦ Directly measures slip and voltage difference

♦ May include slip-compensated advancedangle close

♦ Is superior for slipping applications



System Design

• Design for fault tolerance

• Include redundancy

Single point of failure makes generator unavailable

• Include multilevel control and supervision

Single failure causes faulty synchronization

• Eliminate common-mode failureSingle failure fools multilevel supervision



Advancements



Advanced Synchronizer

• Six VT inputs and programmable I/Oeliminate sensing and control signal switching

• Peer-to-peer synchrophasors allow systems

never before possible

• Fiber-optic remote I/O allows remote control



Synchrophasor Synchroscope

• Improved operator indications

• Independent of automatic synchronizer

• No required physical signal switching

• Part of existing synchrophasor installation



Direct Indication of

Synchronizing Criteria

• Angle

• Slip

• Voltage

difference

• Green / redindication



Lab Testing



Example ANo Local Synchronizing Breaker

Substation Generator Control Room

52AGovernor

Exciter

Fiber-OpticLink A25A

RIO



Example BReliability Islanding System

• System includes process steam and

electricity cogeneration

• Separation points selected depend oncritical load

• All objectives satisfied using only two

A25A devices and two RIO modules



• System islands critical

loads at 3, 4, 5, or 6

• Resynchronization isperformed

♦ By A25A 1 at Sub 27

and Sub 75

♦ By A25A 2 at Sub 66

Example BReliability Islanding System

G

1 2

4

3

5

A25A

1

Sub 75

34 kV

Sub 27

4 kV

Sub 66

115 kV

6

Utility

7 A25A

2

Critical Load

Critical Load

Critical

Load

RIO

RIO



Example CComplex Bus and Multiple

Synchronizing Scenarios

• Alumina processing plant has

double-bus / single-breaker

• Generation control system (GCS)

synchronizes across all breakers

except generator breakers

• Two A25A devices connect to all

six VTs for redundancy



Example CComplex Bus and Multiple

Synchronizing Scenarios

• GCS handles frequency control

and load sharing

• During synchronizing, GCS performs

frequency and voltage matching

• A25A verifies synchronizing criteriaand closes breakers



G5

8

U1

4

6

1

2

3

75

G6U2

A25A-A

25A-1

25A-2

25A-3

25A-4

25A-5

25A-6

A25A-B

25A-1

25A-2

25A-3

25A-4

25A-5

25A-6

GCS

Slip

V Diff

Slip

V Diff

1A

2A

1B

2B

Example CComplex Bus

and MultipleSynchronizing

Scenarios



Summary and Conclusions

• Synchronize generators carefully• Build synchronizing systems for

fault tolerance

• Use multilevel supervision (recommended)

• Simplify synchronizing systems with

microprocessor-based technology



Summary and Conclusions

• New developments improve performance –reducing costs and possibilities of hidden

failures and improving reliability

• Advanced technology such assynchrophasors enables remote

synchronization and improves operator

indications• Examples illustrate synchronizing systems

that were never before possible



Questions?

Documents

Industrial Thompson Fundamentals and Advancements in Generator Synchronizing Systems