IEEE Generator Protection

1

Generator Management Relay

Protection, metering, and monitoring functions for generators.

Presented by:

John Levine, P.E.Levine Lectronics and Lectric, Inc.

[email protected] 565-1556

2

Outline

Overview

Theory

Wiring

Security

3

Generator Protection

What a Generator looks like

4


5

Overview

6

Why Upgrade? Generator and Transformer

• Existing generator and transformer protection (more than 5 years or non-digital) may:– Cause protection security issues

• Tripping on through-faults, external faults, swings, load encroachment and energizing

– May lack comprehensive monitoring and communications capabilities• Not provide valuable forensic info that can lead to rapid restoration

– Not be up to ANSI/IEEE Standards!– Insurance, Asset Reliability and Personal Liability Issues

• C37-102: Guide for the Protection of Synchronous Generators

• C37.91: Guide for Transformer Protection

7

Product Overview• Ideal Protection for Induction and

Synchronous Generators at 25, 50 and 60Hz

• Complete Generator Protection including:

• Generator Stator Differential

• 2 or 3 Zone Distance Backup

• 100% Stator Ground

• High speed sampling, 12 samples per cycle

• Drawout Case Installation

• Powerful Fault Recording: Waveform, Sequence of Events

• Ethernet and Serial Communications

• Metering of all important parameters

Generator Management Relay

8

Theory

9

Show Generator Theory General Overview and Typical System from Training CD

10


• Internal and External Short Circuits

The "Wild"PowerSystem

G

Exciter

StatorGround

StatorPhase

SystemGround

SystemPhase

11

Generator Protection Review

– Abnormal Operating Conditions• Loss of Synchronism

• Abnormal Frequency

• Overexcitation

• Field Loss

• Inadvertent Energizing

• Breaker Failure

• Loss of Prime Mover Power

• Blown VT Fuses

• Open Circuits

12


• Abnormal Operating Conditions

The "Wild"PowerSystem

G

Exciter

Loss of FieldLoss of Field

Overexcitation

Overexcitation

Overexcitation

OpenCircuits

Loss ofSynchronism

InadvertentEnergizing,Pole Flashover

AbnormalFrequency

AbnormalFrequency

BreakerFailure

ReversePower

OverPower

13

IEEE PSRC Survey

– Conducted in early ’90s, showed many areas of protection lacking

– Unwillingness to upgrade:• Lack of expertise

– To recognize deficiency

– To perform the work

• “Generators don’t trip” (wrong)

• Operating procedures will save the day

PSRC = Power System Relay Committee

14

ANSI/IEEE Standards

• Latest developments reflected in:– Std. 242: Buff Book

– C37.102: IEEE Guide for Generator Protection

– C37.101: IEEE Guide for AC Generator Ground Protection

– C37.106: IEEE Guide for Abnormal Frequency Protection for Power Generating Plants

These are created/maintained by the IEEE PSRC & IASThey are updated every 5 years

15

Small Machine Protection IEEE Buff Book

• Small – up to 1 MW to 600V, 500 kVA if >600V

32 Reverse Power

40 Loss of Excitation

51V voltage restraint

51G Ground overcurrent

87 Differential

16


• Medium – up to 12.5 MW

32 Reverse Power


46 Negative Sequence



87 Differential

17


• Large – up to 50 MW

32 Reverse Power



49 Thermal Overload



64 Ground Relay

87 Differential

18

• Unit Connected,

• High Z Grounded

Large Machine ProtectionIEEE C37.102

32 Reverse Power



49 Thermal Overload



64 Ground Relay

87 Differential

19

HYBRID SYSTEM

20

Protection Functions

Protection Functions Include:

• Generator Stator Differential• Backup Distance Protection• 100% Stator Ground• Generator Unbalance• Loss of Excitation• Accidental Energization• Breaker Fail • Phase Overcurrent – Voltage Restraint• Neutral Inst. / Timed Overcurrent• Neg. Sequence Overcurrent• Under / Over Voltage• Under / Over Frequency• Generator Thermal Model• RTD Temperature• Overexcitation – Volts/Hertz

21


22

Generator Protection with GSU Wrap PTs on Low Side

23

Generator Protection with GSU Wrap PTs on High Side

24

Generator Protection PTs on Low Side

25

Desirable Attributes - Generator

– Reverse Power (32)• Should be sensitive to 0.05 pu to properly detect motoring in large steam turbines

– Existing E/M and Static relays not sensitive enough

– May cause shutdown difficulties

– Negative Sequence (46)• Should be sensitive to low values to detect open poles/conductors on system after GSU

– Existing E/M and Static relays not sensitive enough

• Long time low level events may cause excessive rotor heating, thermal tripping and damage rotor

– 100% Stator Ground (59N / 59D)• Protects all of the stator winding

– Existing schemes typically only see 90%

– Stop low level fault near neutral from degrading into a high level fault and causing large amounts of damage

– Very secure

26

Desirable Attributes - Generator

• Inadvertent Energizing (50/27)

– High speed tripping of unit after breaker accidentally closed on dead machine, also pole flashover prior to syncing

• Most existing schemes do not incorporate

– Many schemes fail due to complexity (reliance on breaker auxiliary switches, yard distance relays, etc.

– If breaker is not tripped rapidly, mechanical and electric damage can occur to machine in fractions of a second!

– Pole flashovers must be cleared by high speed breaker failure, as the breaker is open!

27

Line – Ground faults – Delta Connected Generator

28

Line – Ground faults – Wye Connected Generator

29


Generator Stator Differential• Stator Phase Differential• Dual Slope Percent Restraint Operating

Characteristic • Directional Supervision under saturation

conditions

Distance Backup Protection• 2 or 3 Zone Mho Distance Protection• Backup for primary line protection• Configurable Reach and Angle Distance

Characteristic

100% Stator Ground Protection• 95% Fundamental OverVoltage• 15% Third Harmonic UnderVoltage

Dual Slope Phase Differential

Two Zone Distance Backup

30


Voltage Restraint Overcurrent

Undervoltage Trip Curves

Voltage Protection• Phase Overvoltage• Phase Undervoltage• Neutral Overvoltage (fundamental)• Neutral Undervoltage (3rd Harmonic)• Voltage Phase Reversal

Current Protection • Phase, Ground and Negative Sequence Overcurrent Tripping

• IEC, ANSI , IAC and Customizable Overcurrent Curves

• Voltage Restraint increasing sensitivity under low voltage conditions

Frequency Protection• Overfrequency• Underfrequency

31


Loss of Excitation

Thermal Protection• Generator Thermal Model• RTD Alarming and Tripping• RTD Biased Thermal Model

Inadvertent Energization • Prevents Accidentally Closing a Stopped Generator onto a Live Line

• Armed when Generator is Offline and Voltage is below a pre-set level

Loss of Excitation (show Training CD)

• Uses Impedance Circle for loss of excitation detection• 2 Zones for fault detection and control

Volt/Hertz (Overexcitation)• Detects changes in the Volts/Hertz ratio of the generator or associated transformer

Thermal Model – Voltage Dependant Overload Curves

32

Wiring

33

34

35

36

37

Example

38

Security Audit Trail

• Date and time of hardware, firmware or setting changes to your relays

• Logging of the MAC address of computers and users making settings changes

• Track method of how settings changes were made (i.e. keypad, serial port, ethernet)

Security strategy – conforms to industry and regulated guidelines

• Date/time security report was generated

• Description of the GE Multilin Relay

• Summary of the last time the configuration was changed

• History of last 10 occurrences the configuration was changed

Enhanced Security

Prevents Unauthorized Access and Provide Traceability

Documents

IEEE Generator Protection