G E N E S I S E N E R G Y L I M I T E D

Vetti Bala | Principal C&I Engineer

Commissioning and Testing of AVR and PSS

Excitation System Upgradeand commissioning challenges

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Asset Testing - AVR

AVR routine testing requirements

Life Cycle Management

Excitation System Replacement

Related opportunities

PSS Function

Advantage of tuning PSS correctly

Contents

C o m m i s s i o n i n g a n d t e s t i n g o f A V R a n d P S S

Challenges

AVR testing challenges

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Analogue AVRs – 5 yearly cycle

Digital AVRs – 10 yearly cycle

Replacement of AVR (asset life cycle management)

• Life cycle management

• Improve reliability

• Archive compliance

• Protect asset with better limiter controls

Asset Testing - AVRWhat prompts for the testing

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Excitation System Replacement

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Takes over two years to achieve it; justification, status of asset condition,

budget allocation, resources availability, etc..

• Key milestones replacement project

• Project approvals 2 year prior

• Technical spec ready / Tendering 6 - 12 months

• Contract award 9 months prior

• Design phase 6 months

• Build phase (inc FAT) 5 months

• Outage work 4 weeks

• Commissioning system 5 days

• AVR Testing 1 day

Excitation System ReplacementChallenges with life cycle management

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Key information required for proposed model build; (in addition to technical spec)

• Generator parameters

• Gen Transformer parameters

• Grid info at the connection point

Possible sources for Model input data;

• PTI Reports

• ACS

• Previous commissioning data

• New equipment specification

• Injection point Grid data (from SO)

Excitation System ReplacementFirst activity: prepare for Model building

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Design Phase

• New system supplier system design

• Customer interface design (DCS or SCADA interface) control, etc..

• Grid requirements (dialogue with SO)

Design approval

• Owner’s requirements approval

• SO approvals for the proposed AVR settings (3 months)

Excitation System ReplacementDesign and design approvals

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DC ExciterAVR Cabinet

• Analogue AVR installed over 25 years ago

• Electronics drifting with ageing

Original DC exciter from 40’s

coupled to the main shaft

Excitation System Replacement- Asset Life Cycle Management

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Digital AVR Cabinets

Excitation Transformer

- Replacement digital excitation system

Excitation System Replacement

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• Removal of exciter

• Removal of old AVR cabinets and cables

- Decommission old equipment

Excitation System Replacement

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A replacement project brings other opportunities or requirements

• Unit ultimate over-speed protection replacement

• Carbone dust extraction system (if required)

• Removal of previously decommissioned equipment

Excitation System ReplacementRelated activities

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• Single centrifugal switch to shut down the Unit

• Moving parts, shown wear and tear issues

• Unreliable and hidden failure

Original Mechanical Over-speed device from 40’s

Morden Unit Over-speed Protection- Unit Safety and Reliability issues

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• Built in redundancy, 2 out of 3 electronic system

• Fail safe and monitored of any failures

• High level of reliability

• Ease of routine testing

- Replacement tooth wheel and pickup sensors

Morden Unit Over-speed Protection

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• The consequence of exciter removal

• Re-check Unit Balance

• Re-check Unit Vibration

• New speed probes and tooth wheel commissioning

• Unit Start / Stop sequence - recommission

• Unit creep detection and shutdown - recommission

• Complete functional trip test of ultimate over-speed protection by running the turbine to over-speed set point thresholds.

Excitation System ReplacementRelated activities

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Commissioning and AVR Testing

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AVR TestingCommissioning new system

Site acceptance test (owner’s requirements)

• Verify Local / Remote controls

• Functional trip test

• Demonstrate reactive power (MVAr) controls

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AVR TestingFrom Asset testing companion guide

• Purpose of Test:As stipulated in the ancillary services contract, testing is required to determine if the service meets the performance

standards. The system operator needs to ensure the integrity of the voltage-support ancillary-service provision by

issuing requirements to service providers for assessing the voltage support capability of their assets.

To ensure the asset complies with the performance standards outlined in ancillary services

contract

• Outcome:The required outcome of AVR testing is to provide the system operator with a verified mathematical model that

describes the steady state and dynamic behaviour of the equipment. An accurate representation allows the system

operator to model interactions with the system and other generating stations, when subjected to disturbances on the

system, and thereby control the voltage stability of the system.

To validate the mathematical model

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AVR TestingAVR Compliance testing

Intense AVR testing

• Model validation

• Test EIPC requirements

• Demonstrate reactive power support

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AVR TestingGenerator Capability Diagram with limiters

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• Exporting Reactive Power Capability: Minimum

of +50% reactive power at the Grid injection point

of the maximum continuous MW capability in the

voltage range of -10% to +10%

• Importing Reactive Power Capability: Minimum

of –33% reactive power at the Grid injection point

of the maximum continuous MW capability in the

voltage range of -5% to +10%

+50% MVAr

220kV: 198kV to 242kV

110kV: 99kV to 121kV

-33%MVAr

220kV: 209kV to 242kV

110kV: 104.5kV to 121kV

AVR TestingDemonstrate

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• Offline from -10% to +10% of nominal voltage

• Offline step responses

• Online step responses at unity power factor

• Online step responses from under excited regions

• Online step responses from over excited regions

• Under excited limiter tests

• Over excited limiter tests

• Field voltage rise time Tests

• PSS Performance tests

• Unsychronised

• Unsychronised

• UPF

• UER

• OER

• UEL

• OEL

AVR TestingEIPC Testing requirements

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PSS – Power System Stabilizer

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The PSS function improves the stability of the generator and the transmission system as

a whole by using the excitation to damp power oscillations

PSS is not very effective in low power range

• PSS is intended for the improvement of the damping of the electromechanical oscillations by appropriate influencing the AVR control loop

• Increase the working range of the generators

• MW smoothing from hydraulic instability or spikes

• Reduce maintenance issues

Integrated PSS should be available with modern excitation system

PSSAdvantage of modern system with PSS and tuning it correctly

PSS

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PSS

Rangipo

Advantage of PSS function

MW oscillation due to hydraulic instability “PSS On” smooths out MW oscillation

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AVR TestingIn summary

Testing is typically takes a full day and is a very intense activity

• External customers satisfied (Transpower)

• A dialogue is essential during the testing with SO to ensure the attained data is acceptable by SO

• Ensure the dispatch is met by the new excitation system

• Internal customers satisfied (Genesis Ops)

• Ensure the PSS tuning and resultant unit behaviour is acceptable by the operations

• Ensure the MVAr support is acceptable by the operations (the operational regions generator capability)

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AVR Testing Challenges

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AVR Testing ChallengesChallenges during testing

• Peak hours

• Grid emergency

• Parallel activities (other major outages)

• Ops shift change

• Weak Grid

• Plant / hydrology limitations

G E N E S I S E N E R G Y L I M I T E D

Thank you