PROBLEMS WITH NEWER GENERATORS

CLYDE MAUGHAN, PRESIDENT MAUGHAN GENERATOR CONSULTANTS SCHENECTADY, NEW YORK Phone: 518 377 5351 Email: clyde@maughan.com Web: clyde.maughan.com

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PRELUDE A FEW COMMENTS

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LAST 15-YEAR FOCUS (OF A 27-YEAR CONSULTING CAREER)

CONSULTING WORK GENERATOR CONDITION ASSESSMENT FAILURE ROOT CAUSE DIAGNOSIS LITTLE-TO-NO TEST AND INSPECTION, OR REPAIR

WORK

TRAINING (KNOWLEDGE TRANSFER) EFFORTS SEMINAR: ~1000 PARTICIPANTS HANDS-OFF WHEN ASSESSING TECHNICAL PUBLICATION (PASSING ON TO THE NEXT

GENERATIONS THE KNOWLEDGE OF MY GENERATION OF GENERATOR ENGINEERS)

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KNOWLEDGE TRANSFER Book

“Maintenance of Turbine-Driven Generators”, 210 pp, 250 color photographs,. Focused directly on knowledge helpful to utility personnel : Design impact, Operation impact, Failure mechanisms, Monitoring, Inspection, Test, and Repair

Papers “Generator Ground Protection Relay Deficiencies” “A Brief History of Turbine-Generator Electrical Insulation and Support Systems “Uprating and Upgrading of Generators” “Advances in Motor and Generator Rotor Health “Electromagnetic Interference (EMI) Testing of Electrical Equipment “Vibration Detection instrumentation for Turbine-generator Stator Endwindings” “Vibration Sparking and Other Electrical Failure Mechanisms on Large Generators” “Generator Condition Monitor Evolution and Capability” “Monitoring of Generator Condition – and some limitations thereof” “On-Line Partial Discharge Testing on Generator Stator Windings” “Electrical and Mechanical Testing of Medium-Voltage Generators” “Partial Discharge as a Stator Winding Evaluation Tool” “Carbon-Brush Collector Maintenance on Turbine-Generators” “Root-Cause Diagnostics of Generator Service Failures” “Testing of Turbine-Generator Stator Core Lamination Insulation” “Upgrading of Generators to Improve Reliability” “Inspection/Test Impact on Maintenance of Generators” “Partial Discharge as a Concern on Turbine Generators” “Generator Failure Diagnosis” “Testing of Large Electric Generators for Suitability of Service” “Visual Inspection of Large Electric Generators” “Generator Reliability as Influenced by Engineering Design Parameters” “Comparative Measurements – PD/EMI Prototype Test - Ohio Edison – Sammis #6”.

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THIS “NO-ULTERIOR MOTIVE” TRAINING EFFORT . . .

PERSONAL COST . . . MAYBE 3000 HOURS OF UNPAID TIME MAYBE $60,000 OF EXPENSES PRESENTING

PAPERS AT TECHNICAL CONFERENCES PERSONAL BENEFIT . . . WELL, PHONE STILL RINGING ON INCOME-

PRODUCING CONSULTING JOBS AT AGE 87 ABSURD INCOME

AND A CERTAIN LEVEL OF JOB SATISFACTION SO WHY WOULD I COMPLAIN?

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AND MY LIBRARY (OF HOPEFULLY USEFUL KNOWLEDGE)

You can find about everything I have written on generators in the last 15 years on the NEC web site: www.generatortechnicalforum.org

At the Home Page, click on “technical forum” to register. Go to the discussion topic, Inner Water-Cooled Stator Windings (of which I am moderator), click on any thread, click on the Documents tab at the top

Find 24 technical papers on about 20 different generator topics and my 210-page text on generator maintenance

No-cost download by double clicking the titles

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NOW, TO THE TOPIC PROBLEMS WITH NEWER GENERATORS

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PRESENT FLEET INDUSTRY-WIDE

OLDER GENERATORS GENERALLY SUBSTANTIAL MARGIN IN DESIGN BUT MANY ARE 40+ YEARS OLD, i.e WORN OUT LITTLE SIGN OF FUNDAMENTAL CHANGE SOON

NEWER GENERATORS SOMETIMES NEGATIVE MARGIN IN DESIGN NUMEROUS INFANT MORTALITY AND EARLY-FAILURE

PROBLEMS (COST-REDUCED, i.e., “CHEAP”) GENERALLY NOT HIGH EXPECTATIONS FOR LONG-

TERM RELIABILITY

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SOME SPECIFIC PROBLEMS ON NEWER GENERATORS

SOME CONFINED TO SPECIFIC OEMs CORE VIBRATION ISOLATION DRY-TIE

SOME GENERIC PARTIAL DISCHARGE GLOBAL VPI

ON THESE SLIDES WILL NAME NAMES WITH CONCERN RECOGNIZING THAT NO OEM STANDS OUT

PARTICULARLY FROM THE REST (AND ROOT PROBLEM IS THAT UTILITIES BUY THE

CHEAPEST PRODUCT) 9

ALSTOM CORE ISOLATION PROBLEM

2-POLE CORES TYPICALLY OVAL ~2 MILS, i.e., UN-RESISTIBLE VIBRATION MAGNETIC PULL OF THE FIELD

ALSTOM SEEMS TO HAVE AT LEAST ONE LINE WITH LITTLE ISOLATION

BUT YOU MUST ISOLATE (I FIRST KNEW THIS IN MY FIRST YEAR AT GE – 1950)

MAJOR COST REDUCTION NO OBVIOUS REALISTIC FIX – REPLACE STATOR OR LIVE

WITH THE CONDITIONS NOISE – 116 dBA POSSIBLE FRAME CRACKING POSSIBLE FOUNDATION CRACKING

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HIGH LEVELS OF PARTIAL DISCHARGE

PROBLEM ON ALL GENERATORS CONTRIBUTING FACTORS

WORSE ON AIR COOLED HIGH VOLTS/MIL STRESS DESIGN INADEQUATE GROUNDING PAINTS INADEQUATE SPACING IN END ARM REGIONS JUNCTION OF END ARM AND GROUNDING PAINTS

OZONE PRODUCTION POTENTIAL HEALTH HAZARD ATTACK ON SOME MATERIALS

BUT GENERALLY PD DOES NOT CAUSE FAILURE 16

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VIBRATION SPARKING OLD PROBLEM FROM FIRST HARD INSULATION

SYSTEMS – LATE 1950s RECURRED ON A LINE OF SIEMENS GENERATORS

~4 YEARS AGO DRAMATIC AND FAST ACTING

IN-SERVICE FAILURE IF NOT CORRECTED 2-3 YEARS, OR SOONER

COMPLICATED ACTIONS, BUT PRETTY WELL UNDERSTOOD STATOR BAR VIBRATION IN THE SLOT (SIDE OR VERTICAL) LOW GROUNDING PAINT RESISTANCE

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REWINDING GLOBALLY VACUUM PRESSURE IMPREGNATED STATOR WINDINGS

MANY GENERATORS IN SERVICE LOW STATOR WINDING MANUFACTURING COSTS MOST OEMs DO THIS UP TO ~400MVA

CONDITIONS ENTIRE STATOR GOES INTO A VERY LARGE

IMPREGNATION TANK BONDS (GLUES) BARS IN SLOTS VERY DIFFICULT TO REMOVE WINDING

COSTLY AND TIME CONSUMING MAY DAMAGE CORE

MAY DECIDE TO JUST BUY A NEW STATOR 44

GE DRY-TIE PROBLEM IMPLEMENTED FOR SAFETY AND COST REASONS BUT GE ENDWINDING DESIGN IS BASED ON

EVERYTHING BONDING TOGETHER HISTORIC SYSTEM

WET ROVING GLASS, DIRECTLY OUT OF A RESIN BATH HIGH BOND STRENGTH BETWEEN GLASS AND BAR/CONNECTION

RING INSULATION

DRY TIE USES A PRE-IMPREGNATED GLASS TAPE RESIN IS B-STAGED, i.e., RESIN IS DRIED BUT UNDER HEAT SOFTENS AND FLOWS IN THEORY OKAY, BUT BOND TURNS OUT TO BE WEAK

CORRECTION REMOVE ALL DRY TIES AND REPLACE WITH WET TIES

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ALSTOM ROTOR WINDING COPPER BRAZE PROBLEM

FAILURE OF RECENTLY REWOUND FIELD CRACKING AND FRACTURE OF WINDING

COPPER ROOT CONCERN INABILITY TO REUSE COPPER WINDING WHEN

REWINDING FIELD ROOT CONDITION THIN COPPER ATTACHMENT BRAZE CONTROL

PROBABLY TOO HIGH TEMPERATURE WITH BETTER QUALITY CONTROL, MAYBE OKAY

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GE STATOR WINDING TAPE MIGRATION PROBLEM

A RETURN OF A PROBLEM OF THE 1950-60s CONDITION

ASPHALT INSULATION SYSTEM MICA IMPREGNATED WITH ASPHALT (REALLY!) GREAT SYSTEM FROM THE 1915s BUT IF SELECTED ASPHALT BECAME SOFT (LIQUID) AT

OPERATING TEMPERATURES NO MECHANICAL STABILITY INSULATION MIGRATED INWARD IN SLOT WITH LOAD

CYCLING

I AM THE WORLD EXPERT ON THIS PROBLEM (BECAUSE NO ONE ELSE IN THE WORLD IS OLD

ENOUGH TO REMEMBER THE PROBLEM)

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A FEW OTHER (POTENTIAL) PROBLEMS

FRAME CRACKING FIELD FORGING CRACKING

MAIN FIELD FORGING ONE CASE IN SPAIN ABOUT 4 YEARS AGO

RETAINING RINGS GET RID OF YOUR 18/5 RINGS

ONLY COST YOU HALF A MILLION DOLLARS EVEN 18/18 RINGS CAN CRACK IF BAD ENOUGH

OPERATING CONDITION STATOR ENDWINDING VIBRATION NEGATIVE SEQUENCE CURRENTS FIELD WINDING GROUNDS

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IN CLOLSING

LOTS OF OTHER FAILURE OPPORTUNITIES (UNFORTUNATELY) I’M STILL RUNNING INTO THINGS I

HAVE NEVER SEEN BEFORE AFTER 60+ YEARS

GOOD LUCK TO YOU BUT I AM GOING TO HAVE TO STOP

(TALKING AND CONSULTING) BEST WISHES!

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PROBLEMS WITH NEWER GENERATORS

CLYDE MAUGHAN, PRESIDENT MAUGHAN GENERATOR CONSULTANTS SCHENECTADY, NEW YORK Phone: 518 377 5351 Email: clyde@maughan.com Web: clyde.maughan.com

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