PROBLEMS WITH NEWER GENERATORS

Transcription

1 PROBLEMS WITH NEWER GENERATORS CLYDE MAUGHAN, PRESIDENT MAUGHAN GENERATOR CONSULTANTS SCHENECTADY, NEW YORK Phone: Web: clyde.maughan.com 1

2 PRELUDE A FEW COMMENTS 2

3 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) 3

4 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 4 Comparative Measurements PD/EMI Prototype Test - Ohio Edison Sammis #6.

5 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? 5

6 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: 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 6

7 NOW, TO THE TOPIC PROBLEMS WITH NEWER GENERATORS 7

8 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 8

9 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

10 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 10

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16 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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37 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 37

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44 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

45 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 45

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53 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 53

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56 GE STATOR WINDING TAPE MIGRATION PROBLEM A RETURN OF A PROBLEM OF THE s 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) 56

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63 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 63

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71 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! 71

72 PROBLEMS WITH NEWER GENERATORS CLYDE MAUGHAN, PRESIDENT MAUGHAN GENERATOR CONSULTANTS SCHENECTADY, NEW YORK Phone: Web: clyde.maughan.com 72