Monitoring of Shaft Voltage and Shaft Grounding Current - Beth Galano (MPS)

 MPS Gaussbusters are proud to be  “ Safe S a fegu gu a rdin g Mach Ma ch inery Worldw ide” 

Introduction to MPS and

Monitoring of Shaft Voltage and Shaft Grounding Current in

Rotating Machinery By Paul Nippes, P. E. and Beth Galano

Magnet Magnetic ic Produc Products ts and Servi Services ces,, 2135 2135 Highwa Highway y 35, Holmde Holmdel, l, NJ

07733 07733 USA

 MPS Gaussbusters are proud to be  “ Safe S a fegu gu a rdin g Mach Ma ch inery Worldw ide” 

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Fou Founde nder and and Pres Presiiden dent, Mr. Paul aul Ni Nippe ppes, P.E. has been consulting to Petrochemical, Power Utilities and Industry since 1965.

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IEEE C5 C50 Ch Chairma rman fo for ma many ye years, rs, Cigre, ASNT and ASTM Contributor.

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A Mot Moto or and and Gener enerat ator or des designer gner wit with Al Allis lis Chalmers and Elliott Company, Electro Dynamic Division of General Dynamics, a Penn State Graduate and a Professor at the University of Wisconsin.

In Paul’s Paul’s Electr Electrica icall Engi Enginee neerin ring g cons consult ulting ing capaci capacity, ty, due to the freque frequency ncy of “bearing failures” failures” in his consulting consulting practice, practice, Mr. Nippes Nippes championed championed this research and developed products to provide solutions.

 MPS Gaussbusters are proud to be  “ Safe S a fegu gu a rdin g Mach Ma ch inery Worldw ide” 

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Fou Founde nder and and Pres Presiiden dent, Mr. Paul aul Ni Nippe ppes, P.E. has been consulting to Petrochemical, Power Utilities and Industry since 1965.

•

IEEE C5 C50 Ch Chairma rman fo for ma many ye years, rs, Cigre, ASNT and ASTM Contributor.

•

A Mot Moto or and and Gener enerat ator or des designer gner wit with Al Allis lis Chalmers and Elliott Company, Electro Dynamic Division of General Dynamics, a Penn State Graduate and a Professor at the University of Wisconsin.

In Paul’s Paul’s Electr Electrica icall Engi Enginee neerin ring g cons consult ulting ing capaci capacity, ty, due to the freque frequency ncy of “bearing failures” failures” in his consulting consulting practice, practice, Mr. Nippes Nippes championed championed this research and developed products to provide solutions.

 MPS Gaussbusters are proud to be  “ Safe S a fegu gu a rdin g Mach Ma ch inery Worldw ide”  •

Areas of specialization…

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Magnetism and the problems it can cause in Rotating Machinery, Industrial Processes, or in any application.

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Shaft Condition Monitoring - CBM using using Stra Stray y Shaft Shaft Currents and Shaft Voltages in Rotating Machinery for Early Warning of Developing Faults.

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Field Services – Services – Degaussing, Magnetizing Magnetizing and Shaft Shaft Voltage Testing

 MPS Gaussbusters are proud to be  “ Safe S a fegu gu a rdin g Mach Ma ch inery Worldw ide”  SHAFT CURRENT FROSTING Shaft Journal

Bearing Pad

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  SHAFT CURRENT EFFECTS Spark tracks

Gear Pitting

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Electric Current Erosion of Thrust Bearing Pads from a Turbine Driven Natural Gas Compressor Spark Tracks on the Active Pad Face

Pad Steel Backing Erosion on Two Adjacent Pads

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Spark tracks Developing into Heavy Current Discharge Melting into the Babbitt

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Degaussing Turbine Diaphragms

Degaussing Blower Casing

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Demagnetizing Screw Compressor 

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

 Auto Degauss

 Auto “Down-Cycle” Demagnetizing is Systematic Removal of Magnetism

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Measuring Magnetism

MPS Gaussometer 

 Avoid Field Indicators (Magnetometer)

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Red – No Weld, Yellow – Maybe?, Green – Good to Weld

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  South China Sea On Barge Vertical Pipe Welding Magnetic Field Stabilization

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Portable Magnetic Particle Inspections Applied to Military Impellors Procedures Developed by an ASNT Level III (MPS Customer)

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Military Applications – Degaussing Solutions

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Shaft Voltage Surveys

Grounding Brush Performance Checks

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Failure Analysis and Solution Recommendations

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Carbon brush contact surface comparison  Normal Glazed

Figure #4

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  1. Ground the Shaft 2. Check Grounding Devices Often via Local or Remote Monitoring

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Grounding Brush Reliability is Critical

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  SHAFT CONDITION MONITORING (SCM) a Patented Technology  A continuous monitoring technology that uses shaft current and voltage profiles in operating units for early diagnostics and prognostics to identify developing problems in electrical and non-electrical rotating machinery.

Permanent Mount Monitors, Rack Mount, Din-Rail Modules or Sensors = Grounding Brushes Hand-Held Monitors

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  MPS Signal Conditioning VCM-E disposes of numerous and varying frequencies and amplitudes for the purpose of sensing only the important signal changes in waveform fundamental frequency, peaks and averages.  At the earliest changes and/or an excess in these quantities, action can be taken to identify and confirm possible problems.

Confirmation may include collection and analysis of other unit operating parameters.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Shaft Grounding And Voltage Sensing Applied To Industrial Class Rotating Machinery

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

GENERATOR  HP TURB.

IP TURB.

LP TURB.

EXCITER 

NO BRUSHES NO MONITORS AND NO PROTECTION Shaft currents are not confined nor controlled. Shaft current damage to bearings and seals is not prevented. Bearing and seal oil films insulate against stray currents. Stray voltages can damage unit or impair efficiency . Events or oil impurities can establish electrical circuits.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

GENERATOR  HP TURB.

IP TURB.

EXCITER  LP TURB.

SHAFT GROUNDING BRUSH

GROUNDING BRUSH, NO MONITOR , POSSIBLE PROTECTION A quality grounding brush should discharge static electrical charge before damage occurs. A quality grounding brush should establish good shaft contact protecting the nearby bearings. The grounding brush could provide a return path for magnetically-generated current. The brush may require maintenance, with loss of shaft grounding without warning Damage can occur to bearings and/or seals if the generator outboard bearing insulation fails! Shaft current damage to bearings and seals is first indicated by excessive vibration/temperature.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Shaft Voltage Decrease And Current Increase Indicates Shaft Rub. High Voltage At Sb#1, Inversely Proportional To Steam Temperature Indicates Wet Steam In Turbine. High Current In Grounding Brushes And Low Voltage At Brush Sb#2 Indicates Loss Of Bearing Or Seal Insulation . Rapid Escalation In Both Sb#2 Voltage And Grounding Currents Indicates Developing Stator Winding Fault. Erratic And Pulsing Voltage And Current Indicate Stator Lamination Shorting And Melting . Long Term Gradual Increases In Voltage And Current Indicate Shift In Air Gap. Pulsing, Then Gradual Increase In Shaft Voltage And Current Indicate Rotor Winding Faulting. Shaft Voltage Changes As Excitation Changes May Indicate The Need For A Shaft Voltage Harmonic Filter. Trending Of Each Brush Grounding Current, With Maximum Current Alarm On Each Brush. Each Brush Will Alarm On Low Brush Grounding Current Indicating Brush Or Grounding Maintenance Required.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Oscilloscope recordings taken from the identical shaft grounding current  but with different voltage and time scaling. Upper trace = 112mV @ ~ 70MHz

Lower trace = 720mV @ ~ 80Hz

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Erratic grounding on shaft (Voltage source = The blower motor ) Ungrounded OB end – similar to IB end

OB trace, IB end Ground brush skip

Ungrounded IB end – similar to OB end

Grounded IB end skip not apparent

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Oscilloscope trace of shaft grounding current composed of a 60Hz fundamental plus a strong common mode bucking third harmonic. Characteristic of magnetic saturation

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Effect on shaft of Electromagnetic Voltages, determined from different resistances in the shaft grounding cable. Ungrounded (40 Volts)

1k Ohm (40 Volts)

100 Ohm (25 Volts)

10 Ohm (5 Volts)

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Effect on shaft of electrostatic voltages determined from different resistances in the shaft grounding cable. Ungrounded (30 Volts)

10k Ohm (4 Volts)

1k Ohm (0.5 Volts)

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  CHART SCALES - ZERO TO 1.0 VOLTS AND 10.0 AMPERES

BRUSH CURRENT

ONE HOUR 

750MW GENERATOR VCM OUTPUT INDICATING A UNIT OR SYSTEM RECURRING CONDITION Figure #11

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Ground Fault Condition at a Nuclear Power Plant and Root Cause

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

Root Cause

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Unit 1 Shaft Peak Currents and Voltages for Six Days Grounding brush Currents = 3.1 and 8.7 Amperes Generator OB End Shaft Voltage = 23.4 Volts Turbine Shaft Voltage = 0.2 Volts

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  Unit 2 Shaft Peak Currents and Voltages over a Day Grounding brush Currents = 2.2 and 6.7 Amperes Generator OB End Shaft Voltage = 14.0 Volts Turbine Shaft Voltage = 4.8 Volts

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  500 MW Turbine generator  Recorded Field Voltage and Peak Shaft Grounding Current During a Field Ground Fault

Figure #14

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

SCModules , Either Voltage or Current, Battery or  AC Power, Local Alarm Indications; Remote Analysis

VCM-EN-SII Single Enclosure Housing Two Separate VCM-E Boards/Circuits For Large Or Critical Units.

Hand -Held VCM VCM or SCMeter  or use with SCModules, Displays Voltage or Current Peaks and Averages

 Als o A vai labl e…

(Explosion-proof Models) VCM-E, AC Powered, Local VCM-C, Battery Power, Local Display, Ungrounded Peak-Voltage And Grounded Peak and Average Ground Current, Max I = 3 Amps. Industrial Type  Applications.

Display, Alarm LED’s of Shaft Grounding Current And Shaft Voltage. Continuous Signals via 4-20 mA for use in Control Room, via wired or wireless connections.

MPS’ Family of Shaft Condition Monitors…for Early Detection of Rotating Machinery Faults 

VCM-EN-RM Rack Mount Model configurable with 1 to 4 VCM-E units.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

SHAFT MONITORS provide Early Warning …  •

Grounding Brush or Ground has lost continuity.

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Wet steam conditions at the exhaust end of the turbine causing charge separation with possible blade erosion and cavitation.

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Dry Steam conditions at the inlet of the turbine with partial admission, caused charge separation and spark discharge.

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Self Excitation or compounding of shaft voltages and grounding currents from shorted rotor coil.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide” 

SHAFT MONITORS provide Early Warning …  •

Shaft Rubs at bearings, seals due to oil whip, coupling misalignment, thermal growth, loss of lubrication, impurities in the oil, etc.

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Diode Failure in Generator Excitation.

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Intermittent Rotor Winding Ground Fault

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Loss of or Shorting of Insulation at Bearings, Seals, Gear Teeth and Coupling, etc.

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Excessive transients in pulse width modulated rotor and/or stator electrical supply.

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Stator core lamination shorting in an electrical generator.

 MPS Gaussbusters are proud to be  “ S afegu ardin g Mach inery Worldw ide”  •

Simplicity and Value - SCM reduces data to basic terms (a fraction of the digital data), while still preserving critical data events

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Supported by technology and performance of units installed in the Utility and Petrochemical Industries.

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Offers significant enhancement to PDM and Prognostic programs of Utilities, Industry and the Military.

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It could be an important input to the decision-making process as to whether a rotating machine is Operational or “Service” Ready.

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Alerts at earliest possible problem development requiring • • •

confirmation, investigation and possible parts replacement