hydrogen dew point monitoring
TRANSCRIPT
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Hydrogen Purity and Moisture Monitoring in
Hydrogen Cooled Generators
Michael Hicks
Utility Product Specialist
Environment One Corporation
April 16-17, 2013
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Overview
SAFETY INCREASED EFFICIENCY RISK MITIGATION
Hydrogen as a cooling medium
Importance of purity monitoring
Dew point monitoring
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Hydrogen Cooled Generators
First H2cooled generators became operationalin late 1930s
Larger generators require more efficient
cooling methods Helium too costly compared to H2
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Why Hydrogen?
Less windage / frictional losses
Better heat transfer characteristics
More megawatts per pound of iron
Lower moisture levels
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Why Hydrogen?
14 times more efficient at removing heatthan air
Relative density is 4 times less than air
Approximately 90% lighter than air
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Additional Benefits
Sealed environment: prevents contamination
Pressurized vessel: suppresses partial dischargeand increases level of voltage required to
breakdown components Is not an oxidizing agent
Pure hydrogen: will not support combustion
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Typical Shaft Seal
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The hydrogen dilemma
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Gas Purity Monitoring
Why do we monitor hydrogen purity?
Safety, explosive range 4 to 75% H2in air
Most explosive at 13% H2in air
Efficiency
Performed during gassing, de-gassing andnormal operation of the generator
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Hydrogen Purity and Efficiency
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Typical Generator Arrangement
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Considerations
Accuracy, stability, ranges and redundancy
Sampling location, filtering and flows
Area classification, form of protection
Different countries have different specifications
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Why Monitor Dew Point?
Component and insulation failure
Efficiency
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Increased Dew Point
Could support insulation failure (electricaltracking)
Corrosive effects
Retaining rings most highly stressed mechanicalcomponent in the generator
Cyclic generator operation
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Retaining Ring Failure
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Shorted Turns
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Mixture Density
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Where Does Moisture Come From?
Primary source seal oil and seals
Hydrogen coolers
Stator cooling water (clip leaks)
Thermal cycling of generator
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Methods of Monitoring Dew Point
Ceramic
Silicon based
Aluminum oxide
Chilled mirror
Measuring a change in the electrical properties
Capacitance, resistance or impedance
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Considerations
Accuracy, stability, pressure compensation,ranges
Effects of temperature, pressure
Sampling location, filtering, flows
Area classification, form of protection
Different countries have different specifications
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Summary
Hydrogen as a cooling medium
Importance of purity monitoring
Dew point monitoring
SAFETY INCREASED EFFICIENCY RISK MITIGATION
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THANK YOU
www.eone.com/solutions