of 25
8/13/2019 Hydrogen Dew Point Monitoring
1/25
Hydrogen Purity and Moisture Monitoring in
Hydrogen Cooled Generators
Michael Hicks
Utility Product Specialist
Environment One Corporation
April 16-17, 2013
8/13/2019 Hydrogen Dew Point Monitoring
2/25
Overview
SAFETY INCREASED EFFICIENCY RISK MITIGATION
Hydrogen as a cooling medium
Importance of purity monitoring
Dew point monitoring
8/13/2019 Hydrogen Dew Point Monitoring
3/25
Hydrogen Cooled Generators
First H2cooled generators became operationalin late 1930s
Larger generators require more efficient
cooling methods Helium too costly compared to H2
8/13/2019 Hydrogen Dew Point Monitoring
4/25
Why Hydrogen?
Less windage / frictional losses
Better heat transfer characteristics
More megawatts per pound of iron
Lower moisture levels
8/13/2019 Hydrogen Dew Point Monitoring
5/25
Why Hydrogen?
14 times more efficient at removing heatthan air
Relative density is 4 times less than air
Approximately 90% lighter than air
8/13/2019 Hydrogen Dew Point Monitoring
6/25
8/13/2019 Hydrogen Dew Point Monitoring
7/25
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
8/13/2019 Hydrogen Dew Point Monitoring
8/25
Typical Shaft Seal
8/13/2019 Hydrogen Dew Point Monitoring
9/25
The hydrogen dilemma
8/13/2019 Hydrogen Dew Point Monitoring
10/25
8/13/2019 Hydrogen Dew Point Monitoring
11/25
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
8/13/2019 Hydrogen Dew Point Monitoring
12/25
Hydrogen Purity and Efficiency
8/13/2019 Hydrogen Dew Point Monitoring
13/25
Typical Generator Arrangement
8/13/2019 Hydrogen Dew Point Monitoring
14/25
8/13/2019 Hydrogen Dew Point Monitoring
15/25
Considerations
Accuracy, stability, ranges and redundancy
Sampling location, filtering and flows
Area classification, form of protection
Different countries have different specifications
8/13/2019 Hydrogen Dew Point Monitoring
16/25
Why Monitor Dew Point?
Component and insulation failure
Efficiency
8/13/2019 Hydrogen Dew Point Monitoring
17/25
Increased Dew Point
Could support insulation failure (electricaltracking)
Corrosive effects
Retaining rings most highly stressed mechanicalcomponent in the generator
Cyclic generator operation
8/13/2019 Hydrogen Dew Point Monitoring
18/25
Retaining Ring Failure
8/13/2019 Hydrogen Dew Point Monitoring
19/25
Shorted Turns
8/13/2019 Hydrogen Dew Point Monitoring
20/25
Mixture Density
8/13/2019 Hydrogen Dew Point Monitoring
21/25
Where Does Moisture Come From?
Primary source seal oil and seals
Hydrogen coolers
Stator cooling water (clip leaks)
Thermal cycling of generator
8/13/2019 Hydrogen Dew Point Monitoring
22/25
Methods of Monitoring Dew Point
Ceramic
Silicon based
Aluminum oxide
Chilled mirror
Measuring a change in the electrical properties
Capacitance, resistance or impedance
8/13/2019 Hydrogen Dew Point Monitoring
23/25
Considerations
Accuracy, stability, pressure compensation,ranges
Effects of temperature, pressure
Sampling location, filtering, flows
Area classification, form of protection
Different countries have different specifications
8/13/2019 Hydrogen Dew Point Monitoring
24/25
Summary
Hydrogen as a cooling medium
Importance of purity monitoring
Dew point monitoring
SAFETY INCREASED EFFICIENCY RISK MITIGATION
8/13/2019 Hydrogen Dew Point Monitoring
25/25
THANK YOU
www.eone.com/solutions
