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This standard is drafted accordance with the rules given in the GB/T 1.1-2009 Directive for Standardization - Part 1: Structure and drafting of standards.
Please note that some contents of this document may involve patents. The issuer of this document is not responsible for identifying these patents.
This standard replaces DL/T 651-1998. In addition to a number of editorial changes, the following technical deviations have been made with respect to DL/T 651-1998:
—Some terms are revised to make them compatible with the current standards;
—“built power plant: ” is deleted;
—the hydrogen measurement method is changed to "continuous monitoring should be used for hydrogen-cooled generators of 300MW and above";
—the sampling points and test requirements for off-line (hand-held) hydrogen hygrometer are added;
—the content of regular comparison between hand-held hydrogen hygrometer and online hydrogen hygrometer is added;
—the calibration requirements for the hydrogen hygrometer are added;
—the value of saturation water vapor pressure gauge is modified;
—the technical requirements for hydrogen dryers are added.
This standard was proposed by China Electricity Council.
This standard is under the jurisdiction of DL/TC 09 Electric Rotating Machinery of Standardization Administration of China.
Any relevant opinion or suggestion during the process of implementing this standard can be fed back to the Center of Standardization Management of China Electricity Council (Address: No.1, Lane 2, Baiguang Road, Beijing, 100761, the People’s Republic of China).
Requirements for hydrogen humidity of hydrogen-cooled generators
1 Scope
This standard specifies the expression method, standard, measurement of hydrogen humidity of hydrogen-cooled generators and the requirements for hydrogen hygrometer.
This standard is applicable to hydrogen-cooled generators in operation and during hydrogen charging shutdown.
2 Normative References
The following referenced documents are indispensable for the application of this standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
JJF1001-2011 General Terms in Metrology and Their Definitions
JJF1012-2007 Humidity and Moisture Metrological Terms and Their Definitions
JJF1076 Calibration Specification of Humidity Sensors
3 Terms and definitions
For the purposes of this standard, the terms and definitions given in JJF 1001-2011, JJF 1012-2007 and the following apply.
3.1
water vapour
water in the form of gas resulting from water vaporization or ice sublimation
[JJF 1012-2007, Definition 2.1]
3.2
humidity
amount of water in gas
[JJF1012-2007, Definition 2.11]
3.3
dry gas
gas without water vapour
[JJF 1012-2007, Definition 2.2]
3.4
wet gas
mixture of dry gas and water vapour
[JJF 1012-2007, Definition 2.3]
3.5
water vapour pressure
pressure at which the water vapor in wet gas (volume is V, temperature is T) exists alone at the same V, T, represented by the letter e.
[JJF 1012-2007, Definition 2.15]
3.6
saturation water vapour pressure
water vapour pressure at which the water vapor and the water (or ice) are in phase equilibrium at a certain temperature, represented by e_s.
[JJF 1012-2007, Definition 2.16]
3.7
dew-point temperature
t_d
temperature of gas when the water vapour in the gas condenses into water and reaches phase equilibrium, at constant pressure
[JJF 1012-2007, Definition 2.17]
3.8
frost-point temperature
temperature of gas when the water vapour in gas is condensed into frost and reaches phase equilibrium, at constant pressure
[JJF 1012-2007, Definition 2.18]
3.9
uncertainty of measurement
non-negative parameter characterizing the dispersion of the measured value according to the information used
[JJF 1001-2011, Definition 5.18]
3.10
hydrogen humidity meter
hygrometer for measuring humidity in hydrogen
4 Expression of hydrogen humidity
The hydrogen humidity in generator and that for hydrogen charging and replenishing are all expressed in dew-point temperature td, usually in centigrade, ℃.
5 Standard of hydrogen humidity
5.1 The upper limit of the allowable humidity of the hydrogen in generator at the operating hydrogen pressure shall be looked up from Table 1 according to the lowest temperature value in the generator; the lower limit of the allowable humidity is the dew-point temperature t_d=-25℃.
Table 1 Relationship between the minimum temperature in the generator and the allowable high limit of hydrogen humidity
Minimum temperature in generator ℃ 5 ≥10
Maximum allowable humidity of hydrogen in generator during operation
(dew-point temperature td)
℃ -5 0
The minimum temperature in generator may be determined as follows.
——Generator in stable operation: the lower value of cold hydrogen temperature and internal cooling water inlet temperature is taken as the lowest temperature in the generator, whichever is lower.
——Generator out of service and generator during start-up and shutdown: the lowest values of cold hydrogen temperature, internal cooling water inlet temperature, stator winding temperature and stator core temperature is taken as the lowest internal temperature of the generator.
5.2 The allowable humidity of the hydrogen used for charging and replenishing the generator at atmospheric pressure is the dew-point temperature t_d≤-50℃.
6 Determination of hydrogen humidity
6.1 Measurement methods and requirements
a) The hydrogen in the hydrogen-cooled generator and the hydrogen used for charging and replenishing shall be measured regularly.
b) Continuous monitoring should be adopted for hydrogen-cooled generators of 300MW and above.
c) An offline (portable) hydrogen hygrometer that meets the requirements of measurement regulations shall be used to compare the hydrogen humidity regularly.
d) The frequency of off-line (portable) hydrogen hygrometer for humidity monitoring shall be increased, when the on-line hydrogen hygrometer is out of operation due to maintenance and calibration.
6.2 Sampling point and sampling pipeline
6.2.1 A sampling bypass with isolation and control valves may be provided for the hydrogen hygrometer at the sampling place, in order to meet the following requirements when continuous monitoring is adopted:
a. ensure that the installed hygrometer can continuously monitor the hydrogen humidity in the generator when the generator drying device is in the maintenance and shutdown state;
b. ensure that the generator drying device can still dry the hydrogen when the hydrogen hygrometer exits;
c. meet the requirements of hydrogen hygrometer for flow (velocity).
The sampling points should be set:
a. on the inlet section of the generator drying device;
b. on the inlet and outlet pipes of the generator drying device, to monitor the hydrogen humidity in the generator and the humidity of the hydrogen returning to the generator after being dried by the hydrogen drying device, so as to judge the drying performance of the hydrogen drying device, to provide monitoring data for regeneration and replacement of desiccant.
6.2.2 The sampling points for measuring the humidity of hydrogen for charging and replenishing should be set on the outlet pipe section of the hydrogen station. When continuous monitoring method is adopted, a sampling bypass with isolation and control valves may be specially configured for the hydrogen hygrometer at the sampling place, to ensure that the hydrogen station can still charge and supplement the hydrogen-cooled generator when the hydrogen hygrometer exits, and to meet the flow requirements of the hydrogen hygrometer.
6.2.3 When measuring the hydrogen humidity in the generator by off-line (portable) hydrogen hygrometer, the sampling point shall be well ventilated and as close to the generator body as possible, and the sampling pipe should be stainless steel, copper or poly (tetrachloroethylene) pipe.
6.2.4 The ambient temperature where the sampling pipeline passes shall be higher than the humidity dew-point temperature of the measured gas by more than 3℃.
1 Scope
2 Normative References
3 Terms and definitions
4 Expression of hydrogen humidity
5 Standard of hydrogen humidity
6 Determination of hydrogen humidity
7 Requirements for hydrogen hygrometer
Annex A (Informative) Correction of pressure for measuring the humidity value of hydrogen
Annex B (Informative) Saturation water vapor pressure
Annex C (Informative) Technical requirements for hydrogen dryer
Bibliography
