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Evaluation of the uncertainty of measurements


Evaluation of the uncertainty of measurements
In the practice of plant operation, as in performance of laboratory tests, determination of uncertainty in measurement plays a fundamental role.
In metrology, the quality of measurements is represented precisely by the uncertainty associated with the results. In every instance, the value of a measured parameter cannot be completely expressed unless the associated uncertainty is stated.
 
SINT Technology has acquired considerable experience in evaluating the uncertainty of the fiscal metering systems of electric power plants at national level, both relating to fuel gas and steam for technological uses, and hot water for district heating (combined-cycle cogeneration plants).
 
Uncertainty in measurement is evaluated starting with the specifications of the individual instruments making up the measurement chain, referring both to manufacturers’ manuals (calculation of uncertainty in rated conditions) and to periodic calibration certificates (calculation of uncertainty in specific operating conditions) to arrive at determination of the compound uncertainty relating to the whole measurement chain.
 
The calculation is in conformity with standards:
 
  • UNI EN ISO 5167-2004 - “Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full” – Parts 1, 2, 3, 4
  • ISO 5168-2005 – “Measurement of fluid flow - procedures for the evaluation of uncertainties”
  • UNI CEI ENV 13005-2000 – “Guide to the expression of uncertainty in measurement”
 
Integrated services relating to greenhouse gas emissions
 
Since 2005, the year in which the Emissions Trading System was introduced following the Kyoto Protocol, SINT Technology has conducted the annual campaigns of evaluation of uncertainty in measurement of the (natural gas) fuel supply flow in about 30 thermoelectric power plants across Italy.
 
In particular, in connection with measurement of plant gas fuel consumption in a full solar year, evaluation of uncertainty is required for calculating and reporting carbon dioxide (CO2) emissions in accordance with the current standard governing greenhouse gas emissions.
 
The main reference standards are:
 
  • European Commission Decision 2004/156/CE
  • DEC/RAS 854/2005
  • Resolution 1/2008
  • European Commission Decision 2007/589/CE
  • Resolution 14/2009
 
In addition to competency in the methodology relating to uncertainty in measurement, SINT Technology has extensive experience acquired in industrial measurements, including electrical and thermal power plant performance parameter measurements.

 

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