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Bergman A.,Swedish National Testing And Research Institute
IEEE Transactions on Instrumentation and Measurement | Year: 2012

Losses of HVDC converter stations need to be accurately measured and/or estimated in order to support the evaluation of bids for such systems and to underpin efforts to reduce greenhouse gas emissions. The challenge of measurement has risen with modern converters where insulated gate bipolar transistors (IGBT) are used at high switching frequency. The theoretical bases for measurement errors are studied, both for measurement on the IGBT as a component and on complete converter stations. The study shows that electrical measurements are difficult to augment to an accuracy level sufficient for the needs and that a supplemental method such as calorimetric measurement may be needed. In certain cases, there will be a possibility to make temporary connections to permit two converters to operate in back-to-back mode, permitting a direct measurement of losses. The achievable accuracy is studied and estimated. © 1963-2012 IEEE. Source


Bystrom A.,Lulea University of Technology | Cheng X.,Lulea University of Technology | Cheng X.,Hefei University of Technology | Wickstrom U.,Lulea University of Technology | And 2 more authors.
Building and Environment | Year: 2012

A fire experiment with wood crib was conducted in a concrete building under low ambient temperature of-10°C to explore fire development and temperature distribution. The concrete building consists of a two-storey compartment with the size of 9.0m by 5.0m by 4.8m high and a four-storey stairwell with the size of 5.0m by 2.4m by 10.0m high. The fuel mass loss rate and temperatures at different positions were measured. Two fire cases, with different assumed ambient temperatures of-10°C and 20°C respectively, were then simulated by using FDS software to investigate the effect of ambient temperature and compare with the experimental results. The numerical results show that the calculated heat release rate is in reasonably good agreement with the measured full-scale result before water suppression. The calculated temperatures in the hot combustion gas layer at different positions agree also very well with the measured values. However, the measured fresh air temperature at the floor level near the fire source is higher than the calculated value. This discrepancy may partly depend on measuring errors as analyzed in the paper. © 2011 Elsevier Ltd. Source


Tarasso V.,Swedish National Testing And Research Institute | Zachovalova V.N.,Czech Metrology Institute | Mansten T.,Mittatekniikan Keskus Center for Metrology and Accreditation | Pogliano U.,INRIM - Istituto Nazionale di Ricerca Metrologica | And 2 more authors.
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2010

This paper gives a survey of the performance of existing current shunts designed by National Metrology Institutes (NMI's) around Europe. Key characteristics for power measurement; phase displacement, ac-dc transfer difference and power coefficient of the shunt resistance is reported for 5A, 50 A and 100 A shunts. © 2010 IEEE. Source


Bosco G.C.,INRIM - Istituto Nazionale di Ricerca Metrologica | Garcocz M.,Bundesamt fur Eich und Vermessungswesen BEV | Lind K.,Justervesenet Norwegian Metrology Service JV | Pogliano U.,INRIM - Istituto Nazionale di Ricerca Metrologica | And 4 more authors.
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2010

A comparison of the phase of existing shunts for currents between 10 A and 100 A and frequencies from 500 Hz to 100 kHz has been organized. The measurements were performed at INRIM using a first prototype of a new type of phase comparator and a step-up method for the data processing. The results of the relative measurements have shown a good repeatability, but the method for the evaluation of the reference value still needs some improvement. © 2010 IEEE. Source


Juvik J.I.,Swedish National Testing And Research Institute
CPEM Digest (Conference on Precision Electromagnetic Measurements) | Year: 2010

Phase displacements in the reference channel of a digital bridge used for calibrating instrument transformers with digital output have been investigated. Since the sampling in this set-up is controlled from the unit under test the largest correction stems from the virtual time shift caused by the aperture time integration when measuring a sinusoidal voltage with the sampling multimeter in DCV mode. This time shift is found to be equal to half the aperture time. In addition is the correction for the reaction time of the multimeter in this mode found to be 140 ns. © 2010 IEEE. Source

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