Assuring the Quality of Impulse Voltage Calibration Results Issued by a Calibration Laboratory
This paper describes high-voltage impulse measurements made under the controlled conditions of a calibration or national measurement laboratory to establish the best agreement that could be achieved in comparison measurements on small reference dividers. This comparison to establish mutual international traceability between NRC and National Grid has shown that the peak voltage of a smooth lightning impulse was measured by both laboratories to within 0.2% with an estimated uncertainty of ±0.2% at a level of confidence not less than 95%. The authors make recommendations on how calibrations of reference measuring systems should be performed.
Comparative impulse voltage measurements at the National Measurement Laboratory (NML), CSIRO, Australia, and the Institute for National Measurement Standards (INMS), NRC, Canada
This paper describes high voltage impulse measurements made under controlled conditions in two national measurement institutes to establish the best agreement that could be achieved in comparison measurements on small reference resistor dividers. These measurements at NML and INMS show that the peak voltage of a smooth impulse (measured as the peak reading of the record times the scale factor) can be measured in each laboratory with relative agreement within 4 mV/V. The uncertainty of this relative agreement, calculated from the standard deviation of the differences in each set of measurements, is 2 mV/V at a level of confidence of 95%. The relative agreement of front times was within 15 ms/s, with an uncertainty of 4 ms/s. The relative agreement of times to half-value was within 4 ms/s with an uncertainty of 2 ms/s.
Calculation of Complex Radiant Heat Load From Surrounding Radiator Surface Temperatures
Abstract A method for calculating the radiant heat exchange between an absorber and individual radiating components in its surroundings is reported. Radiator surface temperatures, ambient and absorber temperatures, and configuration factors for radiating components in the surroundings are used in the customary radiant heat exchange formulae. Simplified methods for calculating or estimating configuration factors for radiators of various shapes solely from angles, subtended at the absorber by the radiators are presented. The method has been verified in the laboratory under controlled conditions and has been used to advantage in the field studies. The method has advantages over the globe therometer method in certain applications.