The text of the International Standard IEC was approved by ISO/ IEC Guide Uncertainty of measurement -. Find the most up-to-date version of IEC at Engineering also reflected by the older editions of the relevant standard IEC For good practice in HV test fields, this Sect. on HV measurement and uncertainty .
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To obtain a low-noise unit step response for convolution purposes, averaging several step-response records may be used. When the step is generated using a repetitive generator, the duration of the step, and of the interval between steps shall be chosen such that no additional errors are introduced with respect to a single pulse.
The system is approved only for the arrangements and operating conditions included in its record of performance. The permissible deviation should be related to acceptable uncertainties of a measuring system. In both cases the comparison shall be made in accordance with the provisions of lEC The number N of Type B uncertainty contributions may differ for the different types of test quantities Clauses 6 to 9, voltages and time parameters.
The corresponding Indian Standards which are to be substituted in their respective places are listed below along with their degree of equivalence for the editions indicated: General terms relating to electrical measurements – Part The ratio of the reading between the measuring system and the comparison device or system, shall be established as described in 5.
Additional information on the proximity effect and long-term stability is given by the manufacturer. For example, a particular measuring system might be approved: The lead to the converting device shall carry only the current to the measuring system.
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The expanded uncertainty of a corrected time parameter, T, ieec, should be given according to Annex B, Example B. For cases where temperature correction has been applied, the uncertainty Ugc of the temperature correction factor may be taken as the uncertainty contribution. NOTE 2 The recommended minimum value for the assigned operating time is 1 h.
NOTE 1 Care should be taken to ensure that the appropriate “stray” capacitance or coupling and the mutual influence of the components are included in the measurement. These simplified procedures of 600660-2 5 are considered sufficient for the instrumentation and measurement arrangements commonly used in high-voltage testing: Number pairs in Ihe diagram sliow tlie normalised frequency and tine corresponding permitted deviation from tine ideal response at the corner points of the limit lines.
Requirements for instruments lECDigital recorders for measurement in high-voltage impulse tests – Part 2: The amplitude- frequency response outside this range is given for information only.
These limits are under consideration. NOTE 2 Attention should be paid to the equal charging of all stages of a voltage generator. NOTE 2 Some test facilities may choose to approve their measuring systems for only a single set of distances, or for a few sets or ranges of distances. Finally, the complete result of the calibration is expressed as follows: When a switching impulse is used, ff is equal to T which is the time to peak of the impulse. Finally, the complete result of the calibration of the approved measuring system is expressed by the assigned scale factor and its expanded uncertainty: If necessary, several assigned measurement ranges with different scale factors may be defined.
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The output of the measuring system shall be compared with a device or system that has proven its linearity or can be presumed to be linear over the full voltage range see 5. The convolution method uses the step response of the measuring system to calculate its output impulse waveform from the input uec waveform.
The experimental proof can be given either by the comparison method or by the component method. In addition the step response of the measuring system shall be measured according to Annex C.
Other significant influences shall also be taken into account, e. In general, the measurand to be considered is the scale factor of the measuring system, but in some cases other quantities, such as the time parameters of an impulse voltage and their associated errors, should also be considered.
Any temperature corrections to be used should be listed in the record of performance. For impulses, n impulses are applied. The calculated error in the peak amplitude can be compared to the unit step response to verify if the convolution calculation has been performed correctly. NOTE 2 The resolution of ic measuring instrument, e. NOTE 2 A measuring system can have more than one assigned measurement range with different scale factors.
NOTE 2 Design and construction of any component of an approved measuring system should be such that it can withstand a disruptive discharge at the test object without any change in its characteristics.
Smaller size measuring systems or their components may be transported to another laboratory for ief in an arrangement that simulates the operating conditions, provided that the interference test, when specified, is performed in the test facility of the user. The principles of this standard apply also to higher levels but the uncertainty may be greater. Its Type A standard uncertainty is equal to the experimental standard deviation of the mean: The complete linearity test shall be made within lec short time that atmospheric conditions do not change and hence corrections need not be used.
Mj,g is the combined standard uncertainty of the mean front time error, Ar. In such cases, the longest time to half-value of all the impulse types should be used. The dispersion of the n measurement values producing a Type A standard uncertainty may be partially caused by a limited resolution of the recorder and its internal noise.
For the comparison of peak values a sphere gap according to lEC may be used.
The basic principles of the ISO. Definitions, principles and rules I EC The proof may also be given by calculation, using the convolution method on the basis of the experimental step response Annex C and D. This can be done by evaluation of a set of test data with established reference values. NOTE In a case where correlation exists, linear terms will be present in the law of propagation of uncertainty, and the sign of the sensitivity coefficients becomes relevant.
In order to obtain the uncertainty of the complete measuring system, the user has to consider additional uncertainty contributions, either taken from the records of performance of the divider and recorder, or determined by additional tests.