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IEC 61000-4-15 (77A/180/FDIS and 77/187/NP)
(Consideration on the New Standard Revision of IEC 868)
This new standard deals with Flicker design specifications and represents the revision of the famous IEC 868. The need for a new standard comes form the consideration to upgrade the original IEC 868 (1986) "Flickermeter: functional and design specifications" since many reference are aged (e.g. reference to IEC 801 Series). Moreover, it would be congruent for this standard to be in the IEC 1000 Series. The most of the standard is similar to the previous IEC 868, but some small adjustment have been suggested, such as a slight modification in the weighting filter curve, or the wider input bandwidth to deal with fluctuating harmonics producing flicker.
In any case, the most significant upgrade concerns the 77A/187/NP, proposal to deal with some new phenomena, which was not very frequent at the time of the IEC 868 publication.
Some equipment may control their power, switching-on for 1 half-cycle and off for 2 half-cycle (or vice-versa). These multi-cycle control equipment produce a voltage fluctuation at 33.33Hz repetition rate. It has been tested that different IEC 868 instruments, when subject to this flicker disturbance input, have yield different results! It has been found that the cause of these deviations are in the design of the demodulator filter (block n/260 3 of the IEC 868 standard); in fact the original UIE-IEC document had no interest in all flicker frequencies above 25Hz for which a freedom degree was allowed. The IEC 868 Standard did not prescribed the normalized expected Flicker response at 33.3/240Hz, but Table I and Table II listed values up to 25 and 24Hz.
The new proposal is therefore to get the same standardized and unique result in response to this train pulse, fixing the filter type and its order, and adding new reference calibration points such as at 4000V/min.
Of course, Boconsult instruments (B9, B9-dSP and B10) are compliant to all the new requirements of IEC 61000-4-15.