1、BRITISH STANDARD BSEN 60868-0:1993 IEC868-0: 1991 Flickermeter Part0: Evaluation of flicker severity The European Standard EN60868-0:1993 has the status of a British Standard UDC 621.317.7BSEN60868-0:1993 This British Standard, having been prepared under the directionof the General Electrotechnical
2、Standards PolicyCommittee, was publishedunder the authorityofthe Standards Boardand comesinto effect on 15 May1993 BSI 08-1999 The following BSI references relate to the work on this standard: Committee reference GEL/110 Announced in BSI News, January 1992 ISBN 0 580 22132 6 Cooperating organization
3、s The European Committee for Electrotechnical Standardization (CENELEC), under whose supervision this European Standard was prepared, comprises the national committees of the following countries: Austria Italy Belgium Luxembourg Denmark Netherlands Finland Norway France Portugal Germany Spain Greece
4、 Sweden Iceland Switzerland Ireland United Kingdom Amendments issued since publication Amd. No. Date CommentsBSEN60868-0:1993 BSI 08-1999 i Contents Page Cooperating organizations Inside front cover National foreword ii Foreword 2 Text of EN60868-0 3 National annex NA (informative) Committees respon
5、sible 26 National annex NB (informative) Cross-references Inside back coverBSEN60868-0:1993 ii BSI 08-1999 National foreword This British Standard has been prepared under the direction of the General Electrotechnical Standards Policy Committee and is the English language version of EN60868-0:1993 Fl
6、ickermeter Part0: Evaluation of flicker severity, published by the European Committee for Electrotechnical Standardization (CENELEC). It is identical with IEC868-0:1991 published by the International Electrotechnical Commission (IEC). This standard is complementary to IEC868:1986 with Amendment No.1
7、:1990, which has been adopted by CENELEC as HD498.S2 and published as BS6796:1986. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itsel
8、f confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pagesi andii, theEN title page, pages2 to26, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. T
9、his will be indicated in the amendment table on the inside front cover.EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN60868-0 February1993 UDC 621.317.7 Descriptors: Metrology, measuring instruments, flickermeter, evaluation, statistics, fidelity, verification, tests English version Flickermete
10、r Part0: Evaluation of flicker severity (IEC868-0:1991) Flickermtre Partie0: Evaluation de la sverit du flicker (CEI868-0:1991) Flickermeter Teil0: Beurteilung der Flickerschrfe (IEC868-0:1991) This European Standard was approved by CENELEC on 1992-12-09. CENELEC members are bound to comply with the
11、 CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or
12、 to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the offici
13、al versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical
14、 Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1993 Copyright reserved to CENELEC members Ref. No. EN60868-0:1993 EEN60868-0:1993 BSI 08-1999 2 Foreword The CENELEC questionnai
15、re procedure, performed for finding out whether or not the Technical Report IEC868-0:1991 could be accepted without textual changes, has shown that no common modifications were necessary for the acceptance as European Standard. The reference document was submitted to the CENELEC members for formal v
16、ote and was approved by CENELEC as EN60868-0 on9 December1992. The following dates were fixed: Annexes designated “normative” are part of the body of the standard. In this standard, Annex ZA is normative. Contents Page Foreword 2 1 Statistical evaluation 3 2 Short-term flicker severity assessment 4
17、2.1 Choosing the multipoint algorithm 4 2.2 Practical checking of the P stevaluation 5 2.3 Agreement between simplified assessment methods and evaluation 5 3 Accuracy of the P stevaluation 5 4 Interpolation 8 4.1 Linear interpolation 8 4.2 Non-linear interpolation 8 4.3 Pseudo zero interpolation 8 5
18、 Smoothing percentile points 9 6 Non-linear classification 9 7 Performance tests including the classifier 10 8 Evaluation of long-term flicker severity 10 9 Reference 11 Annex ZA (normative) Other international publications quoted in this standard with the references of the relevant European publica
19、tions 24 Page Figure 1 Basic illustration of the “timeat level” method showing flicker level as a time-varying function. Signalpermanence in class No.7 is indicated as an example 14 Figure 2 Cumulative probability function (CPF) of signal premanence in classes1 to ten 15 Figure 3 CPF curves of sinus
20、oidale and rectangular voltage fluctuations 16 Figure 4 CPF curves for two pulse waveforms: waveform B is representative of repetitive motor starting 17 Figure 5 CPF curve for a10min observation period for an arc furnace and for infrequent step voltage changes 18 Figure 6a IEC limit curve and points
21、 of equal severity, P st =1 19 Figure 6b Curve of equal severity, P st =1 20 Figure 7 Maximum relative error as a functionofthe ratio! = P sttrue /P stmaxfor64,128 and256classes 21 Figure 8a Linear interpolation 22 Figure 8b Non-linear interpolation 22 Figure 9 Pseudo zero interpolation 22 Figure 10
22、 Example of application of thefour long-term assessment methods toan actual arc furnace operation 23 Table 1 Voltage changes just permitted byIEC555-3 compared with those giving oneunitflicker severity (P st =1) for variouschanges of voltage per minute usingunsmoothed and smoothed5 point algorithm 6
23、 Table 2 Minimum measurable P stvalues with an error of5% for each range and threeclassifier sizes 7 Table 3 Test specifications for flickermeterclassifier 10 Table 4 Comparison of methods of long-term flicker evaluation 12 Table 5 Application of the “cube law” method of P ltevaluation 13 latest dat
24、e of publication ofan identical national standard (dop) 1993-12-01 latest date of withdrawal ofconflicting national standards (dow) 1993-12-01 T 7 t i i 1,5 = =EN60868-0:1993 BSI 08-1999 3 1 Statistical evaluation The UIE/IEC flickermeter simulates the process of physiological visual perception and
25、gives a reliable indication of the reaction of an observer to any type of flicker, which is independent of the source of the disturbance. The flickermeter monitors individual and sequential flicker occurrences in units of perceptibility; it is necessary to evaluate its output by a method that indica
26、tes severity level for regular and irregular type of flicker. The output of the instrument is one unit, at the threshold of perceptibility. The concern of UIE is to achieve a unique method for flicker evaluation using an evaluation procedure that is equally applicable to any kind of fluctuating load
27、. The specification of limits for the disturbances generated by the various categories of equipment is the task of the appropriate standardization bodies. To take account of the mechanisms of vision and the building up of annoyance, the flicker shall be evaluated over a sufficiently representative p
28、eriod of time. Moreover because of the random nature of flicker caused by some loads it must be assumed that during this time its instantaneous level can be widely and unpredictably variable. It is important to check not only the maximum attained levels but also for what percentage of a significant
29、observation period any given flicker level has been exceeded. To cover all cases, a statistical approach is essential and this requires a function to be established relating flicker sensation levels and the corresponding percentages of duration, over the observation period. The steps to establish th
30、is function are the following: first the measured instantaneous flicker sensation levels at the output of Block4 of the flickermeter are classified according to their value, thus obtaining their frequency distribution; when the observation period expires, the cumulative probability function (CPF) is
31、 established. This method has been called “time at level classification” and is illustrated in Figure 1. Figure 2 shows the graphical representation of a CPF curve where, for clarity, only a small number of classes has been used. Figure 3 to Figure 5 give examples of CPF curves obtained for differen
32、t disturbing loads. It can be seen that the shapes of the curves are dissimilar, yet a common criterion is required to describe them in a concise and meaningful way and so assess flicker severity quantitatively and objectively. If all CPF curves followed a standard type of distribution, such as Gaus
33、sian, they might be characterised by a few parameters such as mean, standard deviation and so on. This not being the case, a multipoint method which could be used to characterise any CPF curve was developed. A suitable algorithm for use with various shapes of CPF curves can be expressed as follows:
34、The weighting coefficients were determined in such a way as to indicate the flicker severity correctly for a wide range of frequencies of rectangular modulation of the input voltage but the response to other waveshapes was also taken into account. A stable solution can be obtained using five gauge p
35、oints or percentiles, namely: where: P stis the value of short-term flicker severity; K 1to K nare weighting coefficients and P 1 , P 2to P nare CPF curve levels with an assigned probability of being exceeded. P 0,1 the level exceeded by only 0,1 % of the observation period P 1 ” ” ” 1% ” ” ” P 3 ”
36、” ” 3% ” ” ” P 10 ” ” ” 10% ” ” ” P 50 ” ” ” 50% ” ” ”EN60868-0:1993 4 BSI 08-1999 The50% reference point is the median level of flicker, giving a general indication of the order of magnitude of the disturbance. The other points am taken toward the low end of the probability scale to weight the high
37、er sensation levels appropriately, because these are more significant in assessing the severity of the disturbance. It should be noted that the maximum flicker level observed during the selected time interval is not included because a single peak level of very short duration cannot be representative
38、 of a flicker occurrence. The foundation of the CPF concept is that time at a given level gives the more useful indication; the choice of0,1% as a minimum percentile provides a suitable response for large, Infrequent flicker amplitudes. A suitable observation period should be chosen. This could be s
39、elected to match the duty cycle of a specific disturbing equipment but it is desirable to adopt a common time, independent of the specific type of disturbing source being considered. In fulfilling this objective it has been necessary to consider again the physiology of flicker perception and the res
40、ults of tests on human subjects and to try to determine what time interval would be appropriate to represent the reaction of the average observer to a wide range of flicker characteristics. An interval of10min has been selected as a good compromise. It is long enough to avoid giving too much importa
41、nce to isolated voltage changes. It is also long enough to allow an unaware subject to notice the disturbance and its persistence, but at the same time it is short enough to allow a detailed characterization of a disturbing equipment with a long lasting duty cycle. It is an important advantage that
42、the same interval is the observation time specified in IEC555-3. 2 Short-term flicker severity assessment 2.1 Choosing the multipoint algorithm In choosing a suitable multipoint algorithm, another problem had to be resolved, that of relating the multipoint evaluation to flicker severity. A limited n
43、umber of human subjective response test results was available, which could be used to relate flicker severity with non-linear CPF curves. However, from investigations made into earlier work concerning human subjective response measurements, it appeared that the higher frequency part of the limit cur
44、ve given in IEC555-3 (Figure 6a) corresponds fairly well to the experimental results which relate flicker severity to consumer complaints for rectangular disturbance waveforms. On the other hand it appeared that the part of the limit curve over the range1 to0,1 changes per minute was not a true meas
45、ure of flicker severity but the3% limit of voltage change had to be introduced for reasons other than that of limiting flicker annoyance. A realistic relationship for flicker evaluation requires that the severity curve be extented to the7,5% voltage change level at0,1 changes per minute (Figure 6b).
46、 It was therefore decided to determine a multipoint algorithm from this modified rectangular response curve and then to test its validity from results of subsequent human subjective response measurements. The following values were obtained for the K coefficients: All chosen coefficients are positive
47、, which ensures that the resulting values for flicker severity remain stable i.e.they do not appear to be oscillatory in relation to variations on the voltage changes per minute scale. For the agreed short-term assessment period of10min, the flicker severity was therefore expressed by the equation K
48、 for 0,1 % level = 0,0314 K for 1 % ” = 0,0525 K for 3 % ” = 0,0657 K for 10 % ” = 0,28 K for 50 % ” = 0,08EN60868-0:1993 BSI 08-1999 5 To check the accuracy of this flicker severity assessment and to ensure that the results were stable for regularly repeated fluctuations, the multipoint algorithm w
49、as used to evaluate every limit level given in the IEC table for the specified period of10min. The results are shown in Table 1 under the sub-columns “unsmoothed” and in Figure 6a. It can be seen in Figure 6a that the greatest difference between the severity curve and the right-hand part of the IEC limit curve is about10%, which is a satisfactory result. A still better fit is however not possible the mason for that is probably the empirical origin of the IEC curve. The precision of such a curve is evidently limited and it
