This section presents cost per event of PQ disturbances related to the frequency of different PQ disturbances by individual industrial sector as illustrated by the bar chart in Figure 18.12.
    These are annualized data giving the frequency of disturbances per sector. In this figure one metallurgical company claiming short interruptions every day has been filtered to avoid distorting the overall picture.
    Frequency of harmonics and flicker expressed in time percentage per year is illustrated by the chart in Figure 18.13.
    The analysis of the average (yearly) values of disturbance frequencies broken down by the two categories of industry and services are shown in Table 18.9.
    On average the MAIFI that has been measured by survey [11] is approximately 6; this is three times bigger than SAIFI. The number of recorded voltage dips identified by the respondents is approximately twice the number of short interruptions. This ratio is somewhat less for the service sectors.


 Figure 18.12 PQ disturbance frequency, dips, interruptions, surges and transients [11] (Reproduced from the 2007 Leonardo Power Quality Initiative Survey, R. Targosz)
    The cost per event identified by the survey is shown in the chart in Figure 18.14.
    To avoid potential distortion, 2 out of the 62 companies surveyed (semiconductors and retail) have been filtered out.
    The average values of cost per event, i.e. the real losses incurred by the respondents as a result of PQ disturbances, are presented in Table 18.10.
    These results can be summarized as follows:
    ? The cost per voltage dip event is between E2000 and E4000.
    ? Single short interruptions on average are 3.5 times more costly for industry and 9 times more costly for services.
    ? The average cost of long interruptions is E90 000 and is more homogeneous across the whole survey sample.
    All these results are quite comparable to different studies described at the beginning of this chapter.


 Figure 18.13 Frequency – annual time occurrence in %, harmonics, flicker [11] (Reproduced from the 2007 Leonardo Power Quality Initiative Survey, R. Targosz)


Table 18.9 Frequency of PQ disturbances [11] (Reproduced from the 2007 Leonardo Power Quality Initiative Survey, R. Targosz)
  
Figure 18.14 PQ cost per event for different disturbances [11] (Reproduced from the 2007 Leonardo Power Quality Initiative Survey, R. Targosz)
Table 18.10 PQ cost per event [11] (Reproduced from the 2007 Leonardo Power Quality Initiative Survey, R. Targosz)
    Assessing the generic cost per event for surges and transients is more problematic because of the lack of other research into these PQ phenomena. For survey [11] it is between E120 000 and E180 000.