AS/NZS 61000.3.6 (referred to subsequently in this Section as the Standard) specifies the conditions for the connection of harmonically distorting loads whose point of common connection (PCC) is in MV and HV power systems [1]*. These voltage levels are defined by the International Electrotechnical Commission and shown in Table 1.1 [Clause 1, Footnote 2] †. TABLE 1.1 IEC STANDARD VOLTAGE LEVELS Voltage level Range (line-line) LV (Low voltage) Un <= 1 kV MV (Medium voltage) 1 kV < Un <= 35 kV HV (High voltage) 35 kV < Un <= 230 kV EHV (Extra high voltage) 230 kV < Un This Section is intended for use by distribution company power quality engineers and installation engineers responsible for preparing connection agreements for MV/HV consumers. It is self-contained, with all equations and all necessary data from the Standard included. All procedures are illustrated with worked out examples (See Appendix A). The Standard itself is based on IEC 61000.3.6:1996 Type 3 Technical Report, with slight modifications made by the Joint Standards Australia/Standards New Zealand Committee EL-034 ‘Power ality’Qu documents are not as prescriptive as International Standards. AS/NZS 61000.3.6 contains several alternative methods for some allocation methods and this may create conflict between utilities and consumers if they use different methods to determine the harmonic allocation. Some techniques are presented incompletely with references to documents which are not readily available in Australia and this might handicap the infrequent user. Some of the assessment methods given are complex and time-consuming and it is not clear that this attention to detail is warranted in Australia yet. This Section contains recommended practices chosen from the Standard. Preference was given to practices which were technically sound and allowed the maximum harmonic capability of the power system to be used with some margin for uncertainties.Some new analysis methods had to be developed to allow straightforward calculation of acceptable accuracy without requiring access to harmonic loadflow programs. The assessment methods were revised to reduce the measurement periods and the amount of data to be analysed. Appendix B describes the relationship of this Section to AS/NZS 61000.3.6. It is acknowledged that, as experience grows and a wider variety of situations is encountered, modifications will be needed to provide stricter conformance with the Standard, and a corresponding increase in complexity.
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