IEEE C62 92 6-2017 en Guide for Application of Neutral Grounding in Electrical Utility Systems Part VI-Systems Supplied by Current-Regulated Sources.pdf

1、IEEE Guide for Application of Neutral Grounding in Electrical Utility Systems, Part VISystems Supplied by Current-Regulated SourcesIEEE Std C62.92.6-2017IEEE Power and Energy SocietySponsored by theSurge Protective Devices CommitteeIEEE3 Park AvenueNew York, NY 10016-5997USA,(6WG i.e., their relativ

2、e phase angle difference is zero. The unfaulted phase voltage, assuming constant current magnitude is maintained, is therefore 3 Isource Zy. Thus, if the pre-fault source power output exceeds one-third of the delta-connected load demand, a ground-fault overvoltage will occur. If the output substanti

3、ally exceeds this threshold, one or more sources may reach its output voltage ceiling. Ideally, unfaulted phase voltage will be limited to this ceiling. This voltage is directly detectable at the source, and protective functions will tend to limit the magnitude and duration of overvoltage.In most pr

4、actical distribution situations, where single-phase inverters dominate, the majority of load will be connected phase to ground.10. Some load, however, may be connected phase-to-phase or in an ungrounded-wye confi guration (e.g., three-phase motor windings). In this situation, the ground-fault overvo

5、ltage is approximately Isource Zeqwhere Zeqis calculated based on the sum of the phase-to-ground connected load demand plus one-third of the ungrounded load demand.Some three-phase inverters are composed of three physically-independent single-phase inverters. If these inverters have controls to main

6、tain 120 phase angle separation of their phase outputs, they may be considered to be three-phase inverters and symmetrical component analysis may be used. If this current phase angle relationship is not maintained, and the inverters operate independently, then the phase-domain calculations of this s

7、ubclause apply.9Effective grounding is defi ned by an unfaulted phase voltage that is 0.83. Phase-to-ground voltage is 3IsourceZLoadso the load demand must be greater than the reciprocal of 0.8 p.u. 10Where single-phase 240 V inverters are connected line to line on the secondary of a distribution tr

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