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IEEE C57.12.59-2015 pdf free

IEEE C57.12.59-2015 pdf free.IEEE Guide for Dry-Type Transformer Through-Fault Current Duration.
For Cacgory I, a single cur-vc applics that reflects both thermal and mechanical damagc considerations.
For Catcgones II and Ill, two curves apply. one of which rcflccts both thermal and mechanical damagc considerations. while thc other reflects primarily thcrmal damage considcrations only. On curves that havc both a solid and dotted portion, thc solid portion represents a total fault duralion beyond which thermal damage to insulation adjacent to current-carrying conductors and anneal-softening of aluminum may occur. whilc the dotted portion rcprcscnts a total fault duration beyond which cumulativc mcchanical damage may occur. Thc increasing significance of mcchanical cffccts for highcr kVA transformcrs is reflected in these curves. The frequency of faults varies with difkrent transformer applications. Applications characterizing frequent and infrequent faults are presented in the annex of IEEE Std C37.9l.
The curves in Figure I, Figure , and Figure 3 are based upon maximum symmetrical short-circuit current magnitude of dry-type transformers not to exceed 25 times base current limited to a short-circuit current duration of 2 s.
For Category I transformers, the symmetrical short-circuit magnitude will normally he limited only by the transformer impedance.
For Category II and Category Ill transfirmers, the symmetrical short-circuit current is calculated based on the sum of the transformer impedance plus a value of system impedance specilied by the user. See IEEE Sid C57. 12.01 lbr additional details.
NOTE-— Rekr to IEEE Std C57.96 lBll for loading capabilities at durations longer than 100 s for Categories II and Ill transformers.
The validity of these damage-limit curves cannot be demonstrated by lest, since the etTecis are progressive over the transformer lifctime The curves are based principally on informed engineering judgment and favorable historical field experience; they provide a uniform minimum standard for all dry-type transformers. For an explanation of how the curves arc derived, refer to Annex A.
The per-unit short-circuit currents shown in Figure I, Figure 2, and Figure 3 are the balanced transformer winding currents. The line currents that relate to these winding currents depend Upon thc transformer connection and the type of fault present. Applicalion engineers shall relate the winding currents to the currents seen by the protective devices in order to protect the transformer within its capability.IEEE C57.12.59 pdf free download.

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