[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)
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FIGURE 2.9.2 Modern fully encapsulated reactor.<br />
FIGURE 2.9.3 Gapped iron-core oil-immersed reactor.<br />
encapsulated construction became the design of choice because its improved mechanical characteristics<br />
enabled the reactors to withstand higher fault currents. Conversely, high-voltage (HV) series reactors<br />
were initially oil-immersed shielded-core designs. However, beginning in the early 1970s, the requirements<br />
of these applications were also met by fully encapsulated dry-type air-core designs. Due to such<br />
developments, the latest revision of IEEE C57.16-1996 (R 2001), the series-reactor standard, is a now<br />
a dry-type air-core-reactor standard only.<br />
The construction technology employed for modern shunt reactors, on the other hand, is more dependent<br />
on the applied voltage. Transmission-class shunt reactors are of oil-immersed construction, whereas<br />
tertiary connected, or lower-voltage direct-connect shunt reactors, utilize either dry-type air-core or oilimmersed<br />
construction. Hence ANSI/IEEE C57.21-1990 (R 1995) covers both oil-immersed and drytype<br />
air-core shunt reactors.<br />
A review of modern reactor applications is presented in the following subsections.<br />
2.9.2.2 Current-Limiting Reactors<br />
Current-limiting reactors are now used to control short-circuit levels in electrical power systems covering<br />
the range from large industrial power complexes to utility distribution networks to HV and EHV<br />
transmission systems.<br />
Current-limiting reactors (CLR) are primarily installed to reduce the short-circuit current to levels<br />
consistent with the electromechanical withstand level of circuit components (especially transformers and<br />
circuit breakers) and to reduce the short-circuit voltage drop on bus sections to levels that are consistent<br />
with insulation-coordination practice. High fault currents on distribution or transmission systems, if not<br />
limited, can cause catastrophic failure of distribution equipment and can present a serious threat to the<br />
FIGURE 2.9.4 Dry-type iron-core reactor (water cooled).<br />
safety of operating crews. In summary, current-limiting reactors are installed to reduce the magnitude<br />
of short-circuit currents in order to achieve one or more of the following benefits:<br />
• Reduction of electromechanical loading and thermal stresses on transformer windings, thus<br />
extending the service life of transformers and associated equipment<br />
© 2004 by CRC Press LLC<br />
© 2004 by CRC Press LLC