IEEE 1277:2020 pdf free download – IEEE Standard General Requirementsand Test Code for Dry-Type and Oil-lmmersed Smoothing Reactorsand for Dry-Type Converter Reactorsfor DC Power Transmission
5.2 Unusual service conditions
Conditions other than those described in 5.1 are considered unusual service,and when prevalent theseconditions should be brought to the attention of those responsible for the design and application of theapparatus.
5.2.1 Unusual ambient temperature conditions
The temperature-rise limits of reactors should be adjusted if the cooling air ambient temperature exceedsthe limits described in 5.1.2. If the cooling air ambient temperature at site exceeds either of the limits, thenthe specified temperature-rise limits for the reactor shall be reduced by the same amount as the excess. Theadjusted temperature-rise limits shall be rounded to the nearest whole number of degrees Celsius.
Minimum ambient temperatures below -40 °C should be specified as they may have an impact on the reactor.
If a particular current rating versus ambient temperature performance is required without additional loss oflife, this shall be clearly defined in the specification.
For indoor reactors, the ambient temperature inside the reactor hall usually exceeds the limits described in 5.1.2Higher ambient air temperature results in lower air density that contributes to reduce the dielectric withstandof air insulation. Thus the specified dielectric withstand voltages shall be associated with the reactor hallambient air conditions(e.g., maximum air temperature and associated minimum air humidity).
If dielectric tests are performed at usual laboratory ambient air conditions, correction factors shall be appliedto test voltages in order to take into account the most stringent ambient conditions prevailing in the reactorhall.Correction factors shall be calculated according to the methodology defined in IEEE Std 4TM,
NOTE—Smoothing and converter reactors may be uniquely (custom) specified and designed for a specific location andsct of operating conditions and, therefore, loading versus ambient temperature condition may be the norm.Establishing acurrent rating versus ambient temperature, etc., involves a number of considerations such as the thermal capability of theinsulation system versus the winding operating temperature under rated conditions. This may be affected by a significantloss evaluation or other aspeets of the specification, which reduces the temperature rise of the winding below the insulationsystem thermal capabilities.
5.2.2 Unusual altitude conditions5.2.2.1 Effect of altitude on insulation
For both oil-immersed and dry-type smoothing reactors, as well as for dry-type converter reactors, the dielectricstrength, which depends in whole or in part upon air for insulation, decreases as the altitude increases becauseof decreased air density. In the case of dry-type reactors, the encapsulated windings depend in part on air fordielectric strength, and the support insulators depend in total on air for dielectric strength.For oil-immersedsmoothing reactors, the bushings depend in part on air for dielectric strength. If dielectric margins are adjustedin the specification to accommodate the operation of the smoothing reactor at a higher altitude, the dielectrictest levels shall be as specified. Otherwise, for dry-type reactors specified for operation at altitudes between1000 m and 3000 m above sea level, but tested at normal altitude, the test voltages for external insulation (airinsulation) shall be increased using the correction factors from Table 1 in IEEE Std C57.12.00TM-2015.Foroil-immersed smoothing reactors, the bushings shall be tested at an appropriately increased test level, but thewindings shall be tested at nominal value. In the case of dry-type reactors, both the insulators and windingsshall be tested at the appropriate higher voltage. In any case, the purchaser’s specification shall state if thespecified test levels have taken the higher operating altitude into account.