IEEE 1277-2020 pdf download
IEEE 1277-2020 pdf download.IEEE Standard General Requirements and Test Code for Dry-Type andOil-Immersed Smoothing Reactors and for Dry-Type Converter Reactors for DC Power Transmission.
5.7 Design and construction—Oil-immersed smoothing reactors
Oil-immersed smoothing reactors arc nowadays widely replaced by air-core dry-type smoothing reactors. Therefore, no separate section for design and construction details of oil-immersed smoothing reactors is now included in this standard. The construction shall follow the principles as per IEEE Std C57.12.1OTM if not stated otherwise in this standard.
6. Rating data of smoothing reactors
6.1 Basis for rating
The rating of a smoothing reactor shall be expressed in the following terms:
a) Rated dc voltage
b) Rated dc current
c) Harmonic current spectrum
d) Rated incremental inductance
e) Basic lightning impulse insulation levels (across terminals and to ground)
Oil and/or winding temperature rise
g) Method of cooling
h) Switching impulse level(s) (across the terminals and to ground)
i) Short-circuit current or surge current
6.2 Rated dc voltage
The rated dc voltage of a smoothing reactor is the maximum continuous dc voltage, terminal-to-ground, that will be experienced by the smoothing reactor.
6.3 Rated currents
6.3.1 Rated dc current
The rated dc current of a smoothing reactor is the maximum continuous dc current at rated conditions.
6.3.2 Rated dc current plus harmonics
Smoothing reactors shall be designed for operation with rated dc current plus harmonics.
6.3.3 Rated dc overload current
Several values may be specified, including 1 h maximum in a 24 h period, dc peak surge, low ambient overload, and redundant cooling (oil-immersed smoothing reactors only) overload. A time limit, usually in milliseconds, should be provided with the dc peak surge current. If not specified. this time limit should be considered to be I s. Allowable temperature rises and conditions should also be specified. See Annex C for more information.
The dc peak surge current can be the result of a converter side-line fault or a fault on the line side of the smoothing reactor. Thus, the characteristics of the Giult current are different and should be specified and described by the purchaser. System design will play a role in defining the surge current parameters (peak, wave shape, duration, and frequency of occurrence).
6.4 Inductance
6.4.1 Rated incremental inductance
For iron-cored reactors operated well below magnetic saturation and air-cored reactors, the inductance is considered to be independent of current. Therefore, the rated inductance of a smoothing reactor is the inductance in henries, determined with low frequency ( 100 Hz) ac excitation.
For iron-cored reactors operated close to or beyond magnetic saturation of the core, the inductance is a function of current. In this case, the inductance of a smoothing reactor shall be defined by its incremental inductance. The rated inductance of a smoothing reactor in henries is the incremental inductance at rated continuous dc current.
6.4.2 Minimum inductance
A minimum inductance shall be maintained over the full operational range of dc plus harmonic current (at harmonic frequency) superimposed. The value of inductance is important to limit harmonic current and the amplitude of fault current. For oil-immersed iron-core smoothing reactors, the minimum incremental inductance shall be defined as a function of the dc current from zero up to the maximum fault current.
6.4.3 Tolerances
The tolerances on inductance apply from zero to maximum specified overload dc current. In the case of oil- immersed smoothing reactors, the degree of linearity should be defined from zero to maximum specified overload dc current. The minimum inductance value and minimum incremental inductance at rated short- circuit current shall also be specified. For dry-type air-core smoothing reactors, only a single tolerance on inductance shall be specified.
6.5 Basic impulse insulation level
6.5.1 Coordination of insulation levels
The specified basic impulse insulation level (BIL) and switching impulse levels at the smoothing reactor terminals to ground and across the smoothing reactor shall be such that the lightning impulse, chopped-wave impulse, and switching impulse insulation levels include a suitable margin in excess of the dielectric stresses to which the smoothing reactor can be subjected to in actual service. The insulation margins are typically not less than 20% for lightning impulse and not less than 1 5% for switching impulse voltages. CIGRE [B7j provides good information on insulation coordination. It should be noted that surge arresters used on dc systems are special designs. Additional information is included in A.9. The bibliography in Annex D also contains other useful resources like IEC 60071-5. For the winding of smoothing reactors, BIL shall be specified for each terminal to ground and across the winding. A different BIL can be specified across the winding than for each terminal to ground.
