IEEE C37.109-2006 pdf free.IEEE Guide for the Protection of Shunt Reactors.
Shunt reactors can be used to provide inductive reactance to compensate for the effects of high charging current of long transmission lines and pipe-type cables. For light load conditions, this charging current can produce more leading reactive power than the system can absorb with the consequent risk of instability or excessive high voltages at the line terminals (Ferranti effect).
5. Reactor construction and characteristics
The two general types of construction used for shunt reactors are dry-type and oil-immersed. The construction features of each type, along with variations in design, are discussed in 5.1 and 5.2.
5.1 Dry type
Dry-type shunt reactors generally are limited to voltages through 138 kV and can be directly connected to a transmission line or applied on the tertiary of a transformer that is connected to the transmission line being compensated. The reactors are of the air-core (corcless) type, open to the atmosphere, suitable for indoor or outdoor application. Natural convection of ambient air is generally used for cooling the unit by arranging the windings so as to permit free circulation of air between layers and turns.
The layers and turns are supported mechanically by bracing members or supports made from materials such as ceramics, glass polyester, and concrete. The reactors are constructed as single-phase units and are mounted on base insulators or insulating pedestals that provide the insulation to ground and the support for the reactor.
Since the dry-type shunt reactor has no housing or shielding, a high-intensity external magnetic field is produced when the reactor is energized. Care is thus required in specifying the clearances and arrangement of the reactor units, mounting pad, station structure, and any metal enclosure around the reactor or in the proximity of the reactor. A closed metallic loop in the vicinity of the reactor can produce losses, heating, and arcing at poor joints; therefore, it is important to avoid these loops or to maintain sufficient separation distances. The magnitude of current induced in the loop, which is responsible for extra losses and heating. is dependent on the orientation of the loop with respect to the reactor, impedance of the loop, size of the loop, and distance of the loop from the reactor. Another consideration is the effect of the magnetic fields on the impedance deviation between phases. Methods of minimizing the deviations include adequate separation or arranging the reactors in an equilateral-triangle physical configuration.IEEE C37.109 pdf download.