Abstract:
Air core reactors (ACR) have been widely used in power systems in several different
applications like harmonic filters, thyristor-controlled reactors (TCR) for static var
compensators (SVC), mechanically switched reactors (MSR) for shunt compensation of long
transmission lines, smoothing and valve reactors for line commutate converter (LCC) and for
voltage sourced converted (VSC), respectively, in HVDC systems, onshore and offshore. As a
global trend, the pursuit of environmentally friendly equipment has increased, leveraging the
use of ACRs in ultra-high voltage (UHV) systems. Applying that equipment in such voltage
levels demands very accurate calculation models to establish the proper design parameters (e.g.,
inductance values, power losses and audible noise levels) as well as the stresses (dielectric,
thermal and mechanical) that the equipment will have to withstand during operation, for their
lifecycle. One typical concern related to those calculation models is regarding the prediction of
the eddy current winding losses by analytical models. Several models have been proposed for
this type of calculation for transformers and electrical machines, but usually with some
constraints that make those models more suitable to that equipment than to others. With the
crescent demand for ACR with lower power losses levels, it makes sense to look for
improvements on those calculation models. One way of supporting the enhancement of those
models is using software based on finite element methods (FEM) that allows for very detailed
simulation of the physical phenomena related to the air core reactors and their applications.
Although the FEM is a powerful tool for complex simulations, it is usually very time consuming
and may require sophisticated computational apparatus to run more complex models. Air core
reactors are equipment composed by one or several concentric windings made of conductive
material (aluminum or copper) and their design may vary significantly, from a few kilograms
to some dozens of tons. The simulation, in a reasonable time, of that equipment with several
windings and sometimes thousands of turns would require computers that are not easily found
in regular industries. In this work an optimized modeling process for simulating ACR using a
2-D equivalent geometry method in a finite element-based software was developed to allow for
faster simulations. The validation of the method is performed by running a full factorial design
of experiments (DOE), screening four design parameters of windings: winding diameter,
winding height, number of strands and strand diameter, as these parameters significantly affect
the two main design characteristics of the air core reactors: inductance and winding power
losses. The results of the finite element simulations are statistically compared to the results of
analytical calculations. With the deployment of this process, an improvement for the calculation
of the eddy current winding losses of that equipment is proposed.