A Discussion on Practical Limits for Segmentation Procedures of Tower-Footing Grounding Modeling for Lightning Responses
Schroeder, M. A. O. S.
; Moura, R. M.
IEEE Transactions on Electromagnetic Compatibility Vol. 0, Nº 0, pp. 1 - 8, May, 2020.
ISSN (print): 0018-9375
Journal Impact Factor: 1,083 (in 2008)
Digital Object Identifier: 10.1109/TEMC.2020.2982358
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In this article, we evaluate the practical limits of length
segmentation of tower-footing grounding modeling. The objective
is to present a relation between computational efficiency and segmentation
for transmission lines lightning performance studies. A
physically consistent electromagnetic model based on field theory
is applied. The segmentation process is designed to improve computational
efficiency, in relation to the proposals suggested in the
literature, and to maintain the precision of the results. The criteria
considered acceptable for a given segmentation (in relation to a
reference) are as follows: 1) the grounding potential rise (GPR)
must have a peak value up to a maximum of 10% higher, 2)
the lightning overvoltages peaks on the tower top (and insulator
strings) must have a peak value up to a maximum of 5% higher,
and 3) the GPR waveforms shall follow the same pattern (the
same being valid for overvoltages). Soils with low (50–300 Ω·m),
medium (300–1000 Ω·m), and high (1000–4000 Ω·m) resistivities
are considered. The relative permittivity is maintained at 10. The
results illustrate that the optimum segmentation can be as great as
1000 times the radius of the electrode. This ratio is higher than the
maximum segment sizes suggested by the technical literature. The
computational gains are quite high (over 30 times faster).