Original scientific paper
Mitigation of common mode failures at multi-circuit line configurations by application of line arresters against back-flashovers
M. Kizilcay
; University of Siegen, Germany
C. Neumann
; RWE Transportnetz Strom Dortmund, Germany
Abstract
Due to the limited number of corridors multi circuit line configurations are often applied. These
overhead lines frequently consist of high towers that are subject to lightning strokes. In case of higher
current amplitudes and higher footing resistances due to bad earthing conditions back-flashovers are
caused leading to common mode failures and to severe outages.
The paper describes investigations performed by means of computer simulations to identify the towers
of a multi-circuit line consisting of voltage levels 380 kV, 220 kV and 110 kV that are endangered by
back-flashovers of the 110-kV double-circuit lines. The footing resistance of towers of the targeted
line section has been measured by an instrument at high-frequency. Influence of various factors on the
back-flashover over 110 kV insulator strings has been studied by means of EMTP-ATP simulations.
Different current waveforms of the lightning stroke have been used to represent the first stroke and
subsequent strokes. The towers are represented by the models described in [3], [8]. Available
flashover analysis methods [7], [8], [12], [13] like leader development method by Pigini et al and by
Motoyama, and voltage-time integration method by Kind have been applied.
The towers at which back-flashover is more likely to occur than at other towers are identified by the
time integral of voltage according to Kind. Various factors like tower footing impedance, tower surge
impedance and tower height are considered. Application of line a surge arrester is shown to be a
successful mitigation technique to reduce the back-flashover rate of those 110 kV lines. The lightning
overvoltage performance of surge arresters has been analyzed by means of digital simulations. Based
on the results of investigations line arresters were installed on the towers in question. Since the
installation no further common mode failure has been observed.
Keywords
Lightning – Overvoltage – Backflashover – Tower – Multi-circuit – Overhead line – Surge Arrester
Hrčak ID:
198414
URI
Publication date:
19.6.2017.
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