Abstract
The voltage distribution along the non-linear resistance of metal oxide surges is of great importance for their proper operation, since the non-uniform potential distribution results in higher thermal stresses of the varistor discs near the high voltage electrode, leading to a faster ageing of the discs at the top and, consequently, a downgrade in arrester effectiveness and reliability or even failures. The current work deals with the examination of the voltage distribution along the non-linear resistance of medium voltage metal oxide gapless surge arresters, using an appropriate computer tool, discussing configuration that improve the voltage distribution. Moreover, the impact of various factors on the voltage distribution is examined. The extracted results can contribute to the more efficient design of modern metal oxide gapless surge arresters, in an effort to ensure their reliable operation to protect the electrical equipment against lightning surges.
Highlights
Surge arresters are widely used in electrical installations, in order to improve their lightning performance, to protect the equipment of the system and reduce the annual failure overvoltage rate.Surge arresters are installed between phase and earth and behave as insulators for the normal operation of the system and as conductors for overvoltage conditions, due to their intense non-linear voltage-current characteristic
This paper proposes a procedure for the computation of the voltage distribution along medium voltage gapless surge arresters, by using an appropriate computer tool
Design Proposals of the Varistor Geometry for the Improvement of Its Voltage Distribution on the steady state performance is of great importance, The uniform study of potential the voltage distribution alongtothe non-linear resistance oxide surge since the non distribution results higher thermal stresses of of metal the varistor discs near arresters on electrode the steady(due statetoperformance is of great importance designof the the high voltage the stray capacitances to ground),(especially leading toduring a fasterthe ageing since the non uniform potential distribution results to higher thermal stresses of the discs procedure), at the top and, the downgrade of arresters’ effectiveness and reliability or even varistor discs near the high voltage electrode, leading to a failures
Summary
Surge arresters are widely used in electrical installations, in order to improve their lightning performance, to protect the equipment of the system and reduce the annual failure overvoltage rate. Surge arresters are installed between phase and earth and behave as insulators for the normal operation of the system and as conductors for overvoltage conditions, due to their intense non-linear voltage-current characteristic. A critical issue for the appropriate performance of the gapless metal oxide surge arresters is the voltage distribution along their non-linear resistance (varistor). The voltage distribution along a metal oxide surge arrester is governed by the capacitances and the resistances of the non-linear resistors, the stray capacitances from the non-linear resistor column and metal flanges to earthed and live parts, and the boundary conditions (applied voltage, proximity and voltage applied to other objects in the vicinity). Stray capacitances result in uneven voltage distribution along the resistor column, with the maximum voltage stress
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