Development of metal oxide arrester block using a rare earth element for very fast transient overvoltage applications

Authors: KANNADASAN RAJU, VALSALAL PRASAD, JAYAVEL RAMASAMY

Abstract: The protection ability of metal oxide arresters against switching, lightning, and steep current surges has been well proven. On the contrary, during the invasion of very fast transients, the existing arrester fails to operate due to delay in its initial response. In order to decrease the delay, it is imperative to improve the electrical properties of the arrester such as nonlinearity and voltage gradient with reduced capacitive effect. In this context, new arrester blocks are developed with the addition of a rare earth element, namely scandium trioxide (Sc$_{2}$O$_{3})$, and then sintered with a microwave sintering process. Owing to the uniform heat distribution characteristic and the requirement of a low sintering temperature, the microwave sintering process provides better microstructural and electrical properties than the conventional sintering process. From the observed results of prepared arrester blocks, one among them is chosen, which contributes a higher voltage gradient (790 V/mm), better nonlinear coefficient (55), and the least leakage current (2.9 $\mu $A). Moreover, the chosen arrester block gives a lower block capacitance of 0.0985 nF at 100 Hz. Hence, this arrester block can afford better protection of the power system against very fast transients.

Keywords: Gas insulated substation, metal oxide arrester, microwave sintering, rare earth element, very fast transient overvoltages

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