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In this paper, ZnO varistors with high voltage gradient, which were doped with 0.75 mol% Y2O3 and different ratio of Bi2O3, were prepared by classic ceramic fabricating method. The obtained samples were degraded under accelerated AC aging stresses of 0.85 V1mA /135°C/168 h. The electrical properties and Schottky barrier parameters of these samples before and after the aging tests were measured and...
A special simulation model for the surge responses of ZnO varistors is introduced in this paper. This model is based on the Voronoi network and contains the actual conduction mechanism of the grain boundaries, as well as the capacitances of the grain boundaries. The surge responses of the actual varistor samples were simulated and compared with the experimental results. The simulated waveforms agree...
The effects of Bi2O3 doping on the electrical characteristics of Al-doped ZnO varistors were studied. The electrical characteristics and the microstructural parameters of the varistor samples with various content of Bi2O3 additive were investigated. With the amount of the doped Bi2O3 increased, the leakage currents of the Al-doped ZnO varistors are inhibited obviously. In addition, their breakdown...
ZnO varistors have been widely used in power systems as metal oxide arresters (MOA) against overvoltage surges due to their excellent nonlinear current-voltage (I-V) characteristics and surge energy absorption capabilities. The MOA applied in power system with rated voltage usually has remarkable huge size, which results in great difficulty for MOA design and manufacture. Thus, ZnO varistors with...
A comprehensive review for the scattered phenomenon of energy absorption capabilities of ZnO varistors was presented in this paper. The pronounced and complex scattered phenomena were revealed according to experiments under varied test conditions. Those experiment phenomena were well explained by numerical simulations with microscopic circuit and heat transfer models of ZnO varistor based on Voronoi...
The influence of the geometry and topology of the granular microstructure, as well as the properties and the distribution of the different types of microjunctions on the features of bulk varistor devices is an important and interesting problem. Simulating analysis on the actual microstructure and electrical characteristics of ZnO varistors is used to effectively analyze the influences of different...
The U-I characteristics of ZnO nonlinear resistors (ZnO varistor) is very important on the protection performance of metal-oxide surge arresters, which protects power apparatus and electronic devices against surges. In this paper, the changes on U-I characteristics of ZnO nonlinear resistors are introduced when some rare-earth oxides are doped, as well as the mechanics which leads these changes. In...
ZnO varistors are vulnerable to be destroyed under high current. The puncturing phenomenon of ZnO varistor under high current is simulated in a microstructure model. The Voronoi diagram can effectively simulate the actual microstructure of ZnO varistors, from which the electrical topology relation of the nonlinear resistor network of ZnO varistor microstructure can be derived. The steepest descent...
By comparing the experimental results of two different systems ZnO varistors, we identify that Sb2O3 is the origin of twinning in commercial ZnO varistors. The additive of Bi2O 3 weakens the effect of Sb2O3 to form twins while the Al2O3 dopant strengthens the twinning. The twins have obvious effect to inhibit ZnO grain growth and uniform its microstructure, because the formed twins result in increasing...
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