返回Google圖書搜尋

Promjene naponsko-strujnih karakteristika metaloksidnih odvodnika prenapona kao posljedica udarnih strujnih opterećenja

其他書名	doktorska disertacija
出版	samozaložba, 1993
URL	http://books.google.com.hk/books?id=mtkmOgAACAAJ&hl=&source=gbs_api

註釋In the first part, the thesis is concerned with changes of electrical characteristics of metal-oxide resistors which are used for metal-oxide surge arresters, caused by a recurrent application of impulse currents of a defined amplitude and shape. The dependence of the power generated in the resistor on the number of applied impulses was found experimentally and by making use of a numerical procedure a suitable relation was defined. Similarly, a relation describing the dependence of the generated power on the temperature was established, too. In the second part, an analysis of electrical and thermal stresses of the model of the arrester was made according to finite-element-method and the NISA II/DISPLAY III program package. The voltage gradient of the suspention insulator string alone and in a combination with the arrester was analysed. The relationship between the power dissipated from the arrester and temperature was found on the basis of and appropriate thermal model. Further on, the established curves for the generated power and dissipated power were used to analyse the dynamical behaviour of the temperature course of different parts of arrester. After an adiabatical process of a certain amount of energy absorption by the resistor at an ageing rate (number of impulses) the temperature course was computed with the aim of finding the number of impulses necessary to lead the arrester to the thermal run-away. Finally, a calculation was made to estimate the number of current impulses expected to appear in the arrester on a 110 kV line each year, and the value of the performance criterion for the arrester.