Metal-oxide surge arrester operating limits defined by a temperature-margin concept

The problem of ascertaining the absence of possible thermal runaway of metal-oxide surge arresters when they are used in applications requiring a very low protective level is addressed. An electrothermal model of arresters is used to predict the temperature-time profile of their active elements in severe (near thermal runaway) conditions. Experimental evidence is produced to validate the proposed method and justify a criterion for the operating limit of any arrester design. This operating limit is proposed as a maximum acceptable temperature for the arrester metal-oxide elements