Surge arresters energy capability

TOV is considered only to select the MCOV and the rated voltage, V, of the surge arrester. This is a reference parameter to define the operating characteristics of an arrester. It plays no part in deciding the protective level of the arrester, which is solely dependent on the transient conditions of the system, as discussed later. V, is used to make the right choice of an arrester and its energy absorption capability to ensure that it does not fail under the system s prospective traiisieut conditions. 

Table 18.11 Protective characteristics of a gapless station class surge arrester for, (1) Line discharge class 4, and (2) Single impulse energy capability = 7 k.J/k.V,...

The arrester chosen has a total energy capability of 7 kJ/kV, (from the manufacturer s catalogue). In service the arrester will be required to discharge much less energy than this as the distance of the arrester from the point of surge origination may be much smaller than considered. 

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