Surge arresters characteristics

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 18.9 Protective characteristics of gapless station class surge arresters for a nominal discharge current of 10 kA ...

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,...

Surge arresters Electrical characteristics of a ZnO surge arrester Basic insulation level (BIL) ... 

He J, Zeng R, Chen S, Tu Y. Thermal characteristics of high voltage whole-solid insulated pol3rmeric ZnO surge arrester. IEEE Trans Power Deliver. 2003 18 1221-1227. 

With this particular arrester, the motor has to be specially designed for the higher level of FOW impulse voltage withstand. But the manufacturer can always modify the protective characteristics of the arrester, depending upon the system s requirements. The matter may therefore be referred to the manufacturer for recommendations. The arrester may be fitted with a 0.25, uF surge capacitor in parallel, to reduce the steepness of the FOW (for the arrester of example 17.5, it is 14/0.2 kV/jUS) to a safer value. 

Arresters or diverters are generally of the following types and the choice between them will depend upon the power frequency system voltage, characteristics of the voltage surges and the grounding system, i.e. 

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