Behaviour of MO-surge-arrester blocks to fast transients

Measured values of the amplitude of the voltage spike for different current impulses are presented. It is shown that this peak is in the nanosecond-range and can only be measured with a coaxial measuring arrangement having a bandwidth of some MHz. The results show clearly that a voltage spike of some 10% can be related to the characteristics of the ZnO used in the metal oxide (MO) surge arresters. The initial peak is influenced by the composition of the material. A physical explanation for this behavior is discussed. A much larger spike is observed. When the voltage divider is placed adjacent to the arrester block. In addition to the voltage spike the influence of the timing of the current impulse on the magnitude of the residual voltage was evaluated. From the experimental results a model of an arrester block that describes the observed phenomena was developed. The experiments and calculations are in good agreement. The results obtained with the arrester blocks are extended to the protection characteristics of complete arresters in power systems