Long-term stability and energy discharge capacity of metal oxide valve elements

Long-term stability of metal oxide surge protectors from four manufacturers has been investigated. Valve elements were energized in ovens at temperatures from 75 to 175°C, and the power dissipation was monitored. The results show the variability in the stability of products available at present. In one case, an observed instability was due to deterioration of the sidewall. The results show that aging can increase or decrease the energy discharge capacity. The findings have application in the selection of arresters and in the development of standards