Tests on the breakdown of air at elevated temperatures in non-uniform electric fields

Sparkover voltage characteristics have been obtained using a 20cm rodplane gap at temperatures between 294 and 770K. Lightning and slow-front impulse and alternating voltages have been applied: pre-breakdown corona has also been investigated under impulse voltages. The nature of the sparkover characteristics depends strongly on the type and polarity of the applied voltage. These are discussed in terms of the changes in relative air density with temperature and the relationship to the recommendations of IEC 60-1 for the adjustment of sparkover measurements to changes in atmospheric conditions.