Effect of humidity on the breakdown of air gaps under oscillatory switching impulse voltages

Experimental investigations were carried out to study the effect of humidity on the breakdown of rod-plane gaps subjected to both unidirectional and bidirectional oscillatory switching impulse voltages. The humidity ranged from 14.1-36 gm/m³ at a constant temperature of 40°C. The gaps were subjected to unidirectional 5.3, 10, 19 kHz and bidirectional 4.2, 10, 20 kHz oscillatory switching impulse voltages. The gap distance was varied from 8 to 30 cm. The experiments were carried out in a controlled atmospheric room. The results indicate an increase in breakdown strength with increase in humidity. The results are of great relevance at atmospheric conditions existing in tropical countries