Generally speaking: Under standard atmospheric conditions, the breakdown voltage of dry air is approximately 3,000 volts/mm² (i.e., 30 kV/cm).

"Air breakdown voltage" is not a fixed value; it varies greatly depending on factors such as the electric field configuration, air condition, distance, and time.

1- Safe Distance and Voltage:

Low-voltage safety: For 220V/380V voltages, the risk of breakdown from the air gap itself is extremely low (requiring millimeter-level gaps and sharp electrodes).

The main risk is contact with live parts.

High-voltage warning: Common 10kV power distribution systems can experience corona discharge a few centimeters from a fingertip;

If there are foreign objects in the gap, breakdown is even more likely.

2- Design standards for "air breakdown voltage"

National standards have mandatory regulations regarding the air clearance between phases and to ground of electrical equipment.

For example, in 12kV switchgear, the standard specifies a phase-to-phase clearance of ≥125mm.

This value is greater than the theoretical value to ensure sufficient safety distance to prevent damage from uneven electric fields, pollution, overvoltage, and other factors.

Interestingly, the "Pashin's Law" phenomenon states that under low air pressure and small gap conditions, the air breakdown voltage is related to the product of (air pressure × gap distance), and there exists a minimum breakdown voltage point.

For example, in a vacuum or under specific air pressures, even a very small gap can be broken down by a relatively low voltage.

This explains the complexity of high-altitude equipment and vacuum circuit breaker design.

Shaanxi West Power Tongzhong Electrical Co., Ltd.

Contact: Melody Sun (Export Sales manager)

Mobile: +86 180 9176 5658 (WhatsApp/Wechat)

Email: xdtz03@westpowerelectric.com