By John G. Webster (Editor)
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Extra info for 46.Power Delivery
The interrupters can be either single-flow or double-flow. Upon current interruption, the movable electrode separates from the stationary electrode producing an electric arc between the electrodes. Compressed gas blasts through the electrodes with a tremendous radial velocity, several times the speed of sound. This radial gas flow cools the axially burning arc. As in all breakers, the current electric arc burns until a natural current zero is reached, and the arc is extinguished. Compressed air and SF6 gas both have excellent heat capacity to deionize the arc plasma and excellent dielectric resistance, so that the breaker can withstand the high transient recovery voltage.
The vacuum bottles have an electrically insulating cylindrical envelope made of glass or ceramic and are typically 10 cm to 18 cm (4 in to 7 in) in diameter and 15 cm to 31 cm (6 in to 12 in) long. Metallic end plates are attached to the insulating envelope. The vessel contains a set of electrodes brazed to electrode stems of which one is fixed to an end plate and the movable electrode stem is connected to the other end plate via a metal bellows. The metal bellows provides a hermetic seal and contacts stem motion.
However, the construction of both is similar. These breakers are rated for 5 kV to 72 kV, 250 A to 2000 A continuous current, and 12 kA to 41 kA fault current interruption. In the United States, these breakers can be oil or vacuum. Some breakers used in power stations have special ratings. Reclosers normally interrupt lower fault currents than breakers. Also, reclosers normally receive all their control power from the power lines, but circuit breakers normally operate from control room battery banks.
46.Power Delivery by John G. Webster (Editor)