Mitsubishi Electric Corp. said it has developed two technologies for gas-insulated switchgear.

The first is an arc-cooling technology that the company claimed can achieve a 25% improvement in the interruption of electrical current in sulfur-fluoride (SF6) gas-insulated switchgear used in high-voltage power systems.

The second is a high-density dielectric coating technology that the company said improves insulation performance by 30% in high-voltage conductors.

In a statement, the company said the technologies are intended to help shrink switchgear size and help to reduce the use of SF6 gas, which has global-warming potential that the company said is 22,800 times greater than that of CO2.

(Learn more at Engineering360 about gas-insulated switchgear, including products, standards and reference material.)

Design details

Mitsubishi Electric said that its interrupter has two pairs of electrodes that remain closed when electric power is supplied. When the electrodes are opened, the current cannot be interrupted immediately due to the conductive arc. In a conventional method, the company said the arc is extinguished by flowing the arc with gas to lower its temperature. Mitsubishi Electric said that its technology uses coolant to generate a high-pressure gas jet to cool and then extinguish the arc.

The company said that the high-density dielectric coating technology makes the dielectric coating layer denser on high-voltage conductors, improving dielectric performance.

In the switchgear, compressed SF6 gas is injected between a metal high-voltage conductor and a grounded tank. If the conductor's metal surfaces are not coated, surface roughness can lead to electric discharges and diminished dielectric performance of the SF6 gas. Mitsubishi Electric's coating is intended to inhibit such discharges. In addition, densifying the dielectric coating layer suppresses discharges due to air in the dielectric coating layer.

A gas-insulated switchgear incorporates an SF6 gas tank, which also contains an interrupter and high-voltage conductor. Conventional designs required two interrupters to conform to Japan's JEC-2300 standard and the IEC 62271-100 international standard. Mitsubishi Electric said that its gas-insulated switchgear requires one interrupter. In addition, incorporating a coating layer in the high-voltage conductor is expected to improve dielectric performance and allow the distance between the conductor and the grounded enclosure to be shortened, allowing a smaller enclosure to be used.