Environmentally friendly gas insulated 40.5kV switchgear

There are two types of 40.5kV environmentally friendly gas insulated switchgear: one is used for ring network power supply, with low current and short circuit current, and the other is used for high current and high short circuit current switchgear in power distribution systems such as the power industry.

Ring network applications, ring network cabinets belong to secondary distribution applications and are also used for grid connection of green and clean energy. The current is generally 630A and the short-term withstand current is 20kA.

The ring main unit adopts load switch as the ring in and out switch, and load switch fuse combination or circuit breaker as the transformer front-end protection.

SF6 sulfur hexafluoride gas, as an excellent insulation and arc extinguishing gas, can be directly used as an arc extinguishing medium for active load breaking. SF6 load switches and dynamic and static contacts are directly installed in SF6 gas, which ensures the electrical insulation strength between the isolated fracture surfaces. During the process of active load breaking, SF6 gas can quickly cool and extinguish the arc.

SF6 load switch has a compact structure and simple operation. However, environmentally friendly gases cannot meet the arc extinguishing application of active load opening and closing. Generally, in environmentally friendly gas ring main units, they are only used for isolation, while if the active load is opened and closed, the arc is extinguished through a vacuum arc extinguishing chamber.

In 12kV applications, there is a load switch with parallel vacuum arc extinguishing chambers, which cuts off the active load and closed-loop current in and out of the application scenario through arc transfer and vacuum. The load switch of parallel vacuum arc extinguishing chamber only requires one set of operating mechanism, and the operation method is the same as SF6 load switch.

At a voltage of 40.5kV, there is currently no load switch for parallel vacuum arc extinguishing chambers, only load switches for series vacuum arc extinguishing chambers. The configuration of a three position switch plus a vacuum load switch is basically equivalent to the configuration of a three position switch plus a vacuum circuit breaker.

Unlike inflatable cabinets that use a lower current rating and require a compact size, the width and depth of the inflatable cabinet need to be significantly smaller than those used for primary power distribution.

The typical layout still adopts the emphasis structure of A, B, and C three-phase front and rear layout, minimizing the size to the greatest extent possible. The side mounted three station switch rotates directly through the spindle, driving the switch blade to rotate, achieving the conversion of connection, disconnection, and grounding positions.

The circuit breaker adopts a clamp plate structure, with the vacuum arc extinguishing chamber fixed in the insulation clamp plate. The insulation spindle rotates to drive the contacts of the arc extinguishing chamber to open and close. Increasing the size in the depth direction can improve the phase spacing and meet insulation requirements.

The inflatable cabinet adopts a three-phase left, middle, and right assembly structure of A, B, and C. The three position isolation switch adopts a direct motion, and the contact is driven by a screw nut to move in the connecting, disconnecting, and grounding positions.

The direct acting three position switch has a large outer diameter, uniform electric field, and does not require solid insulation assistance. The required clearance is reduced, which is more conducive to insulation. For environmentally friendly gas insulation, it is easier to meet the withstand voltage requirements. Although the knife switch three position switch has good heat dissipation conditions, the electric field treatment requires a uniform shielding cover to meet the withstand voltage requirements.

The circuit breaker adopts insulated support poles, with high mechanical strength and good heat dissipation. Shielding insulation is used for the upper and lower ends, and tube type busbars or multiple thick copper bars are used to connect the copper bars to achieve high current and uniform electric field. The tips need to be removed, and all fasteners use round heads or embedded patterns to reduce local electric field strength.

By increasing the inflation pressure, the insulation distance can be effectively reduced. With a uniform electric field design and the replacement of rectangular busbars with tubular busbars, the insulation performance of the product is greatly improved, and the current carrying capacity can also be increased. The auxiliary high heat conduction stamping heat pipe cooling system ensures insulation and temperature rise performance, with high reliability.