Mid mounted and floor mounted 38/40.5kV switchgear

The development trend of switchgear is miniaturization, intelligence, and low carbonization. The development of new technologies, processes, and materials has promoted the miniaturization of switchgear.

The American standard 38kV switchgear requires a compact layout with a width of 42 inches (1066mm) and flexible arrangement. It needs to be on the same switchgear as the voltage transformer handcart, so a miniaturized circuit breaker is required. The height of the circuit breaker compartment is 1450mm and the depth is 1400mm.

The circuit breaker comes with a large roller for easy movement on the ground. The current transformer is mounted on the contact box, with high space utilization.

For domestic 40.5kV circuit breakers, the floor standing type seems more convenient, with the operating mechanism directly located at the bottom of the pole. The depth of the handcart can be reduced, making it easy to pull the handcart out of the cabinet without transferring it. After all, 40.5 circuit breakers are very heavy, usually around 300 kilograms, and it is impossible for one person to push and pull them out. It is also not a simple task to align the guide rails inside the cabinet, and it often needs to be adjusted repeatedly. For the center mounted circuit breaker, it is transported to the front of the cabinet by a transfer handcart, locked in place, and then pushed into the handcart type. The wall mounted guide rail is directly fixed to the side panel.

Mid mounted circuit breaker, the operating mechanism is located in front of the circuit breaker pole, so the depth of the entire circuit breaker will be slightly larger. And for floor standing circuit breakers, the operating mechanism is located below the circuit breaker pole. The depth of the circuit breaker can be smaller, so the depth of the entire switchgear can be reduced.

Therefore, whether it is a mid mounted or floor standing switchgear, the key is which type of switchgear is more suitable, such as the mid mounted ET2 switchgear launched by Eaton in 2008, which is a leader in medium voltage technology. The circuit breaker handcart is a vacuum type mid mounted type, and its design complies with IEC62271-100 and GB/T1984 standards.

Circuit breakers of the same type and rated capacity are completely interchangeable for use. There is an anti misoperation mechanical interlocking device between the circuit breaker handcart and the switchgear. When the circuit breaker is closed, the handcart cannot be pushed forward or pulled out. The circuit breaker can only be closed when the handcart is in the working or testing position. The moving contact is in a plum blossom shape, with a silver plated surface. Elastic fastening allows for a higher tolerance margin. The contact between the dynamic and static contacts is good, the main circuit resistance is small, and the temperature rise is low.

In recent years, Eaton has abolished the mid mounted 40.5kV switchgear in the domestic/IEC market, and the new ET2 adopts a floor standing 40.5kV circuit breaker handcart. Looking into the reasons, several factors have an impact. Standardization design of State Grid, cost factors, and Cooper impact, etc. The new ET2 and ZS3.2 are basically the same as the mainstream KYN61 in the market, with a width of 1200/1400mm

The busbar system has abolished the mid mounted ET2D main busbar design.

The main and branch busbars are made of high conductivity rectangular copper bars with rounded corners.

Epoxy resin coating or installation of heat shrink tubing on the surface of copper bars, with insulation buckle boxes wrapped around the overlap.

The maximum rated current of the busbar system is 3150A, and the short-circuit current is 31.5kA-4s.

Epoxy resin sealed vacuum circuit breaker pole, superior insulation performance verified through condensation test

Adapt to harsh operating environments

Using Eaton's latest generation vacuum arc extinguishing chamber, with long lifespan, low loss, and low current cutoff value

ABB ZS3.2 adheres to a floor standing design. Recently, ABB officially launched the UniGear ZS3.2 air insulated switchgear with a width of 40.5 kV 1400mm, which adopts the new generation of digital technology. It not only meets the safety, performance, and intelligence requirements of users for complete electrical equipment, but also effectively reduces the operating costs of equipment throughout its life cycle, promotes the comprehensive construction of digital power grids, and accelerates the realization of a low-carbon digital future.

The IEC market has a small depth for 36/40.5kV switchgear and simple operation and maintenance for floor standing circuit breaker handcarts, especially in Southeast Asia and other regions where floor standing circuit breaker handcarts are favored.  

Eaton's early mid mounted circuit breaker 40.5kV W-VACi was not abolished, but moved to North America to replace the old Eaton floor mounted circuit breaker. The miniaturized design of the 40.5kV W-VACi can make the switchgear more compact, making it possible to arrange double-layer circuit breakers. The circuit breaker meets the American standard C37.04 and is suitable for IEEE C37.20.2 metal armored switchgear.