American standard data center medium voltage switchgear

The GreySpace of a data center is an area used to store electrical and mechanical facilities such as UPS and distribution cabinets, as well as cooling systems such as chillers. The WhiteSpace refers to the core computing area of the data center specifically designed for storing IT equipment, which is the core area of the data center.

The white area typically occupies 60% -80% of the available space and is the core area where data centers generate value.

The white area is the "power generation" and "computing" area, mainly composed of IT equipment, and the operation and maintenance personnel are mainly IT engineers and HVAC engineers. GreySpace is a "support" area, with operations personnel mainly consisting of electrical engineers.

The requirements for 38kV equipment are as follows:,

Metal armored switchgear

Outdoor type, NEMA 3R protection level

Current 1200A, 3-phase, 3-wire, 31.5kA

Incoming equipment, firmly grounded system

A 1200A main incoming circuit breaker, vacuum or gas arc extinguishing

18 sets of 1200A outgoing circuit breakers are equipped with lightning arresters for each outgoing circuit

The main circuit breaker and outgoing circuit breaker are equipped with current transformers and voltage transformers for power measurement and communication

All circuit breakers provide position auxiliary contact monitoring

Cable underground bottom incoming 125V DC battery system

Outdoor air insulated switchgear, although large in size, has simple operation and maintenance, easy expansion, low cost, in line with long-term usage habits in North America, and is safe and reliable.

This project explicitly requires medium voltage metal armored switchgear, namely IEEE C37.20.2 standard switchgear, rather than C37.20.9 standard inflatable switchgear. For the aforementioned plan, installing gas insulated switchgear using prefabricated warehouses will reduce the overall size of the container. The prefabricated warehouse plan is equivalent to a North American standard outdoor switchgear with an operating corridor, which is compact in space but high in cost, limited in operation and maintenance expansion, and has higher safety and reliability.

It should be pointed out that SF6 gas is restricted from use in medium voltage switchgear in California and other places in the United States. Therefore, environmentally friendly gas insulation will be the mainstream for gas filled cabinets in the future. American standard gas filled cabinet certification still requires the use of environmentally friendly gas in advance. Data centers generally use 38kV 1200A 31.5kA, which can meet the requirements without excessive current levels.

And for each prefabricated power module, namely the 15kV medium voltage cabinet, the transformer from 13.8kV to 480/415V, the low-voltage switchgear or distribution panel, UPS, etc. are centrally installed inside a prefabricated warehouse, with a general power of 2.5/3/3.5/4MW.

The medium voltage cabinet is only used as a lead or protection for the front end of the transformer in prefabricated modules. In theory, it is necessary to provide visible fracture surfaces to ensure the safety of power outage maintenance.

The front-end isolation of the transformer has been proposed by a customer to choose a 24kV (instead of North American 15kV) mid cabinet isolation handcart single in single out solution. If according to the North American C37.20.2 standard, it is a metal armored switchgear, which requires no ventilation holes between compartments, steel plate thickness greater than 3mm, full current insulation of the busbar, and other requirements. In addition, a working channel needs to be reserved in front of the switchgear according to NEC standards. After the door is opened, an additional 22 inches (25.4 × 22=558.8mm) should be added. Taking the cabinet width of 800 as an example, the cabinet door is 750+559=1309mm, which requires a 1.31-meter maintenance channel. This is not suitable in the compact space inside the standard container.

The front end of conventional transformers in North America adopts an air insulated load switch (with fuses) single in single out scheme, which is a fixed load switch that meets the standard C37.20.3 metal enclosed switchgear. It has a small depth and does not require excessive maintenance space. The scheme is flexible, and whether it is single in single out, two in one out fuse protection (only two switchgear are needed), or fixed/withdrawable circuit breaker protection, it can be installed and maintained in front of the cabinet, seamlessly connected to the transformer, safe and reliable, and cost-effective.