Pre-installed American Box Type Cabinet

● Product advantages

1. The Pre-installed American Box Type Cabinet have compact and standard structure, small floor space, far less than the European type with the same capacity.

2. Sealed, insulated structure, strong safety.

3. The Pre-installed American Box Type Cabinet adopt transformers with low loss, low noise, low temperature rise, strong overload capacity, short circuit resistance and strong impact resistance ensures the high performance of the product.

4. Accept various solutions to meet the customized needs of customers and deal with different usage scenarios.

● Structure of cabinet

◆ Overall layout

The appearance and structure of 10kV Pre-installed American Box Type Cabinet are shown in Figures 2 and 3. The oil tank is divided into two parts, the upper part is the high-pressure oil tank, and the lower part is the transformer oil tank. The two parts are only electrically connected and the oil is blocked. The schematic diagram is shown in Figure 1, in which "I" and "I" lines are loop network feeders, "ll" branches are transformer branches, and "V" is low-voltage output. cabinet can be used in both ring network power supply system and terminal system, and the conversion is very convenient. The feed of the line and "lⅢ" branch is switched with the load switch of the ring network. At the same time, the incoming terminal of the high-voltage side of the transformer is equipped with backup protection fuses and plug-in fuses to protect the short-circuit fault and overload and over temperature protection of the branch. At the same time, high-voltage display devices and lightning arresters can also be installed. The low-voltage end of the transformer is output after passing through a meter and a low-voltage circuit breaker.

◆ Transformer

Pre-installed American Box Type Cabinet adopt S11 series three-phase oil-immersed transformer with low loss, low temperature rise and low noise is adopted. Fully sealed structure effectively isolates the air pollution and insulation degradation caused by moisture. The corrugated sheet of the oil tank shell has the functions of heat dissipation and cooling, and effectively reduces the internal pressure.

◆ Two-station terminal load switch

Its structural diagram is shown in Figure 4, in which "I" is connected to the high-voltage incoming terminal. During operation, the user inserts the special operating handle into the rotating shaft of the load switch and rotates it 90 degrees counterclockwise, and the load switch turns to the "off" position. The terminal load switch only cuts off the transformer branch in the terminal power supply mode or works when replacing the plug-in fuse core, so the terminal negative load switch only has two positions of off and on, and the operating force is also small due to its small size. In order to reduce the oil pollution in the oil tank, it is suggested that the user turn off the low-voltage switch before operating the load switch to reduce the pressure side load.

◆ Protection Fuse

The protection fuse of Pre-installed American Box Type Cabinet is connected in series with the plug-in fuse in the transformer branch (see R1 and R2 in Figure 2) to form a full-range protection fuse. It only blows when there is a short-circuit fault inside the cabinet, so the probability of blowing is very low. It is installed in the upper oil tank, and the oil tank needs to be opened if it is to be updated.

◆ Insert Type Fuse

Its melting core has dual sensitivity (temperature and current), that is, it melts when the load side fails (overload or excessive temperature). Plug-IN fuse and backup protection fuse are used in series, which can protect the whole range from small current (several times in) to large current (several tens of kiloamperes), and the maximum breaking current is 50kA.

Note：

1. All listed in the table are ratings of fuses. The backup protection fuse is blown only when there is a short circuit fault inside the Pre-installed American Box Type Cabinet.

2. The selected transformer is only suitable for the connection mode of Dyn11.

3. When selecting the inserted fuse, it should be considered that 3-4 times the full capacity current of the transformer should be melted within 300s, and at the same time, it should be satisfied that 12 times the full capacity current of the transformer should not be melted when 0.1s is used.

4. According to IEC standards, the fuse can work in the political range of -25℃~+40℃. When the oil temperature is higher than +40℃, the rated current of fuse should be reduced by 1% for every 1℃ increase.

◆ Elbow type and "T" type cable head

The high-voltage incoming and outgoing lines of 12kV Pre-installed American Box Type Cabine adopt cable incoming and outgoing lines, and the high-voltage power supply is led out of the oil tank by epoxy-cast insulating sleeves. In order to facilitate the factory's test and user's acceptance test, the insulating sleeves themselves have the ability to withstand 10kV power frequency withstand voltage and lightning impulse withstand voltage. Before installing the cable head, it is necessary to know whether the user requires lightning arresters. If necessary, one set of insulating sleeves at the incoming and outgoing lines of the loop adopts double-pass type, and the other set adopts single-pass type.

Choose an elbow or T-shaped cable head that matches the cable section, clean its inner and outer surfaces and the surface of the insulating sleeve with anhydrous ethanol, apply a little 7501 vacuum silicone grease on the sleeve surface, and install it according to the special installation specifications of the cable work area. At the other end of the double-pass insulating sleeve, install a special fully sealed zinc oxide arrester in the same way. See the instructions for the installation of the cable head.

● Dimensions of the Pre-installed American Box Type Cabinet