Step-up transformers with a capacity of 6 MVA

Step-up transformers with a capacity of 6 MVA(megavolt-amperes):

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### Application Scenarios They are commonly used in new energy fields such as photovoltaic power generation projects, to boost the low-voltage electrical energy generated by photovoltaic panels to high-voltage electrical energy suitable for grid connection.

### Capacity Selection Factors

- **Total Installed Capacity of Photovoltaic Power Generation System**: If the total installed capacity of the system is around 6 megawatts, considering the losses of inverters, line losses and a certain margin, selecting a 6 MVA step-up transformer can meet the requirements for electrical energy boosting.

- **Maximum Output Power of Inverter**: The output power of the inverter needs to match the capacity of the step-up transformer to avoid situations where the transformer capacity is insufficient or over-configured. - **Grid Connection Voltage**: According to the voltage level requirements of the grid connection point, a step-up transformer with an appropriate transformation ratio should be selected to ensure that the electrical energy can be smoothly connected to the grid.

### Examples of Technical Parameters - **Rated Voltage**: The voltage on the primary side (low-voltage side) is usually determined according to the output voltage of the photovoltaic array and may range from several hundred volts to over one thousand volts; the voltage on the secondary side (high-voltage side) is determined according to the requirements of the grid connection voltage, and common ones are 10 kV, 35 kV, etc.

- **Rated Current**: It can be calculated according to the formula \(I = S / (\sqrt{3}U)\), where \(S\) is the transformer capacity (6 MVA) and \(U\) is the rated voltage. For example, when the rated voltage on the secondary side is 10 kV, the rated current is approximately \(6000000 / (\sqrt{3}×10000)≈346.4\) A.

- **Short-circuit Impedance**: It is generally around 5% - 10%. The short-circuit impedance affects the current magnitude and protection performance of the transformer during short-circuit faults, and the specific value needs to be determined according to the system requirements and design.

### Common Types - **Oil-immersed Step-up Transformer**: It has good insulation performance and heat dissipation ability, and is suitable for outdoor installation and large-capacity application scenarios. However, it is necessary to regularly check and maintain the oil quality, etc., to prevent oil leakage and other failures.

- **Dry-type Step-up Transformer**: It has good insulation performance, is not easy to burn, and has a relatively small maintenance workload. It is suitable for places with high requirements for fire prevention, such as indoors. However, its heat dissipation is relatively poor compared to that of the oil-immersed type, and its capacity is generally relatively small.

### Related Equipment and Ancillary Facilities - **Matched Inverter**: It is necessary to select an inverter that matches the capacity and voltage level of the step-up transformer to convert the direct current generated by the photovoltaic panels into alternating current and then send it to the step-up transformer.

- **High-voltage Switchgear**: It is used to control and protect the high-voltage side circuit of the step-up transformer and realize functions such as power transmission, power cut-off and fault protection for the transformer.

- **Measurement, Control and Protection Devices**: They monitor the operating parameters of the step-up transformer in real time, such as voltage, current, temperature, etc. When abnormal situations occur, they will promptly send out alarm signals and take protection measures to ensure the safe operation of the transformer.