3.3.1主变压器台数的确定主变台数确定的要求:(1)对枢组变电站，在

3.3.1 Determination of the number of <br>main transformers: Requirements for the determination of the number of main transformers: <br>(1) In the case of pivot group substations, in the case where a ring network has been formed on the middle and low voltage sides, it is appropriate to install two main transformers in the substation. <br>(2) For primary isolated substations or large-scale special substations that are regionally isolated, three main transformers can be installed in the design to improve the reliability of power supply. <br>In order to ensure the reliability of power supply and avoid the failure of one main transformer or the influence of power supply during maintenance, two main transformers are generally installed in the substation. When three or more units are installed, although the reliability of the substation is improved, the wiring network is more complicated and the investment is increased. At the same time, the occupied area and the complexity of power distribution equipment and power protection are increased. , And bring many complications such as maintenance and trip operation. Considering that the probability of two main transformers failing simultaneously is small. It is suitable for long-term load growth and expansion, and when one main transformer fails or is overhauled, the other main transformer can bear 70% of the load to ensure the normal power supply of the entire substation. Considering that this substation is an important regional substation, it is closely connected with local power consumption. Therefore, two main transformers are selected for parallel operation and equal capacity.

3.3.1 Determination of the number of main transformer stations<br>Requirements for determining the number of main shifts:<br>(1) For the pivot substation, in the case of the medium and low-voltage side has formed a ring network, the substation should be equipped with two main transformers as appropriate.<br>(2) For a single substation or large-scale special substation isolated in the region, three main transformers may be installed at design time to improve the reliability of power supply.<br>In order to ensure the reliability of power supply, avoid - the main transformer failure or maintenance of the impact of power supply, substations are generally installed two main transformers. When three or more, the reliability of substations has improved, but the wiring network is more complex, and investment increases, while increasing the footprint and power distribution equipment and the complexity of electricity protection, as well as the maintenance and reverse operation and many other complications. Considering that the chance of two main transformers failing at the same time is small. Suitable for the growth of long-term load and expansion, and when - the main transformer failure or overhaul, the other main transformer can bear 70% of the load to ensure the normal power supply of the entire substation. Considering that the substation is an important regional substation, it is closely related to local electricity consumption. Therefore, two main transformers are selected, running side by side and with equal capacity.

3.3.1 determination of the number of main transformers<br>Requirements for determining the number of Main Transformers:<br>(1) For the pivot group substation, when the middle and low voltage sides have formed a ring network, it is better to install two main transformers in the substation.<br>(2) For regional isolated primary substation or large special substation, three main transformers can be installed in the design to improve the reliability of power supply.<br>In order to ensure the reliability of power supply and avoid the failure of one main transformer or the influence of maintenance on power supply, two main transformers are generally installed in the substation. When three or more substations are installed, the reliability of the substation is improved, but the connection network and network are more complex, and the investment is increased. At the same time, the occupied area, the complexity of distribution equipment and power protection, as well as the complexity of maintenance and switching operation are increased. Considering that the failure probability of two main transformers at the same time is small. It is applicable to the long-term load growth and expansion. When one main transformer fails or is overhauled, another main transformer can bear 70% of the load to ensure the normal power supply of the whole substation. Considering that the substation is an important regional substation, it is closely connected with local power consumption. Therefore, two main transformers are selected for parallel operation with equal capacity.<br>