Views:2 Author:Site Editor Publish Time: 2018-03-07 Origin:Site
When the reactive power compensation device is designed and ordered, the parameters provided to the manufacturer are usually only the capacitance compensation cabinet type and the reactive power value. However, the two important parameters of capacitor rated voltage and static capacitance are often ignored. Because the capacitor manufacturers do not know much about the voltage condition of the product installation, they often focus on reducing the production cost and reducing the dielectric breakdown in the product design. The rated voltage of the selected capacitor is often higher than the recommended value of the national standard. What effect will this have on the reactive power compensation effect of grid operation? what changes will be caused by the investment in power grid construction? can be analyzed through the following cases.
For example, a 100.4 kV transformer needs centralized reactive power compensation at the low voltage side of the transformer according to the operation requirement of power factor 0.9. The reactive power needs to be compensated for 100 kvar after calculation. If the capacitor is configured at rated voltage U = 450V, the calculation is based on QC = ω CU2 × 10 -3. The static capacitance C of the capacitor bank is 1 572 μ F, and the capacitor bank is connected to the power grid under the operating voltage of 400 V. The reactive power QC provided by the capacitor to the power grid is 79 kvar, and the compensation effect is only 79%. On the contrary, in order to ensure the actual compensation effect is 100 kvar, the reactive power of capacitor must be at least 127 kvar. This means an increase of 27 per cent in equipment investment. In 2004, in Zhongshan City, 898 transformers were added, with a total capacity of nearly 600,000 kvar, and the reactive power needed to be compensated at a 30% compensation rate of nearly 180,000 kvar. According to the above analysis, if the rated voltage is selected as 450V, the amount of reactive power compensation should be increased by 4. 860,000 kvar on the original figure, even if the AC contactor switch static compensation is adopted. The investment in the acquisition of equipment would also need to be increased by $1 800,000 a year. If the dynamic compensation of thyristor switching is adopted, the investment increase of equipment acquisition will reach 19.8 million yuan per year. Therefore, in order to ensure that the actual compensation effect is consistent with the design, the order for reactive power compensation equipment should not only put forward the type of capacitor compensation cabinet and the quantity of reactive power, but also determine the rated voltage of capacitor. At the same time, the equipment manufacturer shall be required to mark the number of reactive power, rated voltage and static capacitance C on the nameplate of the capacitor.