1、 Introduction

After the large-scale construction and transformation of agricultural network in recent years, the health level of rural power grid under the jurisdiction of Jining Power Supply Bureau has been improved obviously. The original high energy consumption transformer is replaced with energy-saving transformer, and 0.4kV reactive power automatic switching device is installed on the transformer replaced. However, the configuration of switching series is unreasonable, basically is secondary system, which makes the reactive power balance of distribution network become a first class The main problems are put in front of the power department. Because the secondary reactive power compensation device is in the state of under compensation of primary input and over compensation of two-stage input for a long time, the reactive power balance of distribution network is out of balance, the power equipment can not be applied reasonably, the line loss increases, and the end-user voltage drops. Therefore, it is an important problem to reasonably allocate the series of reactive power switching.

2、 Analysis of the reactive compensation of agricultural network

The main reasons for the undercompensation of the first stage input and the over compensation of the secondary system reactive power compensation device are as follows:

Most of the secondary reactive power compensation devices installed in rural distribution transformer station area are 2 * 20kvar. However, due to the small capacity of transformer and large fluctuation of reactive load, the input compensation of the first-class 20kvar capacitor can not reach the set value of power factor, while 40kvar is used to start the other stage capacitor to compensate, But the success rate factor is higher than the set value, and the capacitor has to automatically exit the first stage operation. This makes the capacitor switch and retreat frequently, and the power factor can not meet the theoretical calculation value.

3、 Improving the switching measures of reactive power compensation

In 2003, the relevant departments of Ulanchab Electric Power Bureau and Inner Mongolia Academy of electrical technology jointly solved the key problems. Without changing the capacity of capacitors, 64 five lines with rose Ying substation as the export were put forward by increasing the capacitance series and automatic switching contacts The 40kvar secondary reactive power compensation device is transformed into four-stage system (5, 10, 10, 15kvar) for compensation, which avoids the problem that the capacitor capacity is too large to be put on but the power factor can not reach the requirements of the regulation. Thus, the capacitor has been applied to the maximum extent, and the power factor of distribution line and distribution transformer is greatly improved.

4、 Analysis of the economic benefits of the four-level reactive power compensation

The four-stage reactive power compensation device has achieved remarkable results in improving the end voltage of the user and reducing the line loss. In 2003, after the reactive power compensation device was changed to four-stage system, the average power factor of the five 10kV outgoing lines of rose camp transformer was above 0.85. The qualification rate of the comprehensive voltage of the five lines increased from 96.43% in 2002 to 97.67% in 2003. The average line loss of each line decreased from 11.3% in 2002 to 7.4% in 2003. The total sales capacity of five lines was 916724kwh, equivalent to RMB 322500. In addition, the improvement of the voltage quality of rural distribution lines ensures the convenience, fast, safety, reliability and high quality power for the majority of users. The balance of reactive power has greatly improved the end voltage of the users, which has been praised by the majority of users, and also established a good image of the enterprise.

5、 Concluding remarks

With the development of national economy and the improvement of people's material and cultural level, the demand for power quality is higher and higher. Reasonable addition of the switching series of reactive power compensation device, increasing the power factor of load and realizing the local balance of reactive power can not only improve the voltage quality, but also play an important role in improving the economic performance of power network operation, Through the transformation of five line capacitors of Jining Power Supply Bureau, it is widely applied to the transformation of distribution line capacitors under the jurisdiction of Wumeng Electric Power Bureau, in order to reduce the loss of the line, improve the power quality and increase considerable economic and social benefits