Abstract : This paper addresses the issue of low power factor among end-users of electricity by implementing reactive power compensation. Capacitors are automatically switched on or off based on system load changes to compensate for the target power factor. Keywords : Reactive power, capacitors, power factor. Our unit belongs to a 6kV/400V distribution substation under a 110kV substation of a group company. Previously, the power supply bureau measured our electricity consumption at the 110kV substation. Because the main substation has capacitors for centralized compensation, its power factor met the power supply department's requirements for enterprise electricity consumption. Since June 1, 2006, the power supply bureau began to measure and assess the end-users of the group company (i.e., the substations of each branch unit). Because our unit is far from the main substation and lacks reactive power compensation equipment such as capacitors and synchronous motors, our power factor is between 0.7 and 0.75, far below the enterprise's power factor standard. Therefore, we are fined approximately 20,000 yuan per month based on our electricity consumption. Given this situation, it is necessary to add reactive power compensation equipment. 1. Equipment Selection Based on the characteristics of reactive power compensation and ease of maintenance during operation, the selected low-voltage reactive power compensation device must meet the following conditions: ① Flexible and convenient installation, few supporting equipment, and easy maintenance; ② Flexible switching, automatically switching capacitors on and off according to changes in line reactive current to achieve the target power factor; ③ Equipped with a harmonic filter, as our unit has many frequency converters, UPS, DC power supplies, etc., generating large non-sinusoidal currents during operation, and significant harmonic voltages will affect capacitor operation. Based on the above requirements, after comparing several low-voltage reactive power compensation devices, we decided to select the low-voltage automatic reactive power compensation device manufactured by Nokia Capacitors. The tuning and filtering capacitor cabinet of this device mainly uses imported components, including low-voltage dry-type capacitors, dedicated tuning reactors, electromagnetic contactors, fuses (HRC-FUSE), and automatic power factor adjusters. Based on the unit's load, two sets of Q50=400V/236kvar-6 capacitors (main and auxiliary cabinets) were selected, with both cabinets sharing one N-12 (NC-12) controller. 2. Application Effect After installing this low-voltage automatic reactive power compensation equipment, the N-12 automatic power factor regulator automatically detects the magnitude of reactive current based on actual load changes during operation and automatically connects and disconnects capacitors to achieve the set target power factor. To ensure that each capacitor has a similar service life, the capacitor connection mode of the controller is set to cyclic, meaning the capacitor connection and disconnection operation follows the first-in, first-out principle. The controller screen displays the automatically detected power factor, active power, reactive power, total power, total current and voltage distortion rate, number of connected capacitors, and various alarms. Many system parameters are clearly displayed, and fault diagnosis can be performed based on the observed alarm parameters, which is very convenient. The equipment has been in operation for nearly a year, and apart from regular monthly air filter cleaning, it has not experienced any malfunctions, truly achieving maintenance-free operation. It has solved the problem of penalties due to low power factor, and even received rewards when the power factor exceeded 0.95, generating significant benefits. Comparisons of some parameter data before and after installation of this low-voltage reactive power automatic compensation equipment are shown in Tables 1 and 2. 3. Conclusion This equipment is quick to install, easy to maintain, occupies little space, and has excellent harmonic filtering effects. It provides immediate reactive power compensation and has significant application value and meaning in today's energy-saving and efficiency-enhancing society.