Abstract: By detecting and analyzing harmonics in petrochemical power distribution systems, this paper points out that the main factors generating harmonics in petrochemical power distribution systems are frequency converters, uninterruptible power supplies (UPS), and high-voltage mercury lamps. Schemes are proposed to reduce harmonics using multiplexing technology and to control harmonics using LC filters and active filters. Based on the analysis of the interaction between capacitors and harmonics, improvement measures are proposed to rationally select the harmonic order of the capacitor's resonant point in the power distribution system by combining LC filters. Keywords : Petrochemical power distribution system; harmonics; capacitor 0 Introduction With the increasing application of nonlinear loads such as frequency converters and UPS in large petrochemical enterprises, the injection of nonlinear current into the power grid often causes voltage distortion, overheating of power cables and busbars, increased transformer temperature rise, motor overheating and additional torque, and capacitor overheating and overvoltage. For secondary equipment, harmonics can lead to malfunctions of relay protection and automatic devices, interfere with communication, and cause inaccurate measurement by electrical measuring instruments. Harmonics have become a major hidden danger to the stable operation of the power grid. This study, based on the actual situation of petrochemical power distribution systems, detects and analyzes the harmonic sources of these systems and proposes technical measures for harmonic mitigation. [b]1 Petrochemical Power Distribution System and Harmonic Analysis 1.1 Characteristics of Loads in Petrochemical Power Distribution Systems[/b] Taking a company's power distribution network as an example: the internal power distribution system has 360 frequency converters, 70 UPS units, 69 DC power supply units, nearly 20,000 sets of electronic rectifier lighting fixtures, and a large number of computers and DCS loads. All these devices are the source of harmonics in the company's internal power distribution network, and their harms have already become apparent: for example, phenomena such as UPS failure to lock phase properly and excessively high capacitor operating temperatures have occurred in the power distribution network. However, judging from the current situation of petrochemical power distribution systems, no one in my country has paid attention to the harms of harmonics, let alone taken targeted measures to mitigate them. In fact, harmonic hazards have become a major hidden danger to the reliable operation of petrochemical power distribution systems. The following analysis examines the harmonic situation of systems with computers as loads and systems with frequency converters as loads. [b][align=center]For details, please click: Harmonic Analysis and Mitigation of Large-Scale Petrochemical Power Distribution Systems[/align][/b]