For power systems, harmonic disturbances primarily manifest in the following aspects: (1) Increase additional losses in transmission, supply, and usage equipment, leading to overheating and reduced efficiency and economic benefits of the equipment: (2) The impact of power harmonics on transmission lines: Harmonic currents increase power losses in transmission lines, and when harmonic frequencies injected into the grid fall within the resonance zone near the network resonance point, they can cause insulation breakdown in transmission and power cable lines. (3) The influence of power harmonics on transformers: The presence of harmonic voltages increases magnetic hysteresis losses, eddy current losses, and the electric field intensity of insulation, while the presence of harmonic currents increases copper losses. For transformers with unbalanced loads, it significantly increases the harmonic component of the excitation current. (4) The impact of power harmonics on power capacitors: When power harmonics are present, the voltage across capacitors is very small, causing harmonic currents to superimpose on the fundamental current of the capacitor, leading to increased capacitor current, temperature rise, reduced lifespan, and potentially overloading or even explosion. Additionally, harmonics can resonate with capacitors in the grid, exacerbating faults. Aircraft ground power 2, 2,36V aircraft power 1, 400Hz frequency converter power 7, 115/200V power 2, 27V DC power
(5) Impact on the reliability of relay protection and automatic devices: Particularly for electromagnetic relays, power harmonics often cause misoperation or failure to operate of relay protection and automatic devices, leading to the loss of selectivity and reduced reliability, which can easily result in system accidents and severely threaten the safe operation of the power system. (6) Interference to communication systems: Large amplitude odd-order low-frequency harmonic currents flowing through power lines, when coupled through magnetic fields, can generate interference voltages in the communication lines adjacent to the power lines, disrupting the operation of the communication system, affecting the clarity of conversations over communication lines, and in extreme cases, even threatening the safety of communication equipment and personnel. (7) Impact on electrical equipment: Power harmonics can cause distortion in the graphics of televisions and computers, fluctuations in screen brightness, and excessive temperatures in internal components, leading to errors in computers and data processing systems, and in severe cases, even damage to the equipment. Additionally, power harmonics can also have adverse effects on the accuracy of measuring and metering instruments and rectifying devices, becoming a major public scourge affecting the quality of electrical energy in the current power system.
