Harmonics can increase losses in high-voltage shunt capacitors

causing significant heating of the equipment and compromising safe operation of high-voltage shunt capacitors. Existing research offers limited insights into how harmonic combinations affect capacitor thermal stability and lacks precise methods for determining internal temperatures. It is found through the measurement analysis of operation data of capacitors in the substation that the actual operatign conditions of the capacitors exhibit high levels of odd-order harmonics. On this basis

multiple odd harmonics are applied to the shunt capacitors to simulate actual operating condition

and thermal stability tests are performed using a constant current method. Temperature sensors are installed outside and inside of the tested capacitors respectively to measure the shell and core temperature under different operating conditions. The test results indicate that under excitation of single-frequency current

the thermal stability temperature initially decreases and then increases with the frequency. The dielectric and conductor losses of the high voltage shunt capacitors are analyzed to master the effects of harmonic frequencies and their combinations on the hot spot temperatures of the capacitors. At lower frequency ranges

an increase in harmonic frequency can cause voltage to reduce

and then lead to reduction of dielectric losses as well as reduction of thermal stability temperature of the capacitors. In the medium-to-high frequency ranges

dielectric losses are less affected by frequency

but the increased frequency will lead to the skin effect in the metal conductors

resulting in higher conductor losses and a subsequent rise in the thermal stability temperature of the capacitors. These findings can provide a theoretical foundation for optimizing the thermal field design of capacitors.