The high-voltage DC capacitor is one of the core components of the converter valve and a key device in new power system

and it bears the combined effects of DC voltage superimposed with harmonics and high temperature during operation. Whether the electrical properties of biaxially oriented polypropylene(BOPP) film

a key capacitor material

can meet these harsh operating conditions is critical for its domestic production. This paper investigates the influences of temperature on the breakdown

dielectric

and conductivity properties of 5.8 μm BOPP film for DC capacitors. Results show that the breakdown strength of all tested BOPP film types declines with rising temperature

with maximum reductions reaching 16.1% at 70 ℃ and 32.3% at 120 ℃. The conductivity characteristics of all types show a decreasing trend

and a notable inflection point occurs at 60~70 ℃ where the drop accelerates. The dielectric constants of the four BOPP films decrease slightly with the increase of temperature

while dielectric loss increases. Specifically

70 ℃ and 9 ℃ serve as the critical threshold temperatures for the increase in conductivity and dielectric loss of BOPP films

respectively. These critical temperatures require particular attention when evaluating the insulation performance of dielectric film in high-temperature application scenarios such as converter valves. The thermal stability of BOPP films may be the determining factor for their insulation performance variations under high temperatures. The obtained results can provide references for the domestic research and development of BOPP film for high-voltage DC-link capacitors.