The world’s first 220-kilovolt hybrid insulating oil transformer, jointly upgraded by Shandong Electrical Engineering & Equipment Group Co., Ltd. under China Electrical Equipment Group Co., Ltd., State Grid Chongqing Electric Power Research Institute, and Chongqing University, is now fully operational at the Tianjia Substation in Bishan District, Chongqing.
This marks a major breakthrough in hybrid insulating oil technology for 220 kV applications and supports the green, low-carbon transformation of China’s power equipment.
Hybrid insulating oil combines the stability of mineral oil with the antioxidant properties of natural ester oil, achieving comprehensive improvements in key performance indicators such as breakdown voltage, flash point, acid value, and heat dissipation. Test data show that the thermal aging rate of insulating paper in hybrid oil is significantly reduced, extending its service life to 1.91 times that of mineral oil — meaning greater reliability and a longer operational period.
The Tianjia Substation, the first 220 kV substation in Bishan District, has been in continuous operation since March 2001 for 24 years. Over time, its two 150 MVA main transformers have suffered from component aging and corrosion, making it difficult to meet the region’s growing electricity demand.
The upgrade of Transformer No. 1 at Tianjia Substation included multiphysics simulations, structural optimization, vacuum oil filling, and closed-loop hot oil circulation. Lightning impulse, partial discharge, and temperature rise tests confirmed the superior thermal performance of the hybrid insulating oil.
(Executive editor: Yuan Ting)
