Patented thermosyphon & field-proven P&O™ bushings has two series --Type P&O™ I & II according to rated current. The current rated at 8000A and below is called Type P&O I, the current rated above 8000A is called Type P&O II. The Type II also has ANSI/IEEE series per C57.19.04. These two type bushings have thermosyphon design with heat exchange with main oil tank to dramatically reduce hotspot temp rise without any condenser paper but porcelain and oil. By end of 2025, there are 500,000+ pieces of P&O bushings in service world-wide.