Another consideration is the relationship. between insulation class, temperature rise, and ambient temperature. The insulation. class rating designates the maximum. operating temperature for a winding. The. temperature rise is the difference between the.
China claims it has discovered the world's largest hole, and it's in one of the most dangerous places on the planet. 1  Jul.  Good news: China claims it has discovered the world's largest hole. On Wednesday, state broadcaster CCTV announced that the newly found dragon's hole, a 984-foot (300-meter) cavern in the disputed waters of the South China Sea, is now the world's largest hole.
There is a 9.1km borehole in Germany, part of the Continental Deep Drilling Project (KTB), but deeper still is the 12.25km Superdeep hole in the Kola Peninsula near the Arctic Circle in Russia, drilled between 1977 and 1989. The latter is roughly 0.4% of the distance (2,900km) to the core of the earth.