Of all the power utilities I have observed, Pacific Gas & Electric seems to have been obsessed with the use of 12 kV fuse cutouts mounted on the transformer bushings more than others. Shown in this photo are the S&C oil filled glass tube type. They are applied by inserting the lower prong into the transformer bushing and tightening, as with an ordinary wire. The fuse tubes clip in and when overloaded, remain stationary while the oil quenches the arc blowing open inside the tube. This all works very well but the troublesome part has been the bushing insert prong working loose due to vibration and the weight of the cutout coupled with the fact that this is a high device mounted on an already high bushing with no support at the upper end. Consequently, they have fell out of use. I did get an update thanks to Ron Jenkins, the fuse tubes are not filled with oil, but Carbon Tet! Another similar application is a small spring link "grasshopper" cutout, bushing mounted the same way. These seem to have been more successful in PG&E's flirtation with this type of cutout.