EHT=Electron Holding Tank27Kvolt may not be classed as EHT (Extra High Tension) in the power transmission field but in television receivers that is what it is called.
This goes back to the days vacuum tubes where the term EHT was used to differentiate the picture tube voltage from the normal HT (about 250V) that was used to drive the rest of the circuit.
I find this very helpful:It may just be me, but what does "EHT" stand for?. This list doesn't help - http://acronyms.thefreedictionary.com/EHT
by Jake Hertz
by Aaron Carman
by Jake Hertz