I’ve worked close to a 5MVA transformer in recent years after I retired , yet never before. I was testing it for Hipot and Partial Discharge. My false asssumption I made one day was putting plywood over the tank top and testing the 200kV insulator bushings on top of this 33kV transformer up to 200kV and discovering they are only rated for lightning transients at that voltage and they flashed over with a mighty zap from a DC test at around 50kV so I had to put 2 bushings in series each about 0.3m long but more important, a Teflon 4x8 sheets around the top ground plane to reduce the E field gradient as I knew sharp angles or points are only 1kV/mm but smooth flat surfaces 3kV/mm so 600mm ought to be good for 600kV but due to surface creapage gets drastically reduced by just a little dust of any small particles with humidity. So my first tests were external lightning bolts. If I was perfect in alcohol surface cleaning and ground plane coverage, but that wasn’t my concern. it was H2 reaching lower explosive level in the transformer oil. But in the end it was good for 200kV externally but the transformer failed for Partial Discharge at 36kV somewhere invisible inside. this lead to me getting paid $20k to solve their problems.
The CRT is a capacitor with a tube grid charge bleed wire on the back of the tube inserted with a rubber cup. The bigger energy is stored in the Flyback doubler or tripler caps with diodes.
One thing they don’t teach is that all capacitors and all batteries have memory. But the TV caps, have HV. Some have much less than others like NP0/C0G caps.
usually it doesn’t flag an issue because self leakage dissipates fast on most caps, but not on air caps, or triplers or supercaps or large e-caps.
if you don’t believe me. Short a big cap with a wire and release quickly and wait a minute and measure Voltage. same for any Alkaline battery. Same for high k ceramic caps which is why you never use them in S/H because they remember part of the previous sample.
This memory effect is due to what is called in the Supercaps a Double Electric Layer effect. Where you have at least 2 Caps each with vastly difference ESR and C values so the one with the largest RC=T has the memory.
this is why the short must be sustained for a certain length of time, which might be a minute or simply left on with a bleeder R and a clip.
shorter Answer ;)
Use 10kV/cm as your air gap limit to expect a discharge and <1kV/cm for surfaces, like the dust and humidity along a wire insulation surface. otherwise use Alcohal and Silicone for corona leaks. if you hear some hissing that’s corona and if you hear popcorn as well on outside lines with dew in the morning, that’s partial discharge.
the old TV guys wIll tell rookies ... keep one hand in your pocket , then it can’t kill you by going thru your ♥️ ... but even a car plug with 30kV will kick you away from your muscle involuntary contractions like a Karate kick, not from the voltage but the joules of stored charge. 1/2CV^2
With my EE training when I was young and stupid fixing my 1st colour TV, I understood this and learned the one hand rule and had no problems fixing my TV HV and sweep generator Voltage regulator.
just remember voltage has the potential to arc in any insulation even a vacuum or CRT glass tube, but it’s the capacitance of energy and follow on current that has energy. I could generate 50kV on a dry winter day in Winterpeg on old Hotel Nylon carpets with neoprene soled shoes and if I used a key , generate a 5 cm arc with a point source and not feel it be uA se the current density on a wide surface fingers was low. But if you used a finger zap, it might hurt because the zap shrinks to a tiny diameter and high current density.
So using ground is not helpful as Tv’s never used it but using the frame as your 0V Ref becomes your ground.
We could put tinsel from a Xmas tree several feet from the TV CRT and it would fly towards its or flatten out like an antenna or gold leaf cap EV detector.
Static charge build up is from triboelectric friction or stray capacitive current coupling In the case of the <1pF tinsel air gap test to CRT. A HV cap is charged by AC rectifier doublers but the charge Q=CV much bigger.