800 V is NOT High Voltage.
Those security guys have no idea about real threats and go mostly by paragraphs. They have hindered real work to be done so many times that I avoid talking to them. Security Theatre.
Standard resistors (talking small .4 W metal film) have 250 rating). Use ten of them and you have a voltage divider that easily (and legally) withstands 2.5 kV.
OK, I do not use such resistors, although you can find them in many VFDs (to measure DC link voltage!). I use 2 W resistors that are rated a lot higher and have used them when measuring on Dynos at the Scania main plant in Södertälje as well as on Alstom locomotives (I chose a few of the better known customers, but there are lots and lots of others)with no objection or danger to humans or Equipment.
The only problem with resistive dividers is that you lose high speed step response, which can be a problem when you look at PWM edges and the ringing. You need something like 30 ns step response then. But that is also possible if you make the foot resistor 50 ohms and use the scope's 50 ohm internal impedance. But we are not talking high speed here - only milliseconds or fractions of it.
I also use a home-brew recorder that is so cheap that I can leave as many as needed on a plant for weeks. One has to be practical - not only P. C. and better safe than sorry. I have worked in the field for around 50 years and never caused an accident of any kind. And, mind you, I ain't dead either.
Gunnar Englund
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.