Narrow-Bandwidth Television Association

Gents,

Where do you draw the line as to what degree of Voltage you are willing to work with? For the moment we'll assume this is Volts DC.

Steve A.

I've just returned from working on some transmitters, 25kV (25,000V at 7A)....and I'm still alive...though others might dispute that!

...let's just say I love the smell of Ozone!

One's comfort factor must also depend on what current is available too at a given voltage. In telephone exchanges the voltage was only 50 volts DC....

All fine and comfortable, but the amperage available was in the 10,000's.....not so fine nor comfortable if you accidentally put a spanner across a bus bar and finish up in a cloud of molten copper !

Albert.

Albert,

Yes, I know, I used to work with 50V DC battery supplies, and yes, they can deliver to goods! Also remember a cat being vaporized which got into a power cabinet...made one heck of a mess!!....and cleaning that up after a night out on the razz wasn't pleasent!!

Steve A.

There is also a question of what you mean by "comfortable".

When I'm working with 7KV mains-derived EHT in a TV (non-NB, that is), I would hardly describe myself as comfortable. The fact that it could despatch me from this world with no trouble leads me to treat it with great caution and respect.

My start with electrical equipment as a child of three whilst prodding toy train wires into the mains outlet gave me an early boost of resistance to high tension. I built up my resistance still further when about the age of nine I started building radio equipment and fooling around with old tellies as a hobby. This was in the late 50s when everything was valve-driven.

Through a combination of childhood cluminess and stupidity, I managed to tease my nervous system up to about 20 kVAC on a regular basis building or tinkering with electronics. Admittedly, the 20 kVAC stuff was just harmless high frequency CRT anode potential, but I would often get my fingers on 1000 VDC overdriving experimental transmitting equipment. This brings back fond memories of white-hot anodes, sparking control grids and tank circuits catching on fire. It is remarkable that I survived my childhood.

Nevertheless, I got to the point that I could tell electrical potential by touch pretty well. A number of years ago my brother zapped me with a "Taser" device just for fun. To his disappointment, it had no effect.

Albert,

The following picture should be familiar in concept to you. It's part of a UPS battery room for a TV station in Qatar. This will provide 250kVA for 7 minites until the generator fires up and comes on-line.

Steve A.

Yes Steve, that all looks familiar except back in my old days the batteries were all glass constructed.....something else that helped reduced one's 'comfort' zone slightly!

One chap I knew always checked if the mains were on by putting his fingers across it. That's 240v not MV !
Albert.