I heard that if you come into contact with a high voltage DC current, you will ‘stick’ to it until it is switched off. Why is this and how high does the voltage have to be for someone to ‘stick’ to it?
The 'phase' bars refer to an industrial 3 phase surge suppressor that was under final electrical test with 600 VAC between each phase. The phases were connected to banks of MOV modules using copper bus bars.
"Sticking" refers to a current so strong your muscles can no longer function. Your brain is overwhelmed by pain. This can be fatal if the power is not cut off within seconds. This can be AC or DC current, but common in most every case is that a person "grabbed" a live circuit instead of just accidental contact that made the hand jerk away.
DC current tends to hurt more with brief contact as it slams the muscles hard in one direction. I touched a 800 VDC supply once and it went between my index finger and my thumb. My left arm was useless for about an hour.
When I was 15 years old I hit the power transformer output connections to an old color TV (it was all tubes back then), about 600 VAC center tapped. It hit my left wrist and burned 2 small holes like a snake bite. I could not use my arm for hours.
A quick summary would be that:
You touch or are struck by massive power such as lightning of a lightning simulator. You may survive, but will have scars for life. Touching a huge capacitor bank (fully charged) means losing a finger at least.
You touch typical 'hot' wires under 1,000 volts AC or DC, and it really hurts but part of the pain is your hand jerking away so fast you may hyperextend muscles. DC tends to hurt much more as it slams muscles in one direction.
Same as line 2 but you grab the hot wires or exposed circuits. Now your hands can no longer jerk away and you are stuck until you die or someone is there to cut the power.
Just for giggles, in the USA UL considers 48 VDC or 36 VAC to be the maximum safe exposed voltage that you can touch and get just a mild 'tickle'. But each time you double that voltage 4 times as much power is put through your body. This is where \$I^2R\$ becomes such a nasty equation.