Hi guys, I need some professional safety advice from you hardcore theatrical electricians out there. 

In the UK & Europe, we have 415V across the phases with 220V from each phase to ground, so we are doubly interested to make sure all is well!

There is a building regulations requirement here too that in any building that is served with more than one phase, there MUST be a 6ft (2metre)  distance between any socket outlets fed from different phases. Nowadays as well, all socket outlets have to show the phase number or colour (we use red, blue and yellow in the UK) they are connected to.

I would try and find out from the electrical distribution drawings for the theatre, which sockets are served by what phase, and also (very importantly) what phase (or phases) the stage lighting system uses. Unless you use extension cables from the pigtails to lighting positions near architectural/general sockets, you should be OK with these, but check the floor pockets carefully.

Next thing to check is the phase of the sockets serving your audio & video equipment in the lighting and sound booths.

Ideally, every piece of electrical equipment in the auditorium and on stage and in the dressing rooms should be served from just one phase. This can put a large load on one phase, but in most buildings your AC and Heating systems can use another phase, then the kitchen/bar/foyer power and lighting etc can balance it all out on the third phase.

It's always better to have a working knowledge of the entire theatre's power supply system  - unless you do have that knowledge you never know if if going to come and bite you!

This almost happened to me once. In our booth we have a couple of stage lighting circuits wired in to use for testing purposes and also occasionally to poke a small follow spot out of the door (don't ask!). Our stage supply was entirely on the blue phase, so imagine my surprise when I discovered (by looking at those electrical distribution drawings for the building) that the domestic power sockets in the booth were connected to the red phase! So we had the blue phase powering the dimmer racks and the red phase powering the lighting and sound desks etc etc. Needless to say, that got changed VERY quickly!

We have a 440VAc 3 phase & 254VAC single phase here. Also everyone working on presures over 32VAC has to be Licensed under the state Electrical Act by the supply Authority.

You would be some what different as with the UK. Which still Use the 'Ring Mains' system in a lot of situations. (which was an inovative British method of saving on the amount of copper conductors used durning the War to save on the amount of copper cabling.)

I'm an electrical engineer not a real electrician, but it sounds like the buzz you are getting is a 60 cycle hum.  You see any wire acts like an antenna unless shielded--and even when shielded it still acts somewhat like an antenna.  So when power flows thru the wire at 60 cycles it 'transmits' like a radio tower antenna.  The other internal wires associated with the camcorder and laptop audio act as small antennas too.  They 'receive' the sound (60 cycle hum).  But since everything is shielded the antennas don't work as well ( the signal is attenuated), so you only get the hum when the systems are close.  If I'm right, this is not dangerous. (But I'm the type of EE that deals normally with computers not power circuits, or antennas).  This is sort of like when people with metal fillings in their teeth hear the radio through them when they pass a radio transmitter on the road.  The fillings small as they are act as weak antennas and recieve the very strong signal of the transmitter.  This also is what you saw and heard on your tv screen in the old days, when running power equipment near the tv--strong diagonal lines and a funny buzz sound.

Different transformer sources will be out of phase by definition--but expert installers ought to have everything grounded.  Since ground is ground you should be good. (If you ever get shocked, its the electricity flowing through your body on its path to get to the ground.  Electricity takes the path of least resistance.  So given a choice of traveling through you and shocking you, or traveling through a nice low resistance thick wire that connects to the ground, the electricity will choose the wire. So that is why we 'ground' equipment by running a thick wire to something already grounded--like a water pipe.)

Good comments Joe.  In US industry we have a set of standards for "Lockout/tagout"  that cover a similar ground.  You lockout devices by use of a lock that attaches normally to the 'on' switch or like and prevents the device from being used while the technician is working on it.  For instance you would not want a punch press to be turned on when a technician is servicing it.

You tagout a device by placing a prominant tag on the device warning to not use it.  (Your 'danger tag' is probably similar.)