How much/what electrical danger performing on a covered stage during rain?

[wildchildtiedyes]

I believe Boston Edison finally turned off its DC to the Back Bay area
around the late 80's.
When I was working in Boston around 1986, there were live 600V DC slate
boards in a few venues (Orpheum Theatre and Opera House to name a few) that
fed into the Boston MBTA. Tying in show power at the Orpheum used to
involve sitting, with my back up against the wall, and my head fitting just
below the slate board so that there wasn't any chance of it hitting any of
the live DC knife switches mounted just above me, while I tied in my tails
to the show power distro on the opposite wall.
Bruce

 

[David Lesher]

[email protected] (Scott Dorsey) writes:

Part of that is because in the late 60s, everything was transformer-isolated
and there was already a transformer in the input and the output of the console
and on the input of the amp. So telescoping a ground was all you needed to
do to get transformer isolation.

Does anyone use 1:1 120v isolation transformers?

Doesn't folks plug EVERYTHING into a GFI? If the GFI is tripping,
You Have a Problem -- fix it.

Clearly what's needed is fiber-connected mikes, both vocal and
instrument...

 

[BobG]

The metal screen on an SM58 or SM57 is grounded. The guys that touch
the mic with the guitar strings all learned that if your lips hit the
mic grill, the whap that hits you in the face is like a big blue ball
of lightning, followed by little fireflys floating around for a few
more minutes while you get your senses back. It pretty much ruins the
whole set for me. What causes it is the stage backline is plugged into
a breaker box running off phase A, the lights are on phase B, and the
sound is on phase C, and they are all drawing different currents, so
the neutral is floating about 20V above ground because of the
unbalanced load. I can test a 9V battery by licking it, but 20V is
like a mule kick.

 

[Stephen B.]

NYC still had DC mains available until about a decade ago, when Con Edison
finally managed to install rectifier stacks running off three-phase at
the last of the DC customers. Most of them were folks using DC for elevator
service.

http://www.coned.com/sales/business/bus_elec.asp

Shows that the push to elimanate DC was still on in 2005. I think it is
still on going.
The Steam pipe that exploded over the summer was a Con Ed supply for
building uses. I have not heard of any efort to eliminat that service.

 

[Phil Allison]

"BobG"

The metal screen on an SM58 or SM57 is grounded. The guys that touch
the mic with the guitar strings all learned that if your lips hit the
mic grill, the whap that hits you in the face is like a big blue ball
of lightning, followed by little fireflys floating around for a few
more minutes while you get your senses back. It pretty much ruins the
whole set for me.

** That sounds like copping the full 120 AC on the lips.

What causes it is the stage backline is plugged into
a breaker box running off phase A, the lights are on phase B, and the
sound is on phase C, and they are all drawing different currents, so
the neutral is floating about 20V above ground because of the
unbalanced load.

** WTF has the neutral voltage got to do with it ?

Must be a VERY badly wired AC supply system for the safety ground on any
circuit to be more than 1 volt compared from the ground on any other.

Needs to be condemned.




........ Phil

 

[Michael A. Terrell]

Does anyone use 1:1 120v isolation transformers?

Doesn't folks plug EVERYTHING into a GFI? If the GFI is tripping,
You Have a Problem -- fix it.

Clearly what's needed is fiber-connected mikes, both vocal and
instrument...

Sometimes the person is in contact with another current source and is
killed by touching a grounded microphoe or instrument, so somone can die
if the sysytem is properly installed. A GFI won't detect the current
flow to earth from a different source.

There was a recent news story of a pastor dying while baptising
someone. A lot of plumbing is now all PVC, so a bad heating element
that is shorthed to its casing won't trip the breaker, or blow a fuse.
The skin of a water heater is grounded, but the tank may not be.

The man was waist deep (or more) in the water when he picked up the
grounded microphone, and couldn't let go.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

 

[Guest]

The metal screen on an SM58 or SM57 is grounded. The guys that touch
the mic with the guitar strings all learned that if your lips hit the
mic grill, the whap that hits you in the face is like a big blue ball
of lightning, followed by little fireflys floating around for a few
more minutes while you get your senses back. It pretty much ruins the
whole set for me. What causes it is the stage backline is plugged into
a breaker box running off phase A, the lights are on phase B, and the
sound is on phase C, and they are all drawing different currents, so
the neutral is floating about 20V above ground because of the
unbalanced load. I can test a 9V battery by licking it, but 20V is
like a mule kick.

simply not true
what causes it is a ground fault in the backline gear(99%) of the time
and the other % would be other fauklt conditiopns
there is nothing inherently unsafe in useing 3 phase power
george

 

[Guest]

what i find more than I care ton is some yahoo removes the 2 slot edisons
and replaces them with the grouded version , only there is no ground
connected on the back

every outlet get tested before it gets used
George

 

[Guest]

Snipped drivel...


Use wireless devices. Doh!

like what? your cell phone?
here in the USA wireless micsare in turmoil because the government is
selling the bandwidth it exists on
george

 

[Don Pearce]

like what? your cell phone?
here in the USA wireless micsare in turmoil because the government is
selling the bandwidth it exists on
george

In the uk the regulator (Ofcom) is preserving a chunk of UHF spectrum
from the digital switchover for wireless mics.

d

 

[ChairmanOfTheBored]

like what? your cell phone?
here in the USA wireless micsare in turmoil because the government is
selling the bandwidth it exists on
george

Idiot. Live performers use wireless hooks EVERY DAY.

 

[Guest]

Idiot. Live performers use wireless hooks EVERY DAY.

you are so out of the loop no more debate can be had
tell me about the last time you set up 35 wireless mics for a show
I have

oh and while you at it can you name the protocol that will/is replaceing uhf
/vhf as a transmission mode?
put up or shut up
jerk

 

[David Lesher]

David Lesher wrote:

Sometimes the person is in contact with another current source and is
killed by touching a grounded microphoe or instrument, so somone can die
if the sysytem is properly installed. A GFI won't detect the current
flow to earth from a different source.

Please note the word "EVERYTHING" above. Not some of the amps, one of the
mixers... everything on stage running from one GFI or another... [Except
the drummer, of course, who's likely running on crank, but at least he's
not a current source...]

 

[Romeo Rondeau]

you are so out of the loop no more debate can be had
tell me about the last time you set up 35 wireless mics for a show
I have

oh and while you at it can you name the protocol that will/is replaceing uhf
/vhf as a transmission mode?
put up or shut up
jerk

What do you think about Audio Technica's SpectraPulse?

 

[Guest]

What do you think about Audio Technica's SpectraPulse?

I think its exciting also odd that it took 100 years to bring it to market
myself I will not buy or sell any more traditional wireless mics until this
bandwidth stuff settles
and I am down to just 6 in my inventory
but I hope to get some time to talk to the AT guys at AES
George

 

[Guest]

What causes it is the stage backline is plugged into
I have not seen a show hooked up this way
with a single 3 phase hook up we put the sound INCLUDING stage and back line
on 1 leg and lights on the other two
bigger venues have several 3 phase disconnects
generall sound will take the smaller(200 amp or so) and lights will take the
larger(4-600 amps)
but still the backline is IME always on the same leg(s) as the sound
george

 

[Deputy Dumbya Dawg]

message

There was a recent news story of a pastor dying while
baptising
someone. A lot of plumbing is now all PVC, so a bad
heating element
that is shorthed to its casing won't trip the breaker, or
blow a fuse.
The skin of a water heater is grounded, but the tank may not
be.

The man was waist deep (or more) in the water when he
picked up the
grounded microphone, and couldn't let go.

That is why I said earlier to touch the mic with the back of
your hand before grabbing or kissing it.


peace
dawg

 

[Scott Dorsey]

Does anyone use 1:1 120v isolation transformers?

Sometimes, but the NEC in the US limits what you can do as far as breaking
safety grounds, when isolation transformers are in use. Normally folks use
isolation transformers only as low-pass filters, really.

Doesn't folks plug EVERYTHING into a GFI? If the GFI is tripping,
You Have a Problem -- fix it.

NEC says you have to use GFIs on most circuits outside, but not everyone
does. Personally, although GFIs are prone to falsing in high RFI environments,
I think they have saved more lives than they are given credit for.

Clearly what's needed is fiber-connected mikes, both vocal and
instrument...

Yes, but now you need to get power to the mike, as well, since the fibre
can't carry it. There are plenty of systems with fibre links between
the stage box and the console; you can see one at the National Gallery
of Art in their sculpture garden system. Plenty of isolation, and you
can run the skinny little fibre into an existing power conduit rather
than having to pull a big snake. Of course you now have to set the
console trims on the stage box which can be a pain without a big stage
crew.
--scott

 

[Scott Dorsey]

The metal screen on an SM58 or SM57 is grounded. The guys that touch
the mic with the guitar strings all learned that if your lips hit the
mic grill, the whap that hits you in the face is like a big blue ball
of lightning, followed by little fireflys floating around for a few
more minutes while you get your senses back. It pretty much ruins the
whole set for me. What causes it is the stage backline is plugged into
a breaker box running off phase A, the lights are on phase B, and the
sound is on phase C, and they are all drawing different currents, so
the neutral is floating about 20V above ground because of the
unbalanced load. I can test a 9V battery by licking it, but 20V is
like a mule kick.

This is a sign you got a BIG problem, not just with an unbalanced load,
but with poor neutral-ground bonding.

This is when it's time to walk offstage and cut your losses.
--scott

 

[Scott Dorsey]

Sometimes the person is in contact with another current source and is
killed by touching a grounded microphoe or instrument, so somone can die
if the sysytem is properly installed. A GFI won't detect the current
flow to earth from a different source.

Right. The GFI dectects only an imbalance in neutral and hot currents
on the device it's protecting.

This means that EVERYTHING on the stage area needs to be on a GFI, and
that includes backline. If an amp is popping the GFI, you need to fix it.

Now, I know that outdoor festivals it's very common to defeat GFIs in
order to deal with backline equipment that has ground fault issues. I
don't have a real problem with this, IF the power system grounds are
good enough and the crew is watching out.

There was a recent news story of a pastor dying while baptising
someone. A lot of plumbing is now all PVC, so a bad heating element
that is shorthed to its casing won't trip the breaker, or blow a fuse.
The skin of a water heater is grounded, but the tank may not be.

The man was waist deep (or more) in the water when he picked up the
grounded microphone, and couldn't let go.

Note that he was electrocuted by a circuit which BY LAW needs to be on
a GFI, and has been for more than a decade now.

See, in a perfect world, there are no electrical leakage issues. But
the ground is there to protect you when things go wrong. And the GFI is
there to protect you when the ground goes wrong. It's a belt-and-suspenders
thing.

Maybe you'll never need the ground to be there. Probably you'll never
need the GFI. But if you SHOULD need it, you'll be really glad you have it.
--scott