On 2011-10-04, Larry Jaques wrote:
On Tue, 04 Oct 2011 07:36:55 -0500, Ignoramus29750
wrote:

On 2011-10-04, Michael A. Terrell wrote:

Ignoramus19762 wrote:

Harold & Susan Vordos wrote:

Ignoramus23561 wrote:

Well, I kept it. Going through all of them means a few wasted
hours. But I guess I have to bite the bullet and do it.

Your alternative is to buy replacements. You'll experience some serious
sticker shock when you check the price of three phase twist locks. They're
very proud of those suckers.

Harold, why replace them? They are fine, as such, they are simply
dirty and in need of cleaning. What am I missing?


The condition of the contacts. Are they clean, or oxidized & pitted?



They are just fine. The problem is the dust inside.

Why not blow them out?


I still have to open them up. And if so, why blow them, this will ruin
my hair and make a mess. I will just use a brush.

i

On 2011-10-04, David Lesher wrote:
Ignoramus19762 writes:

On 2011-10-03, David Lesher wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?


At startup, the usual reason is someone screwed up; and there
is a shorted cable, connection or...

In a case I know, it was a GE ElectoCenter; a housetrailer-size
structure filled with starters. They get shipped in & installed
onto a slab with a crane. Fed with 4160 through the roof; there
was a main breaker, and 3 busbars & gnd running along the wall
behind the main & starter cabinets. It also had a small 240/120
tranformer to power lights/tools/instrumentation.

A friend was working with a contractor on the installation.
With no starters racked in, he closed the main for the first
time so they'd have local power. Little did they know the
busbars had slid down inside the wall & were touching.

The breaker exploded, blowing the locked door open, knocking
Bill onto his side, with 2nd degree burns to his arms and hands.
Behind Bill, the contractor was also down.

The arcing continued, with the feeds down from the pole to the
building finally burning loose, and flapping in the wind -- the
arc would blow them apart [right hand rule] the arc would stop,
and they'd drift togther again .ZAAAP... ZAAAP...

Bill was trying to get up when the contractor ran OVER him, foot
right on his back, going for the utility substation to pull the
primary disconnect. Before he got there, the utility fuses went
"sounding like a 12 ga. going off in my ear BLAM BLAM".

He was in the hospital for 4-5 days.




Sounds like GE did a bad job on this Electrocenter.

i

Ignoramus29750 wrote:

On 2011-10-04, Michael A. Terrell wrote:

"Lloyd E. Sponenburgh" wrote:

"Michael A. Terrell" fired this volley in
m:

Ok. Don't start whining, when some of them start smoking.

nahhhh... if necessary, disconnect them and wash them with a solvent that
will get all the grinding dust AND coolant out of them.

They're typically bakelite (for the insulators), which is insoluble in just
about everything.


Sigh. I know what the insulators are made of, and some are nylon
instead of bakelite. I was talking about OXIDIZED CONTACTS. They can
oxidize, just sitting on a shelf for years. In an environment of high
humidity and dissimilar metals, they can be in really bad shape. I've
seen them fail in an air conditioned electronics factory. Move a
workbench and discover the outlet gets too hot to touch, when you turn
on the test equipment. No extension cords allowed, per the local
inspectors so you either move the tech to another bench, or send him
home till a grunt from the contract electrical company finally shows
up. I saw it several times in four years, in North Central Florida.
Most of the failed Hubbel twist lock outlets were less than 12 years
old.

The one connector that I took apart, was not oxidized. I will check
out each of them. Those connectors can be bought for $9.95 online.


Good. It takes less time to do them all at once while the building
is fairly empty than one at a time, when you really need them.

The ones that had a plug in them all of the time should have the
cleanest contact surfaces.


--
You can't have a sense of humor, if you have no sense.

On 10/03/2011 04:12 PM, Lloyd E. Sponenburgh wrote:
fired this volley in
:

Can this happen with 240v 3 phase?

My building has only 240v. 800 amps service.


240 VAC (in any phase configuration) is less dangerous than, say 440.

But with 800amps of ability to deliver current, you have a great
potential for plasma-like arcs.

Typical 240 V breakers have a 10,000 Amp disconnect rating, and enough
internal inductance to limit fault current below that.

Typical 480 V breakers are vastly bigger, and have a 100,000 Amp rating.
The arcs there are more severe, due both to the voltage and limiting
current.

While 240 is nothing to ignore, the kinds of explosive arcs and arc
flash injury are really rare on 240.

Jon

On 10/03/2011 06:46 PM, Brian Lawson wrote:

And for Iggy...I've seen 120 volt hanging cables that were in very
damp conitions shorted, and they arc and catch fire and burn like a
dynamite fuse or like a July 4th hand-held "sparkler"...they don't
blow a fuse for about 5 feet.
We had the 4160 feed straight from the utility transformer (a couple
MVA size) short in underground cables. To balance return currents on
the conduit, they run every phase and neutral in each parallel conduit,
in this case 4 conduits in parallel. One of them developed a fault
underground. The chief electrician heard a nasty buzzing coming from
the switchgear room and stuck his head in, and saw blinding blue light
and concrete chunks flying around, and quickly beat a retreat. They
needed the utility to send a truck out to shut off the transformer, they
couldn't do that remotely without blacking out the whole region.

It trenched about 40 feet of concrete and was heading toward the
transformer when the utility got the transformer shut off.

Jon

I'm sure that GE's legal folks would prove (or have proven) that it wasn't
GE's fault.

The entire situation could've been avoided by some simple testing before
connecting the load center.

There never will be a shortage of incompetent people, and in many cases they
will put others' safety at risk.

Always get the asshole bitching about how urgent it is, to climb in there
and throw the switch while anyone with any uncommon sense can be somewhere
safe.

It's a worthwhile practice to open new and used line-operated equipment for
inspection (or thoroughly testing the device) before connecting them to line
voltages. This is especially important with many of the electrical devices
from China.. and many times you won't know if it's a counterfeit device.

I've mentioned in the past the insanely stupid crap that's available in the
present market, such as the normal-looking molded, 3-blade power cord plug
on a grinder, but only 2 conductors in the cord.

--
WB
..........


"Ignoramus29750" wrote in message
...
On 2011-10-04, David Lesher wrote:
At startup, the usual reason is someone screwed up; and there
is a shorted cable, connection or...

In a case I know, it was a GE ElectoCenter; a housetrailer-size
structure filled with starters. They get shipped in & installed
onto a slab with a crane. Fed with 4160 through the roof; there
was a main breaker, and 3 busbars & gnd running along the wall
behind the main & starter cabinets. It also had a small 240/120
tranformer to power lights/tools/instrumentation.

A friend was working with a contractor on the installation.
With no starters racked in, he closed the main for the first
time so they'd have local power. Little did they know the
busbars had slid down inside the wall & were touching.

The breaker exploded, blowing the locked door open, knocking
Bill onto his side, with 2nd degree burns to his arms and hands.
Behind Bill, the contractor was also down.

The arcing continued, with the feeds down from the pole to the
building finally burning loose, and flapping in the wind -- the
arc would blow them apart [right hand rule] the arc would stop,
and they'd drift togther again .ZAAAP... ZAAAP...

Bill was trying to get up when the contractor ran OVER him, foot
right on his back, going for the utility substation to pull the
primary disconnect. Before he got there, the utility fuses went
"sounding like a 12 ga. going off in my ear BLAM BLAM".

He was in the hospital for 4-5 days.




Sounds like GE did a bad job on this Electrocenter.

i

On 10/04/2011 11:28 AM, Bruce L. Bergman (munged human readable) wrote:
The only real advantage to HVDC transmission (and why they use it at
all, because it is not as efficient) is that the two power grids at
each end don't have to be in frequency sync with each other.

There is also no radiation or ground heating from DC.

Jon

Ignoramus29750 wrote:
On 2011-10-04, David wrote:
writes:

On 2011-10-03, David wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?


At startup, the usual reason is someone screwed up; and there
is a shorted cable, connection or...

In a case I know, it was a GE ElectoCenter; a housetrailer-size
structure filled with starters. They get shipped in& installed
onto a slab with a crane. Fed with 4160 through the roof; there
was a main breaker, and 3 busbars& gnd running along the wall
behind the main& starter cabinets. It also had a small 240/120
tranformer to power lights/tools/instrumentation.

A friend was working with a contractor on the installation.
With no starters racked in, he closed the main for the first
time so they'd have local power. Little did they know the
busbars had slid down inside the wall& were touching.

The breaker exploded, blowing the locked door open, knocking
Bill onto his side, with 2nd degree burns to his arms and hands.
Behind Bill, the contractor was also down.

The arcing continued, with the feeds down from the pole to the
building finally burning loose, and flapping in the wind -- the
arc would blow them apart [right hand rule] the arc would stop,
and they'd drift togther again .ZAAAP... ZAAAP...

Bill was trying to get up when the contractor ran OVER him, foot
right on his back, going for the utility substation to pull the
primary disconnect. Before he got there, the utility fuses went
"sounding like a 12 ga. going off in my ear BLAM BLAM".

He was in the hospital for 4-5 days.




Sounds like GE did a bad job on this Electrocenter.

Sounds dubious that the busbars "slid down". Busbars
have to be bolted solid in numerous locations to withstand
the forces generated by the magnetic fields created
from a short circuit. More likely would be a piece of
wire or other debris fell across them.

On 2011-10-06, Jim Stewart wrote:
Ignoramus29750 wrote:
On 2011-10-04, David wrote:
writes:

On 2011-10-03, David wrote:

OSHA has gotten religion on the arc flash issue. The #1 chance
for such that will kill folks is when you close a large
main/sub-main breaker. They can and do explode outward with
enough force to blow apart cabinets, taking out the chump
standing there closing the breaker.

So, why exactly do they explode? Can you explain?


At startup, the usual reason is someone screwed up; and there
is a shorted cable, connection or...

In a case I know, it was a GE ElectoCenter; a housetrailer-size
structure filled with starters. They get shipped in& installed
onto a slab with a crane. Fed with 4160 through the roof; there
was a main breaker, and 3 busbars& gnd running along the wall
behind the main& starter cabinets. It also had a small 240/120
tranformer to power lights/tools/instrumentation.

A friend was working with a contractor on the installation.
With no starters racked in, he closed the main for the first
time so they'd have local power. Little did they know the
busbars had slid down inside the wall& were touching.

The breaker exploded, blowing the locked door open, knocking
Bill onto his side, with 2nd degree burns to his arms and hands.
Behind Bill, the contractor was also down.

The arcing continued, with the feeds down from the pole to the
building finally burning loose, and flapping in the wind -- the
arc would blow them apart [right hand rule] the arc would stop,
and they'd drift togther again .ZAAAP... ZAAAP...

Bill was trying to get up when the contractor ran OVER him, foot
right on his back, going for the utility substation to pull the
primary disconnect. Before he got there, the utility fuses went
"sounding like a 12 ga. going off in my ear BLAM BLAM".

He was in the hospital for 4-5 days.




Sounds like GE did a bad job on this Electrocenter.

Sounds dubious that the busbars "slid down". Busbars
have to be bolted solid in numerous locations to withstand
the forces generated by the magnetic fields created
from a short circuit. More likely would be a piece of
wire or other debris fell across them.


I have learned a lot of very fascinating stuff recently. Thanks a lot.

The factory has a mix of bakelite and nylon body connectors. I bought
8 new nylon body connectors to replace the old bakelite connectors.

i

Jon Elson fired this volley in
:

There is also no radiation or ground heating from DC.

Jon

Jon, that's not right (not completely). ANY conductor carrying a current
induces a magnetic flux around itself, the strength of which is entirely
dependent upon current, not voltage.

Although AC transmission produces a moving (alternating) magnetic field
that can induce currents in still objects (like the ground, yes), the
magnetic field around a DC conductor can still induce currents in moving
objects (like people, vehicles, etc.).

So it's not right to say a DC conductor doesn't "radiate", because it
does radiate a magnetic field. It just happens to be a static field, so
long as the current remains constant. Vary the current, and you have a
varying field with similar (if reduced) effects like those of an AC
transmission line.

LLoyd

On 2011-10-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Jon Elson fired this volley in
:

There is also no radiation or ground heating from DC.

Jon

Jon, that's not right (not completely). ANY conductor carrying a current
induces a magnetic flux around itself, the strength of which is entirely
dependent upon current, not voltage.

But the flux is constant and thus, does not induce any electromagnetc
waves or current in the ground.

Although AC transmission produces a moving (alternating) magnetic field
that can induce currents in still objects (like the ground, yes), the
magnetic field around a DC conductor can still induce currents in moving
objects (like people, vehicles, etc.).

Good point.

So it's not right to say a DC conductor doesn't "radiate", because it
does radiate a magnetic field. It just happens to be a static field, so
long as the current remains constant. Vary the current, and you have a
varying field with similar (if reduced) effects like those of an AC
transmission line.

Very good clarification.

On Thu, 06 Oct 2011 14:51:14 -0500, Ignoramus15921
wrote:

On 2011-10-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com wrote:
Jon Elson fired this volley in
:

There is also no radiation or ground heating from DC.

Jon

Jon, that's not right (not completely). ANY conductor carrying a current
induces a magnetic flux around itself, the strength of which is entirely
dependent upon current, not voltage.

But the flux is constant and thus, does not induce any electromagnetc
waves or current in the ground.

Although AC transmission produces a moving (alternating) magnetic field
that can induce currents in still objects (like the ground, yes), the
magnetic field around a DC conductor can still induce currents in moving
objects (like people, vehicles, etc.).

Good point.

So it's not right to say a DC conductor doesn't "radiate", because it
does radiate a magnetic field. It just happens to be a static field, so
long as the current remains constant. Vary the current, and you have a
varying field with similar (if reduced) effects like those of an AC
transmission line.

Very good clarification.

The only fly in that ointment is...

While it's DC on the transmission lines and should therefore be a nice
steady current, it's being rectified from 60-Hz AC at one end and
turned back into 60-Hz AC at the other end, and as we've noted the
frequencies and phase rotations at either end are most likely
different.

So even with plenty of capacitance at both of the converter stations
and the inherent capacitance of the transmission lines themselves,
that's got to introduce some AC Ripple into the DC. It won't be -
can't be - pure DC. ("Close Enough" will work for the transmission
line itself.)

You can never get the Capacitance and inductance of the tuned
circuits dialed in perfectly - and the minute you do, the loads will
change again. There's a reason they build the entire converter
station inside a steel building and it's switchgear enclosed in a huge
outdoor Faraday Cage, to try and keep the RF noise it will generate
inside the cage.

(That the big cages keep birds and other critters out of the converter
stations is just a convenient side effect.)

-- Bruce --

On Thu, 06 Oct 2011 14:31:45 -0500, Ignoramus15921
wrote:
On 2011-10-06, Jim Stewart wrote:
Ignoramus29750 wrote:

Sounds like GE did a bad job on this Electrocenter.

Sounds dubious that the busbars "slid down". Busbars
have to be bolted solid in numerous locations to withstand
the forces generated by the magnetic fields created
from a short circuit. More likely would be a piece of
wire or other debris fell across them.


I have learned a lot of very fascinating stuff recently. Thanks a lot.

There are procedures for initial power-up of gear that's new and being
energized for the first time, and for gear recently moved and being
reenergized. The main rule is to check for outright shorts and
crosses before you power it up, and then be careful bringing it up to
operating voltage.

It might pass an ohm-meter test when you check for shorts, but have
compromised insulation or a piece of trash that will flash over at
full voltage. 120/208/240V isn't so likely to have flash-over
failures, but you go to 440V and up and it starts being a real
possibility.

About the only way to be somewhat sure is to get a Megger and throw
1000V or more of Hi-Pot Test at a controlled current capacity on it,
and see what happens.

And even then it might fool you. This is when you energize the
circuit using a load bank resistor and a much smaller than normal fuse
that has a high enough arc-fault rating to clear the line if something
goes seriously wrong. If it holds, then you can put the big fuses in.


The factory has a mix of bakelite and nylon body connectors. I bought
8 new nylon body connectors to replace the old bakelite connectors.

The more important thing is to keep the trash from getting in the
boxes again. Unless you start doing grinding and sharpening in that
shop again, your main worry is getting the historic accumulation of
old swarf out of the existing boxes.

If you have a receptacle drop hanging in a machine shop environment,
you should be using the yellow plastic boxes that are sealed from
casual crap entry. Not all that expensive, and they'll keep most
everything outside that needs to be.

Hubbell Kellems 3000H - double sided with 2 Duplex receptacle plates.
There are "Wet Rated" flap covers too - 3056H on 3099H bare box.

http://www.hubbell-wiring.com/catalog.aspx Section F Watertight
Devices.

Best practices would be using the raintight Pin And Sleeve cord cap
devices hanging from the ceiling that can be washed-down with the
covers closed - go look at any McDonalds and they use them on all
their gear. But they are a bloody fortune - those you find in an
auction lot or on eBay..

And the upper cord grip going into the boxes on the rafters needs to
have a woven wire cord grip so all the strain isn't on the SO cord
sheath all in the one spot with the rubber grip gland, but spread out
on the sheath and conductors. Those boxes should be sealed up too,
even if it's just a careful application of caulking to the covers and
all the holes in the boxes.

-- Bruce --

On 2011-10-07, Bruce L. Bergman (munged human readable) wrote:
wrote:
The factory has a mix of bakelite and nylon body connectors. I bought
8 new nylon body connectors to replace the old bakelite connectors.

The more important thing is to keep the trash from getting in the
boxes again. Unless you start doing grinding and sharpening in that
shop again, your main worry is getting the historic accumulation of
old swarf out of the existing boxes.

I am not too worried. I do grind stuff, of course, but comparatively
little.

If you have a receptacle drop hanging in a machine shop environment,
you should be using the yellow plastic boxes that are sealed from
casual crap entry. Not all that expensive, and they'll keep most
everything outside that needs to be.

Hubbell Kellems 3000H - double sided with 2 Duplex receptacle plates.
There are "Wet Rated" flap covers too - 3056H on 3099H bare box.

http://www.hubbell-wiring.com/catalog.aspx Section F Watertight
Devices.

Best practices would be using the raintight Pin And Sleeve cord cap
devices hanging from the ceiling that can be washed-down with the
covers closed - go look at any McDonalds and they use them on all
their gear. But they are a bloody fortune - those you find in an
auction lot or on eBay..

And the upper cord grip going into the boxes on the rafters needs to
have a woven wire cord grip so all the strain isn't on the SO cord
sheath all in the one spot with the rubber grip gland, but spread out
on the sheath and conductors. Those boxes should be sealed up too,
even if it's just a careful application of caulking to the covers and
all the holes in the boxes.

I have not even looked at what is going on under the ceiling.

I am, frankly, exhausted.

i

On 2011-10-07, Bruce L. Bergman (munged human readable) wrote:
On Thu, 06 Oct 2011 14:31:45 -0500, Ignoramus15921
wrote:
On 2011-10-06, Jim Stewart wrote:
Ignoramus29750 wrote:

Sounds like GE did a bad job on this Electrocenter.

Sounds dubious that the busbars "slid down". Busbars
have to be bolted solid in numerous locations to withstand
the forces generated by the magnetic fields created
from a short circuit. More likely would be a piece of
wire or other debris fell across them.


I have learned a lot of very fascinating stuff recently. Thanks a lot.

There are procedures for initial power-up of gear that's new and being
energized for the first time, and for gear recently moved and being
reenergized. The main rule is to check for outright shorts and
crosses before you power it up, and then be careful bringing it up to
operating voltage.

It might pass an ohm-meter test when you check for shorts, but have
compromised insulation or a piece of trash that will flash over at
full voltage. 120/208/240V isn't so likely to have flash-over
failures, but you go to 440V and up and it starts being a real
possibility.

I've had them at 120 VAC. A standard duplex outlet, where the
grounded mounting strap was attached to the Bakelite body with drive
screws. One of the screw cavities apparently had a void near the end
which opened into the area where the hot and neutral conductors were
living. No problem until a thunderstorm induced a high enough voltage
spike to start an arc inside the outlet -- coating it with carbonized
Bakelite. It tripped the breaker (of course), and when I got home and
switched the breaker back on, there was a bzzzzttt-snap! and it tripped
again. I walked through the house until I smelled the burnt Bakelite,
and dug my way into the outlet. (It has one of those 6-way trapezoidal
expanders/surge suppressors screwed into it. The hot pin was welded to
the connector inside the outlet, so I had to pull hard enough to break
the pin loose to get the outlet out and replace it. After that, I could
turn the breaker back on. (I was working against time there, because
it was getting dark while I was yanking it apart. :-)

[ ... ]

The more important thing is to keep the trash from getting in the
boxes again. Unless you start doing grinding and sharpening in that
shop again, your main worry is getting the historic accumulation of
old swarf out of the existing boxes.

Again -- these are not duplex outlets in boxes, but rather
single outlet which mounts onto the end of the cord. Probably
twist-lock connectors, even for 120 VAC drops. Probably something like
the L5-20R shown in the right-hand photo of this URL:

http://www.lockingpowercords.com/Products/79-20a125v-locking-power-cords.aspx

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2011-10-08, DoN. Nichols wrote:

Again -- these are not duplex outlets in boxes, but rather
single outlet which mounts onto the end of the cord. Probably
twist-lock connectors, even for 120 VAC drops. Probably something like
the L5-20R shown in the right-hand photo of this URL:

L15-20

Jim Stewart writes:


Sounds dubious that the busbars "slid down". Busbars have to
be bolted solid in numerous locations to withstand the forces
generated by the magnetic fields created from a short circuit.
More likely would be a piece of wire or other debris fell
across them.

I only know what I was told by Bill, years later. [ISTM this
happened in the early 1970's.] They had all three starters
racked out and no reason to suspect the shipping damage.

Unlike some, I'm not willing to attack someone as incompetent
when I am not able to see the evidence myself. Bill had been a
senior CPO in WWII, and was not just skilled but also cautious.
{We worked in the products pipeline environment; not one to
encourage swaggering & risk-taking.}

I mention the case merely as an example of why remote operation
of a main is not a half-bad idea.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433