Grafton Va School Complex - fire in main electrical distribution room. 2

[FacEngrPE]

February 3 at 1:38 PM · Just before 4 pm today, school administrators initiated evacuation procedures due to reports of an electrical issue in the main electrical room. As emergency responders arrived, an active fire was discovered. The fire was contained to that electrical room though smoke did spread through parts of the building. Due to the nature of this incident, power to the building remains off and Dominion Energy is on site assessing the situation. We do not yet have an estimate for power restoration or a timeline for necessary repairs.

Background
The Grafton complex houses a Grafton Middle School and Grafton High School. Location 403 Grafton Dr, Yorktown, VA USA, Aerial Photograph

https://www.google.com/maps/@37.1638862,-76.469773,690m/data=!3m1!1e3

Complex opened in 1996.

While I do not have specifics it is usual practice here for buildings of this size to distribute electrical power at 480V 3phase, building loads are 480/277 or 208/120, with transformation to 208/120 near using panelboards. The Dominion Power would provide a transformer close to the electrical room. At this voltage level arcing faults can be sustained for a long time.

Sprinkler system did it's job, fire contained to the electrical room, no injuries.

Grafton Va School Complex Update Feb 6, 2020 - good pictures of destroyed main electrical panel.

https://www.youtube.com/watch?v=_TfbMCDJ9i0&feature=youtu.be

Restoration of power to the complex will take months.
Soot is now considered a Hazardous Material, cleanup in progress.
Students will now share space with York Highschool, and Tabb Middle school.

Friday, February 7, 2020 – Letter from the Superintendent York County Schools

https://www.facebook.com/yorkcounty...p9M7PqL3Ym_k-CdXvFI3JWj8W22CgzN8wi&__tn__=K-R

Disrupted students - will be sharing school space in shifts for several months.
Grafton Middle School 882
Grafton High School 1185
York High School 1075
Tabb Middle School 921

Disaster? depends on definition - for sure disruptive and costly.

 

[waross]

480 Volt distribution in a large complex is common and is good engineering, economically for both installed cost and for line losses.
480 volt distribution, stepped down to 120/208 Volts may be argued as safer than a higher voltage distribution.
Anecdote alert:
I may have avoided a similar disaster in a school complex.
There were four dormitories, a school building, a main administration building including a kitchen and mass hall/assembly hall.
I had done a lot of volunteer work at the school and had much more leeway to take action than would be normal for a visitor.
I was walking though the boiler room with the maintenance chief when I felt a blast of heat radiating from the main switch.
I opened the switch and saw several mini-arcs inside the switch.
The arcs were between the movable switch blades and the contacts that the blades closed into.
The arcs were only a pin point of intense light.
I measured several Volts drop across each arc. Incoming was a couple of hundred Amps at 120/208 Volts.
From the heat radiated I estimate that a few thousand Watts was being lost.
It was on the weekend, no parts were available nearby.
There was no budget.
The school was empty but classes were due to start in a week or so.
Step one. Measure and record voltage drops across the arcs and across point that were not arcing for comparison.
Step two. Call the utility emergency number for an emergency disconnect. I requested and they agreed to leave the high voltage fuses in my possession as an added safety measure.
Step three. Dismantle the switch and scrape, file and polish the blades and the contact clips including the pivot points.
Memory fails but I probably cleaned up the fuse holders as well.
Step four. Work harden and re-tension the contact clips.
Step five. Call the utility for a re-energization.
Step six. Measure and record the voltage drops across the switch terminals.
Step seven. Prepare and submit a report to the owners trying to indicate the seriousness of the situation and recommending replacement of the main switch ASAP.
While this was not as large as the Grafton Complex, I am sure that we were just a couple of weeks away from a similar, though smaller, meltdown.
A similar micro-arc in one or more connections may have been the root cause here. As the damage escalated to and through complete failure any evidence of the original cause may have been destroyed. Maybe not.
Anecdote two. A failure in a new safety switch on the first day.
Root cause: The installer left one of the main terminal connections loose to the point that heat was developed.
Point of failure: The heat was transmitted up the copper conductors so that the insulation was softened.
A conductor pushed through the softened insulation and made contact with the grounded entry conduit.
There was no significant damage to the loose connection other than slight surface discoloration, but it was obvious that the loose connection was the source of the heat that caused the damage elsewhere.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[FacEngrPE]

WoW That's a scary close shave.

 

[Alistair_Heaton]

Why the big issues in the USA with medium voltage?

I see this on solar panel installations as well.

My setup runs at between 400 and 550v but the USA users seem absolutely terrified of that. They are more than happy to run at 40-50 amps compared to my 9 amps. I use 6mm2 solar cable rated at 1000v. They are all using 21mm2 or more and running hurrenous losses and hot.

My house supply is 22kW 3ph 400v 32amp breaker.

I do have 10mm2 from the main distribution panel to the subs. But I could use 6mm2 if I wanted to. Just didn't seem worth not spending an extra 30 euro on cable.

The solar lot are talking 100amp circuit breakers on heating/Aircon radials and main breakers of 300 amps. There are numerous pics of earth bolts cherry red in distribution panels. Quiet why they are using M6 bolts as earthing bus bars is also a bit strange to me. I have a length of copper bar with holes drilled through it and grub screws to hold the wires in.

I was always taught voltage is shocking current kills.

I am under cultural shock at the moment anyway after being brought up in the UK with electrics. And am now building a house in the EU, sockets and switches which are utterly cheap shite if you get the local ones. Thankfully Amazon UK will deliver UK standard gear through the post. And you can get UK standard EU fit mk sockets. And the switches are good anyway. They cost three times as much but fixing the local crap every couple of months will hopefully not need doing.

PS I don't think we can use blade main power switches legally any more and haven't been for some 30 odd years due to this inherent risk of arcing followed by fire, I don't have a single one.

 

[waross]

I was always taught voltage is shocking current kills.

Quite right, but the current that kills is generally less than 1 Amp.
600 Volts against 120 Volts to ground._ In the event of contact with your body, 5 times as much current that kills.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Alistair_Heaton]

As you say it's milliamps that kill.

1 amp or 5 amp is the same as falling 10 meters or 50 meters.

Have 300 amps going to earth is a load of extremely hot wire. In fact why are they using M8 bolts for earth? They would be needing M40 at least. ;-)

Edit to had thinking about it over the last 30 years I have had two unintended zaps. One was 220v across a finger and the other I was fixing an ossicilascope. First one resulted in swearing, second I ended up on my back 1 meter away from the work bench with the old boy say, that's why you always keep one leg on the foot rest.

Intended zaps to many to count. I used in old days my right hand clenched fist knuckle to check cables to see if they live on 220v . Clench fist with index finger knuckle slightly out and then swipe down brushing end of wire. These days with glow when hot screwdrivers I use them instead.

 

[Alistair_Heaton]

Mainly because I am bored stuck in a hotel.

USA has 330 million people and in 2002 20 000 deaths were due to electicution.

UK has 60 million people and it's 70 deaths per year.

This for in the home.

Haven't looked yet at electrical induced house fires.

Looks like I am going to be sticking to my medium voltage, low current setup.

Wood house 15 meters of 1000v 6mm2 cables inside a fireproof channel inside the wall. No connectors between roof and inverter just 4 cables. Running max 10 amps at 570 volts versus 120V running at 40 amps plastic channel inside internal walls...

Not that your going to be able to change things now away from how things are in the USA. Just seems particular silly. And the stats seem to prove the excuse for having it that way don't give any safety benefit.

 

[CWB1]

Not sure I'd call a small fire in a small school a disaster, much less an engineering disaster.

 

[LionelHutz]

550V isn't medium voltage....

 

[dik]

AH: "Edit to had thinking about it over the last 30 years I have had two unintended zaps."

I still remember being zapped by the anode wire on a colour TV circuit about 60 years back... it was a real 'eye opener'. When people used to throw out TVs, we used to scrounge the parts... I could tear the flyback system out in a short time and had a relatively safe source of 20K volts... just what every kid needs.

Dik

 

[waross]

I had a Neon transformer at about 15,000 Volts.
It powered a nice Jacobs ladder.
As well I had an old foot X-ray machine from a shoe store, 100,000 Volts.
I tried making a capacitor with sheets of window glass and tinfoil, encased in paraffin wax.
After a couple of failed capacitors I gave up on that.
Safety? NO, I was extra careful around those two.
The third prize was a very old distribution transformer.
I never back energized that one. I stripped the wire to use for other projects.
Hands up if you remember when transformers were wound with DCC, Double Cotton Covered wire?
I just googled and was surprised to see that DCC wire is still available.
Here's what the Neon transformer looked like.

This is what my other toy looked like.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Alistair_Heaton]

I only used the term medium because that's what the solar lot call it.

Low voltage to them is 12/24/48 V with the string voltages at sub 140 V.

 

[Eufalconimorph]

550V isn't medium voltage....

My general (entirely personal) rule is as follows:

Human body resistance can be as low as 500 Ohms (wet skin). Ventricular fibrillation can start occurring at 100mA. So 50V is about the limit I'd want to risk touching without taking extra precautions (PPE). And I try to keep it below 30V.

So anything under 50V is "low" voltage: probably don't need too much care to be safe from the direct electrical hazard.

IEC defines high voltage as 1000V AC or 1500V DC. US NEC defines high voltage as >= 600V. Other organizations are similar, usually the cutoff is around 1kV. So I tend to go with 1kV (either AC or DC) as "high".

The rest is "medium". So 550V does make sense as medium, though I'm not aware of an electrical safety code that uses the term "medium voltage" that is probably just because I don't work in power systems. NEC would call it "low voltage"!

 

[Cool_Controls]

ANSI C84.1-1989 defines 5 voltage levels
Low < 600
Medium 2400 to 69kv
High 115kv to 230kv
Extra high 345kv to 765kv
Ultra high 1100kv

Link

 

[Alistair_Heaton]

Must admit to me as a mechie and I know I am not the only mechie that thinks this way.

low voltage is anything under mains 220/400V and you need something to bring it down.

High voltage is anything on the grid side of things above mains that the local transformer brings down.

And Medium is anything between Low and High... With Mains at 220/400V. very low current is anything under 5amp, low 5 to 16 amp, medium 16 to 32 and high anything over 32amp.

I realise and expected that this doesn't comply with any known standard. For me the currents which are normal on 110V domestic systems are mind boggling high and so must be the wire losses.

 

[LionelHutz]

When you work with the various voltage levels, you use levels lik ANSI defines. Otherwise, you tend to make up some definition that varies depending on the person and overall means little.

You lost all credibility on your voltage level arguments when you posted a ridiculous number like 20,000 home deaths per year in the USA due to electrocution.

Solar systems in NA can run at 400-600VDC into a single inverter that converts it to 240VAC for grid connection.

 

[Alistair_Heaton]

That's what the stats sites say. Although you seem to collect labour accidents federally and the domestic stuff by state if at all. And there is no consistent definition, so some of those could be dead in an electrical house fire.

Its not really surprising UK is lower by a large margin. Its always had quiet strict electrical codes and standards. Plus we tend to live in brick houses. Mainland Europe is about the same as the USA with variations between countries.

 

[LionelHutz]

LOL, because it makes perfect sense that 55 people are being electrocuted to death at home per day.

 

[3DDave]

https://www.nickleelectrical.com/safety/electrical-safety-statistics

Seems like 400 as the top range for estimates of USA household electrocution deaths, more on job sites; this from 5 years ago, so even more GFCIs should mean even fewer in-home electrocutions.

I was originally going with the fact that the UK has so many Lucas electrical components that there isn't any electricity to escape.

Why do Brits drink warm beer - Lucas refrigerators. Many more:

http://www.mez.co.uk/lucas.html

 

[waross]

Lucas also built braking systems for trucks.
The motto of their brakes division;
WE PRESS ON WHERE OTHERS HALT.
No joke.
A customer brought a Ford school bus into my friend's shop with factory original Lucas brakes.
Any one familiar with North American air brakes knows the yellow button on the dash that sets or releases the spring applied, pressure released parking brakes or Maxi Brakes.
Lucas made a spring applied, hydraulic pressure released parking brake for hydraulic brake systems.
Quite rare. Almost impossible to source repair seals.
Oh, the same yellow button on the dash. Instead of being mounted on a special air valve, a rod went through the fire wall and operated a hydraulic dump valve.


Bill
--------------------
"Why not the best?"
Jimmy Carter