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Old 06-09-2010, 08:34 PM   #1
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My electrical adventure from a few days ago


A few days ago my net was down so I decided to actually do productive stuff like go mow the lawn, and go to Canadian Tire to buy wire so I can install a dedicated outlet for my new AC unit. For now it is plugged into an extension cord. I fired it up before so I could see how well it works when I walk in the room after mowing the lawn.

So I do all that stuff, get in the room, and push the button to make the oscillation go on so it blows on me. BOOM power goes out. My first thought is I was borderline and activating the small motor for the blades made the breaker trip. The Unit pulls 14.5 amps on it's own. I heard my UPS beeping, which is on another circuit then realized the whole house was out. I figured MAYBE I blew the main fuse, but had trouble believing it given I'm not using even close to 100 amps total.

I determine that it's not just my house, and that it's a pure coincidence. It was my whole street that was out. Other streets around had power. Something told me the power company did not know about this so I called them up, and they did not know and sent someone. About half an hour later (it's dark by this time) I see a truck stop a few houses from me, two guys with flashlights come out, and are talking and go up to the post in the back yard of the house. I see their lights flashing around and can hear them talking but can't really make out much. At this point I'm guessing maybe a pole fuse went. By the way they're talking and pointing the flashlights I'm assuming they have one of those big poles and are about to push the fuse in. I hear a big POOF! with sparks followed by profanities. Guessing they did not bring spares. They leave and come back 15 minutes later. This time I see and hear an arc flash and hear one say "It's not slamming all the way". Then I hear a click and the power comes back on.

Was quite neat to see it all happen like this. Not really sure what exactly happened. I'm nervous every time I touch that AC unit, or turn a high usage device on now. I doubt it was me, but wow, what a coincidence.

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Old 06-09-2010, 08:54 PM   #2
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My electrical adventure from a few days ago


Same type of thing happened to me the other day.

Just finished wiring a new circuit, flipped the breaker, went into the room and turned on a light plugged into the socket and the whole house went dark. Half the city was down for us, so don't think it was me.

We have also been having a lot of flickers lately, where the power goes off for less than a second and it keeps me second-guessing my connections.

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Old 06-09-2010, 09:23 PM   #3
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My electrical adventure from a few days ago


My wife and I were visiting my parents and my Mom put some food in the microwave and press the button, about 3 seconds later the transformer at the end of the street exploded---the look on her face was one I could not even describe LOL.
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Old 06-09-2010, 09:51 PM   #4
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My electrical adventure from a few days ago


it was obviously your fault red squirrel. I suspect you next bill will be a big surprise with those repair costs and all.


it would be surprising to see that it was you but it is a heck of a coincidence if it wasn't.
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Old 06-09-2010, 09:57 PM   #5
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My electrical adventure from a few days ago


I was installing a server with the Tech rep
We had it all setup in a quasi server room
Technically as a Project lead I was supposed to have a network guy present
But they had already set up the wires & LAN, so had told me to go ahead

The Tech rep leaned over & flipped the switch on
Sirens start going off, lights flashing...powers out !!
Whole building went down...nothing to do with us
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Old 06-10-2010, 03:58 AM   #6
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My electrical adventure from a few days ago


I deal with POCO pretty often so I know excatally what they are up to so anyway Red.,

The reason why they have issue with slamming all the way due some fuse or recloser aka high voltage resetable circuit breaker with lock out feature on it.

Most common curpit useally overload that when the fuse go out and when the POCO try install new one and it flash over it will tell you either have short circuit or serious overload { more common to find overload circuit during refuseing it } so that one thing you will noticed the lights will flicker few time then after that it stay on steady.

{ note a tip if you see light blink in sequince like go off then back on first two or so seconds if go off again it stay off little longer then thrid time repeat if still trip out it will go in lockout mode that what the recloser will do and many time they will reclose it pretty quick due some case have tree branches and from time to time POCO lines will touch each other and trip the recloser.}


If you have more question just holler I will be more than happy to answer it.

READERS:
If you see your house or your area lights are blinking or go out just call the POCO one way or other they will send someone out and fix or verify the system.

Merci,Marc
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Old 06-10-2010, 09:36 AM   #7
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My electrical adventure from a few days ago


Yeah I suspect it may have been tree branches, there are trees very near the lines, I actually got a letter saying they will be coming to trim my trees, I'm sure lot of others got the same letter. It's nice that they do that, saves me from going close to those lines. :P

Actually one thing I did notice is there is only 1 high voltage conductor, how does that work? Figured you needed at least two so you could step down to residential voltage. There is a a transformer on the switch pole and a low voltage line below the high voltage one, and the houses are fed from it.
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Old 06-10-2010, 10:41 AM   #8
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My electrical adventure from a few days ago


Quote:
Originally Posted by Red Squirrel View Post
Yeah I suspect it may have been tree branches, there are trees very near the lines, I actually got a letter saying they will be coming to trim my trees, I'm sure lot of others got the same letter. It's nice that they do that, saves me from going close to those lines. :P

Actually one thing I did notice is there is only 1 high voltage conductor, how does that work? Figured you needed at least two so you could step down to residential voltage. There is a a transformer on the switch pole and a low voltage line below the high voltage one, and the houses are fed from it.
It works really well
My power company uses a wye system. From the sub station, three phases and the neutral are distributed around the rural area. About 4 miles away from my place, there is a tap that brings one phase to my area - the live and the neutral. I was told this phase is 7200 V to neutral.
On the power pole next to my place there is a transformer that is connected to this distribution power. The secondary side is a "center tap" winding that is connected to my house - three wires, two hots and the neutral (central tap). The transformer neutral on the pole is grounded with a ground rod and wire. At my house, the three wires are connected to the panel and the panel is also grounded with a #6 copper and 8' ground rod.
This is just one example of power distribution.

Last edited by a7ecorsair; 06-10-2010 at 10:48 AM.
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Old 06-10-2010, 01:06 PM   #9
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My electrical adventure from a few days ago


But 1 phase should still be two conductors right? I can't see how 1 conductor is enough, or does it use ground as the second? I'd have to notice more how the transformer is wired.
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Old 06-10-2010, 01:37 PM   #10
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My electrical adventure from a few days ago


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But 1 phase should still be two conductors right? I can't see how 1 conductor is enough, or does it use ground as the second? I'd have to notice more how the transformer is wired.
The "one wire" is 7200 volts. This enters a transformer, which is basically 2 big coils of wire. The ratio in this case is 30:1..... we're stepping the voltage down 30 times to 240V. On the "low voltage" coil, we see 240 volts from "bottom" to "top." They place a "tap" in the middle of this coil, which is the neutral.

So, the voltage difference between the "bottom" and the neutral is 120 V. this is one leg that comes into your house. The voltage difference between the "top" and the neutral is 120V. This is the other leg that comes into your house.

Hope I made that clear enough. Probably not. Lemme know.
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Old 06-10-2010, 01:41 PM   #11
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My electrical adventure from a few days ago


Quote:
Originally Posted by Red Squirrel View Post
But 1 phase should still be two conductors right? I can't see how 1 conductor is enough, or does it use ground as the second? I'd have to notice more how the transformer is wired.
You said there were two wires on the pole:
Actually one thing I did notice is there is only 1 high voltage conductor, how does that work? Figured you needed at least two so you could step down to residential voltage. There is a a transformer on the switch pole and a low voltage line below the high voltage one, and the houses are fed from it.

Go look at your transformer. You are correct in that you need two connections to the primary side of the transformer.
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Old 06-10-2010, 01:43 PM   #12
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My electrical adventure from a few days ago


I understand the secondary side with the tap, but what about the primary side? don't you need two wires going into a transformer, and at least two coming out? Or does the neutral just bypass the whole transformer and go straight to the house? Did not figure that could work.

This is how I figured it had to work:
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Old 06-10-2010, 02:12 PM   #13
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My electrical adventure from a few days ago


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I understand the secondary side with the tap, but what about the primary side? don't you need two wires going into a transformer, and at least two coming out? Or does the neutral just bypass the whole transformer and go straight to the house? Did not figure that could work.

This is how I figured it had to work:

You have it mostly correct, although I don't think the neutral is grounded at the transformer. That would setup the ability to have a "ground loop" current over the neutral between your house and the transformer, which I don't think would be desirable.

You have the mechanics of the situation perfectly understood. You've got a "semantics" or "frame of reference" problem instead!

On the left-hand side of your drawing, you've labeled both lines coming into the transformer as "Hot." Really,we would consider one to be "Hot" and one to be "Neutral." It doesn't honestly matter which one, as we know that AC "flows" in both directions. The important point is that there is 7200V of electrical potential between those two wires.

Similarly, we COULD name our terminals differently on the right side of the transformer. We could call the bottom one "Neutral" and the middle one "H120" and the top one "H240." This would mean that we would connect all of our 120V appliances to one leg, and all of our 240V appliances to the other leg. HOWEVER, this would lead to more confusion, an uneven balance of loads in the system, and less flexibility and redundancy in the system. The "Wye" configuration (I think) is the most common for single-phase power. (you can google "Wye" and "Delta" as methods of transmission for 3phase power)

Clear as mud? good!

ETA: I saw that the other guy said his neutral is grounded at the transformer.... So I was was wrong about that. I was wrong one other time: I thought I was wrong about something, but it turns out I was right. :^)

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Old 06-10-2010, 02:45 PM   #14
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My electrical adventure from a few days ago


Quote:
Similarly, we COULD name our terminals differently on the right side of the transformer. We could call the bottom one "Neutral" and the middle one "H120" and the top one "H240.
well, sort of.


the code tends to stay away from the term neutral because not all transformers have a neutral. More often, the term "grounded" conductor is used.

In the center tapped windings (on the right) the only terminal that could properly be called a neutral would be the center tap. It is the neutral because it is the center point of the windings. In hooking it up as you suggested, yes, the voltages would work out as you describe.


another thing that RS might want to know:

the neutral of the low side does not have to be grounded for the system to work. Grounding it has nothing to do with functionality. Grounding is a safety system.

with no grounding what so ever on the low side, you will still have your 120 v end to center and 240 end to end.



Quote:
Similarly, we COULD name our terminals differently on the right side of the transformer. We could call the bottom one "Neutral" and the middle one "H120" and the top one "H240." This would mean that we would connect all of our 120V appliances to one leg, and all of our 240V appliances to the other leg. HOWEVER, this would lead to more confusion, an uneven balance of loads in the system, and less flexibility and redundancy in the system.
while correct for a service power supply, this exact type of connection is very common in multi-tap transformers. You have 1 tap at one end of the windings that is the "common" that one connection from any load would attach and then you can have any number of taps along the winding to provide different voltages as needed. Very common for a HID ballast transformer in lighting only the multi-tap winding is on the primary side rather than the secondary side.
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Old 06-10-2010, 04:17 PM   #15
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My electrical adventure from a few days ago


Yeah was not 100% sure if it was grounded but assumed so, and knew it was for safety and not functionality. but I'm still confused as to how this can work when there is only a single high voltage conductor like on my street. How is the other side of the first winding terminated? The way the wires are layed out is, there is one conductor on top of the pole, then below is the low voltage circuit, possibly more then one, it's fairly thick and hard to tell how many wires but guessing at least 3, and each house connects to it, then below that is cable TV and phone.

Quote:
Originally Posted by a7ecorsair View Post
You said there were two wires on the pole:
Actually one thing I did notice is there is only 1 high voltage conductor, how does that work? Figured you needed at least two so you could step down to residential voltage. There is a a transformer on the switch pole and a low voltage line below the high voltage one, and the houses are fed from it.

Go look at your transformer. You are correct in that you need two connections to the primary side of the transformer.
The low voltage line is on the secondary side of the transformer though, how is the primary fed with just one wire? I can't see properly how it's wired though because of a tree in my path of view. Maybe there's a feed coming from the ground up the pole through a conduit or something to feed the second conductor. Can't see why they'd seperate them like that though.

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