Eerie Glow

Reply

  #1  
Old 01-08-02, 05:48 AM
miles
Visiting Guest
Posts: n/a
Eerie Glow

The Power Company had to work on a transformer on the street one night, so they cut the power off at our house. The funny thing was that while they were out there, I could see something like a "2watt" glow in our houses light bulbs that were on when the power was "cut" . Didn't they disconnect us completely? What would be the source of such a feeble glow in the bulbs?
 
Sponsored Links
  #2  
Old 01-08-02, 07:17 AM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
Received 0 Votes on 0 Posts
How long was the outage, and how long was the glow after the outage.
I haven't the faintest clue why the glow, but these questions might start a detective session.
 
  #3  
Old 01-10-02, 12:44 AM
miles
Visiting Guest
Posts: n/a
I recon it was about an hour they had that power "off" and I think the glow was there the whole time.
 
  #4  
Old 01-10-02, 07:29 AM
Wgoodrich
Visiting Guest
Posts: n/a
The only explaination that I can think of is while the power company had replaced or repaired the transformer they had yet to make a good connection to the neutral conductor. If your home had the hot line connected the only return path would be the ground rod or other grounding electrode. Especially if you only have a made grounding elecrode such as a ground rod you would not have enough return path to make the lights work properly but may have enough current to allow a dim glow while using a leak to earth as your return path until they found the bad connection concerning your neutral conductor allowing to complet your return path to the center tap of the transformer where it is supposed to go. A ground rod is actually one of the poorest return paths in the dwelling electrical system. It is there primarily to assist the electrical system to accept a large spike in power such as a lightening strike. When a ground rod is used as a return path often times you only get a glow of the light bulbs and not enough return path to start a motor.

Hope this helps

Wg
 
  #5  
Old 01-11-02, 02:46 PM
I
Member
Join Date: Jul 2001
Posts: 186
Received 0 Votes on 0 Posts
miles, you have a very interesting phenomenon there. Can you furnish some more info? Such as:

Is this an overhead transformer, on a pole, or a padmount transformer, on the ground?

Do the service conductors to your house go overhead or underground?

Did the crew change the transformer? And how did you know it was a transformer they worked on? Could have been a circuit breaker, capacitor bank, or some other equipment and most lay people would not know.

Are there other customers on this transformer?

What kind of ground do you have? Is it a ground rod, water pipe, both? Any other connections to the ground, like cable TV, telephone?

Thanks,
Ichabod
 
  #6  
Old 01-15-02, 04:13 AM
miles
Visiting Guest
Posts: n/a
Wow! We really do have some hot experts on this chat. Thanks for the replies. Other surrounding facts are that it was a 95 year old house and only some of the rooms had been properly grounded. As I recall, the rooms in which I noticed the glow had not been grounded yet. Other lights that were tried, were dead. I think there were only a couple of grounding rods under that house, but the wiring update was only in progress.
Our service came into a big conduit above the second floor and as far as I could tell, the power Co. guys were up on a pole replacing a large battleship grey xformer. Other neighbors were also blacked out.
Can anyone crystalize in a few sentences, what was causing the glow? I think Wgood has it, but I'd like it re-stated. Thanks
 
  #7  
Old 02-07-02, 09:05 AM
I
Member
Join Date: Jul 2001
Posts: 186
Received 0 Votes on 0 Posts
I have a theory about what caused the glow. There is normally a difference in voltage between the electric utility's primary neutral and a remote, unconnected ground rod. Most people, including electricians and electrical engineers are unaware of this, but it's there. It should not be surprising because the primary neutral in my town, for example is connected from one end of the county to the other, must be close to 20 miles. The primary conductors themselves stand open to separate them from other substations since they are radial, but the neutrals get connected. Go to www.google.com and search for "stray voltage" and you will find tons of info about it. What happens to cause stray voltage is the utility connects the primary neutral and the secondary neutrals together at each transformer. It's required by NEC. There can be many other causes for stray voltage, but in Miles' case this is the most likely scenario. During the process of changing the transformer the primary fused cutout (switch) would have been opened, then the secondary leads disconnected and possibly grounded at the transformer pole. If the service drop neutral to your house is disconnected from the utility neutral at the pole then there is a voltage difference from your ground rod to the utility company primary neutral, where the temporary safety grounds are connected. According to most sources I have read, 10 volts is not at all uncommon in such a case. This should be enough to make your lamps glow.
 
  #8  
Old 02-07-02, 09:28 AM
HandyRon's Avatar
Member
Join Date: Dec 2001
Location: New York
Posts: 1,365
Received 0 Votes on 0 Posts
I would have thought that the utility is using a delta wye transformer, hence no neutral on the primary.
 
  #9  
Old 02-07-02, 10:02 AM
I
Member
Join Date: Jul 2001
Posts: 186
Received 0 Votes on 0 Posts
Ron, most substation transformers feeding distribution loads are delta-wye. In my county, which is probably typical, there are about 8 substations, belonging to one utility, that serve the city and surrounding county. All the neutrals of all the feeders of all the substations get tied together somewhere. This is not necessarily bad. The typical transformer feeding residential load, either pole mount or pad mount, is connected from phase to neutral.

Stray voltage seems to be more common in some areas than others, or maybe it's just noticed more. In my more than 30 years in the utility business as an engineer I only knew of a couple of cases. As a result, some utilities have more and some less experience with the causes and solutions. Cows are extremely sensitive to electric shock, much more so than humans. Dairy cows will refuse to eat or drink water when there is only a very small voltage difference between their hooves and their mouths. Because of this utilities in dairy states are more experienced in the detection and the solution of stray voltage problems.

According to what I have read, more ground rods is not the solution and may even make the problem worse. In fact in the case of the mysterious glow, there would be no glow at all if miles' panel ground were disconnected.
 
  #10  
Old 02-09-02, 11:11 AM
Wgoodrich
Visiting Guest
Posts: n/a
What Ichabod is saying is about what I was saying. To confirm what he was saying about dairy cattle and other animals being more affected by this stray voltage try looking at Article 547 for agricultual buildings. YOu will find what is called an expotential grounding plain with insulated grounding elecrode conductors. The expotential plain is a design required where farm animals are involved to try to block or obsorb this stray voltage limiting the stray voltage exposure to these farm animals. The stray voltage has been a recognized problem with these farm animals. I also support that when you have this stray voltage problem the more grounding electrodes you install the worse the stray voltage problem can occur. Actually if the ground composition is correct and the stray voltage combination is in the right conditions of existance the more grounding electrodes you create to a dwelling the more chance for an electrical shock exposure to humans is produced around those grounding electrodes and other metal parts of the building. The better the grounding electrode design creating the difference of potential between these two entities the more likely harm can come to a human from the grounding electrode system designed to protect them from shock.

I know this sounds contrary to beliefs but the knowledge is growning in this area of electrical design. A lot depends on the electrical high voltage design and the composition of the earth around it. Moisture, type of soil, and many other conditions will change this stray voltage existance. Stray voltage could exist with the better grounding electrode system provided yet may become lethal in the spring and fall and non existant in the mid summer months.

It is a growing concern within the electrical industry.

Good points Ichabod !

Wg
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: