gthomas785
Member
- Location
- MA
- Occupation
- Physicist
Hi Everyone, I am not an electrician but this isn't a DIY post I'm just curious about something I observed. Wondering if anyone on this site has any insights.
The other night we had a power outage. A storm came through and presumably knocked a branch onto a wire, my whole street was out as well as a couple of adjoining streets. However, My neighbors around the corner still had power. I live in a single family house with 240/120 single phase service and share a transformer with 4 other houses on my street.
So I get up in the middle of the night to use the bathroom and notice that the LED night light plugged into the GFCI above the sink is glowing. Nowhere near the usual brightness mind you, but bright enough that I can see my way around the bathroom. I unplugged it and it went out, plugged it back in and it came back on. As I watched it longer, I noticed that the brightness was kind of slowly pulsating, it would fade away (like a capacitor discharging) and then suddenly come back on. The time between pulses was completely random. Keep in mind none of the other lights in the house were doing anything like this, it was a total blackout. Kinda freaky actually. I didn't bother to do any further testing because it was the middle of the night and I wanted to go back to bed.
We've had power outages in the night before and this is the first time I've seen this. So I'm trying to figure out why it happened. I have a couple of ideas.
I've seen the "LEDs glow when off" threads on here and it's usually blamed on either a switched neutral or some capacitive coupling across switch terminals. But this is different, a power outage on my whole street, those scenarios would not apply.
Obviously, there was some small amount of voltage on the line that was enough to light up my tiny little LED night light. But how? My first thought was, my neighbors had a generator running and maybe they managed to somehow backfeed to my house. But the voltage was so low, their generator should have been way overloaded for that to be the case.
The second thought, which I think is more likely. My neighbors around the corner still had power, and I assume that our neutral wires are connected together either through the POCO neutral or the metallic gas and water piping. And, since the "hot" wire was not hot but still connected from my house, to the street through the transformer, there would probably be a very large capacitance available on the hot side. So even a tiny amount of voltage on the neutral/ground coming from the neighbors might supply enough current to drive an LED. What do you think of that? Any other ideas? What would cause that "pulsating" effect?
The other night we had a power outage. A storm came through and presumably knocked a branch onto a wire, my whole street was out as well as a couple of adjoining streets. However, My neighbors around the corner still had power. I live in a single family house with 240/120 single phase service and share a transformer with 4 other houses on my street.
So I get up in the middle of the night to use the bathroom and notice that the LED night light plugged into the GFCI above the sink is glowing. Nowhere near the usual brightness mind you, but bright enough that I can see my way around the bathroom. I unplugged it and it went out, plugged it back in and it came back on. As I watched it longer, I noticed that the brightness was kind of slowly pulsating, it would fade away (like a capacitor discharging) and then suddenly come back on. The time between pulses was completely random. Keep in mind none of the other lights in the house were doing anything like this, it was a total blackout. Kinda freaky actually. I didn't bother to do any further testing because it was the middle of the night and I wanted to go back to bed.
We've had power outages in the night before and this is the first time I've seen this. So I'm trying to figure out why it happened. I have a couple of ideas.
I've seen the "LEDs glow when off" threads on here and it's usually blamed on either a switched neutral or some capacitive coupling across switch terminals. But this is different, a power outage on my whole street, those scenarios would not apply.
Obviously, there was some small amount of voltage on the line that was enough to light up my tiny little LED night light. But how? My first thought was, my neighbors had a generator running and maybe they managed to somehow backfeed to my house. But the voltage was so low, their generator should have been way overloaded for that to be the case.
The second thought, which I think is more likely. My neighbors around the corner still had power, and I assume that our neutral wires are connected together either through the POCO neutral or the metallic gas and water piping. And, since the "hot" wire was not hot but still connected from my house, to the street through the transformer, there would probably be a very large capacitance available on the hot side. So even a tiny amount of voltage on the neutral/ground coming from the neighbors might supply enough current to drive an LED. What do you think of that? Any other ideas? What would cause that "pulsating" effect?
