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Power line follies (was cars)
wrote:
On Thu, 25 Apr 2019 07:36:13 -0400, "Mr. Luddite" wrote: On 4/24/2019 8:48 PM, wrote: On Thu, 25 Apr 2019 00:39:30 -0000 (UTC), Bill wrote: wrote: On Wed, 24 Apr 2019 19:35:19 -0400, Alex wrote: wrote: On Tue, 23 Apr 2019 18:36:36 -0700 (PDT), Its Me wrote: On Tuesday, April 23, 2019 at 8:41:50 PM UTC-4, wrote: On Tue, 23 Apr 2019 17:28:35 -0400, wrote: On Tue, 23 Apr 2019 17:01:36 -0400, wrote: On Tue, 23 Apr 2019 16:08:55 -0400, wrote: On Tue, 23 Apr 2019 14:11:32 -0400, wrote: They are assuming coal fired electric plants but I agree all electric cars do is move the smoke stack down the road a ways. === In my opinion that's an over simplification. For one it ignores the fact that stationary, large-scale power plants are much more efficient than the average internal combusion engine used in vehicles. Secondly, the charging is usually done at off peak hours when there is typically excess grid capacity. Last but not least, the trend is pointing in the direction of renewable energy such as wind and solar. If we live long enough (doubtful), we might even see clean nuclear fusion some day. As an additional benefit, electric cars have done quite a bit to advance the state-of-the-art for light weight, high efficiency batteries. Those gains will eventually prove useful for the storage of wind and solar energy. That all assumes a clean power plant in the first place. The article was talking about coal plants and we still have plenty of them. Your solar power is not going to do much if the cars are charged at night. === At least in this country, coal plants are rapidly going away. Solar power at night is not going to happen of course. New battery technology, and other energy storage devices, will eventually help with that issue however. If every south facing roof in Florida was covered with high efficiency solar panels, there would be plenty of energy to spare for battery charging. I think that will eventually happen as the price of solar panels steadily decreases. My problem is drilling holes in a roof that isn't leaking now. My roofer neighbor says solar is great for his business. I also only have about 3kw worth of south facing roof. Solar is getting a lot cheaper tho. I was looking the other day and there are lots of collectors in the 75 cents a watt neighborhood. I wonder how FPL would feel if I built an array on their property ;-) Running those cables to/from that array near their power lines may be the biggest problem.You may create a transformer that neither of you want. :) That is way overstated. I have tried to scavenge power from those lines for 35 years with absolutely zero success. If you believe what you see on you tube I should be able to hold an F40 tube in the air and have it light up ... nope. I should be able to string a wire parallel to the line and generate something ... nope. Coil of wire ... nope. I really wanted a light in my boat house under those lines without stringing another wire but no joy. If you really look at these lines it is easy to see why. They are a twisted triplex. They just have a twist about every half mile or so but that is still way smaller than the wave length. (roughly from here to California) Besides, my wires would be running at 90 degrees to the power line and underground. There are a lot of LED lights that are charged with small solar panels. Pretty cheap, too. How much light do you need? I have 20 amps down there now. It is not an issue. The reality is 60 feet of rope light around the top of the lift is perfect. That ends up being about 100 watts. If I was still interested in trying to scavenge some power I might try something with an LED but I doubt I could even get a glimmer out of one. I have pretty much given up and debunked a lot of the urban legends. If anyone has another experiment, let me know. It is just a short walk across the Ed Labrador Memorial Bridge now, not Bwana hacking through the jungle like before. I am up there 4 or 5 times a day with the Deuce man. The setup is 1 delta high voltage line running 230kv and 2 delta medium voltage lines running 26kv. It is about 70 feet off the ground behind the house going up to more like 85' where it crosses the river. Bring out your fables. I love science. Need more voltage. The 500kv lines that run down the center of California induce lots of current in the parallel line. When a crop duster took out 5 towers, engineers thought an airplane would take out 4. Our friend worked for the power company. A special crew works on the line. Has a faraday cage suit. They shut down the downed line, reduced power in the parallel line and grounded the don line a mile each side of the break. He said the ground line at the tower by the break carried 200 amps. Why wouldn't it be somewhat proportional? I am not really able to see much of anything beyond tickling a digital meter and that happens just about anywhere. Because like RF, the high voltage lines produce a near field and then a quickly diminishing "far field" as distance from the lines increases. It's not proportional, is dependent on current flow and, at 60hz is not anywhere as strong as at RF frequencies. It's still something I think about though. The greatest risk is at ionizing potentials that can cause immediate damage to living cells. Non ionizing potentials may cause an affect, causing cell molecules to vibrate (which is the whole idea behind an MRI scan) but the jury is still out on damage due to long term exposure. Frankly, I am more concerned with the RF energy ... as low as it is ... of a cell phone held up to your head to use. There is much scientific controversy as to if long term exposure constitutes a danger. Because of the balancing effect of a 3 phase delta I am far less concerned about the transmission line behind the house than I am the single phase wye distribution in front. I also wonder just how much energy we are really talking about. I certainly have not been able to turn it into any measurable "work". Again, the low voltage operators are running miles of wire parallel to these medium voltage distribution lines and we are not seeing and significant current induced into the phone or TV cables. In most cases they are actually attached to the neutral return "strand". Dr Kirchoff tells us the current in this strand will be as high as the current in the medium voltage line, minus what returns through the earth. (and I think that is more than they want to admit). There are generally 2 of them so it is a little less than half of what the primary carries I suppose (one strand for the PoCo and one for the Telco/cable guys but they are both connected to the grounding conductor) All of this is trivial compared to the fields you generate right in your house, just because they are closer to you. The fact remains that we have been living, bathed in 60hz fields for over 100 years and we are not seeing any real effects. The cell phone thing is far more recent. I guess we will know soon tho as more people have one up to their head all day long. I guess I will be one of the control group. I still do not carry a phone. Maybe the result of all the 60hz gets you an AOC? |
Power line follies
On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote:
"Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. |
Power line follies
On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me
wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. |
Power line follies
On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote:
On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. |
Power line follies
On Sat, 27 Apr 2019 11:21:11 -0700 (PDT), Its Me
wrote: On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. More likely you were simply seeing the ground shift induced by using earth as part of the return path. That is inevitable with wye distribution, even if you do have a neutral conductor. Current does not take the path of least resistance, it takes ALL paths. The voltage drop on distribution lines is imposed on the earth. When we were investigating blown interface cards at a college campus I found up to 35 volts between "ground" on the various buildings. We found a number of solutions depending on the topology and geography but some customers just turned it over to the phone company, using leased phone lines between buildings that were a hundred yards apart. The other solution was copper, bonding "grounds" together, usually from machine frame to machine frame directly. We had to call it a "drain" and use black wire to avoid NEC problems. |
Power line follies
On Saturday, April 27, 2019 at 4:00:01 PM UTC-4, wrote:
On Sat, 27 Apr 2019 11:21:11 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing.. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. More likely you were simply seeing the ground shift induced by using earth as part of the return path. That is inevitable with wye distribution, even if you do have a neutral conductor. Current does not take the path of least resistance, it takes ALL paths. The voltage drop on distribution lines is imposed on the earth. When we were investigating blown interface cards at a college campus I found up to 35 volts between "ground" on the various buildings. We found a number of solutions depending on the topology and geography but some customers just turned it over to the phone company, using leased phone lines between buildings that were a hundred yards apart. The other solution was copper, bonding "grounds" together, usually from machine frame to machine frame directly. We had to call it a "drain" and use black wire to avoid NEC problems. Nope, this was voltage induced into long runs of unshielded, twisted pair wires. Across the pair you didn't see it, but compared to ground you (properly) did. It's basic electronics 101. Unbalance the pair, which the MOVs did, and now the differential between the conductors is significant and you can hear the induced noise. It's exactly why RS-232 data is only good for 50ft (or with special, low capacitance cable up to 1,500 feet), and RS-422 is good for nearly 5,000 feet.. RS-232 is single ended and is compared to ground (which you can't shake with induced noise), while RS-422 (or 485) is twisted pair. Hit the 232 with a 25 volt spike, and you just changed a 0 to a 1. But with 422, you are looking for a 5 volt difference between the wires. You don't care if they are 0 and 5 volts, or 20 and 25 volts, the data is still intact. Well, until it hits 1000 and 1005 volts, then you've blown up the receiver chip. But the data was still good! |
Power line follies
On Sat, 27 Apr 2019 13:31:59 -0700 (PDT), Its Me
wrote: On Saturday, April 27, 2019 at 4:00:01 PM UTC-4, wrote: On Sat, 27 Apr 2019 11:21:11 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. More likely you were simply seeing the ground shift induced by using earth as part of the return path. That is inevitable with wye distribution, even if you do have a neutral conductor. Current does not take the path of least resistance, it takes ALL paths. The voltage drop on distribution lines is imposed on the earth. When we were investigating blown interface cards at a college campus I found up to 35 volts between "ground" on the various buildings. We found a number of solutions depending on the topology and geography but some customers just turned it over to the phone company, using leased phone lines between buildings that were a hundred yards apart. The other solution was copper, bonding "grounds" together, usually from machine frame to machine frame directly. We had to call it a "drain" and use black wire to avoid NEC problems. Nope, this was voltage induced into long runs of unshielded, twisted pair wires. Across the pair you didn't see it, but compared to ground you (properly) did. It's basic electronics 101. Unbalance the pair, which the MOVs did, and now the differential between the conductors is significant and you can hear the induced noise. It's exactly why RS-232 data is only good for 50ft (or with special, low capacitance cable up to 1,500 feet), and RS-422 is good for nearly 5,000 feet. RS-232 is single ended and is compared to ground (which you can't shake with induced noise), while RS-422 (or 485) is twisted pair. Hit the 232 with a 25 volt spike, and you just changed a 0 to a 1. But with 422, you are looking for a 5 volt difference between the wires. You don't care if they are 0 and 5 volts, or 20 and 25 volts, the data is still intact. Well, until it hits 1000 and 1005 volts, then you've blown up the receiver chip. But the data was still good! I am not going to argue with you but I was a physical Planning rep in a place with 200 thunderstorms in a typical year and I know what works and what doesn't. I have seen a lot of well credentialed EEs, usually from up north, fail miserably with their theories. The proof is always in the magic smoke that escapes when they guess wrong. We went from a couple "lightning" calls a day to a couple a year once we started implementing our strategies and ignoring all of the "ground loop" loonies. |
Power line follies
On Saturday, April 27, 2019 at 5:46:28 PM UTC-4, wrote:
On Sat, 27 Apr 2019 13:31:59 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 4:00:01 PM UTC-4, wrote: On Sat, 27 Apr 2019 11:21:11 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise.. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. More likely you were simply seeing the ground shift induced by using earth as part of the return path. That is inevitable with wye distribution, even if you do have a neutral conductor. Current does not take the path of least resistance, it takes ALL paths. The voltage drop on distribution lines is imposed on the earth. When we were investigating blown interface cards at a college campus I found up to 35 volts between "ground" on the various buildings. We found a number of solutions depending on the topology and geography but some customers just turned it over to the phone company, using leased phone lines between buildings that were a hundred yards apart. The other solution was copper, bonding "grounds" together, usually from machine frame to machine frame directly. We had to call it a "drain" and use black wire to avoid NEC problems. Nope, this was voltage induced into long runs of unshielded, twisted pair wires. Across the pair you didn't see it, but compared to ground you (properly) did. It's basic electronics 101. Unbalance the pair, which the MOVs did, and now the differential between the conductors is significant and you can hear the induced noise. It's exactly why RS-232 data is only good for 50ft (or with special, low capacitance cable up to 1,500 feet), and RS-422 is good for nearly 5,000 feet. RS-232 is single ended and is compared to ground (which you can't shake with induced noise), while RS-422 (or 485) is twisted pair. Hit the 232 with a 25 volt spike, and you just changed a 0 to a 1. But with 422, you are looking for a 5 volt difference between the wires. You don't care if they are 0 and 5 volts, or 20 and 25 volts, the data is still intact. Well, until it hits 1000 and 1005 volts, then you've blown up the receiver chip. But the data was still good! I am not going to argue with you but I was a physical Planning rep in a place with 200 thunderstorms in a typical year and I know what works and what doesn't. I have seen a lot of well credentialed EEs, usually from up north, fail miserably with their theories. The proof is always in the magic smoke that escapes when they guess wrong. We went from a couple "lightning" calls a day to a couple a year once we started implementing our strategies and ignoring all of the "ground loop" loonies. That's nice and all, but we aren't talking about thunderstorms. I've worked with many non-engineering types that thought they knew what they were talking about, but many of their practices were flawed, and it showed through in the end. Your attitude isn't uncommon. It's similar to class warfare, eh? :) Bottom line, I was dealing with induced AC on a twisted pair that was enough to turn on 180v MOVs. You can talk about ground differentials all you want, but that had absolutely NOTHING to do with what was happening in that situation. Have a good evening! |
Power line follies
On Sat, 27 Apr 2019 17:37:48 -0700 (PDT), Its Me
wrote: On Saturday, April 27, 2019 at 5:46:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 13:31:59 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 4:00:01 PM UTC-4, wrote: On Sat, 27 Apr 2019 11:21:11 -0700 (PDT), Its Me wrote: On Saturday, April 27, 2019 at 1:44:28 PM UTC-4, wrote: On Sat, 27 Apr 2019 09:59:10 -0700 (PDT), Its Me wrote: On Thursday, April 25, 2019 at 10:02:15 AM UTC-4, wrote: "Flop around"? Each conductor is securely attached to insulators. They are not physically twisted in a bundle, they just get an electrical twist by having the phases change positions from pole to pole. They call it transposition. It allows the lines to be balanced. (Relative inductance to each other and to the environment around them) Oh, I thought you were saying that each *leg* consisted of three twisted conductors. I've never seen that but who knows what FPL might be doing. Transmission lines overhead are bare wires. They are twisted strands but that is just to increase flexibility and skin effect. The twist I was talking about is how the lines get "transposed" on the poles every half or so where they all get swapped around Those solar panels aren't part of the grid, and have no "sync". Sunlight isn't 60 Hz. :) The inverter will be grid tied so the transport to the house would be in sync. Of course, but it wasn't the feed to the house that I was talking about. You think there will be some voltage induced into the panels? I am not seeing that on anything that is terminated in any way. In this case the panels would be terminated into the inverter and if there was any 60hz present it would simple be chewed up and spit out by the inverter anyway. After all it would be "in sync" with the grid anyway. I don't know, I've never played with it, but it can induce some noise. Probably not enough in that situation to do anything at all. Years ago I installed some comm equipment in a train yard. We had built some interface cards for some comm circuits that was just a 600 ohm twisted pair that ran along the track for miles until it hit a transmitter shack, sometimes with a handset in there to talk back to dispatch. The interface card had a transformer and some audio switching circuits, and was protected by a couple of MOV's rated at 160-180 volts, one for each side of pair going to ground. When we installed the new equipment and started testing, some of those circuits had a horrible amount of noise and buzzing on them. Doing some troubleshooting with a butt set, I discovered that if our interface card was disconnected, the noise went away. Then I hung an oscilloscope on one side of the pair, then the other. There was a HUGE 60hz component coming in on some of the circuits, in some cases around 200 volts. Since the twisted pair was doing what it does, you didn't hear that on the circuit (when you induce a signal on a twisted pair, the same signal is present on both wires. Since you only care about the difference in potential between the two wires, the signal stays intact.). It wasn't until our interface card was connected that the MOVs saw that voltage from each wire to ground and turned on, unbalancing the circuit and causing the noise to be audible. Turns out that the pairs left the yard and were run on power poles, occasionally in some cases dropping down to fence posts on the right-of-way, then back up to the posts. They picked up the induced signal from the power lines and brought it right back to our interface cards. We clipped out the MOVs, and all was good. We had to depend on primary lightning protection to protect the equipment. The MOVs were secondary. More likely you were simply seeing the ground shift induced by using earth as part of the return path. That is inevitable with wye distribution, even if you do have a neutral conductor. Current does not take the path of least resistance, it takes ALL paths. The voltage drop on distribution lines is imposed on the earth. When we were investigating blown interface cards at a college campus I found up to 35 volts between "ground" on the various buildings. We found a number of solutions depending on the topology and geography but some customers just turned it over to the phone company, using leased phone lines between buildings that were a hundred yards apart. The other solution was copper, bonding "grounds" together, usually from machine frame to machine frame directly. We had to call it a "drain" and use black wire to avoid NEC problems. Nope, this was voltage induced into long runs of unshielded, twisted pair wires. Across the pair you didn't see it, but compared to ground you (properly) did. It's basic electronics 101. Unbalance the pair, which the MOVs did, and now the differential between the conductors is significant and you can hear the induced noise. It's exactly why RS-232 data is only good for 50ft (or with special, low capacitance cable up to 1,500 feet), and RS-422 is good for nearly 5,000 feet. RS-232 is single ended and is compared to ground (which you can't shake with induced noise), while RS-422 (or 485) is twisted pair. Hit the 232 with a 25 volt spike, and you just changed a 0 to a 1. But with 422, you are looking for a 5 volt difference between the wires. You don't care if they are 0 and 5 volts, or 20 and 25 volts, the data is still intact. Well, until it hits 1000 and 1005 volts, then you've blown up the receiver chip. But the data was still good! I am not going to argue with you but I was a physical Planning rep in a place with 200 thunderstorms in a typical year and I know what works and what doesn't. I have seen a lot of well credentialed EEs, usually from up north, fail miserably with their theories. The proof is always in the magic smoke that escapes when they guess wrong. We went from a couple "lightning" calls a day to a couple a year once we started implementing our strategies and ignoring all of the "ground loop" loonies. That's nice and all, but we aren't talking about thunderstorms. I've worked with many non-engineering types that thought they knew what they were talking about, but many of their practices were flawed, and it showed through in the end. Your attitude isn't uncommon. It's similar to class warfare, eh? :) Bottom line, I was dealing with induced AC on a twisted pair that was enough to turn on 180v MOVs. You can talk about ground differentials all you want, but that had absolutely NOTHING to do with what was happening in that situation. Have a good evening! You said the line to line was nominal so where was the MOV referenced? To "ground"? |
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