Re: Reminder: Never connect a generator to home wiring without transfer switch
On 8/25/21 12:03, Jay Nugent wrote:
Greetings, And in that moment before the circuit breaker on your generator trips, your 120/240 volts has been stepped up to 7200 through the "pole pig" transformer in your neighborhood, and has KILLED the lineman working to fix that 7200 feeder circuit.
It only takes a MOMENT to stop someone's heart through electocution. It takes several milliseconds to pop a breaker.
And it would have only taken that lineman a few seconds to attach a grounding bond to the supposedly dead feeder and transformer before grabbing it bare-handed while speculating as to why it sounds like there's an engine running at constant RPM coming from the house connected to the service drop. Serious accidents are often caused not by a single failure but several. -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant. Things people underestimate in my opinion: Water. Wind. Transformers. Earthquakes. —L.B. Ms. Lady Benjamin PD Cannon of Glencoe, ASCE 6x7 Networks & 6x7 Telecom, LLC CEO lb@6by7.net <mailto:lb@6by7.net> "The only fully end-to-end encrypted global telecommunications company in the world.” FCC License KJ6FJJ
On Aug 25, 2021, at 12:22 PM, Jay Hennigan <jay@west.net> wrote:
On 8/25/21 12:03, Jay Nugent wrote:
Greetings, And in that moment before the circuit breaker on your generator trips, your 120/240 volts has been stepped up to 7200 through the "pole pig" transformer in your neighborhood, and has KILLED the lineman working to fix that 7200 feeder circuit. It only takes a MOMENT to stop someone's heart through electocution. It takes several milliseconds to pop a breaker.
And it would have only taken that lineman a few seconds to attach a grounding bond to the supposedly dead feeder and transformer before grabbing it bare-handed while speculating as to why it sounds like there's an engine running at constant RPM coming from the house connected to the service drop.
Serious accidents are often caused not by a single failure but several.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground? -A
Aaron, If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted. -mel On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG <nanog@nanog.org> wrote: On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE <lb@6by7.net<mailto:lb@6by7.net>> wrote: Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant. Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground? -A
I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area. That's what Ben seemed to be implying. -A On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org> wrote:
Aaron,
If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted.
-mel
On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG <nanog@nanog.org> wrote:
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
-A
On Mon, Aug 30, 2021 at 12:47 PM Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area.
I suspect that there is a non-zero amount of "in an ideal, perfect world, when all of the wires are simply lines on a piece of paper, and you can look at them from the comfort of your office chair, this is easy" - but, in the real world, linesmen are rushing about and trying to get the lights back on, cut through the big ash tree that is wedged between the oak and the pole, etc. Even the nice idea of "well, just take the conductos and tie 'em to ground" means that you need to go trudging through hedges and vegetation and tree limbs and lions and tigers and bears, often while it is pissing down with rain or baking hot. I guess I'm missing how we've moved from the "some people are putting their lives on the line, let's try to make their life less dangerous" into a "weeeeell... if they simply followed these set of steps perfectly at all times, and never made a mistake they'd be fine." This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot. Now consider this, but with the added drama of potentially ending up dead... W
That's what Ben seemed to be implying.
-A
On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org> wrote:
Aaron,
If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted.
-mel
On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG <nanog@nanog.org> wrote:
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
-A
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
During the February 2021 storm that swept through the US, power got knocked out on my rural street due to a tree coming down and taking out a pole. While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment. I doubt it's "if you follow every step perfectly at all times and never make a mistake". There are usually redundancies built-in when it comes to safety. i.e. what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED? -A On Mon, Aug 30, 2021 at 10:19 AM Warren Kumari <warren@kumari.net> wrote:
On Mon, Aug 30, 2021 at 12:47 PM Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area.
I suspect that there is a non-zero amount of "in an ideal, perfect world, when all of the wires are simply lines on a piece of paper, and you can look at them from the comfort of your office chair, this is easy" - but, in the real world, linesmen are rushing about and trying to get the lights back on, cut through the big ash tree that is wedged between the oak and the pole, etc. Even the nice idea of "well, just take the conductos and tie 'em to ground" means that you need to go trudging through hedges and vegetation and tree limbs and lions and tigers and bears, often while it is pissing down with rain or baking hot.
I guess I'm missing how we've moved from the "some people are putting their lives on the line, let's try to make their life less dangerous" into a "weeeeell... if they simply followed these set of steps perfectly at all times, and never made a mistake they'd be fine." This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot. Now consider this, but with the added drama of potentially ending up dead...
W
That's what Ben seemed to be implying.
-A
On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org> wrote:
Aaron,
If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted.
-mel
On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
-A
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
There are usually redundancies built-in when it comes to safety. i.e. what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED?
My uncle was a high tension lineman for much of his career. He was frequently on response teams that went all over the country helping restore power after severe weather or natural disasters. There are not 'usually' redundancies. There are ALWAYS redundancies. Because in that world, especially doing restorations, there are rarely opportunities to learn from a mistake. On Mon, Aug 30, 2021 at 1:48 PM Aaron C. de Bruyn via NANOG <nanog@nanog.org> wrote:
During the February 2021 storm that swept through the US, power got knocked out on my rural street due to a tree coming down and taking out a pole.
While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment.
I doubt it's "if you follow every step perfectly at all times and never make a mistake". There are usually redundancies built-in when it comes to safety. i.e. what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED?
-A
On Mon, Aug 30, 2021 at 10:19 AM Warren Kumari <warren@kumari.net> wrote:
On Mon, Aug 30, 2021 at 12:47 PM Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area.
I suspect that there is a non-zero amount of "in an ideal, perfect world, when all of the wires are simply lines on a piece of paper, and you can look at them from the comfort of your office chair, this is easy" - but, in the real world, linesmen are rushing about and trying to get the lights back on, cut through the big ash tree that is wedged between the oak and the pole, etc. Even the nice idea of "well, just take the conductos and tie 'em to ground" means that you need to go trudging through hedges and vegetation and tree limbs and lions and tigers and bears, often while it is pissing down with rain or baking hot.
I guess I'm missing how we've moved from the "some people are putting their lives on the line, let's try to make their life less dangerous" into a "weeeeell... if they simply followed these set of steps perfectly at all times, and never made a mistake they'd be fine." This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot. Now consider this, but with the added drama of potentially ending up dead...
W
That's what Ben seemed to be implying.
-A
On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org> wrote:
Aaron,
If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted.
-mel
On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
-A
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
On Mon, Aug 30, 2021 at 1:57 PM Tom Beecher <beecher@beecher.cc> wrote:
There are usually redundancies built-in when it comes to safety. i.e.
what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED?
My uncle was a high tension lineman for much of his career. He was frequently on response teams that went all over the country helping restore power after severe weather or natural disasters.
There are not 'usually' redundancies. There are ALWAYS redundancies.
Yup - and even with this, "an average of 45 linemen a year loses their lives in the line of duty, leaving families who depend on them." -- https://fallenlinemen.org/frequently-asked-questions/ The original point remains: "Reminder: Never connect a generator to home wiring without transfer switch".
Because in that world, especially doing restorations, there are rarely opportunities to learn from a mistake.
Indeed. W
On Mon, Aug 30, 2021 at 1:48 PM Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
During the February 2021 storm that swept through the US, power got knocked out on my rural street due to a tree coming down and taking out a pole.
While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment.
I doubt it's "if you follow every step perfectly at all times and never make a mistake". There are usually redundancies built-in when it comes to safety. i.e. what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED?
-A
On Mon, Aug 30, 2021 at 10:19 AM Warren Kumari <warren@kumari.net> wrote:
On Mon, Aug 30, 2021 at 12:47 PM Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area.
I suspect that there is a non-zero amount of "in an ideal, perfect world, when all of the wires are simply lines on a piece of paper, and you can look at them from the comfort of your office chair, this is easy" - but, in the real world, linesmen are rushing about and trying to get the lights back on, cut through the big ash tree that is wedged between the oak and the pole, etc. Even the nice idea of "well, just take the conductos and tie 'em to ground" means that you need to go trudging through hedges and vegetation and tree limbs and lions and tigers and bears, often while it is pissing down with rain or baking hot.
I guess I'm missing how we've moved from the "some people are putting their lives on the line, let's try to make their life less dangerous" into a "weeeeell... if they simply followed these set of steps perfectly at all times, and never made a mistake they'd be fine." This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot. Now consider this, but with the added drama of potentially ending up dead...
W
That's what Ben seemed to be implying.
-A
On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org> wrote:
Aaron,
If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted.
-mel
On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG < nanog@nanog.org> wrote:
On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE < lb@6by7.net> wrote:
Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant.
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
-A
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
-- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
Aaron, I think you didn’t get that the lineman was talking about equipotential grounding. The school of “waiting for a few more trucks to arrive” probably doesn’t get into the full depth of the subject :) -mel On Aug 30, 2021, at 10:46 AM, Aaron C. de Bruyn <aaron@heyaaron.com<mailto:aaron@heyaaron.com>> wrote: During the February 2021 storm that swept through the US, power got knocked out on my rural street due to a tree coming down and taking out a pole. While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment. I doubt it's "if you follow every step perfectly at all times and never make a mistake". There are usually redundancies built-in when it comes to safety. i.e. what's the point of installing grounds on the upstream side if you have the switch open? If the lines are de-energized, why wear gloves? If you're doing all that, why carry an AED? -A On Mon, Aug 30, 2021 at 10:19 AM Warren Kumari <warren@kumari.net<mailto:warren@kumari.net>> wrote: On Mon, Aug 30, 2021 at 12:47 PM Aaron C. de Bruyn via NANOG <nanog@nanog.org<mailto:nanog@nanog.org>> wrote: I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area. I suspect that there is a non-zero amount of "in an ideal, perfect world, when all of the wires are simply lines on a piece of paper, and you can look at them from the comfort of your office chair, this is easy" - but, in the real world, linesmen are rushing about and trying to get the lights back on, cut through the big ash tree that is wedged between the oak and the pole, etc. Even the nice idea of "well, just take the conductos and tie 'em to ground" means that you need to go trudging through hedges and vegetation and tree limbs and lions and tigers and bears, often while it is pissing down with rain or baking hot. I guess I'm missing how we've moved from the "some people are putting their lives on the line, let's try to make their life less dangerous" into a "weeeeell... if they simply followed these set of steps perfectly at all times, and never made a mistake they'd be fine." This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot. Now consider this, but with the added drama of potentially ending up dead... W That's what Ben seemed to be implying. -A On Mon, Aug 30, 2021 at 9:09 AM Mel Beckman <mel@beckman.org<mailto:mel@beckman.org>> wrote: Aaron, If you read back in this thread (using the NANOG mailing list archive), you’ll find this has been explained in great detail. In a nutshell, phase grounding won’t help if a generator is energized from the customer end, and this technique was discontinued in the 1970s due to the many deaths that resulted. -mel On Aug 30, 2021, at 9:02 AM, Aaron C. de Bruyn via NANOG <nanog@nanog.org<mailto:nanog@nanog.org>> wrote: On Mon, Aug 30, 2021 at 7:35 AM Lady Benjamin Cannon of Glencoe, ASCE <lb@6by7.net<mailto:lb@6by7.net>> wrote: Yes, this is a real and dangerous problem. Today. Even with grounding I’m afraid. Source: I’ve been working in an engineering capacity for 27 years and I have the license you’d need to build a nuclear power plant. Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground? -A -- The computing scientist’s main challenge is not to get confused by the complexities of his own making. -- E. W. Dijkstra
On 8/30/21 10:46, Aaron C. de Bruyn via NANOG wrote:
While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment.
I don't think anyone participating in this forum was remotely close to suggesting that anyone connect a generator to home wiring without a transfer switch in place. It's stupid and dangerous. The point that several brought up is that doing so is not only a bad idea, but that it simply won't work in the vast majority of power outage scenarios. Unless the outage is on your service drop or on your pole pig, the impedance of the neighborhood or city downstream of the outage as reflected through the transformers will vastly overwhelm any portable generator capable of being connected with a "suicide cord" by several orders of magnitude. The other point is that, assuming that the utility is following their safety protocols, the utility worker is going to ground the load side as well as the incoming feed specifically to prevent backfeeding the grid from a miswired generator. Yes, never connect a generator to home wiring without a properly installed transfer switch. Yes, the utility workers should ground the load side to avoid being killed in the event that someone does so. Yes, if the utility follows all procedures correctly, and you happen to connect your miswired generator at the exact instant that the utility worker removes the ground after making the connection, and said worker grabs the conductor with bare hands, and there's a path to ground through the worker's body at that instant, that worker is probably going to die. The probability of this happening is somewhat greater than that of winning the lottery, but if they're on a pole in the middle of a storm working on overhead wires, the odds of their being struck by lightning are also worth considering. It's a warning worth repeating, but probably not to this extent.
This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot.
Don't forget the classic "switchport trunk allowed vlan" vs. "switchport trunk allowed vlan add". -- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
The point that several brought up is that doing so is not only a bad idea, but that it simply won't work
Jay, I’ve had this scenario play out several times: DIYguy: Check out my new generator! It’s big enough to power the whole house! Me: You run extension cords from the generator to all your devices then? DIYguy: No need! I built this special “suicide cord” I read about online in a prepper forum. I just plug that into any wall outlet and it powers the whole house! Me: Um, you haven’t tested this, have you? DIYguy: Sure. I fired up the generator and plugged the dryer into it. Works a treat! Me: No, I mean your special cord. Have you tested that? DIYguy: Hey, if it'll power the dryer, it’ll power my whole house. No need to test! Me: Ok, first of all, that’s not a “suicide cord”. That’s a “homicide cord”. Second, … The problem with this scenario is that the DIYguy never finds out that it won’t work, at least not until the trial. :) -mel
On Aug 30, 2021, at 11:25 AM, Jay Hennigan <jay@west.net> wrote:
On 8/30/21 10:46, Aaron C. de Bruyn via NANOG wrote:
While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions. They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator. They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment.
I don't think anyone participating in this forum was remotely close to suggesting that anyone connect a generator to home wiring without a transfer switch in place. It's stupid and dangerous.
in the vast majority of power outage scenarios. Unless the outage is on your service drop or on your pole pig, the impedance of the neighborhood or city downstream of the outage as reflected through the transformers will vastly overwhelm any portable generator capable of being connected with a "suicide cord" by several orders of magnitude.
The other point is that, assuming that the utility is following their safety protocols, the utility worker is going to ground the load side as well as the incoming feed specifically to prevent backfeeding the grid from a miswired generator.
Yes, never connect a generator to home wiring without a properly installed transfer switch.
Yes, the utility workers should ground the load side to avoid being killed in the event that someone does so.
Yes, if the utility follows all procedures correctly, and you happen to connect your miswired generator at the exact instant that the utility worker removes the ground after making the connection, and said worker grabs the conductor with bare hands, and there's a path to ground through the worker's body at that instant, that worker is probably going to die. The probability of this happening is somewhat greater than that of winning the lottery, but if they're on a pole in the middle of a storm working on overhead wires, the odds of their being struck by lightning are also worth considering.
It's a warning worth repeating, but probably not to this extent.
This is NANOG -- I'm sure that we've all followed a set of steps perfectly and still managed to redistribute BGP into the IGP, or apply an ACL and lock ourselves out of a box, or types "show run" and watched the router randomly reboot.
Don't forget the classic "switchport trunk allowed vlan" vs. "switchport trunk allowed vlan add".
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
I was catching 5 minutes of CNN earlier this morning down here, and Gov. Edwards (LA) was appealing to folk running generators to make sure they don't die from smoke inhalation, due to using them inside the house so as to keep them away from water. Apparently, many have died post-storm due to fume inhalation toxicity. Perhaps advising folk not to run the units without a changeover switch might have been too much to ask, as well. Thoughts and prayers for all the folk out in LA, this week. Mark.
Aaron, Your incorrect assumption is that lineman are tying phases to earth ground, a discontinued practice that killed many lineman up through 1980, despite its seeming faultless logic. The current safety practice is called “equipotential grounding”, which doesn’t go to earth. Thus an backed can change the balance of potentials, resulting in lethal currents. As other have pointed out with real-word examples, this is a major safety issue, cause by the many “dumb enough” DIYers out there. All explained elsewhere in the thread. I recommend you review the previous discussion, to avoid creating a NANOG bridge loop :) -mel On Aug 30, 2021, at 9:43 AM, Aaron C. de Bruyn <aaron@heyaaron.com<mailto:aaron@heyaaron.com>> wrote: I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area. That's what Ben seemed to be implying.
Yes, most grounding out now that utilities do for work is all phases to one another, to the neutral and to the ground. From: NANOG <nanog-bounces+john=vanoppen.com@nanog.org> On Behalf Of Mel Beckman Sent: Monday, August 30, 2021 10:59 AM To: Aaron C. de Bruyn <aaron@heyaaron.com> Cc: NANOG Operators' Group <nanog@nanog.org> Subject: Re: Reminder: Never connect a generator to home wiring without transfer switch Aaron, Your incorrect assumption is that lineman are tying phases to earth ground, a discontinued practice that killed many lineman up through 1980, despite its seeming faultless logic. The current safety practice is called “equipotential grounding”, which doesn’t go to earth. Thus an backed can change the balance of potentials, resulting in lethal currents. As other have pointed out with real-word examples, this is a major safety issue, cause by the many “dumb enough” DIYers out there. All explained elsewhere in the thread. I recommend you review the previous discussion, to avoid creating a NANOG bridge loop :) -mel On Aug 30, 2021, at 9:43 AM, Aaron C. de Bruyn <aaron@heyaaron.com<mailto:aaron@heyaaron.com>> wrote: I've been following the thread. If I'm dumb enough to back feed through the transformer into the downstream side of the downed line, how is it going to be a problem if linemen are grounding the phases on *both sides* of the work area. That's what Ben seemed to be implying.
On 8/30/21 17:59, Aaron C. de Bruyn via NANOG wrote:
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
I'm not sure if it applies to work sites for linesmen, but my limited understanding is that you don't generally want to ground at more than one point. Mark.
https://www.csemag.com/articles/grounding-points-single-or-multi/
On Aug 30, 2021, at 09:10, Mark Tinka <mark@tinka.africa> wrote:
On 8/30/21 17:59, Aaron C. de Bruyn via NANOG wrote:
Would you care to educate me on this? If you ground the phases on both sides of the work-site, how are you going to end up being a better path to ground?
I'm not sure if it applies to work sites for linesmen, but my limited understanding is that you don't generally want to ground at more than one point.
Mark.
On 8/30/21 18:20, Herb L wrote:
https://www.csemag.com/articles/grounding-points-single-or-multi/
Even they conclude that multiple grounding points should all converge at the main single point. Grounding is probably the most misunderstood element of electricity. In cases where earth and neutral may be bonded, grounding at more than one point is generally ill-advised. Mark.
participants (9)
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Aaron C. de Bruyn -
Herb L -
Jay Hennigan -
John van Oppen -
Lady Benjamin Cannon of Glencoe, ASCE -
Mark Tinka -
Mel Beckman -
Tom Beecher -
Warren Kumari