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Utility poles

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101–110 of 213 posts

Re: Utility poles

#101

Post by femto »

andmarios wrote: post #94
s_tec wrote: post #41

Regarding three-phase power: The electrical outlets in your home have two power-carrying prongs. The third prong is just for safety (it connects to the ground), and should never carry power unless something is going horribly wrong. In that case, the power should hopefully prefer to reach the ground through that third wire than through your human body. Anyhow, the voltage in those two power-carrying wires is constantl…

There aren't any mathematical tricks, rather how the real world (generator) translates to math. The generator at the power company has 3 stators that are on equal distance between each other on a circle. As the rotor rotates, it induces AC voltage at each of them. Because the rotor rotates at a stable speed, the AC voltage follows a sine function. Because the stators are placed 2/3pi apart, their sine waves have a ph…

Expanding on this: because the neutral current is close to zero, the conductor for the neutral current has looser requirements on its impedance. With perfectly balanced phases the neutral conductor can be eliminated, saving money and material. In practise, the Earth itself gets used as the neutral conductor. This is why one sees three wires in transmission lines and not four.

Incidentally, the closely spaced multiple wires within each conductor of an electrical transmission line, typically held apart by spacers, act to reduce the inductance of the transmission line, which reduces losses. The little "dumbbells" which are on each side of each tower, are vibration dampers to reduce metal fatigue.

Re: Utility poles

#102

Post by phasetransition »

andmarios wrote: post #94
s_tec wrote: post #41

Regarding three-phase power: The electrical outlets in your home have two power-carrying prongs. The third prong is just for safety (it connects to the ground), and should never carry power unless something is going horribly wrong. In that case, the power should hopefully prefer to reach the ground through that third wire than through your human body. Anyhow, the voltage in those two power-carrying wires is constantl…

There aren't any mathematical tricks, rather how the real world (generator) translates to math. The generator at the power company has 3 stators that are on equal distance between each other on a circle. As the rotor rotates, it induces AC voltage at each of them. Because the rotor rotates at a stable speed, the AC voltage follows a sine function. Because the stators are placed 2/3pi apart, their sine waves have a ph…

Typical large generators will have between 12 and 24ph (in multiples of three). They're split out in triplets 120 degrees apart. If you see 12+ phases out in the wild, you're probably close to a power plant.

Re: Utility poles

#103

Post by phasetransition »

peteey wrote: post #72
dnm wrote: post #63

Earlier quoted context omitted.

> the voltage in those two power-carrying wires is constantly switching directions I'm not buying this (in the USA). I've been in my breaker box. For a typical 110 volt outlet, the black (hot) wire is connected to the breaker, which is connected to one of the wires coming into the house from the street. The white (neutral) wire is connected to the same ground bracket that the bare (ground) wire is connected to. 240 v…

Ground is literally the ground. The Earth makes a good return path. The hot wire is going positive and negative relative to the land you stand on.

This isn't true in your home. The neutral is bonded to ground at a single point, in the main panel of your house. Current essentially all returns on the neutral to secondary of the pole xformer. The Earth is much higher impedance than the path back to the pole. Even during a ground fault event the current returns on the ground (technically EGC) to the bond point in the panel, and then from there back to the secondary of the utility pole.

Grounding to earth itself mainly serves to hold the potential of your house near that of the pole.

Re: Utility poles

#104

Post by etimberg »

Sort of related, but if anyone finds this topic interesting and is looking for software positions related to power systems engineering the startup I work for is hiring. We create 3 phase unbalanced distribution system simulation and optimization software to enable PV & battery integration by utilities.

We currently have a number of open positions: https://www.opusonesolutions.com/careers/#navigation-positio...

Re: Utility poles

#106

Post by phasetransition »

ars wrote: post #51

> There are three because that is one way to change the three-phase power to single-phase, something I wish I understood better. No, that's not correct. Three transformers is for changing 3 phase medium power, to 3 phase regular voltage (for commercial customers). For single phase home customers, you run a single one of those phases along a street and attach center tapped transformers to it. The center tap means from…

FYI, this is the correct description of the vast domestic power in the US, which is a single phase of distribution on the primary side to a center tapped secondary transformer.

Re: Utility poles

#107

Post by gilbetron »

grzm wrote: post #22
gilbetron wrote: post #19

My dad was an electrician for about 40 years - one story he told me when he was training apprentices years ago was teaching them how to climb telephone polls. You wore boots that had spikes in the side of them, but when climbing, you had to keep your knees away from the poll so the spikes would dig in properly. Unfortunately, when you get to the top of the pole and look down, some people panic due to the height. And…

Nit: s/poll/pole/g

Sigh, thanks ;)

Re: Utility poles

#109

Post by eptil »

Dangeranger wrote: post #32
jedberg wrote: post #26

Earlier quoted context omitted.

> that there were perhaps 1000 poles out there that weren't on any of there maps I can totally see how this would happen. When I bought my house, the power/utility lines were hanging about four feet off the ground in my backyard. Apparently the previous owner didn't care. I called the utility company to complain, and they sent someone out with a new full size pole, who basically just shoved it in the ground in the co…

This is common at every utility. Part of the issue is based on the fact that the GIS systems do not align with the paper systems 100% and the paper systems are typically regarded as the standard. Another problem that must be considered is that utility workers, while highly competent at their profession, are not always great with working on computers. They generally write everything down on paper and then have one of…

This is only true at dysfunctional utilities. We dont even have paper maps and havent since the 90s. GIS is the standard for all our employees.

Re: Utility poles

#110

Post by Dangeranger »

adonovan wrote: post #47

Those cans are filled with transformer oil, which until relatively recently consisted mostly of polychlorinated biphenyls or PCBs. Imagine how many of those cans exist across the United States and you get a sense of how big the PCB industry used to be, and why rivers such as the Hudson in New York [1] and the Housatonic in Massachusetts [2] are polluted with olympic swimming-pool sized quantities of the durable oily…

The story about Kenyans selling PCB oil is truly sad. I cannot imagine the damage that is doing to children and families in that country.

It reminds me of the Vice News story about the illegal oil refineries which are present in the Niger River delta and the environmental and humanitarian destruction they are causing.

Additionally when authorities find illegally refined oil they simply dump it on site, contaminating the villages and markets where it is stored.

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