Power cords

[agedhorse]

Holy smokes, I studied power systems and industrial controls as part of my EE specialty course work back in the day and I recall the generators topping out around 500MW because of issues with the dimensions growing so large that torsion, shaft/armature (or rotating stator) sag caused the magnetic gap to grow to account for expansion and wear. This impacted efficiency, even running in a hydrogen atmosphere.

I looked at the GE website and I see they have crossed the 1000MVA mark and the 99% efficiency barrier. Mind blowing.

I mention the magnetic gap clearance challenge in the generators affecting efficiency which is exactly the same issue we have in speaker design, gap clearance is a tradeoffs common to both (similar) technologies.

 

[beans-on-toast]

In addition to the electrical ratings, there are other physical considerations.

Some power cords are rated to be used outdoors as well as indoors. Outer jacket sheathing material matters. Some are physically more flexible than others. There are different outlet plug sizes, compact vs ones that you can get a good grasp on. Some you can walk on although it’s not recommended. Length matters.

All amp power cords should come with a velcro strap.

 

[TomB]

What a cool thread! Thanks, y’all!

 

[OogieWaWa]

I mention the magnetic gap clearance challenge in the generators affecting efficiency which is exactly the same issue we have in speaker design, gap clearance is a tradeoffs common to both (similar) technologies.

I learned that somewhat when re-surrounding some home audio speakers (Infinity SM150s) and getting the coil centered. Very touchy. Find where it scratches in each direction and put it in the middle before the glue dries!

On the GE generator, if it comes to a stop for more than 5 minutes or so hot, you have to put it on 'turn gear' (aka jacking gear,) at about 3 RPM, until the sag (eccentricity) reduces to acceptable levels before spinning it back up, usually a few hours. If you look at it torn apart during maintenance, it actually 'clearances' itself during the first few hours of operation, you can see the wear marks! That doesn't quite work for speakers!

Yes, hydrogen gas core cooling (the gas with the lowest windage losses (= heat generation)) with fan blades on each end of the armature, they recirculate the H2 through external cooling coils; and the stator bars are cooled with demineralized water inside each one. Those "only 1%" losses still add up in the form of a lot of heat being generated, 10MW thermal must be removed somehow!

In case you can't tell, after well over a decade of operations, I went to training for twenty-five years, and the turbine-generator was one of my specialized systems. Extremely interesting, especially the mechanical side for me. I loved my job!

 

[TomB]

I learned that somewhat when re-surrounding some home audio speakers (Infinity SM150s) and getting the coil centered. Very touchy. Find where it scratches in each direction and put it in the middle before the glue dries!

On the GE generator, if it comes to a stop for more than 5 minutes or so hot, you have to put it on 'turn gear' (aka jacking gear,) at about 3 RPM, until the sag (eccentricity) reduces to acceptable levels before spinning it back up, usually a few hours. If you look at it torn apart during maintenance, it actually 'clearances' itself during the first few hours of operation, you can see the wear marks! That doesn't quite work for speakers!

Yes, hydrogen gas core cooling (the gas with the lowest windage losses (= heat generation)) with fan blades on each end of the armature, they recirculate the H2 through external cooling coils; and the stator bars are cooled with demineralized water inside each one. Those "only 1%" losses still add up in the form of a lot of heat being generated, 10MW thermal must be removed somehow!

In case you can't tell, after well over a decade of operations, I went to training for twenty-five years, and the turbine-generator was one of my specialized systems. Extremely interesting, especially the mechanical side for me. I loved my job!

Cool! This is very off-topic but has anyone in the engineering chain speculated about the recapture of 10 MW thermal? That’s hefty…

 

[dbase]

I was kinda thinking I knew something about power cords on page 1 of this thread but now we're on page 8 and I'm thinking, I have no business being here. Goodbye cruel world.

 

[agedhorse]

Cool! This is very off-topic but has anyone in the engineering chain speculated about the recapture of 10 MW thermal? That’s hefty…

Recapturing energy, either combined cycle from a conventional power plant or from mechanical losses is common these days when it can be used for things like space heating or process energy in manufacturing, or pre-heating feed/makeup water for the boilers.

 

[agedhorse]

I learned that somewhat when re-surrounding some home audio speakers (Infinity SM150s) and getting the coil centered. Very touchy. Find where it scratches in each direction and put it in the middle before the glue dries!

On the GE generator, if it comes to a stop for more than 5 minutes or so hot, you have to put it on 'turn gear' (aka jacking gear,) at about 3 RPM, until the sag (eccentricity) reduces to acceptable levels before spinning it back up, usually a few hours. If you look at it torn apart during maintenance, it actually 'clearances' itself during the first few hours of operation, you can see the wear marks! That doesn't quite work for speakers!

Yes, hydrogen gas core cooling (the gas with the lowest windage losses (= heat generation)) with fan blades on each end of the armature, they recirculate the H2 through external cooling coils; and the stator bars are cooled with demineralized water inside each one. Those "only 1%" losses still add up in the form of a lot of heat being generated, 10MW thermal must be removed somehow!

In case you can't tell, after well over a decade of operations, I went to training for twenty-five years, and the turbine-generator was one of my specialized systems. Extremely interesting, especially the mechanical side for me. I loved my job!

Agreed, fascinating stuff.

 

[OogieWaWa]

Cool! This is very off-topic but has anyone in the engineering chain speculated about the recapture of 10 MW thermal? That’s hefty…

Unfortunately the heat rejected in these systems is "low quality," in that the cooling water flow has to be high enough to maximize heat removal, but that means that its overall temperature rise is fairly low; like only 10-15 degrees above inlet temperature in the lake. This also minimizes the environmental impact, but makes it really difficult to use for anything else.

Sorry for being so off-topic, I tend to get carried away on this topic.

 

[agedhorse]

Unfortunately the heat rejected in these systems is "low quality," in that the cooling water flow has to be high enough to maximize heat removal, but that means that its overall temperature rise is fairly low; like only 10-15 degrees above inlet temperature in the lake. This also minimizes the environmental impact, but makes it really difficult to use for anything else.

Sorry for being so off-topic, I tend to get carried away on this topic.

Yup, as the delta T is lower, the recapture becomes proportionally more difficult. One way to recover thermal energy for process use is by using this energy in a large scale heat pump type process and this might be advantageous for plant or municipal heating but not as easy as extracting heat from the combustion gasses of a natural gas turbine.

As you might guess, lots of research goes into this topic because of the sheer scale of waste energy involved. Each segment of the process can contribute a fraction of a percent to the overall efficiency of a power plant but must also be weighed against the safety of the process. Especially in the nuclear power industry (which obviously can’t be overstated).

 

[byacey]

The three conductors from the generator to the main transformer are basically 18" diameter aluminum pipes, about an inch or so thick, because about 90% of the current is conducted in the outer 10% of any conductor anyway; so the design eliminates the entire inside of the conductor, and uses it as a tube for cooing air flow. Air goes into the inside in the middle of the three conductors, flows outwards towards the connection boxes at each end, and back to the water-cooled cooling unit in the housing around the conductors. Without cooling, load is restricted to 60%, I think.

Yup, as the delta T is lower, the recapture becomes proportionally more difficult. One way to recover thermal energy for process use is by using this energy in a large scale heat pump type process and this might be advantageous for plant or municipal heating but not as easy as extracting heat from the combustion gasses of a natural gas turbine.

As you might guess, lots of research goes into this topic because of the sheer scale of waste energy involved. Each segment of the process can contribute a fraction of a percent to the overall efficiency of a power plant but must also be weighed against the safety of the process. Especially in the nuclear power industry (which obviously can’t be overstated).

Years ago, we had the contract at one of our larger coal fired plants maintaining the emergency paging system. They had about eight 45RU racks loaded up with Bogen HTA 250W paging amps, installed on the second level of the generator hall. It was sweltering hot there in the summer, and I questioned why any engineer would have specified that placement, when there were much cooler locations available. It was a slow cook, with coal dust thrown in for good measure.

 

[OogieWaWa]

A Gai-Tronics system by chance?

A powerhouse is definitely a warm place. I fondly remember taking readings on the feedwater heater deck 60 feet above the turbine as a young equipment operator. 125 degrees. In the winter. You walked up, and using the handrails wasn't a good idea! Efficiency!!!

 

[byacey]

I don't recall who the original engineer was, or the installation contractor.
The whole affair seemed like an after-thought.

 

[S-Bigbottom]

I was kinda thinking I knew something about power cords on page 1 of this thread but now we're on page 8 and I'm thinking, I have no business being here. Goodbye cruel world.

How about how Oprah got her name?




For those that will not play Oprah's old audition tape where she explains her name, here is the transcript.

“Hi there. My name is Oprah Winfrey. Oprah, spelled O-P-R-A-H, and if you notice, it’s Harpo spelled backwards,” she says. “My folks did not really like Harpo Marx — we did not even have a television set for a number of years.

“Originally, I was named from the Bible by Aunt Ida, who named me from Ruth, the first chapter at the 14th verse, Orpah, but no one knew how to spell in my home, and that’s why I ended up being Oprah.”

 

[BlueTalon]

Cool! This is very off-topic…

Sorry for being so off-topic...

Don't sweat it. It's an interesting and educational diversion.

Besides, the power cord stuff was addressed previously.

 

[1958Bassman]

e controls the end voltage proportionally.

The three conductors from the generator to the main transformer are basically 18" diameter aluminum pipes, about an inch or so thick, because about 90% of the current is conducted in the outer 10% of any conductor anyway; so the design eliminates the entire inside of the conductor, and uses it as a tube for cooing air flow. Air goes into the inside in the middle of the three conductors, flows outwards towards the connection boxes at each end, and back to the water-cooled cooling unit in the housing around the conductors. Without cooling, load is restricted to 60%, I think.

At the transformer voltage is raised up to 345KV nominal at a couple of thousand amps and is sent down the four highlines. The MG set and voltage regulator I mentioned were redundant supplies for the control rods power. There are four reactor coolant pumps churning out 6,000HP on line (8,000 @ cold startup); the two main feedpump turbines were 12.5KHP each, 4KHP for four tertiary loop (cooling tower) pumps. Like I said, big stuff. Kind of a hoot to operate. Imagine 1.2 million Mesa 800s cranked....

How hot is the air coming out of the pipes, on average? Is there a way to use the heat?

 

[OogieWaWa]

How hot is the air coming out of the pipes, on average? Is there a way to use the heat?

Hmmm, it's been 40 years since I took local readings on that, but probably 150-200 degrees F. I think that the temperature rise on the heat exchanger coil's cooling water might have been 10-15 degrees at about, oh, thirty to a hundred gallons per minute. Ish. Somewhere in that area.

There are always ways to use heat, but from a return on investment perspective you reach a point where it isn't cost effective to do that any more. And not just financially, you'd have to balance the environmental impact, reliability and eventual system decommissioning costs of adding yet another system and maintaining it. There's a point where capturing and using the heat may take as much energy as it saves.

Edit: the reliability thing is a huge factor. You don't want to add a system for a million bucks, only to have it break and cause a 3-day outage that runs a million bucks a day for downtime.

The economics of scale are very high when you build something like one of these, so there's already a lot of advantage there, but there's also the law of diminishing returns. Like my favorite quote goes: "In theory, theory and practice are the same. But not in practice." These power plants are pretty much maximized for real-world efficiency, and frankly the biggest bang for the buck. This stuff is taken into account in the design process, it's not like it's ignored or anything.

Taking it back to the original topic, you could use a "bigger cord" for the plant than what the design requires, but is it really worth it?