Generator and electricity flow

[Lineman North Florida]

I'll throw in 2 cents worth here, most people think that all they are putting back on the line is 120/240 when in fact all they are putting back in the distribution transformer is 120/240 on the secondary side which operates in reverse as well if your normal primary voltage is 7200 volts phase to ground that is exactly what the voltage reading will be at the top of the distribution transformer when it is being backfed via a home generator. A lineman can do everything right on his side open check open, test, tag and ground the line and step up a pole where the fuse is blown on the transformer and if he doesn't hear the generator running over all the chain saws equipment etc he could get in trouble even with all his protective devices in place. Backfeed is very real and distribution transformers work just as well stepping up voltage as they do stepping it down, what I have written here is fact not here say. Charlie.

 

[CNC Dan]

Actually it isn't the largest unit. All connected generators and connected rotating mass at the loads (pumps, fans, motors, etc) are all acting as one big animal.

I thought that was only for synchronous motors.

 

[Ken]

Actually it isn't the largest unit. All connected generators and connected rotating mass at the loads (pumps, fans, motors, etc) are all acting as one big animal. All this rotating mass connected together is against the next item to sync in. The electric grid of the united states is the largest machine in the world. The eastern interconnect of America (east coast to Rockies) is the largest grid on the same frequency. The rest of the country is tied to it via DC ties allowing a different frequency.

O'k I was refering to 60 hertz or old time cycles. Not all systems or frequencys used in this world.
The Freq. Monitering Network Located at Univ.of Tenn.&Tenn. power system sets the freq. of N.American power grid. For the primary reason of accurite frequency control. And a mismatch of freq. or phase of 0.5Hz. will result in Automatioc load shedding to maintain the network control.
Not getting into my little 5 k.w. gen will upet your power system .The rotating Mass the Volts and Amp.keeps the system running smoothly the Vars is like foam on top of beer looks good and keeps the flaver in but keeping it down is the desirable condition. Any large upset Its like a turtle running over a slug. it all happens so fast.
ken

 

[lostcause]

just curious... the original poster said that installing a transfer switch required open slots for breakers... the house i live in has had a transfer switch for 12-14 years - it's a 10 circuit manual transfer switch. basically, for each of the 10 circuits it controls, it has a 3 position switch - line, generator and center off. the essential circuits were plumbed in: furnace, water pump, fridge/freezer, and the rest to lights and outlets. it taps in to the existing branch circuits after the breaker, so there are no extra slots required.

it's not a dirt cheap alternative, but it is simple enough for even the technologically challenged to use safely. i backfed the panel in my old house during the ice storm of '98. my old house didn't have any sort of generator hookup, and during that 14 day power outage in february there wasn't any chance of doing a proper job before things froze. i knew how to safely hook things up safely so nobody could get hurt, and i made sure to undo all my changes each time i shut the generator off. i know this matters not to the safety police, because i could have died of a freak heart attact at the fit age of 28, or someone could have broken in and caused havoc. sleep well tonight knowing that i'm not placing anyone in danger with my shoddy electrical practices today, though i'm sure i am endangering them in some other way.

 

[dave1949]

just curious... the original poster said that installing a transfer switch required open slots for breakers... the house i live in has had a transfer switch for 12-14 years - it's a 10 circuit manual transfer switch. basically, for each of the 10 circuits it controls, it has a 3 position switch - line, generator and center off. the essential circuits were plumbed in: furnace, water pump, fridge/freezer, and the rest to lights and outlets. it taps in to the existing branch circuits after the breaker, so there are no extra slots required.

it's not a dirt cheap alternative, but it is simple enough for even the technologically challenged to use safely. i backfed the panel in my old house during the ice storm of '98. my old house didn't have any sort of generator hookup, and during that 14 day power outage in february there wasn't any chance of doing a proper job before things froze. i knew how to safely hook things up safely so nobody could get hurt, and i made sure to undo all my changes each time i shut the generator off. i know this matters not to the safety police, because i could have died of a freak heart attact at the fit age of 28, or someone could have broken in and caused havoc. sleep well tonight knowing that i'm not placing anyone in danger with my shoddy electrical practices today, though i'm sure i am endangering them in some other way.

Thank goodness! :laughing: I think the issue is that predictability and adhering to some simple rules promotes safety. We don't drive down the road and decide which STOP signs we will actually stop at and expect to live very long.

I just don't get the mulish reluctance to conform to something that can save a life--no matter how slim the chances, or risk a ruined generator due to simple human error. Nobody is error free, I do question the human part for some posters :thumbdown: They don't appear to put much value on the lives of others.

The '98 ice storm was something else. I could say you should have been prepared, but in lieu of that, if you knew what to do to be safe and did it, or got advice, then you were meeting an emergency situation as best you could. I lived in Wells then, we never lost power. But, at the time I had an eight circuit transfer panel installed and no generator so, I wasn't prepared either.

 

[jejeosborne]

I thought that was only for synchronous motors.

I believe asynchronous motors as well but I am no motor expert. Even asynchronous motors rpm is based off frequency. Just not directly linked because they have some slip. If frequency drops so does the speed of both.

 

[jejeosborne]

O'k I was refering to 60 hertz or old time cycles. Not all systems or frequencys used in this world.
The Freq. Monitering Network Located at Univ.of Tenn.&Tenn. power system sets the freq. of N.American power grid. For the primary reason of accurite frequency control. And a mismatch of freq. or phase of 0.5Hz. will result in Automatioc load shedding to maintain the network control.
Not getting into my little 5 k.w. gen will upet your power system .The rotating Mass the Volts and Amp.keeps the system running smoothly the Vars is like foam on top of beer looks good and keeps the flaver in but keeping it down is the desirable condition. Any large upset Its like a turtle running over a slug. it all happens so fast.
ken

Not sure where you are getting your information but some of it is not correct. The North American grid is made up of 4 separate grids that each have their own frequency. Each of the 4 interconnects have their own time monitor. The largest interconnect (eastern) is the one I am most familiar because I work for an electric utility in this interconnect. Our time monitor is MISO (Midwest Independent Transmission System Operator) based in Carmel Indiana and St. Paul Minnesota. Not Tennessee. Before MISO it was AEP. When the time error reaches 10 seconds fast or slow, ALL generators in our interconnect, will adjust the generator governors to either 59.98 if fast or 60.02 if slow to get the time back and close to equal of the atomic clock in Boulder Colorado (NIST Laborities). If all the generators were not participating, the governors of those not participating would fight and try to maintain 60 hz and nothing would get accomplished. We adjust this frequency in our computer system all at the same start and end times.

As far as load shedding, there are different schemes for different purposes. I have the authority to manually shed load if I feel it is necessary. Can be done with a couple of mouse clicks. Load shedding is set up to take place in steps. Something like, first stage at 59.7 hz, second stage at 59.3 hz. And so on. Hopefully the system will stabilize before more drastic things happen. The grid being so large is much more stable and reliable because it is somewhat self healing. Imagine all the generators and load and the stored energy that is connected. A lot of mass spinning together. When frequency dips, the rpms of all the connected motors slow and the energy saved from this makes it self healing to a point. Same thing for high frequency but more energy is being used. Unfortunately though there is also more to lose in the event of a major disturbance and it could be a lengthy outage if the whole interconnect were ever to go down.

Reactive power (VARS) is another story. VARS or MVARS in my case are VERY important to the grid. Reactors and capacitors are strategically placed throughout the system to keep the values in check. Capacitors need to be close to the consuming loads because vars are difficult to transfer down the transmission lines from the generator. Your beer comparison makes it sound like they are not desirable but they are.

http://www.nerc.com/docs/oc/rs/NERC Balancing and Frequency Control 040520111.pdf

 

[jejeosborne]

jejeosborne thanks for clearing up my misconception about power generation phase angles.

A few years ago the scouts were touring Lake Barkley KY power control room. They brought online another dynamo. The guy synced it up with a dial I think but there was still a lot of shaking and another guy was ragging him about it.

Well we share some common interest. I was a scout leader for years and my family makes it to Kentucky and Barkley lake a couple of time a year to boat or motorcycle ride at turkey bay. The dial is called a sync scope, I have been to that control room as well. Hydro units are interesting. Wish we has some on our system. Our green energy is wind that we have no control of.

 

[Qapla]

Let's let the linemen alone for a moment and consider this.

Person A loses power, as does his neighbor, person B. Mr. A back-feeds his house withOUT a correct disconnect for it, thus opening his system to the line. Mr. B back-feeds his home. He also does not have proper protection for his system and also is "feeding the line".

Now, you have two houses both feeding the line. When one, or both, of the generators fails do to the other, who is to blame? The one who hooked up second?

Now, suppose for this example, Mr. C, who has also lost power, goes out to check his system and finds that he has a downed line in his back yard. The line is down from a pole in his back yard, broken at the power company end ... thus should be dead. His dog hears him and comes running out from his doghouse and steps on the down line. Of course, the line is not dead because one of his neighbors has the generator running and the don is electrocuted. Who is to blame? The dog? Mr. C?

Think ... DON"T improperly/illegally feed power to a house ... PERIOD!!!!

 

[Ken]

Not sure where you are getting your information but some of it is not correct. The North American grid is made up of 4 separate grids that each have their own frequency. Each of the 4 interconnects have their own time monitor. The largest interconnect (eastern) is the one I am most familiar because I work for an electric utility in this interconnect. Our time monitor is MISO (Midwest Independent Transmission System Operator) based in Carmel Indiana and St. Paul Minnesota. Not Tennessee. Before MISO it was AEP. When the time error reaches 10 seconds fast or slow, ALL generators in our interconnect, will adjust the generator governors to either 59.98 if fast or 60.02 if slow to get the time back and close to equal of the atomic clock in Boulder Colorado (NIST Laborities). If all the generators were not participating, the governors of those not participating would fight and try to maintain 60 hz and nothing would get accomplished. We adjust this frequency in our computer system all at the same start and end times.

As far as load shedding, there are different schemes for different purposes. I have the authority to manually shed load if I feel it is necessary. Can be done with a couple of mouse clicks. Load shedding is set up to take place in steps. Something like, first stage at 59.7 hz, second stage at 59.3 hz. And so on. Hopefully the system will stabilize before more drastic things happen. The grid being so large is much more stable and reliable because it is somewhat self healing. Imagine all the generators and load and the stored energy that is connected. A lot of mass spinning together. When frequency dips, the rpms of all the connected motors slow and the energy saved from this makes it self healing to a point. Same thing for high frequency but more energy is being used. Unfortunately though there is also more to lose in the event of a major disturbance and it could be a lengthy outage if the whole interconnect were ever to go down.

Reactive power (VARS) is another story. VARS or MVARS in my case are VERY important to the grid. Reactors and capacitors are strategically placed throughout the system to keep the values in check. Capacitors need to be close to the consuming loads because vars are difficult to transfer down the transmission lines from the generator. Your beer comparison makes it sound like they are not desirable but they are.

http://www.nerc.com/docs/oc/rs/NERC Balancing and Frequency Control 040520111.pdf

jejeosborne. Good information. took the information from Measurments and Electriacl Engineering book part 2 written by Roland Marshall Prof of engineering Purdue University. Ind. Uhmm in 1943

A side note also Retired from Ark power and Light 18 years ago Company now Entergy of Ark. Breaking away from Entergy group System due to we had the transmission lines 500 K.V. and 2 900 Mw units Nuke plant and 2 900 Meg. Watt coal fired plants and having to give the profits to Miss or La. to pay there continous bills. by Federlly mandated equalization payments. (Never let the camel stick its nose in the tent because soon the whole animal is in inside telling you how to generate power.)Also merging the trasmission lines with ITC Holdings to be completed in 2013. Talk about a fresh breeze blowing 30 years of legal wrangling
over who owns power plants we built.
Your giving good electrical information I was trying to get those who think any method to lite a bulb is o'k . To rethink the methods.
ken