How is power sold directly between generator and remote user across different utility entities?

[rockman7892]

This is a question which I've wondered about for quite some time and although I think the answer comes down to commercial agreements as opposed to flow of electrons I was curious to hear from some of the experts here.

As an example I've heard of scenarios where a new generation plant or renewable asset was being built to provide power to a particular customer (say large data center) or load center that may be located in a very remote geography from the generation plant (for example lets say across a state or even multiple states away). There is an example here in FL where I am with a generation plant in the central part of the state being used to alleviate generation and cost in the southern part of the state.

In the example above lets say there are no direct transmission lines to serve load centers directly from generation and thus power must flow across bulk power transmission system to reach its load. Obviously the flow of electrons and power cannot be controlled and thus in above scenarios generation power may flow through multiple utilities, municipals, etc... In this case how exactly does a remote generator impact a customer in a remote location directly when it has to pass through several other utilities or stakeholders?

I'm assuming it has something to do with commercial and bilateral agreements between stakeholders but cant quite put my finder on it. I don't see how a bilateral agreement between two remote locations can stand alone when the power flow from point a to b is impacted by general electrical wholesale market (day ahead trading etc..).

Would love to learn how this process works if anyone has insight.

 

[LittleInch]

There should have been a "not" in front of supplying power....

The way grid systems work in actuality is clearly complex with interweaving responsibilities and actions so no wonder most people don't have a clue...

 

[crshears]

Quoting waross:
In a wheeling situation, the generating system may have a transformer to connect to the wheeling grid.
That is what I meant by the supply transformer.
By grid I meant the wheeling system and its transformers.

If I'm picturing what you're saying correctly, that places "supply transformers" and grid transformers" in series, if viewed in a brutally simplistic power flow way.

 

[waross]

We have three grids or systems.
A the supplying system.
B the wheeling system.
C The receiving system.
At the Point of Common Coupling between A and B, and at the PCC between B and C, the PF or the flow of VARs may be adjusted by voltage adjustments.
Wheeling power at unity power factor is the most efficient use of transmission line KVA capacity for a given kW transfer.
While VAR flow by voltage adjustments may be theoretically possible, it appears from information provide here that there may be technical reasons why this is not always done in practice.
That is my point, CR.

 

[crshears]

Hi Bill,

Gotcha.

In my practice, VAR flows on both our system and between us and our neighbours were indeed optimized to provide for the maximum system capacity, whether for simple power flows within our own system or for wheeling purchases through.

Interestingly enough, though, at the Ontario-Michigan interface, the tie line voltage regulators were essentially always operated on manual, and periodically adjusted so as to maintain the preferred voltages on either side of the international border; some nominal VAR flows therefore tended to be present the vast majority of the time, but since in the main these did not constrain the transfer of real power through the tie lines the presence of said MX was mostly ignored.

Fun thread!

 

[waross]

Thanks for adding real world practice to the theory, CR.

 

[crshears]

Any time.

 

[rockman7892]

Thanks for all the input, this has been an interesting read and learning experience.

To add to my earlier example here in FL, given that FPL seems to be the transmission owner/operator in most of the state i'm assuming they'd be the one wheeling the power in example of power purchase agreement between two entities in north and south of state. For example if an IPP in north Florida generates power for a municipal in south FL then it seems like the municipal would have a direct agreement with IPP for that power and would pay FPL for wheeling or transmission of that power. Is that correct?

Since FPL also generates power I'm assuming that any municipal wishing to purchase power from FPL has this purchase power agreement directly with FPL in this case for the generation and transmission of power?

Since FL does not have a regional transmission system operator or balancing authority, is it likely that FPL responsible for this role along with other IOU's operating in FL?

 

[rockman7892]

We have three grids or systems.
A the supplying system.
B the wheeling system.
C The receiving system.
At the Point of Common Coupling between A and B, and at the PCC between B and C, the PF or the flow of VARs may be adjusted by voltage adjustments.
Wheeling power at unity power factor is the most efficient use of transmission line KVA capacity for a given kW transfer.
While VAR flow by voltage adjustments may be theoretically possible, it appears from information provide here that there may be technical reasons why this is not always done in practice.
That is my point, CR.

To follow this simple example lets say receiving system in C is pulling load at a .85 lagging pf. Are you saying that the voltage between A & B could be adjusted to that B had a higher voltage than A to the extent necessary to offset lagging reactive power from A and thus make unity PF on B. And then likewise at the exchange between C & C operate the voltage at B slightly higher than C to the extent necessary to supply the reactive power to the loads in C?

 

[LittleInch]

A couple of good reads here.Florida did look a little odd the way it works but it is all part of a bigger grid so needs to pay by FERC rules.

Florida's Electricity Generation by Source: Gas Rules but Solar Gains Ground | PCI

Explore Florida's electricity generation by source powering its unique landscape, from reliance on natural gas to growth in solar capacity.

www.pcienergysolutions.com

Power Grid Fundamentals and Electricity Pricing | EnergyCAP

This eBook provides energy stakeholders an overview of the structure and function of the electricity grid in North America.

www.energycap.com

 

[crshears]

rockman7892: To follow this simple example lets say receiving system in C is pulling load at a .85 lagging pf. Are you saying that the voltage between A & B could be adjusted to that B had a higher voltage than A to the extent necessary to offset lagging reactive power from A and thus make unity PF on B. And then likewise at the exchange between C & C operate the voltage at B slightly higher than C to the extent necessary to supply the reactive power to the loads in C?

More or less, yes; if B has a Static VAR Compensator it would typically be capable of metering the [sum of the] reactive power coming in from A and then ramping itself on a feedback basis until the vectorial sum of reactive power flowing from A to B is zero. Note however that providing more control options increases capital cost, and the control scheme may very well be set up quite simply with only one control option, viz., to hold the HV bus voltage at B to a set value by modulating the SVC output as required.

And yes, B may be asked to supply reactive power to C, and if line loading is light this may well be a helpful voltage control strategy, especially overnight during spring and fall weekends. Indeed I have seen at such times entire 500 kV circuits removed from service exclusively for voltage control purposes.

If however line loadings are near their limits, the transmission line operator may well refuse this request, meaning that VAR resources local to C would be employed - and this is probably what C would do during peak anyway, as local voltage profiles are generally improved when this is done.

 

[davidbeach]

Of course, the supplier dumps their output into a vast pool and the consumer draws from that same vast pool. Accountants can link supplier to consumer but there are no laws of physics that can produce the same result.

Just like on the west coast, BC Hydro can sell to San Diego, but I doubt that BC Hydro’s output even makes it into Oregon. Heck, BC Hydro can sell to San Diego while power flow across the California-Oregon border is south to north.

 

[cuky2000]

Hi Rockman, in your initial post you mentioned that the electricity is a flow of electrons, but in reality is not the case.
The electron drift velocity in a conductor is very slow where the average speed at which electrons travel in a conductor when subjected to an electric field, is about 1mm per second.

If there is a transformer or capacitor, as shown in the picture below, the path of the flow of electron have some challenger but the energy flow uninterrupted.

 

[LittleInch]

Thanks for all the input, this has been an interesting read and learning experience.

To add to my earlier example here in FL, given that FPL seems to be the transmission owner/operator in most of the state i'm assuming they'd be the one wheeling the power in example of power purchase agreement between two entities in north and south of state. For example if an IPP in north Florida generates power for a municipal in south FL then it seems like the municipal would have a direct agreement with IPP for that power and would pay FPL for wheeling or transmission of that power. Is that correct?

Since FPL also generates power I'm assuming that any municipal wishing to purchase power from FPL has this purchase power agreement directly with FPL in this case for the generation and transmission of power?

Since FL does not have a regional transmission system operator or balancing authority, is it likely that FPL responsible for this role along with other IOU's operating in FL?

It would appear that yes FPL would be the entity charging for transmitting power from generator to user.

Yes if FPL is supplying power then they will roll up their own transmission / grid costs into the power purchase agreement. They might have to split them out for regulatory purposes, but maybe not.

Its not clear how the entities in Florida work together, but they are interconnected and are part of the eastern US grid system. It would appear that each party is their own grid system, but with the ability to import or export power as required or needed to keep the lights / A/C on. The FPL grid is probably bigger than some smaller countries entire system so it can smooth out loads and generation itself normally, but has the back up of a larger system if something happens like a hurricane or extreme weather event (hot or cold or wet).

 

[crshears]

Hello all,

I've been searching for info to fill out my understanding of the operation of Florida's bulk power system, and came across this: https://www.nrel.gov/docs/fy21osti/79385.pdf

The document is principally about the growing amount of solar power feeding Florida's grid, but beginning on page 12 does provide an overview of the state's bulk electricity system. I haven't read it in minute detail, but a preliminary scan suggests this might help those of you with questions about it.

 

[dauwerda]

I feel like this video from "Practical Engineering" is very relevant to this discussion (or maybe this thread was started as research for this video ):

Which Power Plant Does My Electricity Come From?​

 

[crshears]

I had a look at it; pretty good! Shows just how ridiculous the electricity markets have gotten and can get at times . . .

 

[crshears]

I had a look at it; pretty good! Shows just how ridiculous the electricity markets have gotten and can get at times . . .

More on this . . .

Also watched the same content producer's "The Most Confusing Thing About The Power Grid", where he mentions Australia converting retired thermal generating station units into synchronous condensers to maintain better system inertia; anyone know more about this? You may recall I used to run one of these . . .

Moreover, found the video on IBR [Inverter Based Resources} interesting; I was not aware of MPPT controllers, but it makes perfect sense.

 

[waross]

The transmission line feeding the city of La Ceiba in Honduras had reached full capacity and the city was still growing.
The capacity was governed by the ability of the OLTCs to compensate for transmission line voltage drop.
An old diesel plant, that was the first electric power supply to the city was put back into into service and run as synchronous condensers to supply VARs and raise the voltage at the city end of the transmission line.
The sets were run a very low throttle settings to save on the cost of fuel. They needed the KVARs more than the kWatts.