Parallel operation with STATE GRID

You mean that you want to feed the power to the grid. The parallelling gives a bit different meaning (as if you want to have a grid parallel to the state grid .

The question is, you said you are self reliant in power, but what is the excess power that you have?

If you have significant amount of excess, then only it is worth it, and that includes the off peak hours for you.

Next is the type of the prime mover. If it is say DG set, quick start and off, then may be you don't go for this aspect, Our factory has about 20MVA DG Set and they are stand alone, Switched on when the power supply fails, and off rest of the time. We can take the interruption, being machining industry, the critical portion, computers, hospitals etc are fed through UPS.

Feeding to grid is not much problem and a number of smaller generators are also feeding to the grid without any problem, you need the equipments and controls for this purpose- synchronising, load controlling etc.

And also check the beureaucratic angle - how comfortably can you get back your due.

There is no technical difficulty, nothing will happen to your machines, with proper controls in position, and already quite a few may be there since you are having your own grid with the sets in parallel.

The decision is management and economic.

This also needs the additional Stability Study of your system if fault occurs at the grid side so that your system doesn't have loss of synchronism in case of such fault.

-MS

Dear Friends

Thanks for the propmt replies from all of you.

I would elaborate a little more about our plant.

We have the DG set based power plant supplying power to our cement line, We are not connected to the state Grid as of date. However seeing the additional capacities in our engine , we have a plan to sell the excess power to the State grid. ( Lol ... nah nah i dont wish to have a grid parallel to state grid... We are not that BIg Players...lol ) The excess power which we can give to the state grid is in the range of 5-9 Mw , depending upon the availability of my engines..

I would like to know that if we connect to the STATE GRID, is there any compulsory rule that i have to give them some mimimum power all the time or take some minimum power from them all the time.. What i understand is that it should be on give and take basis , whatever extra i am producing, they will be giving it & if any of my engine trips then that extra power wont be available to them...without any legal obligation. & if i am in use of any additional power then i will be able to take from the STAte GRID.

Plgive your valuable comments.

Thanks & Best Regards

Technical issues here include:

- Export and import limits, control gear for kW and kVAR control

- Fault level when connected to grid Vs fault level of plant switchgear

- Grid-interconnector, location, voltage, control and protection

- Possible modification of existing generator parallelling controls

- Operator control systems modification to include for above

- Installation, commissioning and training

Interconnection with the grid may improve the availability of power to the plant as the grid becomes another option, depending on your circumstances.

- Ope

You are forgetting to give us the most important information first.

Where do you live, what country are you trying to do this in? Why haven't you contacted your local utility and asked them the very same questions you are asking us?

Most countries will let you tie into their grid, and they will allow you to us power off the grid if you need it. I have been involved in many co-generation projects and you have completed the first step (calculating how much power you can produce), now complete the second step by contacting the utility provider in you jurisdiction and find out what their rules are. If they are not too willing to have you connect in, maybe you can find another industry who might be willing to buy you power from you. Both of you can use some paralleling equipment keep the power separate.

Dear Friends..

Thanks you all for your valuable comments...

I do agree that every country have Grid regulations of their own. Main reason for my posting this querry was to understand various problems experienced by the Plants who have shared their Grid with the STATE ELECTRICITY GRID. ( Problems related to the overloading / load shedding )

Actually we are in saudi arabia. Irrespective of the country , you guys can share your experience of the technical problems experienced ( in the Power ) after sharing of your GRID with the STATE Electricity grid.Additonally you can also share your views about the tariff rules / Peak loading criteria /any special terms of condition of power sharing etc etc of your respective electricity board.

Once again thank you all for your valuable comments.

Thanks & Best Regards

Unless you are getting free fuel, it is unlikely that you can produce enough energy to sell to the "Grid" that will realistically matter for either you or the "Grid", at any cost savings/recovery for your generating system.

Do the math-- just how much does it cost you to generate power, and make sure you include costs for R & R. The longer you run an engine under the heaviest loads the sooner you will need replacement and scheduled maintenance. Add in every possible cost including price increases for parts and labor expected over the life of the equipment, and estimate the inflation factor for replacing the system at some time in the future based on cost per kwh. Then consider that you will not get the same price for the energy that you sell to the grid, as you would pay to the grid for commercial power.

TooMuchFun

Actually we were doing it with primary industry especially refineries since they product a lot of heat. Since its the byproduct of the process, it allows them to use the heat to run turbines and reuse it as electrical power and send the remaining onto the grid.

Payback was less than three years.

That is right along with what I was referring to. There is energy needed to produce the the product, likely natural gas, and as you say, there is available "free heat" that might be otherwise lost into the surrounding atmosphere, And: said heat is used to provide enough electricity to fill the needs of the facilities own requirements and still have a surplus that can be offed to the "Grid" at a price that offers a rapid payback and therefore said income offsets some of the cost of the original energy, like natural gas.

Not at all unlike raising cattle, the cost of the feed is offset by the dung that is recovered and sold as organic fertilizer. The calves produced will offset the cost of buying the cow in the first place, and ultimately return a profit, then, there is the tax savings one derives from having cattle on the land, "that is a lot" as the land increases in value, and this is all compared to the unreasonably high taxes one would pay for said land if it were only taxed as green belt or some other classification.

Just good business to consider the actual cost vs return!

Toomuchfun

Yep, anyway so the theory goes.

Hello Everyone,

I have a different problem concerning the same heading.

we have a captive power plant of 32 MW ( 5 Gas turbine generators of 11 KV, 6.5 MW each)

We are also connected to the state grid through 220 KV / 11 KV transformers and we have contractual demand of 2.5 MVA from the state grid. At a time we import around 2 MW from grid as per our needs.

We are self sufficient in our power consumption and thus we want to minimise grid billing charges to minimum. We want to this by putting grid in floating condition i.e. grid would always be synchronized to our system but we will not either import or export through it. In case any of our GTGs trips, we want grid to be our reliability option.

we have distance protection terminal REL 511 (ABB) and overcurrent earthfault prot terminal REL 505 (ABB) installed on our grid incomers.

Can you please tell me how should i change the settings of these two relays such that any fault on grid does not effect my captive power plant with this new condition of floating grid ?

Has a protection study of the interconnection system been prepared?

In order to achieve adequate protection, it may be more complex than a matter of adjusting some settings, due to the number of different scenarios.

During import, the interconnector performs the function of an incomer. During export, it performs the function of a feeder. For the zero import / export condition, directional elements and inter-trips may need to be considered. Therefore the protection relays may need to be configured with separate groups, each activated according to the function being performed.

For a zero import / export condition, additional protection may need to be considered such as rate of change of frequency and vector disturbance, in case there is a grid failure.

A protection study would cover it comprehensively.