Connecting a Generator in Parallel

Using a "ATS" Automatic Transfer Switch from any reputable generator company will be able to help you automatically switch back to utility in the event the gen-set trips. some companies I have worked with in the past are. Asco, Caterpillar, Onan, Kohler, Eaton, Siemens and the like. Usually the ATS is arranged as the utility as the main source of power with the gen-set as a backup since using fuel converted to electricity is quite a bit more expensive than using the utility provided power source. If you were doing a co-gen application by using both the utility and gen-set together and synchronized the ATS would not work as it is for connecting your electrical distribution system to either the utility or the gen-set.

the generator is coupled by steam turbine.not a diesel engine

yes,with a properly designed panel,but with a laps for resynchlonizing.

Dear sir,
no i think you did n`t understand me,let me say it as an example.
example:
First:i connect both the generator and power grid feeder in the same bus bar to make the synchronization.
second:i disconnect the circuit breaker of feeder after making synchronization and supplying loads from generator only.
third:all loads supplied from generator only.


my question is i want to keep the power grid feeder to be connected with the generator on the same bus bar even after making synchronization,to supply loads if generator stops for any reason?so is it possible to do it? and how?

Why do you remove Gen from grid ???

To take into your account it`s our generator and it supply our sulfuric acid plant,and we take a feeder from power grid but i want to supply the unit from generator all the time,but when the generator stops for any reason,so at the same time the feeder of power grid automatically continue supplying the loads.

Why don't you keep the generator On line feeding to the grid and from the generator output take in your supply ?

It becomes as if you are feeding to grid and the same amount taking out of it.

Only the loss will be when you feed more and take less from the grid.

When the Generator tripe (due to mech fault) , its input supply can be cut off -till then any way it will run as Induction motor)

idon`t want generator to supply the grid, i want generator to supply my loads,but to make sure of stability of suppling my loads i want to put aslo feeder of power grid in the same busbar even after making synchronization and never remove feeder to sure my loads never stops.

It's a bit confusing, but one gets the impression that you are producing your own power supply from some economic source with in your own plant, and it would not be to your advantage to export this into the main bus where you would not be payed for it, hence the reason to isolate the main bus? It would seem that you need to negotiate with your supply utility?

Regards JD.

Hi there,

The solution is very simple. You need a synchronising panel to sync your generator to the main grid. You will then only use the power you require. If your generator supplies more power - you will be pushing power back into the main grid. If your plant requires more power than the generator can provide - you will be pulling power from the main grid. If the generator trips - you will still be pulling power from the main grid. You will also need a breaker for the genset as well as the generator control module.

Basically the following steps will happen.

1. Generator breaker open

2. Main breaker from power company closed

3. Generator starts

4. Synchro panel controls generattor control module to synchronize generator to main grid

5. Generator breaker closes once synchronised

If the main grid trips - main breaker should open. When the main power comes back, the synchronization takes place again and when done the main breaker will close.

You can look on google for Deep Sea Electronics. www.deepseaplc.com They have the generator control units as well as synchro panel components you need. You can even get circuit typicals from them. You will need some good breakers for this, you can try Merling Gerin (I remember they have a range that can do this) If I remember correctly Scneider Electric is the distributor for them.

You will have to do your own sizing calculations and that sort of thing - but they do offer advice.

Regards,

Craig

By the way,

You should also have undervoltage tripping coild on your two main breakers. I would also make sure that I have a dip proof inverter as well, to cope with any voltage fluctuations that might drop out the under voltage tripping coil unintentionally.

Cheers

Craig

idon`t want generator to supply the grid, i want generator to supply my loads,but to make sure of stability of suppling my loads i want to put aslo feeder of power grid in the same busbar even after making synchronization and never remove feeder to make sure my loads never stops.

Hi there,

Unfortunately whatever you do not use will be given back to the grid - unless you have load control for your generator.

What I have stated above will work for you. The main grid will be your backup as long as it has power.

Take a look at the circuits in the above mentioned web site and you will see what I mean.

For simplicity - your breaker to the main grid will always be closed as long as your generator is synchronised and on load and the main grid has power. If the main grid goes down, this breaker must open and you will now be running on generator power. When the main grid power comes back, you should synchronise your generator to the main grid again. Then you close the main grid breaker. This can be done automatically or not. The principle is the same.

I did mention that you will need under voltage coils to trip the main breaker. i.e. under voltage signifies main power gone. I also mentioned that to prevent spurious trips you should use a dip proof inverter. This is just a capacitor bank that will hold your relay coils in for roughly 0.3s in the case of a voltage dip. This is used if you have power fluctuations or problems therrewith.

Regards,

Craig

but if the generator stop working, is the feeder of grid will continue of supplying loads?.and what will happened when i want to restart generator again without stopping my loads.

Hi there,

If the generator trips - your main grid feeder will still be closed, hence you will now be automatically pulling power from the main grid. So you have no plant trip there.

When your generator trips, it's own breaker with it's own undervoltage coil will open it.

So now you have the following situation. Generator tripped and generator breaker open. Main breaker still closed and Main grid supplying plant.

Now you go and fix the problem with the generator. You have completed your work and are ready to start. So you will have the following:

Generator starting but generator breaker still open. Main grid feeding plant and main breaker closed. The synchronising takes place via generator control module and synchronising panel. When synchronised, the generator breaker closes. Now you bring generator up to load.

Now you have the following situation. Generator supplying plant, generator breaker closed. Main breaker closed and main grid is there when you need it.

Now we lose main grid. So we have the following. Generator running and generator breaker closed, so generator supplying the power. Main grid breaker opens from undervoltage.

Now the main grid power comes back. You have the following. Generator running and generator breaker closed, generator supplying power. Main power grid back, main grid breaker open.

Now the generator syhncronises to the main grid. When syhnchronised, main grid breaker closes. Now you have main grid as backup again.

Go back to step one and repeat the process as needed. Look at the schematics that I refered you to and you will see the light.

Regards,

Craig

Do you presently have a tie with the system at all?

yes we have.

Tarek,

I have several customers who do this to minimize their power costs. Your design has nearly everything you need.

• You already synchronize to the grid, so you must have a synchronizing system.
• Your generator can operate as an island or in parallel, so it must have a decent governor control system.
• You should already have a generator protection package. Make sure it includes, at minimum, reverse power (40), generator differential (87) and loss of excitation (40) functions. Other functions should be added as dictated by the design of your distribution system.

You need to add a load balance function to your governor control system, if not already included. Most modern governor systems can operate in 3 different modes:

• Frequency Control: With the tie breaker to the grid open, the governor system monitors generator frequency and maintains it at a constant 50 (or 60) Hz.
• Peaking: With the tie breaker closed, the governor system monitors generator output power and maintains it at generator design capacity.
• Load Balance: With the tie breaker closed, the governor system monitors power flow through the tie, and maintains it at a selected setpoint. From your comments, your tie setpoint would be 0 MW in this mode.

In any mode, loss of the generator will cause the generator breaker to trip open. In Load Balance and Peaking modes, the plant load would instantaneously be supplied by the utility grid.

NOTE: Make sure the local grid can handle a step increase of the total plant load. Unless you are very near a major substation, I suspect you'll at least experience low voltage until the line regulators can ramp up.

You'll need to add governor inputs for tie breaker position (discrete) and power flow (analog). If this is an existing installation, adding Load Balance may be as simple as setting up the parameters and activation functions already in the governor control software. If it's new construction, add the Load Balance function to the specification, and the vendor will set it up at the factory.

Dear Mr.tarek_10,

Why do you want to synchronize with Grid and then you connect to your Loads, and then isolate the grid. What is the total load on the Generator, and what type of starters are used.

What I understand from your text is unless you synchronise with Grid, you cannot start your equipment. If so it indicates STARTING CURRENT of the equipment is the problem.

Pl. give some more details.

Thanks,

rajeswari.