Parallel Operation Of DG

Ofcourse it is possible.

In order to connect DG in parrallel the following should be checked:

1. Phase Sequence
2. Voltage Magnitude
3. Frequency
4. Phase Angle

Regards,

Hisham

I this case how they contribute power .

You will need to learn the basics of power system operation by reviewing an elementary textbook on AC circuits. Here's the short course: increasing fuel causes increasing real power flow, increasing excitation/field current causes increasing reactive power flow. If you do not understand or know this already then follow the instructions in the first sentence.

This subject has been discussed previously on this site. Try searching and then come back with a specific question.

Dear Mr.hisham.i,

I want to supplement to your reply.

In addition to the points referred by you, the following conditions also should be matched for proper load sharing.

1. The SPEED DROOP CHARACTER for the engine should be considered, the Engine Governor plays a major role.

2. The VOLTAGE DROOP CHARACTER to be considered.

The above two points will decide the LOAD SHARING of the DG Sets. The higher the Droop from NO-LOAD to FULL-LOAD, LESSER WILL BE THE LOAD SHARED and ViseVersa.

For example, If one Generator has 6.0% Droop and the other one has 4.0% droop, the SET with 4.0% will share more load than the other set with 6% droop. and it will be in the ratio of 60% and 40%

DHAYANANDHAN.S

I am sorry, but I do not agree with your figures you used in explanation of droop for gen sets. Before the advent of electronic governing, hydraulic governors for any gen set that I ever worked on was between 1% - 1,5%, probably closer to 1,25% on the high end of the droop. Main propulsion systems were in the order of 9% droop.

If you had anywhere near 6% droop on a gen set you would have big problems with any electrical equipment that required steady voltages or Hertz, they would be forever tripping out.

No. It cannot be done. More accurately it should not be done by you until you get properly trained in AC power distribution. There are many more ways to damage you, your diesel generator or the grid than there are correct ways to connect.

It can be done if the genset control system is designed to manage correctly the load sharing among several generators. In modern systems it's mostly done by interconnecting each genset controller using a fielbus or Ethernet.

If the gensets controls are not designed for appropriate load sharing it can't be done as all sorts of problems will occur.

I'd suggest to read some Woodward or Deif literature which can be downloaded freely (Woodward requires a registration but acccess is immediate after registering), especially Woodward features some general documents and white papers.

apart from other factors mentioned you have to ensure load sharing is in proportion to the machine ratings

"Can we operate 2 or more dg(desile genrator) of different rating in parallal."

Theoretically, anything is possible if properly designed.

"what are the condition for parllal operation of DG ?"

The conditions are to have a trained Electrical Engineer design the system that will take in power from the two generators, harmonize them with each other, and provide the combined power out to the load.

Please note that asking vague, open-ended questions on a semi-anonymous forum does NOT count as 'having a trained Electrical Engineer design the system.' You will know you have had a trained EE design the system when you have the design prints in your hand, SIGNED by the EE who is staking his license, reputation, and possibly his freedom, on those plans being correct and accurate.

Once you have gotten the plans, you will need to have an EE (the same one who drew up the plans or another EE, it does not matter) oversee the construction installation and testing of the equipment.

---

If this is for a temporary or small-scale setup, it might be easier and safer to set up the generators completely independent of and isolated from each other, so Generator A supplies power to all the equipment over in section A, on the West side of the camp/village, and Generator B supplies power to the East side. Neither generator is connected to the other in any way, except possibly for them both being hooked up to the same tank of diesel fuel to run off of.

---

Also Welcome to CR4, you will find a lot of helpful advice here. For example, you will notice that the advice you are getting on this question is all shades of 'Your question shows that you do not understand the project you are proposing, you should get a trained, qualified person to design and build the project for you.'

One more detail: if operating several emergency gensets in parallel the required time for a conventional synchronization is not sufficient to meet code requirements. In such case the gensets are started simultaneously and breakers close so common voltage ramping is possible and gensets are forced in "synchronicity" (don't know if it's the correct English word). Of course it must be made sure that if one genset prime mover doesn't start correctly it won't end driven by its generator (see multi-stage reverse power threshold and delay settings and other careful startup alarms inhibition settings).

Of course I only referred to synchronous generators. Gensets with other types of 3-phase AC generators are a joke.