GENERATOR LOAD SHARING
GENERATOR LOAD SHARING
(OP)
Anyone know where to get some literarture on why load sharing is required when generators are run in parallel?
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RE: GENERATOR LOAD SHARING
RE: GENERATOR LOAD SHARING
Why not operate load sharing? what if the generation is needed for the system, but its governor is unstable.
RE: GENERATOR LOAD SHARING
In fact the term parallel implies that they will be sharing the load, whether or not equally is other question.
Ideally they should share the load in proportion of their ratings. And when do that they will not be 'fighting' for frequency or in other words they will run at same speed with least trouble when sharing the load properly and not otherwise. So I am not sure where you are coming from.
There are other issues other than load sharing, like maintaining power factor (reactive power flow)and all those issues get much more easier to set and control when load sharing is done properly.
RE: GENERATOR LOAD SHARING
Since they're both connected to the same load, wouldn't the load sharing percentage be determined by Ohms law? Each generator is (hopefully!) outputting a very similar voltage- as both see the same load, I=V/R, current will be split pretty much evenly, with small fluctuations just due to individual voltage output as well as whatever differences in manufacture and wiring.
RE: GENERATOR LOAD SHARING
they will only be generating the same voltage if at the same power factor, if one is overexcited and one under then there will be a few % difference in their voltages. The AVR's will sort this out though, if set up correctly.
Remember - the governor controls power and frequency only.
Whereas, the excitation (AVR) controls voltage and powerfactor only.
Fundemental, i know but surprising how many people forget this
Richard
RE: GENERATOR LOAD SHARING
RE: GENERATOR LOAD SHARING
RE: GENERATOR LOAD SHARING
So if you add a second generator into this isolated system (and imagine that at some instant the load and speed are stable), both governors will see a speed change and react. However, they will not react identically, and the load supplied from each generator will be different. This is a real time process so the load will possibly oscillate, but more likely one generator will be take all the load and the other will go into reverse power.
To provide a stabilising influence on this system feedback from the governor output can be used, this feedback is called droop. Typically it is set up so that speed is allowed to drop, proportionately, by 5% for a 100% governor output. This is how simple mechanical governors on diesel engines work. As governors have moved into the electronic age the feedback can be from an actuator or real power output of the generator, and the govenors can communicate between each other to balance out the load and maintain the frequency at the setpoint.
To cvirgil I haven't provided any literature, but I hope I have explained why/how load sharing is needed and is done.
Niall
RE: GENERATOR LOAD SHARING
RE: GENERATOR LOAD SHARING
Load sharing lines are needed when we run isochronous mode with motor controller and VDC or cross current with AVR. Basler have that cross current system and ABB VDC. Baslers cross current is for user little more complicated because if you have system where you are normally parallel with grid and if grid disapear your AVR:s must have sychronized all units with same voltage or you must go to AVR and set the values same by hand (practically all have little different values).ABB Unitroll had beginning problems with VDC but they have now upgaded the sofwares and it is easy also upgrade at site. One thing for these load sharing lines, you must remember when you trouble shooting from one engines function the problem can be the other unit. Also the cabling for load sharing lines must be done very carefully.
Merry Christmas happy new Year
RE: GENERATOR LOAD SHARING
For example, Cat engines like to be 50% or more loaded to reduce oil consuption and be in the turbo "happy range". Two engines online sharing load would be better than one loaded base and the other only partially loaded.
JTK
RE: GENERATOR LOAD SHARING
Hope this helps