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Generator circuit breaker

Generator circuit breaker

Generator circuit breaker

(OP)
Hi,

Can you please give me a concrete example how to set the currents and time delays on an air circuit breaker protecting a generator?

I know that when you have a cable, the "characteristic" is an inverse curve, but what does the "characteristic" of a generator look like?

Thanks.

RE: Generator circuit breaker

All the info about your system needs to be known, I suggest you have a PE determine this for you.  

RE: Generator circuit breaker

The instruction manual for a good generator protection relay should be able to provide considerable guidance, but you still have to know a great deal about the machine.

RE: Generator circuit breaker

(OP)
I have all the parameters:

T'd = 0.51404 s
T'd0 = 7.1960 s
T"d = 0.0118 s
T"d0 = 0.0145
Te = 0.2225
Ta = 0.0608

Instantaneous LLL fault: 23589 A
Instantaneous LL fault: 20718 A
Instantaneous LN fault: 29952 A  (I thought LLL would be highest)

Rated current: 3615 A
 

RE: Generator circuit breaker

Actually, you don't have all the parameters, and if you thought that LLL would be the highest fault current you probably don't understand generators all that well.  I'd echo what Zogzog said and recommend that you have someone more familiar with generator protection assist.

RE: Generator circuit breaker

(OP)
I have more parameters, which ones exactly do you want?

RE: Generator circuit breaker

It doesn't matter, no one here will, nor should be trusted if they do, provide your settings; that's not the purpose of the site.  Then there's the whole question of what the rest of the system looks like, settings wise, as seen from the generator.  Beyond that, there are no right answers per se, plenty of wrong answers, and a bunch of different answers that are all acceptable.  But none of it in a vacuum as it would be looking at just the generator.  Find someone locally who can see the whole picture, which nobody here can, and who can provide guidance.

If you want to come back with specific questions, and lots of supporting material as to how you have approached the problem, I'm sure you can get plenty of discussion.  At this point, though, the problem is too wide open to be meaningfully solved here.

RE: Generator circuit breaker

(OP)
The application is straight forward: the building is isolated. There is no mains supply. The generator is the only supply. There is only one generator straight connected to the MDB.  

RE: Generator circuit breaker

The generator will have a damage curve and a fault decrement curve. You'll need to get both of those from the manufacturer. Then take a look at the IEEE Buff Book as a staring point on how to go about setting the breaker. There are lots of consideration and unfortunately there's not a simple answer.

Alan
----
"It's always fun to do the impossible." - Walt Disney

RE: Generator circuit breaker

Hi AusLee.
What Alehman said!!!!.
ONLY, ONLY generator mnf. can give you answer !!!!
It's really hard Q.
It's not only simple O/C 50,51 protection, probably you need also 51V protection.
Try ask generator mnf..
Good Luck.
Slava

RE: Generator circuit breaker

I suggested you obtain the thermal damage curve and fault decrement curve. Neither of those are included.

Alan
----
"It's always fun to do the impossible." - Walt Disney

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