pole slipping in islanded conditions 3

[unniyarcha]

Hello,
i am using Digsilent power factory for studies,Recently was doing some transient stabiluty studies for an islanded network after a fault,There is only one genrator in the islanded condition and it gives pole slipping error message after 8 seconds.Is it possible to happen since there are no other reference machine?can anyone help with this?

 

[ScottyUK]

Sounds like an error in the simulation, or an error in the data fed in to the simulation. A machine can't pole-slip if it is the only generator on the system.

 

[electricpete]

I guess in theory some motors might act like a generator. To put together conditions for pole slip would probably require several motors fed from the generator through a large series inductance. I’m not sure about induction motors but definitely sync motors.

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(2B)+(2B)' ?

 

[waross]

I had that thought also Pete. Then I considered that there may have to be some seriously overhauling loads before motors would contribute to pole slip, particularly after 8 seconds. It may be possible during recovery, when UFRO has reduced the voltage due to frequency decay. The combination of reduced generator terminal voltage and an over excited, over driven synchronous motor may develop into pole slip, but it may be special cases only.
We really need more information as to the load profile that you have given your software to work with. Scotty's suggestion may be the most probable.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[electricpete]

I agree the 8 second part makes it very unlikely.

A 2-machine system without fixed bus can be transformed to equivalent 1-machine system against infinite bus. The first swing is the worst, so 8 seconds doesn't make sense.

=====================================
(2B)+(2B)' ?

 

[unniyarcha]

Thanks all for the answers. i tried to plot the rotor angle and i could see that the rotor angle keeps on increasing and the pole slip message occurs after it completes 360 degrees.

 

[davidbeach]

The software is keeping track of some reference angle and your island is running a bit faster. Certainly not a pole slip condition, just a bit too much generation relative to the load.