Transient Stability in industrial network

[sabersteg]

Hi All
I have done transient stability simulations on isolated electrical network using ETAP 7.5 software.
Problem: On buses Faults generators return to stable stade
But on cable faults, rotor angle is diverged so the system is not stable.
To be noted that we have 2 SOLAR generators of 5MW, exciter is AC8B and governor is ST70.
Please can you help me to know what can be the problem!
Regards

 

[zoki85]

As far as I can *decipher* your post this would mean the fault conditions on cable terminals (or somewhere in the network far from generator) gives more difficulty for the generator's rotor to stay in synchronism after the fault. This can happen in various ways if the faults are not cleared in time. But I've never work with that software and don't know about your generators and cables network parameters to be more specific.

 

[sabersteg]

Thanks zoki85 for your reply.
Time fault is reduced to 80ms. What I don't understant that when fault applied on Bus loacted at the extremity of the cable or on the beginning we have no problem even if time fault increase to 250ms.So I can Conclud that I have no parameter problem on generators. But when fult is applied in the cable at any distance we have the rotor angle unstable. I have tried many types of exciters with different parameters : the same problem.

 

[zoki85]

But when fult is applied in the cable at any distance we have the rotor angle unstable. I have tried many types of exciters with different parameters : the same problem.

Is there maybe some element (transformer?) between generator's bus terminals and cable terminals?

 

[sabersteg]

Due to number of elements in the network, I try to isolate the problem by deleting sub systems. I will inform you in few time
Thanks