transitory stability

[bunda222]

Hi,

I am performing a simple work to evaluate the transitory stability of the system shown attached when a three-phase fault happens in the substation S. Osorio. Due to this fault three-lines shown in the picture have been cut off from the system. Now the system lost its synchronism, I need to find a way to make it come back to synchronism again. I was trying to cut off the generation that is attached to the S. Osorio bus, but according to the simulation I'm doing that is not the solution of the problem because the machine's angle grows forever to different directions. I would like to know if you have some tip on what to do to keep this system operating without the 3 line transmissions.

Thanks.

 

[Mbrooke]

@Mbrooke
No problem, even rudely beg to differ is fine for me. What I imply is for an "existing system", if there is a bus fault causing three elements out, typical utility way nowadays is to save money by either trip generation or load other than re-configure the system like what you proposed. But for a new system to be designed, your proposal flies.


There is no exception here in North America, I agree with you if one fault tripping out three elements, then in the old NERC TPL standard, it is treated a multiple contingency and allow load shedding. However, in the new NERC TPL standard001-04, NERC keeps silent on the number of elements out but more focus on single contingency or multiple contingencies. The scenario you described belongs to P2 -bus section fault taking out three elements, if the bus section is EHV system then non-consequential load loss is not allowed and utility has to spend money to fix the problem such as what you proposed.
Cheers!

Honestly, now that I think about it its more if my bias speaking then all of reality. You are correct. Around here the tendency is to reconfigure existing substations rather than shed load (even if just HV) when a bus fault of breaker failure results in a certain amount of load or generation being lost. It is not so much a NERC standard but I guess one from the local ISO.

So I do hold guilt in speaking as though local standards apply when they do not everywhere else.

@MBrooke
you said about too many load drops can back fire the whole system, I think for this N-3 scenario there's not much to be done tbough. The two unfaulted substations (P. Branco and Xanxere) are fed by the Generator tied to S.Sorio bus, so if I don't drop those loads the voltage level will drop too, the same happens to substation C. Mourao, the voltage drops to 0.7 pu due to generator disconnection. I know there are other options to restore the voltage level such as a bank of capacitors there, but they do not exist in the substation when fault happens, so I cannot account with them, maybe the substation does not have physical space to shelter those bank of capacitors.

Well- if the entire system (hundreds of substations) has load shedding implemented through out. For just this substation I honestly can not think of a major problem.