System Stability. Help !!!!!!!!!!!!!!
System Stability. Help !!!!!!!!!!!!!!
(OP)
Hi ,
We are designing the system network of a new factory. The estimated load is around 10 MW and a nearby IPP will be supplying us power @ 11 k V . The IPP is requesting us to install a 11 / 6.6 k V ( or 1 / 1 isolating transformer ) transformer on our side with the ultimate idea to isolate their network from ours which is understable from the stability point of view.
However, as we have got a very tight budget , we are proposing the IPP to feed directly our 11 k V cell and we will be limiting the ICC through suitable reactor on their 11 k V system. It is understood that the system stability on both our sides and the IPP is questionable as we will be having a common earth .
The second solution will result in considerable saving as we have already in the group transformers , MV panels etc.
I trust that through grading and co-ordination, the second option is as valuable as the first one.
Suggestions ?
Bob
NB Is it possible to insert attachment file to a post ?
We are designing the system network of a new factory. The estimated load is around 10 MW and a nearby IPP will be supplying us power @ 11 k V . The IPP is requesting us to install a 11 / 6.6 k V ( or 1 / 1 isolating transformer ) transformer on our side with the ultimate idea to isolate their network from ours which is understable from the stability point of view.
However, as we have got a very tight budget , we are proposing the IPP to feed directly our 11 k V cell and we will be limiting the ICC through suitable reactor on their 11 k V system. It is understood that the system stability on both our sides and the IPP is questionable as we will be having a common earth .
The second solution will result in considerable saving as we have already in the group transformers , MV panels etc.
I trust that through grading and co-ordination, the second option is as valuable as the first one.
Suggestions ?
Bob
NB Is it possible to insert attachment file to a post ?






RE: System Stability. Help !!!!!!!!!!!!!!
If they are feeding your plant directly (without interface to a utility company), I can understand why they may want a transformer for ground isolation or limit fault current. It seems like if they plan to be in the business of selling power, they should provide the necessary equipment to interface with their customers. Keep in mind though, that one way or another, you as the customer will be paying for the equipment whether you buy it or they buy it.
RE: System Stability. Help !!!!!!!!!!!!!!
If all of your 11 KV transformer primaries are delta there will be no noticable difference under normal conditions. The only normal flow of neutral current would be from your own step change voltage regulators if you have them.
Downstream of the voltage regulators you might want to have a trifiliar wound inductance that acts strictly to increase the zero sequence impedance that any ground faults will see.
RE: System Stability. Help !!!!!!!!!!!!!!
The 11 kV transformers are all delta connected on the 11 k V sides and we will be having both overcurent and earth fault protection relays on the 11 kV cell .
Bob
RE: System Stability. Help !!!!!!!!!!!!!!
If the IPP is generating directly at 11kV, this is even more important.
Will it work without the transformer? Probably. But it is a really good idea.
RE: System Stability. Help !!!!!!!!!!!!!!
In other words, a few lucky devils get their power back early when the utility is recovering from a blackout.
I did not know that you were this close to the generating facility. As long as you are using an overhead lightning wire you should not have any trouble with operating directly from generation. The generation buses should have resistance grounding or a zig-zag set to provide solid grounding. If the 11/66 KV transformers are YDY with a 6.36 KV delta tertiary winding then the 11 KV generator buses can be solidly grounded or resistance grounded using the step up transformers.
An alternative way to connect voltage regulators is to use the open delta configuration of two single phase units.