Transformers parallel work
Transformers parallel work
(OP)
We have a 60/80 MVA onan/ Onaf 154 / 34.5 kV Step Up transformer with Dyn1 vector group and 8.22% uk.
Our other transformer will be a 100 MVA onan 154 / 34.5 kV
step up YNd1 8.22% uk.
My problem is the vector groups. I cannot be sure if they can work in parallel. Some says it's ok some says it's not..What I know is they should be the same..
I know this is the place where I can get the real answer..
Thank you in advance..
Batu
Our other transformer will be a 100 MVA onan 154 / 34.5 kV
step up YNd1 8.22% uk.
My problem is the vector groups. I cannot be sure if they can work in parallel. Some says it's ok some says it's not..What I know is they should be the same..
I know this is the place where I can get the real answer..
Thank you in advance..
Batu






RE: Transformers parallel work
Phase angle shift from HV to LV is OK. I think the two transformers can be paralleled but you have to consider the following "what if's":
1. If the new YNd1 transformer trips, will the other transformer(80MVA) get overloaded?
2. If the new YNd1 transformer trips, will you lose the 154kV system's neutral grounding?
3. Are you going to maintain the 34.5kV neutral of Dyn1 transformer grounded? How does it influence your 34.5kV system neutral grounding if the Dyn1 transformer trips?
RE: Transformers parallel work
4. What if the transformer tap changer steps are in different value?
RE: Transformers parallel work
It may be a good idea to do lowside phasing-voltmeter checks before closing the tie. Else, a “dynamic’ test of your relaying can be needlessly disconcerting and stressful.
As implied by others, with the assortment of winding types, [zero-sequence] protective-relaying response will vary depending on switching.
If there are OLTCs on the two units, do they have a parallel-operation feature? Excessive loop-var circulation my occur if taps are not adjusted to limit this.
Consider also the fault-duty increase with a closed tie.
RE: Transformers parallel work
Digitrex you are right. I find out that both of the transformers are step-down..
The parallel work will occur only during transferring ( For maintenance or etc. ) which will last 3 minutes approx...
The other problem is since the load curves are different uk may not be the same during the transferring too..
Sorry for taking your extra time..
Batu
RE: Transformers parallel work