It's under a "N" condition where the ISO looked at the project providing the maximum real & reactive power limits and stated that the transformers ONAF2 rating is exceeded. We were able to review the model and show that it actually won't be an issue but they wouldn't budge on it. It's a 325MW...
The response I'm getting from vendors via sales reps has not been helpful. One said it was "outside of their scope".... which makes no sense to me.
The ISO's system impact study says there was a thermal violation for a condition that is not very likely to happen so they are making the project...
I've tried reaching out to a couple transformer vendors without any luck so I figured I'd give it a shot here.
IEEE C57.12.10-2017 Table 2 says for typical transformer ratings, the 1st stage and 2nd state cooling ratings are 133% and 166% of base rating however there is a line that reads...
Typically we run a pf test before submitting to the ISO using PSSE to determine if we need adjust quantity of inverters, adjust taps of GSU transformers, or increase Main Power Transformer base rating. We typically try to avoid Cap Banks and OLTCs altogether. On large PV projects with very...
Thank you. Your comment has led me down a rabbit hole of trying to figure out if we are going to be okay due to this. The Aspen model says yes but Easypower model is saying maybe.
Sounds like another good way to reduce the fault current. It would also be subject to the ISO's review of the overall impedance change of the system just like changing the transformer impedance. We are also dealing with a limited footprint for the stie so I'm not sure we would have the space...
From reviewing some responses on other threads from forum user PRC and also reviewing some modeling data I have access to, it appears that the impedance between two secondary windings of a 3 winding transformer is roughly 0.95 the summation of the impedances between the primary and each of the...
I'm reviewing a project where there is a 270MVA 161/34.5kv transformer and no main circuit breaker on the 34.5kv bus. (I don't know of any circuit breaker for 34.5kv that is higher than 3000A which is a force air cooled switchgear breaker)
The 34.5kv bus has (8) 600A breakers. (7) of the...
I believe the ISO would accept a difference of the total impedance of 10% or less from the originally studied transformer. We would have to develop the transformer spec. to match it as best as possible.
We have a 325MW renewable site that was studied with a Y-g 345kv / Delta 34.5kv 350MVA two winding transformer but we are kicking around the idea of changing it to a three winding transformer to reduce the secondary current. If we kept the impedance the same between the primary and the two...
Thank you. I recently read that shell type transformers are more energy efficient and have better fault duties thus more likely to be specified. I have no real world data points on this so I was wondering if you had any insight that could be shared?
From reading the excerpt below from IEC 60076-8, I'm interpreting Z0 to be .85-0.9 the value of Z1. Is this a correct interpretation? I've recently seen utilities/ISOs requesting Z0 data on transformer during the interconnection studies and I can't seem to get a good understanding on this...
I was searching for OLTC topics as I'm currently looking at a inverter based project where we didn't show an OLTC but the client insists that they want it. From speaking to a few people at work, and from what wcaseyharman said above, it sounds like the inverters should be able to handle the...
