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I really appreciate the comments. The balancing on the loads on the delta will help out. On the existing connection straight to the 4160V wye grid, we've seen a lot of unbalanced load current on the generators. The unbalanced loads on the genset makes it difficult to apply all of the relay...

I can accommodate for the grounded wye 12.47kV on the transformer. I'm also interested in making sure that I can run these units islanded and push a limited amount of MW out to the 12.47kV grid if needed.

Thanks for your comment. Is delta better due to no line-ground fault levels at the genset, or are there voltage stability (or harmonics) consideration in having a delta? These gensets were installed in the 80's and were connected directly to our 4160V wye system.

I need some comments and/or standards to refer to regarding wye-delta choices for a step-up transformer for diesel generators. I have (3) 1.5 MW DG Units (with a resistor ground) generating at 4160V. We need to get this connected to the 12.47kV grid, so we will install a step-up transformer...

Same primary current. Only feeding an SEL 321 in this case.

Thanks, I'll go back to Blackburn to review. The parallel CT's were on a different breaker, but still in the same yard.

Thanks for the comments. Probably was a burden consideration on the original design. The relays in the series were IBC's, CHC (breaker failure), PJC, and a CPD (Pilot wire). The other bus in the station has similar relays on the breakers, but the CT's were not connected in series. Likely...

I have a customer who has a 115kV breaker with two 10L800 CT's (1200/5) driving a string of electromechanical relays. These CT's are hooked up in series prior to connecting to the relays. I've never seen this connection. Any good explanations as to why CT's would be hooked up in series prior to...

Thanks for all the comments. I don't know enough details on the hospital's system yet. I do know that the hospital receives power at 34.5kV and steps it down for about 3/4 of their load through a 3000kVA YgYg padmount transformer. I have been told that this transformer has a five legged core...

I've thought about using negative sequence current, but there is a question about sensitivity when the hospital is at minimum load. We also would need to struggle with the concept of picking a CT ratio that is low enough to be sensitive, yet high enough to allow for system load growth. If I...

I'm familiar with that paper, but it's not practical at this site (physically or politically) to sense on the low side of a DY transformer. We need to sense only on the high side.

I need some advice. Looking at a hospital complex with a mix of 3 phase DY, YY, and YD transformers (not sure of the exact numbers of different types of transformers yet). Hospital has installed wye type voltage magnitude sensors on utility interconnect end to detect single phase loss. During...