jwaugh2014
Electrical
- Dec 24, 2019
- 4
I am working with a utility who has a very unique system. This portion of the system is 21kV. The 21kV apparently comes from the delta tertiary from an 18/24/30 MVA (230/60/21kV) transformer. They pick-up their ground reference from a 3-phase zig-zag 500kVA (21kV) grounding transformer. From what I understand the bank was should have been sized to handle the voltage unbalance. How can I confirm that it was sized appropriately and what does the grounding transformer's 500kVA capacity imply about the system's overall capacity (30MVA)?
Also, they only use 3-wire for the majority of this system. Does the introduction of the grounding transformer change the system from a delta to a unigrounded wye system?
Most of the trunk is 3-wire except on the farthest reaches of the system where there are a number of 12kV rated distribution tranformers that weren't upgraded. At this point, they established another ground reference ran a neutral conductor and used phase to neutral for the 12kV transformers. What is this system at this point it's no longer unigrounded and it doesn't fit the multi-grounded parameters, does it?
Also, they only use 3-wire for the majority of this system. Does the introduction of the grounding transformer change the system from a delta to a unigrounded wye system?
Most of the trunk is 3-wire except on the farthest reaches of the system where there are a number of 12kV rated distribution tranformers that weren't upgraded. At this point, they established another ground reference ran a neutral conductor and used phase to neutral for the 12kV transformers. What is this system at this point it's no longer unigrounded and it doesn't fit the multi-grounded parameters, does it?