132/33kV YNd transformers in petrochem
132/33kV YNd transformers in petrochem
(OP)
Hi,
I recently came across YNd1 and YNd11 transformers at 132/33kV (or similar) in new petrochemical installations. The 132kV system is solidly earthed at the star points of the generator transformers. The 33kV system is resistance earthed using zig zag transformers.
Question 1: What are the benefits of using this configuration instead of the more common one with Dyn11 or Dyn1 transformers?
Question 2: If the 33kV system supplies transformers only, does it have to be resistance earthed or solidly earthed is acceptable?
Thanks in advance...
I recently came across YNd1 and YNd11 transformers at 132/33kV (or similar) in new petrochemical installations. The 132kV system is solidly earthed at the star points of the generator transformers. The 33kV system is resistance earthed using zig zag transformers.
Question 1: What are the benefits of using this configuration instead of the more common one with Dyn11 or Dyn1 transformers?
Question 2: If the 33kV system supplies transformers only, does it have to be resistance earthed or solidly earthed is acceptable?
Thanks in advance...






RE: 132/33kV YNd transformers in petrochem
The medium voltage may work with one ground fault for a while then is better to reduce ground fault current. The system may be designed so that the ground potential is still reduced [not the full grounded phase potential] using zig-zag transformer and other.
RE: 132/33kV YNd transformers in petrochem
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If we learn from our mistakes I'm getting a great education!
RE: 132/33kV YNd transformers in petrochem
And how does a star secondary (resistance earthed) compare with a delta secondary (resistance earth via zig zag transformer) at 33kV? What's the best technical solution?
RE: 132/33kV YNd transformers in petrochem
Star secondary at 33 kV is used predominantly used in a 3 phase 4 wire system. Resistane earthing serving the purpose of limiting the fault current.