Neutral current in Transformers
Neutral current in Transformers
(OP)
In a substation feeding to arc furnace transformers continuous neutral current is noticed. Transformer 80 MVA 220/33 kV Ynyn connection with a stabilising tertiary winding.. HV transformer neutral is continuously showing 6-7 A irrespective of load.Because of this to avoid tripping on charging REF relay had to be set at 20 %. What can be the reason for this neutral current on HV? How to prevent this?
The current values on HV- 24,22,25,7 A (R,Y, B,Yn)(9.5 % of rated load)
LV- 167,163,168,0.21 A
HV- 3.8,3.8,4.0,6 A
LV- 27,26,28,0.2 A
The current values on HV- 24,22,25,7 A (R,Y, B,Yn)(9.5 % of rated load)
LV- 167,163,168,0.21 A
HV- 3.8,3.8,4.0,6 A
LV- 27,26,28,0.2 A






RE: Neutral current in Transformers
RE: Neutral current in Transformers
1. Correct the unbalance or phase angle errors. (This may not be reasonably possible.)
2. Open the delta.
3. Float the primary neutral. (Not recommended because of possible over-voltage switching surges.)
Bill
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"Why not the best?"
Jimmy Carter
RE: Neutral current in Transformers
Thank you waross for your points esp the transmission line transposition issue.Let me check up.
RE: Neutral current in Transformers
This issue sometimes happens in our utility, in such cases we float the primary neutral (which for our distribution transformers is generally fully insulated at primary voltage),
If the stabilizing delta winding is buried, this should be the only solution.
Si duri puer ingeni videtur,
preconem facias vel architectum.
RE: Neutral current in Transformers
RE: Neutral current in Transformers
RE: Neutral current in Transformers
If this is with the rectifiers/converters disconnected, then I'm with waross.
Unless there's a mismatched tap on the transformer someplace, its due to in imbabance on the incoming supply.