Calculation for sizing zig-zag transformer
Calculation for sizing zig-zag transformer
(OP)
How to size zig-zag transformer. Has anyone know how to calculate its size?
Tks in advance.
Tks in advance.
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Calculation for sizing zig-zag transformer
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Calculation for sizing zig-zag transformerCalculation for sizing zig-zag transformer(OP)
How to size zig-zag transformer. Has anyone know how to calculate its size?
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RE: Calculation for sizing zig-zag transformer
RE: Calculation for sizing zig-zag transformer
But I do no know how to size my zigzag transformer in my single line diagram.
Thanks in advance.
RE: Calculation for sizing zig-zag transformer
- is it hydrogenerator or turbogenerator ?
RE: Calculation for sizing zig-zag transformer
You may use three off the shelf 33 kV distribution transformers connected in or a wye:delta for grounding. Some advantages are:
Lower initial cost.
Replacements are readily available.
Special order is not required.
The current limiting resistor may be inserted from either the primary wye point to ground or in series with the delta secondary. This gives a little flexibility when selecting the resistor or impedance.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Calculation for sizing zig-zag transformer
Odlanor: There is no generator. It just distribution system network.
Waross: Thanks. But how to size my zigzag transformer? My NER current is 524.8A (33kV).I attached here the single line diagram for your reference.
Thanks in advance
RE: Calculation for sizing zig-zag transformer
Regards
Marmite
RE: Calculation for sizing zig-zag transformer
RE: Calculation for sizing zig-zag transformer
M.A.Sh.
Elect. Engr.
RE: Calculation for sizing zig-zag transformer
That is a newer MS word file format.
Go to openoffice.org and download open office writer. It is free and it will open .docx files.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Calculation for sizing zig-zag transformer
M.A.Sh.
Elect. Engr.
RE: Calculation for sizing zig-zag transformer
Ig = E (phase-neutral) / (NGR + Z zig zag transf.)
Do we ignore Z zig zag transf. due to some codes? if yes what code?
M.A.Sh.
Elect. Engr.
RE: Calculation for sizing zig-zag transformer
I just found some information on sizing zig zag transformer as attached. Pls comment.
RE: Calculation for sizing zig-zag transformer
This another info. Pls comment.
RE: Calculation for sizing zig-zag transformer
Pls comment.
Tks in advance.
RE: Calculation for sizing zig-zag transformer
What maximum Ig (ground fault current)do you think your NER will be subjected to? Since you indicated that your NER is rated for 30 seconds (this is new to me, the usual ratings are 10 seconds or 1 minute), recommend that you rate your grounding trafo to withstand the ground fault current longer than your NER (>30s), say 1 minute. Your power multiplier for a 1 minute fault is 7% (3% for a 10 seconds rating).
Here's my guess (not enough data for me):
Assuming a full winding voltage appearing across your NER, your fault current will be 33kV/sqrt(3)/36.3 ohms = 525 amps! Your zigzag transformer winding current would be 1/3 of the fault current = 525/3 = 175 amps. Zigzag transformer rating will be sqrt(3)X 33,000 X 173 X 7% = 700 kVA.
RE: Calculation for sizing zig-zag transformer
M.A.Sh.
Elect. Engr.
RE: Calculation for sizing zig-zag transformer
Regards
Marmite
RE: Calculation for sizing zig-zag transformer
88 or 69kV delta are grounded by zig-zag transformer.
zig-zag transformer is sized for 3 < X0/X1 <10.
That is to say that the short-circuit current phase to ground should be equal to or less than the three-phase short circuit. When X0/X1> 10 the system tends to become high-impedance grounded and lightning arresters (unfaulted phases) during a fault-to-ground are damaged due to overvoltage.
It is time to change the zig-zag.
RE: Calculation for sizing zig-zag transformer
RE: Calculation for sizing zig-zag transformer