If the load is drawn between phase and neutral of the transformer, there may be other restrictions than those given by the rated current of the winding. Subclause 8.1 of IEC 60076-1 requires that the neutral terminal shall always be dimensioned for the recognised earth fault current and for...
In a Y-Y bank with grounded neutral and supply system isolated, without delta terciary, the limitation following may be noted:
a) The third harmonic hazards.
b) Possible neutral inversion.
c) Overexcitation
Thus problems doesn´t exist if both system and Y-Y transformers Grounded.
In a Y-delta bank, whether the Y is primary, the grounding of the neutral of the Y permits grading of the transformer insulation and also tends to stabilize the 60-cycle potencials of its terminals.
When the source (grounding upstream) is efectively grounded, a line fault eliminates one phase...
Standard IEC 60076-1.
The rated withstand voltages of the winding are:
A rated short-duration power-frecuency withstand voltage for the line terminals according to Table III. based in current practice in the USA: 34 KV
A rated lihtning impulse withstand voltage for the line terminals according...
In the papers of GE "The whys of the wyes", we understand that only the Y-Y bank of single-phase units exhibits a third-harmonic voltage as 60%-65%, then is neccesary a terciary delta winding. But the core type three-phase transformer exhibits 2% or less third-harmonic voltage, for...
I am currently designing a core type three-phase transformer, with three-legged core, 220/110(69) KV, 60/70 MVA, Y-Y connection. Can I do using serie-parallel winding for the secondary with reconnection. Is neccesary in this case, ysing a delta winding for reduce the third-harmonic voltage. Thanks.