I want to get data of zero and positive sequence impedance of distribution transformer sized 2,000 and 400 kVA (33,000/400-230 V).Where does I can get these datas?
The following is an over simplified method to estimated the Impedance of the transformer will consider standard impedance and not load tap changer (LTC) on the transformer.
The Basic Insulation Level (BIL) is the dominant factor to estimate the impedance of the transformer. Thus for 33 K primary voltage the closest rating nominal voltage is 34.5 kV and the std BIL= 200 KV per Table 4 ANSI/IEEE Std C57.12.00.
From Table 7, ANSI/IEEE Std C57.12.10.(% Impedance Voltage) for HV BIL= 200 kV & LV = 480V-->Zt=7.25%.
The impedance should be on the nameplate. If not, you need to get factory test results.
If the secondary is solidly grounded, the zero-sequence impedance equals the positive-sequence impedance (nameplate impedance). If the secondary is impedance grounded, add 3 times the neutral impedance.
Note that the zero-sequence equivalent circuit has an open in the high (delta) side and a short on the source side of the impedance. That is, the zero-seq impedance is infinite when seen from the delta side and equal to the transformer impedance (without any source impedance) when seen from the wye side.
Suggestion: Normally, a manufacturer is selected first. Then, you obtain data from the manufacturer.
Impedances will vary according to the transformer winding connections.
See References:
1. Electrical Transmission and Distribution Reference Book, Westinghouse Electric Corp., e.g. 1964, Table 5 in the rear.
2. IEEE Std 241-1990 Table 34 indicates transformer design impedance of Z=6% for a transformer of your size and voltages.
Based on the above postings and References, impedances will be:
Z1=Z2=Z=6%
Z0=6% depending on the transfomer connection and grounding.
