A 3-phase transformer has rating of 20 MVA, 220 kV (star) -33 kV (delt...
Transformer Reactance Calculation
Given Information:
- Transformer rating: 20 MVA
- High voltage (HV) side: 220 kV (star)
- Low voltage (LV) side: 33 kV (delta)
- Leakage reactance: 12%
Step 1: Calculation of the HV current
The HV current can be calculated using the formula:
IHV = P / (sqrt(3) x VHV)
Where:
- P = Transformer rating = 20 MVA
- VHV = High voltage side = 220 kV (star)
Substituting the values, we get:
IHV = 20 x 106 / (sqrt(3) x 220 x 103) = 57.36 A
Step 2: Calculation of the LV current
The LV current can be calculated using the formula:
ILV = P / (sqrt(3) x VLV)
Where:
- P = Transformer rating = 20 MVA
- VLV = Low voltage side = 33 kV (delta)
Substituting the values, we get:
ILV = 20 x 106 / (sqrt(3) x 33 x 103) = 105.56 A
Step 3: Calculation of the transformer impedance
The transformer impedance can be calculated using the formula:
ZT = VHV / IHV
Where:
- VHV = High voltage side = 220 kV (star)
- IHV = HV current = 57.36 A
Substituting the values, we get:
ZT = 220 x 103 / 57.36 = 3831.6 Ω
Step 4: Calculation of the transformer reactance
The transformer reactance can be calculated using the formula:
XT = ZT x sin(θ)
Where:
- ZT = Transformer impedance = 3831.6 Ω
- θ =