Main power transformer: loading, reactive burden, loss and fault screen

Companion to the SolarSoftwares substation design page. Defaults reproduce the page's worked example.

Screening tool, not the text of any standard. Defaults are assumptions: 100 MW at the MV busbar, 0.95 power factor at the high side with vars supplied, 10% impedance, loss figures from one unnamed 100/60/60 MVA, 50 Hz three-winding datasheet (50 kW no-load, 330 kW load; scale example, applied here to a 10% two-winding unit), a pvlib typical-year profile for Greensboro, NC, and a placeholder 2,500 MVA system short-circuit level. Replace every one with your project's data.

Maths: Q at the MV side = Q at the high side + X × S² ÷ rating. S = √(P² + Q²). Load loss scales with S²; no-load loss runs all 8,760 hours. Voltage is 1.0 per unit, series reactance only. Type 0.95 with a dot for decimals; 1,000 means 1000. Annual figures scale the embedded pvlib typical-year shape to your plant size.