Re: Question about case9

[Carlos E Murillo-Sanchez]

Ahmad Bariq Al Fahri wrote: Thank you Carlos for the information.  As in Case 9, all bus voltage is specified to be 345 kV. If the transformer defaults ratio is 1:1, does it mean that the generator is connected in 345 kV as well? Thank you. Best regards, Ahmad Dear Ahmad: No, it just means that the winding ratio corresponds exactly to the ratio of the nominal voltages on both sides of the transformer.  The TAP setting corresponds to off-nominal deviations, not to the physical winding ratio.  In fact, the nominal voltages at the generator buses for case9.m are really  16.5, 18, and 13.8 KV, while the nominal transmission voltage is 230 KV if I recall correctly.  MATPOWER only uses the (already converted to pu) branch impedances, the system MVA base, and the off-nominal TAP ratio; the BASE_KV column in the bus matrix is not used for power flows. Carlos.