standards / manuals / guidelines for small hydro development - AHEC

Datai) Sub transient reactance of generator on own base - 24%ii) 100 MVA transformer impedance - 12%iii) 132 KVA transmission lines impedance - 8%iv) Power house is interconnected with grid at bus B.v) Equivalent system X 1 = 0.03 of X 0 = 0.041. Consider the fault at M which is fed by the grid system and the hydrogeneratorswhich is considered worst.2. Three phase fault calculations:- In the system shown in figure 4.5 per unitreactances are indicated.Apparent power is 100 MVA base and nominal voltage 132 kV is used as base at alllevels. 0.24 0.12 x0.08 0.032 2X 1 = 0.24 0.12 0.08 0.03 2 2 =0.18x0.110.18 0.11= 0.068X 1 =0.24X 1 =0.12X 1 =0.24X 1 =0.12X =0.08 1OPENX 1=0.03X 1 =0.08Base voltage 132 kVBase current 437The value of operating voltage corresponding to the highest operating voltage at faults is145 kV or 1.098/unit1.098Isc = x 437 = 7056A0.0683. Single line to ground fault current4-24