Last name
ID number
First name
Due Date
SMGR-HW2001
2 6 0 3 2 0 2 2
Submit by
4 April
A typical Italian Primary Substation (PS) is shown in figure. Applying the per-unit method, with both
transformers in service (CB11, CB12, CB21 and CB22 closed) and the bus-tie breaker (TB) open, you
have to calculate:
1. at HV Bus-Bar level
1.1.
the actual voltage level in kV;
1.2.
the equivalent sequence circuits;
1.3.
the phase-to-phase short circuit current in amps;
2. at MV Red Bus-Bar level and when the neutral is directly grounded (Rn=0 Ω)
2.1.
the actual voltage level in kV;
2.2.
the equivalent sequence circuits;
2.3.
the three-phase short circuit current in amps;
3. at MV Green Bus-Bar level and when the neutral is compensed (Rn||Xn=587||57.75 Ω)
3.1.
the actual voltage level in kV;
3.2.
the equivalent sequence circuits;
3.3.
the phase-to-ground fault current in amps through the impedance RF = 5 Ω with the busbar at no load (i.e., with all circuit breakers at the beginning of each line open);
HV upstream network
HV Bus-Bar
CB11 CB21
TR1
MV Red
Bus-Bar
TR2
CB12 CB22
TB
P1MV Q1MV
P2MV Q2MV
MV Green
Bus-Bar
HV upstream network
U Net =132 kV
I 3 ϕ sc =10.556 kA
I 1 ϕ sc =8.458 kA
X d / Rd =8
X 0 /R 0=4
Transformers (TR1=TR2)
S=40 MVA
k r=142.56 /21.6
Po =21.488 kW
Pk =185.882 kW
u sc %=15.5 %
Ż o ,o =2.529+ j 7.590 Ω
Rn =0 Ω
or
Rn∥X n=587∥57.75 Ω
Loads
U MV =20 kV
P1 MV =20 MW
Q1 MV =10 Mvar
P2 MV =17 MW
Q2 MV =8 Mvar