Per Unit System(13/09/2024)

A synchronous generator rated 11 KV,50 MVA has a per unit impedance of 0.2 per unit on its own base,then its impedance referred to 22KV,150 MVA would be

• 0.133 PU

• 0.1 PU

• 0.2 PU

• 0.15 PU

A 33 KV,25 MVA Transformer has a per unit impedance of 0.9 per unit on its own base, then its impedance referred to 11KV,50 MVA would be

• 10.4

• 12.2

• 14.4

• 16.2

The per unit impedance Z_pu of 3-Phase system is

• Z(ohm)*(MVA_B)/(kV)²_B

• Z(ohm)*(kV)²_B/(MVA_B)

• 1000*(kV)_B/√3.I_B

• 1000*[(kV)_B/I_B]*10⁶

A synchronous generator is rated at 40 MVA,14.6 kV,50 Hz. The base impedance of generator will be

• 5.33 ohm

• 6.29 ohm

• 3.57 ohm

• 7.25 ohm

A 50 MVA, 15 kV synchronous generator has a per unit impedance of 0.25 per unit on its own base. What would be its impedance referred to 30 kV, 100 MVA?

• 0.083 PU

• 0.125 PU

• 0.2 PU

• 0.167 PU

The base impedance Z_base for a 3-phase transformer rated at 20 MVA and 11 kV is calculated as:

• Z(ohm) = (kV)²/(MVA)

• Z(ohm) = (MVA)/(kV)²

• Z(ohm) = (kV)²/(3*MVA)

• Z(ohm) = (3*MVA)/(kV)²

A 25 MVA, 33 kV transformer has a per unit impedance of 0.12 per unit on its own base. If referred to 22 kV, what would be its impedance?

• 0.08

• 0.1

• 0.12

• 0.15

A 60 MVA, 20 kV transformer has a per unit impedance of 0.15 per unit on its own base. If referred to 10 kV, what would be its impedance?

• 0.075

• 0.1

• 0.15

• 0.2

A synchronous generator rated at 30 MVA, 12 kV has a base impedance of:

• 4.8 ohm

• 5.0 ohm

• 6.0 ohm

• 7.2 ohm

A 40 MVA, 25 kV synchronous generator has a per unit impedance of 0.3 per unit on its own base. What would be its impedance referred to 50 kV, 100 MVA?

• 0.12 PU

• 0.15 PU

• 0.18 PU

• 0.2 PU