A 4bus 115kV power system is specified above The impedance o

A 4-bus 115-kV power system is specified above. The impedance of all lines is 0.1 + j0.4 /km. Assume that the loads are constant impedance loads. Assume generator reactances are 0.2 per unit on 100 MVA, 115 kV base. For the system mentioned above, answer Questions 1 through 5, working with impedances in Ohms (not per unit).

Question 1

YBUS (1,1) in S is

Question 2

YBUS (2,2) in S is

Question 3

YBUS (3,4) in S is

Question 4

If line 2-4 is taken out for maintenance, which of the following elements of bus admittance matrix will be affected? Check all that apply.

Question 5

If 70 MVar capacitor is switched off, YBUS (2,2) in S becomes

d) 0.0288 + j0.0941

Question 6

The value of magnetizing reactance in the transformer equivalent circuit models

Question 7

Transformer core is laminated to reduce

Question 8

When transformer is not loaded – check all that apply

Question 9

For a 230 kV/12.47 kV Delta/YG transformer, the angle of the voltage phasor VAC on Delta side is X degrees, and the angle of the voltage phasor Van on the YG side is Y degrees.

X - Y is

Question 10

For a 230 kV/12.47 kV Delta/YG transformer the angle of the line current phasor ILA on Delta side is X degrees, and the angle of the line current phasor ILa on YG side is Y degrees.

X-Y is

A transformer rated 2400/240 V, 50 kVA has following parameters with conventional notations:

RP = 1 , XP = 2.5 , RS = 0.070 , XS = 0.12 ,

Admittance of the shunt branch is 0.0003 – j0.0002 S referred to primary.

For its approximate equivalent circuit, answer Questions 11 through 1

Question 11

ZEQ-P in Ohms is

Question 12

ZEQ-S in Ohms is

Question 13

ZEQ-pu is

Question 14

per unit admittance of the shunt branch is

The transformer analyzed is supplying the rated load at 0.85 power factor lagging, at rated voltage on the 240 V side. Answer Questions 15 through 17.

Question 15

Voltage regulation of this transformer is

Question 16

Efficiency of the transformer is

Question 17

Input power factor of the transformer is

Question 18

Bus admittance matrix cannot be exclusively used to solve power systems because (check all that apply)