2. The balanced load of three-phase system having Van 230Ɖ0 Vrms and positive phase sequence. Find the reading of each wattmeter and the total power drawn by the load using two wattmeter method if the impedance per phase is 3+j4 2. =

Design a three-phase system such that the phase current in the generator, lines and charging phase is the same. The phase voltage in the generator must be 1000 [V] with ACB sequence. The connected load must be such that the phase current in each load is 10 [A] and its power factor is 0.97 “lagging”.

In a three – phase system with the unbalanced loads, total power can be measured by using three wattmeter method is given by, 3 x Wattmeter reading O P1+P2 P1+P2+P3 O P1-P2-P3

Select the following statement that is TRUE for an advantage of a three-phase ystem: a) Three different voltages available to the load in a wye-connected source. b Less efficient system than single-phase systems. C) A plot of total instantaneous power versus time is constant. d) A plot of total instantaneous power versus time is fluctuating.

In a +ve sequence 3-phase supply, _________________________ a. Angle between voltages in Y  and R phase  is  0 degree b. Angle between voltages in Y  and R phase  is 180 degree c. Angle between voltages in Y  and R phase  is 120 degree d. Angle between voltages in Y  and R phase  is 90 degree

n 3-phase alternator, the change of terminal voltage from no load to full load is more in case of leading power factor as compared to unity power factor. Select one: True False

2. (A) In a 440 V, 3-phase balanced AC-system, a wattmeter is connected as follows: curren- coil(CC) on Y and presser-coil(PC) between R and B. Load is balanced-A with per phase impedance 5.5415°. Draw phasors: Icc and VPC. Calculate wattmeter reading.

3 phase balanced Wye connected inductive loads have PLOAD When connected to VGEN three phase generator as shown in figure below. In this figure Van is reference voltage. (Generator internal resistance and line impedance are neglected. PLOAD and Van values are given in Table1.) a. Calculate the line currents (laA,IbB,and IcC) b. Calculate the line voltages (Vab,Vbc,and Vca) A N IbB b

Figure 1 shows a three-phase power system network comprises of synchronous generator, transformers, transmission lines and loads while Table 1 shows the ratings of the components. Using per unit analysis, 100 MVA base and 20 kV as the voltage base at the generator, answer the following questions: Ig T2 TLine Load C Load A Load B Figure 1: A simple power system network. Table 1: The power system component ratings G 90 MVA, 20 kV, XG = 120% T1 80 MVA, 20/132 kV, XTI = 16% T2 80 MVA, 132/11 kV, XT2 = 10% TLine 132 kV, XLine = 18 2 Load A 7 MW +j 3 Mvar Load B 30 MW +j 15 Mvar Load C 22 MVA, 0.89 power factor leading (a) Calculate the impedance per-unit values of all independent components based on given conditions.

Topic: "Measurement of Power in a 3 Phase Circuit"—Two Wattmeter