Problem 3: Three loads are supplied by a voltage source, Vs, through a line. The given are as follows: L1 = 60W @ 0.8 LAG L2 = 40W @ 0.5 LEAD ZLINE = 0.5 + j0.5 N V, = 5040 S, = 200VA @ 0.75 LAG Find: 1. The complex power associated with Load 3 2. The impedance (Z.) of Load 3 3. The KVAR rating of the capacitor to be connected parallel to the loads that will raise the PF to unity. V, Load 3 Load 2 Load I

Problem 3: Three loads are supplied by a voltage source, Vs, through a line. The given are as follows: L1 = 60W @ 0.8 LAG L2 = 40W @ 0.5 LEAD ZLINE = 0.5 + j0.5 N V, = 5040 S, = 200VA @ 0.75 LAG Find: 1. The complex power associated with Load 3 2. The impedance (Z.) of Load 3 3. The KVAR rating of the capacitor to be connected parallel to the loads that will raise the PF to unity. V, Load 3 Load 2 Load I

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter2: Fundamentals

Section: Chapter Questions

Problem 2.42P: A balanced -connected impedance load with (12+j9) per phase is supplied by a balanced three-phase...

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A balanced -connected impedance load with (12+j9) per phase is supplied by a balanced three-phase 60-Hz,208-V source, (a) Calculate the line current, the total real and reactive power absorbed by the load, the load power factor, and the apparent load power, (b) Sketch a phasor diagram showing the line currents, the line-to-line source voltages, and the -load currents. Use Vab as the reference.
Figure 2.33 gives the general -Y transformation. (a) Show that the general transformation reduces to that given in Figure 2.16 for a balanced three-phase load. (b) Determine the impedances of the equivalent Y for the following impedances: ZAB=j10,ZBC=j20, and ZCA=j25. ZAB=ZAZB+ZBAC+ZCZAZCZA=ZABZCAZAB+ZBC+ZCAZBC=ZAZB+ZBAC+ZCZAZAZB=ZABZBCZAB+ZBC+ZCAZCA=ZAZB+ZBAC+ZCZAZBZA=ZCAZBCZAB+ZBC+ZCA
Let a series RLC network be connected to a source voltage V, drawing a current I. (a) In terms of the load impedance Z=ZZ, find expressions for P and Q, from complex power considerations. (b) Express p(t) in terms of P and Q, by choosing i(t)=2Icost. (c) For the case of Z=R+jL+1/jC, interpret the result of part (b) in terms of P,QL, and Qc. In particular, if 2LC=1, when the inductive and capacitive reactances cancel, comment on what happens.
The three-phase source line-to-neutral voltages are given by Ean=100,Ebh=10+240, and Ecn=10240volts. Is the source balanced? (a) Yes (b) No
A three-phase line, which has an impedance of (2+j4) per phase, feeds two balanced three-phase loads that are connected in parallel. One of the loads is Y-connected with an impedance of (30+j40) per phase, and the other is -connected with an impedance of (60j45) per phase. The line is energized at the sending end from a 60-Hz, three-phase, balanced voltage source of 1203V (rms. line-to-line). Determine (a) the current, real power. and reactive power delivered by the sending-end source: (b) the line-to-line voltage at the load: (C) the current per phase in each load: and (d) the total three-phase real and reactive powers absorbed by each load and by the line. Check that the total three- phase complex power delivered by the source equals the total three-phase power absorbed by the line and loads.
Consider a three-phase Y-connected source feeding a balanced- load. The phasor sum of the line currents as well as the neutral current are always zero. (a) True (b) False
Figure 3.32 shows the oneline diagram of a three-phase power system. By selecting a common base of 100 MVA and 22 kV on the generator side, draw an impedance diagram showing all impedances including the load impedance in per-unit. The data are given a follows: G:90MVA22kVx=0.18perunitT1:50MVA22/220kVx=0.10perunitT2:40MVA220/11kVx=0.06perunitT3:40MVA22/110kVx=0.064perunitT4:40MVA110/11kVx=0.08perunitM:66.5MVA10.45kVx=0.185perunit Lines I and 2 have series reactances of 48.4 and 65.43, respectively. At bus 4, the three-phase load absorbs 57 MVA at 10.45 kV and 0.6 power factor lagging.
For a balanced- load supplied by a balanced positive-sequence source. the line currents into the load are 3 times the -Ioad currents and lag by 30. (a) True (b) False
Two balanced Y-connected loads, one drawing 10 kW at 0.8 power factor lagging and the other IS kW at 0.9 power factor leading, are connected in parallel and supplied by a balanced three-phase Y-connected, 480-V source. (a) Determine the source current. (b) If the load neutrals are connected to the source neutral by a zero-ohm neutral wire through an ammeter, what will the ammeter read?
A three-phase line with an impedance of (0.2+j1.0)/ phase feeds three balanced three-phase loads connected in parallel. Load 1: Absorbs a total of 150 kW and 120 kvar. Load 2: Delta connected with an impedance of (150j48)/phase. Load 3: 120 kVA at 0.6 PF leading. If the line-to-neutral voltage at the load end of the line is 2000 v (rms), determine the magnitude of the line-to-line voltage at the source end of the line.
It is stated that (i) balanced three-phase circuits can be solved in per unit on a per-phase basis after converting - load impedances to equivalent Y impedances. (ii) Base values can be selected either on a per-phase basis or on a three-phase basis. (a) Both statements are true. (b) Neither is true. (c) Only one of the above is true.
What is the main direct cause of reactive power in AC system?A. Resistance of transmission linesB. Inductance and capacitance in the loadsC. Ideal transformer connected in the systemD. Power produced by generator2. “Reactive power in a system is dissipated generally as thermal energy?”A. TRUEB. FALSE3. Which of the following statements are correct for three phase circuit:A. Sum of all the three phase currents is zero in unbalanced networkB. Total power transfer to load is constant with timeC. Neutral conductor is same size in terms of material used as in single phase conductorsD. Net apparent power consumed is equal to real power