most st algus 1. A three-phase load draws 720 kW from the grid with 0.8 lagging power factor. The load is balanced and star connected. For reactive power compensation, a bank of capacitors is connected in star across the load terminals. With this compensation, active power loss across the lines is reduced 10% (Meaning that If the power loss is 1 unit before compensation, power loss is 0.9 unit after compensation). Assuming that compensation does not change the load terminal voltage, calculate a) b) c) The kVAr rating of capacitors in each phase The improved power factor The new power factor if the same bank of capacitors is connected in delta Hint: The power loss across the line is proportional to the line current and hence the apparent

most st algus 1. A three-phase load draws 720 kW from the grid with 0.8 lagging power factor. The load is balanced and star connected. For reactive power compensation, a bank of capacitors is connected in star across the load terminals. With this compensation, active power loss across the lines is reduced 10% (Meaning that If the power loss is 1 unit before compensation, power loss is 0.9 unit after compensation). Assuming that compensation does not change the load terminal voltage, calculate a) b) c) The kVAr rating of capacitors in each phase The improved power factor The new power factor if the same bank of capacitors is connected in delta Hint: The power loss across the line is proportional to the line current and hence the apparent

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 2.30MCQ: Under balanced operating conditions, consider the three-phase complex power delivered by the...

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The voltage v(t)=359.3cos(t)volts is applied to a load consisting of a 10 resistor in parallel with a capacitive reactance XC=25. Calculate (a) the instantaneous power absorbed by the resistor, (b) the instantaneous power absorbed by the capacitor. (c) the real power absorbed by the resistor, (d) the reactive power delivered by the capacitor, and (e) the load power factor.
Consider a load impedance of Z=jwL connected to a voltage and V let the current drawn be I. (a) Develop an expression for the reactive power Q in terms of ,L, and I, from complex power considerations. (b) Let the instantaneous current be i(t)=2Icos(t+). Obtain an expression for the instantaneous power p(t) into L, and then express it in terms of Q. (c) Comment on the average real power P supplied to the inductor and the instantaneous power supplied.
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 instantaneous voltage across a circuit element is v(t)=400sin(t+30)volts, and the instantaneous current entering the positive terminal of the circuit element is i(t)=100cos(t+10)A. For both the current and voltage, determine (a) the maximum value, (b) the rms value, and (C) the phasor expression, using cos(t) as the reference.
While the instantaneous electric power delivered by a single-phase generator under balanced steady-state conditions is a function of time havi ng two components of a constant and a double-frequency sinusoid, the total instantaneous electric power delivered by a three-phase generator under balanced steady-state conditions is a constant. (a) True (b) False
A generating station has a maximum demand of 30,000 kW. Calculate the cost per unit generated from the following data: Capital cost = P 130M; Annual load factor = 50%; Annual cost of fuel and oil = P7.5M ; Taxes, wages and salaries etc. = P7M and Interest and depreciation = 12%
An AC generator having an internal resistance of 2 k*(omega) is connected to an LCR circuit in series as shown in the figure. If the generator supplies an electromotive force, E = 282 sen (100*pi*t) volt, calculate:a) the impedance of the circuitb) the rms value of the current in the circuitc) the voltage drop across L, C and R
S.2) The serial impedance of the 300 km power transmission line is 23 + j75 ohm / phase and the shunt acceptance is j500 microS / phase. A power of 50 MW with a power factor of 0.88 under 220 kV interphase voltage from the end of the power transmission line being shot. Using these data of the energy transmission line, a) Characteristic impedance of the energy transmission line, b) Natural apparent power of the energy transmission line according to the 220 kV interphase operating voltage, c) The values of the line parameters A, B, C and D of the transmission line using hyperbolic functions, d) Calculate the maximum power that the power transmission line can transmit.
The sending-end voltage in the circuit seen is adjusted so that the load voltage is always 13,800 V(rms). The variable capacitor is adjusted until the average power dissipated in the line resistance is minimum. 1. a) If the frequency of the sinusoidal source is 60 Hz, what is thevalue of the capacitance in microfarads?2. b) If the capacitor is removed from the circuit, what percentageincrease in the magnitude of Vs is necessary to maintain 13,800V(rms) at the load?3. c) If the capacitor is removed from the circuit, what is thepercentage increase in line loss?
A generating station supplied the following loads: 150 MW, 120 MW, 85 MW, 60 MW, and 5 MW. The station has a maximum demand of 220 MW. The annual load factor of the station is 48%. Calculate : 1) the number of units supplied annually 2) diversity factor 3) demand factor
A generating station distributes the following loads. 3000 kW ,8000 kW,14000 KW and 4000 kW. The maximum demand of the station is 30 MW. The annual load factor is 60%. So – find (1) diversity factor (2) demand factor and (3) number of units supplied.
An example power system has two distinct manufacturing areas, one with harmonic loads, and another with only linear loads. The portion of the system with the harmonic loads draws 75 A rms at 60 Hz, 10 A rms at 300 Hz, and 5 A rms at 420 Hz. The part of the system with only linear loads draws 75 A rms at 60 Hz. (i) What is the total load current (at 60 Hz) if both manufacturing plants are running? Calculate the THD. (ii) What is the total load current (at 60 Hz) if only the manufacturing plant with harmonic loads is running? Calculate the THD.