What is Reactive power: Definition and 56 Discussions

Instantaneous power in an electric circuit is the rate of flow of energy past a given point of the circuit. In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow.
The portion of instantaneous power that, averaged over a complete cycle of the AC waveform, results in net transfer of energy in one direction is known as instantaneous active power, and its time average is known as active power or real power. The portion of instantaneous power that results in no net transfer of energy but instead oscillates between the source and load in each cycle due to stored energy, is known as instantaneous reactive power, and its amplitude is the absolute value of reactive power.

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  1. F

    Engineering Find the reactive power before power factor correction

    Relevant Equations: My solution: Could someone please verify my answer?
  2. shehanshashika

    Figuring Out the Reactive Energy Measurement Method with Field & Lab Tests

    The digital CT (current transformer) operated energy meters are tested in field using consumer's load conditions by means of a parallel test equipment. It was observed that the reactive energy measurement has high accuracy mismatches on harmonic polluted loads. Some literature indicates that...
  3. E

    Why is a capacitor a generator of lagging reactive power?

    An ideal capacitor has power factor of zero degree leading as current leads the voltage in capacitor.But it also means that capacitor is generator of lagging reactive power.What does that mean.How does it do so.Capacitor is used for reactive power generation at inductive load sites.
  4. J

    Reactive power requirement requires which element

    Homework Statement Homework Equations I think it should be A for 1st and B for 2nd Shunt capacitor is used to improve power factor by giving reactive power to line. Series capacitor is used to improve efficiency of line as it nullifies effect of line inductance. And for 2nd Q proportional to...
  5. J

    Calculate Real and Reactive Power and write equation for S = P + jQ

    Homework Statement v = 141.4sin(wt + 15) i = 14.14 cos(wt - 45) Homework Equations Draw Phasors. P = VI cos(theta) Q = VI sin(theta) S = P + jQ theta is angle between V and I The Attempt at a Solution [/B] V = 141.4sin(wt + 15) So Vrms = 141.4/1.414 sin(wt + 15) = 100 sin (wt + 15) I = 14.14...
  6. A

    Calculating the reactive power of a transmission line

    I have a single machine connected to an infinite bus with the following parameters: - Sending end power = 3.75MW - RL=5.18 ohms - XL=130 ohms - VS (Generator bus)=161kV - VR (Infinite bus)=161kV - Sending end voltage angle (delta) = 0.01877 (Angle which allows 3.75MW to be transferred)...
  7. L

    Why reactive power is not tranferred between source and load

    I have read that at a balanced three phase AC system reactive power is not tranferred between source and load but instead it is exchanged between system phases. Is this true? I can't find any book or paper that corroborate this
  8. peroAlex

    Engineering RL Circuit Power Computation: What Am I Missing in My Solution?

    I'm having some problems understanding why my computation deviates from solutions. I thank in advance to anyone who can give me some tips where I've gone wrong. Homework Statement Compute real power on resistors ## R_1 ## and ## R_2 ## and reactive power on inductor ## L ##. Circuit is powered...
  9. G

    How does an equivalent impedance consume a real power?

    Hello. Please looks at the attached image first. The left image is LCC impedance matching network (one of T-type impedance matching networks) and the right is the corresponding equivalent circuit when CT and CL are adjusted such that an equivalent impedance of the sub-circuit surrounded by...
  10. cnh1995

    Reactive power compensation in power system

    I am trying to understand the solution provided to a numerical problem based on reactive power compensation. Here's the problem: Two buses A and B are connected by a transmission line of reactance j0.5 pu. Voltages at both the buses are 1 pu. Bus A is connected to a generator. If the complex...
  11. Deniz

    Complex Power Homework: Is My Solution Right?

    Homework Statement y = 27 Homework Equations The Attempt at a Solution - I calculated the total impedance. - Divide it with the voltage to get the current. - Then I use the load impedance to find the voltage load. - And I calculated the complex power for the load. I am not comfortable...
  12. G

    Engineering Circuit analysis -- Find active and reactive power in the branch....

    Homework Statement Given the circuit of sinusoidal current (attachment 1) with given data: \underline{E}=100V,\underline{E_1}=40V,\underline{Z}=(10+j10)\Omega,\omega=10^5rad/s,L=1mH, C=0.1uF. Find \underline{I_L},\underline{U_{16}}, active and reactive power in the branch 2-5. 2. The...
  13. O

    Voltage and Reactive Power Relationship

    Hi, I have some trouble regarding the relationship between voltage and reactive power. From what I've read you control the amount of reactive power the generator is producing or absorbing by increasing or lowering the excitation of the generator. I have some trouble getting my head around...
  14. L

    Why are reactive power and voltage related?

    I have read that reactive power sustains/ supports voltage. What is the reason behind this?
  15. V

    Why isn't Reactive Power defined as Q = S - P ?

    The instantaneous power in an AC circuit is given by: p = i(t)⋅v(t) = VrmsIrmscosφ + VrmsIrmscos(2ωt -φ). The average power P = VrmsIrmscosφ is often a useful quantity to know. For example, it can tell me the work being done by a motor. The apparent power S = VrmsIrms is also a useful...
  16. nothing909

    Apparent power, true power, reactive power and power factor

    I calculated the apparent power, true power, reactive power and power factor by using: S=VI S=17684.5 at an angle of 135 In rectangular, that's = -1261.83+j1261.83This is probably a stupid question, but I have S= 17684.5 P= - 1261.83 Q=1261.83 power factor = -0.707 In the marking...
  17. Passionate Eng

    Reactive Power: Consumption, Production and Instantaneous Power

    Why does a load consume reactive power? How can we produce reactive power? And what is the relationship between instantaneous power and complex power?
  18. P

    Tap Changing (ULTC) Transformers and Reactive Power Control

    So I am trying to understand how a ULTC operates in the Reactive Power Control mode (it adjusts taps to control the reactive power in a line). What equation is governing it's operation, and what variables does it adjust in order to increase/decrease reactive flow? Is it just the simple reactive...
  19. Ahmad Kishki

    Understanding Reactive Power and Reactance: Exploring Complex Power Components

    Complex power has two components the "active" and the "reactive". I am comfused. What is the physical interpretation of the complex component? Also what is the reactance?
  20. F

    Apparent Power, Real Power and Reactive Power

    A voltage source of v(t) = 169.7sin200t V is connected across a series combination of a resistance of 10 ohm, an inductance of 10mH, and a capacitance of 500 uF. Determine the current in the circuit, the apparent power, the real power, and the reactive power supplied by the source. What is the...
  21. R

    Reactive Power Control: Relationship to Voltage

    Friends,i was asked once the relationship between reactive power and voltage.ques is"if i am providing reactive power at some particular bus,voltage at that bus is going to improve".why??i answered that if u will provide reactive power remotely to that bus by some shunt compensation device then...
  22. D

    Calculate and plot real and reactive power matlab

    Homework Statement Write a Matlab function to compute and plot real and reactive power consumed (or supplied) by a known impedance (the value of complex impedance should be used as the function’s input) as a function of either current or voltage (use a character: V or I as a second input) for...
  23. N

    What Could Be Causing Negative Reactive Power in a Three Phase Power System?

    In a three phase power system,delta connected 66kV transmission line,the reactive power in one of the line/phase is negative(capacitive) while the reactive power in the other two lines/phases is positive.What is causing the reactive power to be negative(capacitive) in this phase?What are some...
  24. P

    Understanding Negative Reactive Power in Inductive and Resistive Power Systems

    What would it mean if in a power system with purely inductive and resistive elements (No Capacitance) if you were seeing a negative value of reactive power when there was no load connected? E.g. If the load was disconnected but the transmission line contained both resistance and inductive...
  25. C

    Engineering AC Circuit; find average and reactive power to load (and load V and I)

    Homework Statement In the circuit shown, a load having an impedance of 39 + j26Ω is fed from a voltage source through a line having an impedance of 1 + j4Ω. The rms value of the source voltage is 250V. a) Calculate the load current IL and voltage VL b) Calculate the average and reactive...
  26. D

    Generating Reactive Power: Exploring Methods and Measurements

    Hi everyone! I always use this forum to consult but I had never had the need to post something. I need to create an experiment in which I measure reactive power with a meter (see attachment). I was thinking on using a transformer with a resistive load on it's secondary, but I'm not sure if...
  27. E

    Reactive power with electromagnetic sources in free space

    Good morning, in circuit theory I know that reacting power arise from phasors and represents a power which can't be used, because not delivered to any load, but continuously flows back and forth between the load and the generator with a zero mean during one period. I can't understand very well...
  28. W

    How to calculate reactive power for 3 phase induction motor

    Hi all, I would like to install Capacitor Bank into my control panel board which contains of few 10HP induction motors. Currently I'm just able to measure the Ampere for every induction motor by using current meter. How to calculate the reactive power for 10HP 3phase 4pole induction motor by...
  29. D

    Voltage, real reactive power question

    Homework Statement A 33 kV single phase generator is supplying a customer a load through a cable with an impedance j2 ohms a.What voltage would the customer experience if rated current of 500 A is drawn at power factor of unity at the customer end? b. How much active and reactive power...
  30. J

    Explaining reactive power on a subatomic level

    I am currently studying electric power engineering, which in my case is most about models and approximations, which makes it hard to understand the real physics behind some of the model. I would say that I understand the definition of current and voltage. But is it possible to explain the...
  31. M

    What's the physical meaning of the reactive power signs?

    I wonder what really happens to powers in capacitors and inductors when they are connected in a circuit either in series or in parallel. I know that inductors have a positive reactive power while capacitors a negative one, so I imagine inductors release energy while capacitors absorb it, but it...
  32. G

    How Do Capacitors Compensate Reactive Power in Inductive Loads?

    how capacitor compensate reactive power requirement of inductive load .? please explain...
  33. S

    Exploring the Physics of Reactive Power

    Hi I am studying instrumentation and during my internship at a power plant i have come across many basic Power engineering stuff. My concept in the field are not very clear and a term i fail to understand is Reactive power.. I had studied that reactive power just travels back and forth in a...
  34. B

    Reactive power, RL RC circuits

    Trying to understand the power network and synchronous machines, led me to the fact that I am not sure about the basics. The terms the generator is delivering or consuming reacting power made me halt. So I went back to my old course(which I allegedly passed) where the reactive power is...
  35. A

    Electricity True, Apparent and Reactive power

    Electricity "True, Apparent and Reactive power" This is the problem: "The power factor of a load on 120 volt, 60Hz source is raised from 0.707 to 0.866 power factor lagging by connecting a 53 micro-farad capacitor across the load. How can i solve for the "true" power?" i know that power...
  36. S

    What is the difference between apparent, reactive, and real power?

    hi dudes... i m confuse about apparent, reactive and real power, please explain...any help wll be appreciated..thanks in advance
  37. R

    Calculating Armature Current from Active & Reactive Power & Voltage

    How do calculate the current when I have the active power and reactive power and voltage? A single-phase, full-wave controlled bridge rectifier supplies a permanent magnet dc motor. The rectifier is connected to a 240V ac voltage source and absorbs 1200W of active power and 1000VAR of...
  38. E

    Is Reactive Power Useful? When Should It Be Minimized?

    Yes I understand the definition of reactive power. It is the power that flows back and forth on transmission lines and does not do work(correct me). My question is, is reactive power useful? In what case reactive power has to be minimized as low as possible? I read an article about the...
  39. A

    Reactive Power Apparent Power Issue

    This is not a HW question. Assume you have a sinusoidally varying voltage, such that current lags by some phase angle phi Then you can write the power as a function of time as p(t)=i(t)v(t)=2*Vrms*Irms*cos(omega*t)*cos(omega*t-phi) You can break this up via trig identity into the following...
  40. A

    Effect of sudden loss of reactive power for an induction generator

    So I am having this problem at work where a 150kW induction motor is being used as an induction generator. There is a capacitor bank in parallel to the induction generator which is primarily for PFC(the reactive power requirement of the generator is fed by the grid). Assume the induction...
  41. M

    Understanding Reactive Power Measurement with Wattmeter Configuration

    Does anybody understand how this wattmeter configuration is measuring reactive power? Thanks
  42. G

    Confused about the reactive power

    hey, i am a little bit confused about the reactive power. we defined it as Q=UI sin(a) and the apparent power as S=UI Now I have to solve this excercise: Which percentage of heat loss in a power grid is caused by the reactive power, when the powerfactor is cos(a)=0,85? Now I...
  43. H

    Understanding Induction Motors & Reactive Power

    I was reading about induction motors and speed controller(self commutated inverters for cage motor), and i didn't understand this sentence:"The induction motor can either absorb or deliver reactive power". Thanks for any help.
  44. W

    Electric Power measurement Current Transformers and reactive power

    Apparently my modern electronic home electric meter uses a 'current transformer' to measure the current in order to calculate the wattage I am using. My question: is the flux generated in the current transformer also proportional to the reactive part of the current as well as the in-phase...
  45. E

    Reactive Power: A Strange Concept?

    Hi! What is your opinion about this article: [PLAIN]"www.bme.hu/ptee2000/papers/fetea.pdf"[/URL]
  46. B

    Optimizing Reactive Power Injection with a Single Phase Inverter

    Hello, I am trying to simulate reactive power injection with a single phase inverter. The constant dc bus voltage on the input side is maintained much higher than 169.71V (considering 120V rms ac output). I have generated the current reference for the control (a PI based system) but it doesn't...
  47. F

    Voltage source -> Ideal switch -> Resistance = Reactive power

    This is a problem i just can't get my head around. When you have a circuit consisting of a "Ideal Voltage source -> Ideal switch -> Ideal Resistance" all in series. The voltage source produces a sinusodal voltage and the switch is set to cut off a part of any rising curve...
  48. W

    Solving Reactive Power for Purely Inductive and Capacitive Circuits

    Hello! From what I have learned now is the topic of sinusoidal steady-state power.In this topic,the reactive power for purely inductive and purely capacitive confuse me for a long time. Try check out the problem I faced from this...
  49. S

    What Distinguishes Real Power from Reactive Power in Electrical Systems?

    Homework Statement What is the exact difference between real an reactive power? Homework Equations As far as i know real power =V*I*cos(teta) reactive power = V*I*sin(teta) The Attempt at a Solution...
  50. S

    How Does Reactive Power Compensation Affect Power Factor and System Efficiency?

    Calculate the capacitance C needed for the load compensation to unity power factor. Calculate the rms value E of the needed distribution voltage e before and after compensation. Calculate the active power loss (delta)Ps at energy delivery before and after compensation. U = 2.4kV (line to...