Power Factor

-

Power Factor:

Power factor is defined as the cosine of the angle between voltage and current. Power factor is the measure of how effectively the incoming power is used from total/apparent power in an electrical system.

A high power factor indicates that the power supplied to the electrical system is effectively used. 

A system with low power factor doesn’t effectively consume the incoming electric supply and results in losses. There is no power factor involved in DC circuits due to zero frequency. But, in AC circuits, the value of power factor always lies between 0 and 1.

Cause of Low Power Factor:

Some causes of low power factor are 

a) The presence of harmonic current in the system reduces power factor. 

b) Improper wiring leads to three-phase imbalance causing low power factor. 

c) When the system is loaded lightly, the voltage increases, increasing the magnetization current demand of the machine. This causes a poor power factor in the system. 

d) The current drawn by inductive loads is lagging and results in poor power factor.

Effect of Low power Factor:

Some effects of low power factor are as follows: 

a) Large Copper Losses 

b) Large kVA rating

c) Poor Voltage Regulation.

Power Factor Correction:

The power factor correction can be done by the following two methods

a) Power Factor Correction Method using Capacitors

b) Power Factor Correction Method using a Synchronous Condenser

c) Power Factor Correction Method using a Phase Advancers

Active Power:

Real Power (kW) is the power that actually powers the equipment and performs useful, productive work. It is also called Actual Power, Active Power or Working Power.

Reactive Power:

Reactive Power (kVAr) is the power required by some equipment (eg. transformers & motors) to produce a magnetic field to enable real work to be done. It’s necessary to energise this equipment however it does not perform any productive work.

Apparent Power:

Apparent Power (kVA) is the vector sum of Real Power (kW) and Reactive Power (kVAR) and is the total power supplied through the mains that is required to produce the required amount of Real Power for the load. It is also known as the ‘demand’.


Comments

Post a Comment

Popular posts from this blog

Reactive Power

-
Reactive Power Reactive power is used to control voltage over transmission line or in power systems network. Mathematically, Reactive Power is product of volage and current with sin(phi).        Q = VI sin(phi) -----------(1) Here, we observed that from eq.(1), Reactive Power depends upon flux (phi). And We have,   V = E1 = 4.44 Nf(phi) ----------(2)     Where, phi = magnetic flux(Weber)                     N  = No. of turns                     f   = freuency(Hz) From eqn(2), We can says that, voltage depend upon flux. By this way we can say that, Reactive Power depends upon voltage. In case of synchronous machine: Over excitation ---> Over flux ---> Over R.P Need of Reactive Power : Voltage control in power system is important for proper operation for electrical devices/elements to prevent from damage such as :  -To reduces Transmission lines losses -To mantain the ability of system and prevent Voltage collapse. -Over heating of Electrical machine - Reactive Power (VARs) is used
Read more

Surge impedance Loading

-
Surge Impedance Loading: A transmission line may considered as generating capacitive reactive volt-amperes in shunt capacitance and consuming (absorbing) inductive reactive volt-amperes in its series inductance. The load at which inductive and capacitive reactive volt amperes are equal and opposite is called the surge impedance Loading or (nature load of the line). "The power delivered by the line to purely resistive load equal to its surge impedance the load at which the inductive and capacitive reactive volt-amperes are equal and opposite, is called surge impedance Loading of the line." Capacitive volt-amp. generated in the line = V *I = V / Xc = V² / ωL Inductive volt-amp.  absorbed in the line = V * I = I *XL = I² *ωL Under natural load conditions, Capacitive volt-amp. = Inductive volt-amp.             V² * wc   =    I² * ωL    or,  V / I   = √(L/C) =  Zo = Surge impedance At this load V and I are in same phase. At this Zo is purely resistive. There is not present imagina
Read more

Ferranti Effect

-
Image
 When Recieving end of the transmission line is operating under no load condition or lightly condition,sending end voltage(Vs) is less than Recieving end Voltage (VR). Ferranti Effect is due to charging current Ic of the line. In medium Transmission lines; At No-Load,   Hence, Recieving end Voltage is more than sending end voltage. This is Ferranti Effect. This is also show that Ferranti Effect depends on the frequency and Electrical Length of the line. Now Let's see; At Load condition, Here, we saw that, No Ferranti Effect occurs at Load condition. **Ferranti Effect is more dominanting in communication Lines.** ## Elimination of Ferranti Effect: --To eliminate/nullify Ferranti Effect, we need inductor parallel to the capacitor.
Read more