Defination related to Electrical Power System


Defination of Electrical Power System

Dear friends,

Today i am going to learn you about basic defination of electrical power system.

Following definations of electrical power system :-

  1. Power
  2. Active power
  3. Reactive power
  4.  Apparent power
  5. Power factor
  6. Transmission line
  7. Generating station
  8. Distribution line
  9. SAG
  10. Skin effect
  11. Corona
  12. Ferranti effect
  13. Proximity effect
  14. Feeder
  15. Distributor
  16. Service mains
  17. Per unit value
  • Power :- it is the product of the voltage(V) and current (I).

P = VI (for DC supply)

P = VI cosØ (for AC supply)

power factore

  • Active power (KW) :- which is subjected to the resistance(R)

KW =I2R (for DC supply)

KW = VI cosØ (for AC supply)

  • Reactive power (KVAr):- it is subjected to the inductance (X).

KVAr =I2X (for DC supply)

KVAr = VI sinØ (for AC supply)

  • Apparent power (KVA):-it is subjected to impedance (Z).


It is the vector sum of active power and reactive power

KVA = (KW)2+(KVAr)2

  • Power factor:-

it is the ratio of Active power and Apparent power.

Also define as the cosine angle between voltage and current.


  1. Lagging :- Power Factor < 1   

lagging power factor

When the voltage is lags the current as the two alternating waves. This is called lagging power factor. In case of inductive loads. 

  1. Leading :- Power Factor > 1

leading power factor

When the current leads the voltage as the two alternating waves. This is called as the  leading power factor. In case of capacitive load. 

  1. Unity :- Power Factor = 1

unity power factor

It is define as the voltage and current both are in the same phase. In case of                             resistive load or capacitive load is equal to inductive load.

  • Transmission line :- which is connected between the generation station and distribution station by the conductor. Which collect power from generation station deliver to the distribution station (load center).
  • Generating station: – which is generate electrical power and that power deliver to distribution station through transmission line.
  • Distribution line: – which is connected between transmission line to the consumer. Its collect power from the transmission line and fed to the consumer.
  • SAG :- its define as a difference between the two point of supports & lowest point of the conductor. Which is connected between to supports.


                                      SAG (S) =WL2 /8T

Where, W = weight/meter length of conductor in KG

         L=length of span meter

         T=tension of conductor


  • Skin effect: – DC current flow through the conductor is uniformly. But flow of AC current is nonuniformly. Hence current concentrated on the surface of the conductor. “That tenancy of the AC current concentration on the surface called skin effect.”
  • Corona: – its define as the phenomena of the violet glow, hissing noise and corrosion surrounding the power conductors.
  • Ferranti effect: – at no load condition the receiving end voltage is become more then the sending end voltage is called ferranti effect.
  • Proximity effect:-when two conductor are place nearly then the magnetic field of one conductor is affect to the other conductor is called proximity effect. When current flow direction of both conductor are not same. The flux is link and that effect is occur on the half of the nearer conductor which is more to the further half.

proximiy effect

Where, A and B are conductor

  • Feeder: – the line conductor which is connect the major substation to the distribution.
  • Distributor :- the line which deliver electric power to the consumer by no of tapping.
  • Service mains :- conductor which is connected between distributor to the consumer.
  • Per unit value :- its ratio of the actual value and base value(reference value).


if any query about this electrical power system defination, comment below…………………. 🙂


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