All Topics  
One-line diagram

 

 
   Email Print
   Bookmark   Link
 

 

One-line diagram
 
 
  Topics One-line diagram Topic Home

In power engineering
Power engineering

Power engineering, also called power systems engineering, is a subfield of electrical engineering that deals with the electric power generation, electric power transmission and electric power distribution of electric power as well as the electrical devices connected to such systems including electric generators, electric motors and tr...
, a one-line diagram or single-line diagram is a simplified notation for representing a three-phase
Three-phase

In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are 2p/3 radians offset in time....
 power system. The one-line diagram has its largest application in power flow studies
Power flow study

In power engineering, the power flow study is an important tool involving numerical analysis applied to a power system. Unlike traditional circuit analysis, a power flow study usually uses simplified notation such as a one-line diagram and per-unit system, and focuses on various forms of AC power rather than voltage and Electric current....
. Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors are shown by standardized schematic symbols. Instead of representing each of three phases with a separate line or terminal, only one conductor is represented.






Discussion
Ask a question about 'One-line diagram'
Start a new discussion about 'One-line diagram'
Answer questions from other users
Full Discussion Forum



Encyclopedia


In power engineering
Power engineering

Power engineering, also called power systems engineering, is a subfield of electrical engineering that deals with the electric power generation, electric power transmission and electric power distribution of electric power as well as the electrical devices connected to such systems including electric generators, electric motors and tr...
, a one-line diagram or single-line diagram is a simplified notation for representing a three-phase
Three-phase

In electrical engineering, three-phase electric power systems have at least three conductors carrying voltage waveforms that are 2p/3 radians offset in time....
 power system. The one-line diagram has its largest application in power flow studies
Power flow study

In power engineering, the power flow study is an important tool involving numerical analysis applied to a power system. Unlike traditional circuit analysis, a power flow study usually uses simplified notation such as a one-line diagram and per-unit system, and focuses on various forms of AC power rather than voltage and Electric current....
. Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors are shown by standardized schematic symbols. Instead of representing each of three phases with a separate line or terminal, only one conductor is represented. It is a form of block diagram
Block diagram

Block diagram is a diagram of a system, in which the principal parts or functions are represented by blocks connected by lines, that show the relationships of the blocks....
 graphically depicting the paths for power flow between entities of the system. Elements on the diagram do not represent the physical size or location of the electrical equipment, but it is a common convention to organize the diagram with the same left-to-right, top-to-bottom sequence as the switchgear or other apparatus represented.

The theory of three-phase power systems tells us that as long as the loads on each of the three phases are balanced, we can consider each phase separately. In power engineering, this assumption is usually true (although an important exception is the asymmetric fault
Asymmetric fault

In power engineering, specifically three phase Electric power, an asymmetric or unbalanced fault is a fault which does not affect each of the three phases equally....
), and to consider all three phases requires more effort with very little potential advantage.

A one-line diagram is usually used along with other notational simplifications, such as the per-unit system
Per-unit system

In electrical engineering in the field of power transmission a per-unit system is the expression of system quantities as fractions of a defined base unit quantity....
.

A secondary advantage to using a one-line diagram is that the simpler diagram leaves more space for non-electrical, such as economic
Energy economics

Energy economics is a broad science subject area which includes topics related to energy supply and energy demand of energy in society. Due to diversity of issues and methods applied and shared with a number of academic disciplines, energy economics does not present itself as a self contained academic discipline, but it is an applied subdisci...
, information to be included.