Single-line diagram

Source: Wikipedia, the free encyclopedia.
A typical one-line diagram with annotated power flows. Red boxes represent circuit breakers, grey lines represent three-phase bus and interconnecting conductors, the orange circle represents an electric generator, the green spiral is an inductor, and the three overlapping blue circles represent a double-wound transformer with a tertiary winding.

In

three-phase system the line represents all three phases (the conductors are both supply and return due to the nature of the alternating current circuits).[1]

The one-line diagram has its largest application in

power flow studies. Electrical elements such as circuit breakers, transformers, capacitors, bus bars, and conductors are shown by standardized schematic symbols.[2]
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 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. A one-line diagram can also be used to show a high level view of conduit runs for a PLC control system.

Buses

The lines in the single-line diagram connect nodes – points in the system that are "electrically distinct" (i.e., there is nonzero

synchrophasor) using the phasor measurement units.[6]

Balanced systems

The theory of three-phase power systems tells us that as long as the

asymmetric fault
on only one or two phases of the system.

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

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

Unbalanced systems

When using the method of

phase sequences are identified on the diagrams. For example, in general a generator
will have different positive and negative sequence impedance, and certain transformer winding connections block zero-sequence currents. The unbalanced system can be resolved into three single line diagrams for each sequence, and interconnected to show how the unbalanced components add in each part of the system.

See also

References

  1. ^ a b Oliver 1991, p. 38.
  2. ^ a b McAvinew, Thomas; Mulley, Raymond (2004), Control System Documentation, ISA, p. 165,
    ISBN 1-55617-896-4
  3. ^ Meier 2006, p. 197.
  4. OCLC 1259189630
    .
  5. OCLC 1043202630
    .
  6. S2CID 115678159
    .
  7. ^ Guile, A.E.; Paterson, W. (1977), Electrical Power Systems (2nd ed.), Pergamon, p. 4,
    ISBN 0-08-021729-X
  8. OCLC 1026831292
    .
  9. ^ Tleis, Nasser (2008), Power System Modelling and Fault Analysis, Elsevier, p. 28,
    ISBN 978-0-7506-8074-5

Sources
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