![]() Since the generated ems of synchronous motor loads contribute to the fault current, they are always included in making fault calculations. Static loads (i.e., the loads which do not involve rotating machines) have little effect on the total line current during a fault and are usually omitted. Since the resistance of a syste is very small as compared to its inductive reactance, the resistance is often omitted when making fault calculations. The shunt admittance is usually omitted in the equivalent circuit of the transformer because the magnetizing current of a transformer is usually insignificant compared with the full load current. Medium and long lines are represented by nominal PI circuits, whereas very long lines are represented by equivalent PI circuits. A short line is represented by its series impedance. Transformers and motors are represented by their equivalent circuits. Representation of Power System Components on the Single Line DiagramĪ generator is represented by an emf in series with an impedance. The equivalent circuit of the system drawn by combining the equivalent circuits for the various components shown in the one-line diagram is known as the impedance diagram of the system. In order to analyze a power system under load conditions or upon the occurrence of a fault, it is essential to draw the per-phase equivalent circuit of the system by using its one-line diagram. Three phases are denoted by a single conductor i.e., power system is assumed in a balanced steady state. Concept of a Bus in Single Line DiagramĪ single line diagram is method of simplified representation of a three phase power system.Representation of Power System Components on the Single Line Diagram.The errors mean their calculation gives a higher value than the actual value. If the resistance and reactance ignored errors up to 12% may be introduced. It is considered that if the resistance is less than one-third of the reactance, and resistance is ignored, then the error introduced will be not more than 5 %. The winding resistance, including the line resistance, are quite small in comparison with leakage reactance and shunt path which includes line charging and transformer magnetising circuit provide a very high parallel impedance with fault. The reactance diagram gives an accurate result for many power system studies, such as short-circuit studies, etc. Reactance diagram of the power system is shown below. Reactance diagram is drawn by neglecting the effective resistance of generator armature, transformer winding resistance, transmission line resistance line charging and the magnetising circuit of transformers. The impedance diagram can further be simplified by making certain assumptions and reduced to simplified reactance. The three separate impedance diagrams are used in the short circuit for the studies of unsymmetrical fault. Three separate diagrams are also used for representing the positive, negative and zero sequence networks. It is also called positive sequence diagram. The diagram shown below is the balanced 3-phase diagram. Neutral earthing impedance does not appear in the diagram as the balanced condition is assumed. The load is assumed to be passive and are represented by a resistive and inductive reactance in the series. In impedance diagram, each component is represented by its equivalent circuit, e.g., the synchronous generator at the generating station by a voltage source in series with the resistance and reactance, the transformer by a nominal ∏-equivalent circuit. So for simplification, the impedance diagram is used for representing the power system components. It is difficult to draw the line diagram of the few components. The figure shown below represents the single line diagram of a typical block system. Generator and transformer connections, star, delta and neutral earthing are indicated by symbols drawn by the side of the representation of these elements.Ĭircuit breakers are represented by rectangular blocks. In the single line diagram, the system component is usually drawn in the form of their symbols. It is not necessary to show all the components of the system on a single line diagram, e.g., circuit breaker need not be shown in the load flow study but are the must for a protection study. The single line diagram of a power system is the network which shows the main connections and arrangement of the system components along with their data (such as output rating, voltage, resistance and reactance, etc.). ![]() Single line diagram is the representation of a power system using the simple symbol for each component.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |