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<< Click to Display Table of Contents >> Power Flow Calculations Flat Start Tap Start Gauss-Seidel Newton-Rhapson Fault Level Calculations |
  
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<< Click to Display Table of Contents >> Power Flow Calculations Flat Start Tap Start Gauss-Seidel Newton-Rhapson Fault Level Calculations |
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Once the network has been designed, performed the following:
•Click the 
button
- OR -
•On the Main Menu, select Calculate and choose a calculation method.
Note:
1.Having Flat Start checked, sets all voltages to 1 p.u. before the calculation begins.
2.Selecting Tap Start will allow the user to set the initial Tap positions for all transformers with automatic Tap changing enabled
3.All elements that are outside the limits specified in the Options->General Tab-sheet, will be flagged accordingly.
4.To view the required parameters e.g. % loading for elements, set the default display parameters in the Options->Display Tab-sheet.
5.To view and change the selected calculation methods and parameters go to Options->Calculation.
Enabling Flat Start will allow the application to initialize all the Bus Bar voltages to input voltage and appropriate phase shift angles according to the connectivity of components in the electrical system.
If not connected to the system or if they are part of an Island (Disconnected System) voltages will be initialized to 0 .
Fault Levels will be reset to 0 and Transformers with automatic Tap changing enabled will be set to Nominal Tap.
Selecting Tap Start will allow the user to set the initial Tap positions for all transformers with automatic Tap changing enabled to Nominal, Intermediate or Maximum.
This implies that the user can specify a different "starting" position where complicated networks do not solve, in order to obtain a valid set of results, from which point problems can be resolved.
This is one of the simplest iterative methods known. It was also one of the most popular methods used in the early days of digital power-flow analysis. The more powerful Newton-Rhapson method is today dominating the field.
Some of the disadvantages of the Gauss-Seidel method are:
•Slow convergence to a solution, increasingly so when the system size grows,
•Impossible to converge with zero impedance branches.
The generalised Newton-Rhapson method is an iterative algorithm for solving a set of simultaneous equations in an equal number of unknowns. At each iteration of the Newton-Rhapson method, the non-linear problem is approximated by a linear-matrix equation.
The Newton-Rhapson method converges equally fast, measured in the number of iterations, for large as well as small systems, unlike the Gauss-Seidel Method. It has therefore become very popular for large power system studies.
All methods will converge to the same result as all use the same iteration tolerance set in the Options.
Note:
•If a network solution blows, then the recursive algorithm cannot converge. This could be due to the network being too heavily loaded or has some large conductor impedances / lengths as an example.
•For large networks that do not converge to a solution try the following:
oCalculate using the more stable Gauss-Seidel method with Flat Start checked. This provides an initial solution even if it doesn't converge.
oThen solve the network using the Newton-Rhapson with the Flat Start unchecked.
oTry to adjust the α and β parameters of the solution method: Options->Calculation.