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An IEC 60909 calculation is performed for the selected nodes and branches. The calculation can be performed in two different ways:

•With only one selected node

•With multiple selected objects.

 

In an IEC 60909 calculation, a distinction is made in the presentation of results between a calculation in which only one node is selected (single-node calculation) or multiple objects. In the case where only one node is selected, all branch and element flows which contribute to the short-circuit current at the selected node (the partial short-circuit currents) in the network are calculated and displayed.

Prior to a single-node calculation, Vision checks whether the clock numbers are correct for parallel transformers in the network. In the event of an incorrect parallel connection, Vision gives a message and the calculation is not performed.

 

An IEC 60909 calculation takes place as follows:

•choose Calculate | Basic | IEC 60909

•specify the fault type (symmetrical/one-phase/two-phase)

•select the calculation sort (maximum short-circuit currents or minimum short-circuit currents)

•select the desired tap positions (all transformers with their nominal tap position or all transformers with their set tap position)

•select the c-factor for low voltage

•exit form via [Ok]

 

The following are calculated for each node per fault type:

 

The following are calculated for each branch per fault type:

 

An accelerated choice can be made for a short-circuit calculation with the previously indicated settings, by using the speed button. Also with the help of F9 the last calculation is repeated.

 

See also:

•General

•Result