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The calculation is started with: Calculate | Security | Enexis | Loadflow.

In the calculation settings form, the scaling percentages for load and generation can be specified.

 

First, a normal loadflow is performed. The voltages of nodes and currents of branches and switches are tested at normal limits. Already tripped protections are signalled.

 

Successively, one by one, all transport cables (mains cables) are switched off and a load flow is performed. Voltages and currents are tested for fault limits. Already tripped protection devices are signalled.

 

The load flow calculates:

•in normal situation: voltages and currents and tripped protective devices

•in fault conditions: voltages and currents and tripping protections

 

 

RESULTS

 

Network

After running the load flows, results are displayed as text in the diagram.

 

For nodes, the results are:

•The normal voltage

•The minimum and maximum voltage, across all n-1 situations

 

For branches, the results are:

•TheItoe (for cable only)

•The normal current and associated load degrees in relation toInom andItoe

•The maximum current over all n-1 situations and the corresponding load degrees in relation toInom andItoe

 

Colour indication

Nodes, branches and switches are displayed in colour when voltage and load limits are exceeded. A distinction is made between limits for a "normal situation" and limits for a "fault situation". Limits for a normal situation are closer to nominal values than limits for a fault situation. Limits are definedin the Options, under Calculation | Limits.

Load limits for connections and transformers can be defined separately.

 

The corresponding colour indications can be defined in the four levels: higher, high, low and lower. Colour selection takes place in the Options, at Calculation | General.

 

 

 

General

Calculate | Results | Overview displays a list of problem objects:

•Node with over- or undervoltage

•Node becoming de-energised

•Branch with overload

•Switch with overload

•Circuit breaker already tripped

 

Details

Calculate | Results | Details (or right-click on an object in result mode) displays detailed information of selected nodes, branches and protections in a form.

 

The results displayed for a node are:

•The normal voltage

•How many times the node is de-energised, across all n-1 situations

•The maximum voltage and at which n-1 situation

•The minimum voltage and at which n-1 situation

 

The results shown for a branch are:

•Itoe (only for cable)

•The normal current

•The normal load degree in relation toInom

•The normal load degree in relation toItoe

•The maximum current

•The maximum load degree in relation toInom

•The maximum load degree in relation toItoe

•At which n-1 situation

 

The results shown at a secondary are:

•The normal voltage

•The normal current

•The normal load degree

•Whether the protection already trips normally

•The maximum current

•The maximum load degree

•Whether the protection already trips in any n-1 situation

 

Graph

With Calculate | Results | Graph the results can be viewed as a bar graph.

For nodes the stress band Umin...Umax.

For branches the load degree band normal...max.

 

Export

The results can be exported to Excel using Calculate | Results | Export. The export is a report of all objects, in a fixed format, on three worksheets: Nodes, Branches and Switches and Safeguards.