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<< Click to Display Table of Contents >> Navigation: Options > Options Calculations |
The calculation options are:
•General (base power, frequency, conductor temperature, connection ampacity, colour indication)
•Limits (voltage, load for normal/faulted situation, connection ampacity)
•Loadflow (advanced)
•Costs (losses, interest)
•Reliability (restoration durations)
•Protection (calculation steps, short circuit resistances)
•IEC 61363
•Arc flash (IEEE 1584 or Box test)
•Network analysis
•Macro (limits for the number of iterations and run time)
•Pseudomonitor
•Fault finder
•Transmission analysis
General
Base power
All power data is converted into normalised per unit values to ensure a stable numerical process inside the calculation procedures. It is not necessary to have an exact value for Sbase. A general formula does not exist. The default value of 10 MVA will generally suffice.
The value assigned to Sbase is usually the estimated average of power required by and the power supplied to the nodes. This will typically be something like 1, 10, 100 or 1000 MVA.
Attention! A wrong value may in some cases lead to unpredictable results.
Frequency
The system frequency can be specified. It influences the reactances of components like cables, reactance coils and capacitors.
Link impedance
1 µΩ to 10 mΩ
Conductor temperature
The conductor resistance has been specified at a specific conductor temperature. For the cables this has been specified in the type file. For connections this can be specified in the form. For the Loadflow and Fault Analysis calculations the conductor resistance will be calculated for the temperatures which has been set in the options if the checkbox at Apply is checked. By removing the check at Apply the resistance as specified in the cable type and line be used without a correction.
In the IEC 60909 calculation a temperature of 20 degrees C is always assumed for calculation of Ik"max.
Colour indication
For various calculations network components are coloured if they exceed certain limits. The colouring scheme can be specified here.
See also: View.
Limits
A distinction is made between limits for the "normal situation" and limits for the "fault situation". The limits for the normal situation are closer to the nominal values than limits for the fault situation. These limits are used for various purposes, depending on the calculation.
The boundaries for nodes can be defined separately for the four fixed voltage levels: LV (less than 1 kV), MV (between 1 and 30 kV), IV (between 30 and 100 kV) and HV (greater than 100 kV).
The load limits for connections, transformers and elements can be defined separately. These limits are used for various calculations.
If Thinnest cable part is selected in a custom view, the type name of the thinnest cable section is displayed, together with the nominal current (Inom') and this current is multiplied by the value of Bmax for the fault situation.
Connection ampacity
It is possible to choose from three values for the indication of the connection ampacity, for example for a high-voltage line. In this way the influence of the season (summer/winter) on the maximum connection ampacity can be set. However, this does not apply to the cables, where the choice of connection ampacity per cable part must be specified.
Loadflow
There are a number of advanced loadflow options which can be applied if the loadflow diverges. Most of these options will not be saved in the options file.
And an option to use whole tap positions in transformer controls.
Costs
Here the cost-related parameters regarding losses (service time and energy price), interest and load factor can be specified.
See also: Cost.
Reliability
Here the reliability parameters, e.g. the restoration time durations, can be specified.
See also: Reliability.
Protection
Form to input parameters for the Protection calculation.
| Cable calculation steps: | The number of equidistant places within the cable/line where a short circuit should be simulated, can be specified with the number of cable calculation steps. An option has been added to simulate short-circuits close to the from and to nodes (at a 1% and 99% distance). |
| Fault resistances: | Range from which the short-circuits resistances are chosen in order to obtain the selectivity curves. |
| Influence element protection: | Dependent on this setting, disconnecting an element by switching a fuse or a circuit breaker may influence the selectivity or not. |
See also: Protection.
IEC 61363
Here the parameters for the IEC 61363 calculation can be specified.
Arc flash
Here the parameters for the arc flash calculation can be specified.
Network analysis
Voltage dip analysis and protection analysis
| Cable/line steps | The number of cable calculation steps determines how many short-circuits have to be simulated in all cables and connections. The number of calculation steps is set to zero by default. The maximum is 9. An option has been added to simulate short-circuits close to the from and to node ( at a 1% and 99% distance). |
| Fault type share | The fault type share is a range of numbers, defining the weight of all possible fault types in the failure frequency parameter. |
Protection analysis
| Fault resistances | Values for the fault resistance at the fault location: 0 Ohm and two additional values. The last additional value is not used for faults in cables and in case of single phase to ground fault the last additional value will be doubled. |
| Refusal level | The number of sequentially protections/switches which refuse to operate (analysis of 0, 1 or 2 refusing switches). |
| Signalling limit | Functionality to determine the latest large switch-off times. |
| Report | Choose the reported items |
Disturbance analysis
| Maximum number of switchings | The maximum number of switching actions that can be performed to restore power. |
| Limits | Determines whether the normal or failure situation limits are used when rerouting the network. |
| At cost of overload | If checked a temporary overload is allowed when rerouting the network to restore power after a fault, i.e. the restoration process has priority over overloading prevention. |
| At cost of under voltage | If checked a temporary under voltage is allowed when rerouting the network to restore power after a fault, i.e. the restoration process has priority over the provision of an adequate voltage level. |
| At cost of subnet border switching | If checked subnet borders can be deactivated during the restoration process. |
Macro
This allows a limitation to be built in, in case a macro calculation inadvertently ends up in an infinite loop. The limitation can also be included in case a macro calculation would take too long. The options are:
| Maximum number of iterations (while and repeat): | The maximum number of iterations for a single loop |
| Maximum execution time: | The maximum execution time of a macro. When 0 is specified the maximum execution time is set to infinity. |
Pseudomonitor
Number of iterations
The number of iterations that should be performed in order to obtain a matching with the measurements
Store monthly value in measurements of measurement units
The monthly maximum values are automatically added to the field in the measurement unit
Save extreme networks
The five time instances for which the network loading is maximal are saved as network files.
See also: Pseudomonitor