Skip to content
Grøft Design Logo Grøft Design documentation

Simulation Options

There are several types of simulation available in Grøft Design® and one must be selected when creating a scenario. The different types are selected based on the type of situation and result you want to simulate. There are currently four different options:

  • Steady State
  • Cyclic load
  • Cyclic load, 24h
  • Variable load

Steady State

The simplest type of scenario, with the fastest simulation. It shows how conditions will stabilize if they last indefinitely. If maximum current load is used, this will give a conservative estimate of the current carrying capacity. The simulation is based on static values, and it is not possible to use variable values.

Cyclic Load

A time analysis where all loads repeat in fixed cycles. The simulation result will show what each cycle looks like after the system has stabilized over time. The simulation has a minimum period of 6 hours, and it is recommended that the period is set as long as the longest time series in the scenario. The input values are based on at least one variable value. The result of the Cyclic load shows the period when the system has stabilised but is does not show how long time it takes to stabilize.

Cyclic Load, 24h

A variation of cyclic load where the period is fixed to 24h and only the current load is variable. This opens the use of load factors according to IEC 60853 if one does not have access to complete load profiles.

When using load factors, the simulation result will be limited to the maximum temperature during a stabilized cycle.

The method introduced by Goldenberg (IEC)1 is incorporated in GRØFT Design® if the rated current IR and daily load factor lf for a cable circuit are specified for cyclic rating of cables only. The method was found a satisfactory, however, a conservative approximation. However, if a daily load profile is given by the user, the full cycle analysis will be simulated in the software instead.

Variable Load

A general time analysis, which can be used if none of the more specific scenario types cover the need. For example, for emergency loads, short-circuit currents or non-cyclical loads.

The simulation is very versatile and as a user it is possible to configure the scenario to meet your specific needs. The results in the Variable load simulation shows the whole simulation duration, not just one stabilized period as in cyclic load.

A simulation that includes time must have a constant initial state. A default configuration is specified in the scenario configuration, but this can be overridden for each time dependent property.

  • First values: The initial state will use the first value in each time series. This gives a good result for time series where the first value actually reflects the starting point, but not necessarily for time series with an arbitrary start.
  • Average values: The initial state will use average values for each time series. Especially for periodic time series, this can provide a much better starting point than a random start.
  • From existing scenario: Another (constant load/steady state) scenario will determine the initial state for all properties that support time variation. This applies regardless of whether the property in the new scenario is configured as variable or constant.

Time Series

For more information on adding time series click here

References

Footnotes

  1. NEK IEC 60853-2:1989 Calculation of the cyclic and emergency current rating of cables. ↩