Performing a transient calculation in SafeGrid Earthing Software means calculating an earthing system's time-varying voltage and current response. Lightning impulse waveforms may consist of up to 20,000 distinct frequencies, which causes a transient calculation to be time-consuming. Due to the in-built frequency subset selection algorithm, the response for all individual frequencies is unnecessary. However, the calculation time is proportional to the study's voltage points (or grid points). Therefore, they need to be carefully selected for a transient calculation.
The voltage points for an earthing study are configured under the Voltage Profiles tab in the Safety Criteria module.
Tip 1: Do not use Rectangular voltage profiles; use Line profiles instead.
Rectangular voltage profiles are useful for single-frequency grid energisation but inefficient for transient calculations. Therefore, Rectangular voltage profiles should be converted to Line profiles or removed and swapped with grid points.
If you use Line profiles, increase the Maximum spacing between points to minimise the number of voltage (response) points that need to be calculated along the line.
Tip 2: Use Grid Points for transient calculations.
Grid points are designed to be used for transient calculations. The user can place grid points near the grid at any location (in 3D), and the voltage and/or current response will be measured. Using Grid points, the transient response at critical points on the earthing system can be obtained whilst minimising the calculation time required.
To add a grid point, press Add Point, and a new point will appear in the grid preview. Then move the grid point near the location on the grid.
The video below shows how to use Grid Points for transient earthing calculations.
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