Short Circuit Calculation

Run a short circuit calculation on the entire grid or a specific grid. The short circuit is calculated for each bus in the grid under the assumption that the short circuit occurs at that bus and the results are shown cummulatively.

INFO

All calculations are derived from the european norm DIN EN 60909-0 (VDE 0102)

Calculation

All short circuits are assumed to be far from generator.

Four short circuit types are computed:

• Phase to Ground: represents an asymmetric single-phase-to-ground fault (L-G)
• Two-Phase: represents an asymmetric double-phase fault without ground (L-L)
• Two-Phase to Ground: represents an asymmetric double-phase fault with ground (L-L-G)
• Three-Phase: represents a symmetric three-phase fault without ground (L-L-L)

Calculated Properties

The following short circuit results are calculated for all types:

• $I_k^{″}$ (min/max): Initial short circuit current
  • The minimum and maximum current (rms) at the beginning of the short circuit. It is equal to the steady-state short circuit current $I_k$.
• $I_p$: Peak short circuit current
  • The highest possible instantaneous current at the beginning of the short circuit
• $I_{th}$: Thermal equivalent current
  • A current that has the same thermal impact as the time-varying actual current. Used to easily assess the thermal stess to grid components in case of a short circuit.
• $Z_k$ (min/max): Impedance from the network feeder to the fault location
  • The minimum and maximum impedance (for high and low line temperature) from the network feeder to the fault location.
• $\mathrm{\angle }{Z}_k$ (min/max): Impedance angle
• $S_k^{″}$ (min/max): Short circuit power
  • The theoretical power that occurs during the short circuit. Can be used to dimension switches.

Settings

Click on at the top of the page to change the settings of the short circuit calculation.

Zero Sequence Impedance

The zero sequence impedances are derived from the positive sequence impedances. Choose factor 1 for a conservative calculation. For lines, the actual zero sequence impedance can also be defined directly in the grid model. When this value is set, the factor here has no effect.

Voltage Tolerance

The voltage tolerance affects how the voltage correction factors $c_{min}$ and $c_{max}$ of low voltage buses are set. During the short circuit calculation, the min/max current and power values are calculated using the bus voltages, scaled with the voltage factors $c_{min}$ and $c_{max}$. The factors models temporal voltage fluctuations, voltage deviation due to tap changers or load/generation. The c-factor on low voltage buses depends on the voltage tolerance:

Tolerance	$c_{min}$	$c_{max}$
6%	0.95	1.05
10%	0.9	1.1
IEC 60909-0 2001	0.95	1.1

Medium and high voltage buses are not affected by this setting. They always have a voltage tolerance of $c_{min}$ = 1 and $c_{max}$ = 1.1.

TIP

For a conservative analysis, use a voltage tolerance of 10%.

Short Circuit Duration

The short circuit duration is used to calculate the thermally equivalent currents $I_{th}$.

Branch Temperature

The branch temperature defines the temperature of the line at the end of the short circuit (after the time defined in Short Circuit Duration). This affects the minimum short circuit values.

Warm lines have a higher impedance, which leads to smaller minimal short circuit currents. It is important that the minimal currents are not too small such that protection devices (e.g. fuses) work properly. For a conservative analysis, use 160°.

Generator Contribution

Generators can feed three phase short circuits that occur nearby. Depending on their connection type, they contribute to a greater or lesser extent to the short circuits:

• Direct: No contribution
• Inverter: 1x rated current
• Synchronous Machine: 8x rated current
• Asynchronous Machine: 6x rated current
• Converter: 1x rated current
• left blank: No contribution (Direct connection is assumed)

The rated currents of the generators are calculated using their active power assuming them to be connected by a three-phase connection.

Grid

A single grid can be calculated by selecting it from the Grid dropdown list on the top of the page. If no grid is chosen, the calculation is run for the entire grid (longer run time).

For small grids the short circuit calculation starts automatically. The short circuit calculation can be started manually by clicking .

The following electrical parameters are required to run a short circuit calculation:

• Network feeder: reactance to resistance ratio $\frac{X}{R}$, short circuit power $S_{k{Q}_{min}}^{″}$, $S_{k{Q}_{max}}^{″}$ in MVA or short circuit current $I_{k{Q}_{min}}^{″}$, $I_{k{Q}_{max}}^{″}$ in A.
• Transformer: vector group, star point grounding

Optional parameters may improve the calculation result for phase to ground faults:

• Lines: zero sequence impedance

WARNING

A short circuit calculation can only be run if the grid is consistent.

WARNING

If the required parameters are missing, fallback values will be used. This might influence the result a lot, especially close to the transformer.

Grid Upgrades, Connection Request and Scenarios

Grid Upgrades and Connection Requests are applied to the grid by default depending on their status. They are part of the grid model for the duration of the simulation. The selected Grid Upgrades and Connection Requests are visualized in the grid.

To change the default selection, just select or deselect the desired add-ons from the list. The selection is saved for the duration of the session, even when navigating to other simulations within the Adaptricity software. Reloading the page or clicking on the refresh button will restore the default selection.

Scenarios and Load Situations are never applied by default. They need to be specifically selected.

INFO

If any grid upgrades or connection requests cannot be applied to the grid (for example, because a grid element no longer exists), then they are deselected and a warning is shown stating the reasons why they could not be applied.

Interactive Result

All short circuit types and properties are calculated in the background. Use the buttons to select the type of short circuit that you would like to see. The result is automatically plotted in the grid viewer.

Each current/power shown in the grid viewer represents the current/power of a fault occuring at that bus (with no other faults in the grid).

INFO

The and buttons automatically plot the min/max short circuit current among all short circuit types.

Results

The short circuit results are visualized in the results table and in the grid viewer. The results can be exported by clicking the download button at the top of the page. A print friendly output can be created by clicking at the top of the page.

Results Table

The short circuit results for all buses are shown in the results table, grouped by current, power, impedance. The results in every column can be visualized in the grid viewer by clicking next to the column name. This will also change the setting from the interactive result

More columns can be added to the table by clicking on .

Each row represents the short circuit results that would be measured if the short circuit occured at that bus.

TIP

• Sort the table by descending or ascending values by clicking on the column name.
• Filter the table by condition or by specific values by clicking next to the column name.
• Center the grid viewer on a bus by clicking on next to the element's ID.

Grid Viewer

The grid viewer will color the buses based on the selection in the Interactive Result or the Results Table. A standard color scale will be applied. The scale can be edited by clicking the icon next to the variable name. Clicking on will show the results next to the buses.

Clicking on a bus in the grid viewer reveals the short circuit results for that bus on the right.

Buses that are not electrically connected to the grid are marked with a .