Calculation
S''k = √3 · U · Ik
Short-circuit power is a measure of network stiffness at a connection point and is used to select switching devices.
Definition der Kurzschlussleistung S''k = √3·Un·I''k nach IEC 60909-0 (DIN EN 60909-0/VDE 0102)
Three-phase network short-circuit power
Short-circuit power is a measure of network stiffness at a connection point and is used to select switching devices.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Short-circuit power S''k — Apparent power corresponding to the short-circuit current at the considered network point; shown here in the same unit as a real power, conventionally labelled kVA/MVA.
- Network rated voltage U — Rated line-to-line voltage at the considered network point.
- Short-circuit current Ik — Expected or measured three-phase short-circuit current at the network point.
Example
U=400 V and Ik=5,000 A give S''k=√3·400·5,000≈3,464 kVA (3.46 MVA).
Assumptions and limits
Balanced three-phase fault with steady short-circuit current; initial symmetrical short-circuit current, peak short-circuit current and network impedance behaviour are not distinguished separately.
Understand Three-phase network short-circuit power
This calculator determines short-circuit power at a network connection point from rated voltage and the short-circuit current occurring there, a key figure for grid-connection assessment.
What does this quantity describe?
Short-circuit power combines voltage and short-circuit current into an apparent power: S''k=√3·U·Ik. It describes how "stiff" the network is at that point.
Formula and variables
S''k = √3 · U · Ik
S''k = √3 · U · Ik
| Symbol / input | Meaning |
|---|---|
| Short-circuit power S''k | Apparent power corresponding to the short-circuit current at the considered network point; shown here in the same unit as a real power, conventionally labelled kVA/MVA. |
| Network rated voltage U | Rated line-to-line voltage at the considered network point. |
| Short-circuit current Ik | Expected or measured three-phase short-circuit current at the network point. |
Choose the inputs correctly
U is the rated line-to-line voltage at the network point, Ik the expected or measured three-phase short-circuit current there.
How to use the calculator
Take U from the grid connection, Ik from a short-circuit calculation, a network operator's datasheet or a measurement.
Worked example
U=400 V and Ik=5,000 A give S''k=√3·400·5,000≈3,464 kVA (3.46 MVA).
Understand the result and units
High short-circuit power means a stiff network with low internal impedance; it determines the required breaking capacity of fuses and circuit breakers.
U is a voltage, Ik a current. S''k is shown in the same power unit as a real power, conventionally labelled kVA or MVA.
Typical applications
Selecting switching devices and fuses by rated short-circuit breaking capacity, and assessing grid connection quality for high-power loads.
Assumptions, limits and common mistakes
Balanced three-phase fault with the steady-state short-circuit current; initial symmetrical short-circuit current, peak short-circuit current and the exact network impedance per IEC 60909 are not distinguished separately.
Common mistake: Do not confuse the single-phase with the three-phase short-circuit current; this formula assumes a balanced three-phase fault.
Frequently asked questions
What is “Three-phase network short-circuit power” used for?
Selecting switching devices and fuses by rated short-circuit breaking capacity, and assessing grid connection quality for high-power loads.
Where do the input values come from?
U is the rated line-to-line voltage at the network point, Ik the expected or measured three-phase short-circuit current there.
What does the result not cover?
Balanced three-phase fault with the steady-state short-circuit current; initial symmetrical short-circuit current, peak short-circuit current and the exact network impedance per IEC 60909 are not distinguished separately.