Correction Factors

Voltage Corection Factor c

The voltage correction factors \(c_{min}\) for minimum and \(c_{max}\) for maximum short-circuit currents are applied in calculating short-circuit impedances for some elements (transformer, ext_grid) as well as for the equivalent voltage source for the calculation of the initials short-circuit current \(I''_k\).

It is defined for each bus depending on the voltage level. In the low voltage level, there is an additional distinction between networks with a tolerance of 6% vs. a tolerance of 10% for \(c_{max}\):

Voltage Level \(c_{min}\) \(c_{max}\)
< 1 kV Tolerance 6% 0.95 1.05
Tolerance 10% 1.10
> 1 kV 1.00

Peak Factor \(\kappa\)

The factor \(\kappa\) is used for calculation of the peak short-circuit current \(i_p\), thermal equivalent short-circuit current \(I_{th}\) and unsymmetrical short-circuit currents.

In radial networks, \(\kappa\) is given as:

\[\kappa = 1.02 + 0.98 e^{-\frac{3}{R/X}}\]

where \(R/X\) is the R/X ratio of the equivalent short-circuit impedance \(Z_k\) at the fault location.

In meshed networks, the standard defines three possibilities for the definition of \(\kappa\):

a ) Uniform Ratio R/X b ) Ratio R/X at short-circuit location c ) Equivalent frequency

pandapower implements version b), in which the factor \(\kappa\) is given as:

\[\kappa = [1.02 + 0.98 e^{-\frac{3}{R/X}}] \cdot 1.15\]

while being limited with \(\kappa_{min} < \kappa < \kappa_{max}\) depending on the voltage level:

Voltage Level \(\kappa_{min}\) \(\kappa_{max}\)
< 1 kV 1.0 1.8
> 1 kV 2.0

Thermal Factors m and n

The factors m and n are necessary for the calculation of the thermal equivalent short-circuit current \(I_{th}\).

pandapower currently only implements short-circuit currents far from synchronous generators, where:

\[n = 1\]

and m is given as:

\[m = \frac{1}{2 \cdot f \cdot T_k \cdot ln(\kappa - 1)} [e^{4 \cdot f \cdot T_k \cdot ln(\kappa - 1)} - 1]\]

where \(\kappa\) is defined as above and \(T_k\) is the duration of the short-circuit current that can be defined as a parameter when running the short-circuit calculation.