[bug] Possibly incorrect Ik'' results.

[dafuqbruv]

Bug report checklis

• Searched the issues page for similar reports

• Read the relevant sections of the documentation

• Browse the tutorials and tests for usefull code snippets and examples of use

• Reproduced the issue after updating with pip install --upgrade pandapower (or git pull)

• Tried basic troubleshooting (if a bug/error) like restarting the interpreter and checking the pythonpath

Reproducible Example

import pandapower as pp
import pandapower.shortcircuit as sc
import numpy as np

net = pp.create_empty_network(f_hz = 50.0, sn_mva=100) # Create empty network

gen_bus = pp.create_bus(net, name= "gen_bus", vn_kv=13.8, type="b")
fault_bus = pp.create_bus(net, name= "fault_bus", vn_kv=230, type="n")

pp.create_ext_grid(net, fault_bus, s_sc_max_mva = 10., rx_max = 0.1, vm_pu=1.02, va_degree=0.0) # Create an external grid connection with limited fault level

trafo1 = pp.create_transformer_from_parameters(net, pp.get_element_index(net, "bus", 'fault_bus'), pp.get_element_index(net, "bus", 'gen_bus'), sn_mva = 210, vn_hv_kv=230, vn_lv_kv=13.8, vkr_percent=0.0, vk_percent=8.0, pfe_kw=0, i0_percent=0, shift_degree=0, name="230/13.8 kV transformer")

gen = pp.create_gen(net, pp.get_element_index(net, "bus", 'gen_bus'), vn_kv = 13.8, vm_pu=1.03, sn_mva = 200, p_mw=150, xdss_pu=0.252, rdss_ohm = 0.027, cos_phi = 0.85, slack = True, name='SM')

pp.plotting.simple_plot(net, plot_gens=True, gen_size=10, trafo_size=10, ext_grid_size=5)

sc.calc_sc(net, fault = "3ph", case="max", ip=True, ith=True, branch_results=True, inverse_y= True, return_all_currents=True )
net.res_bus_sc # WRONG RESULTS HERE??

net.res_trafo_sc # CORRECT RESULTS HERE

Issue Description and Traceback

Hi. This is the output of net.res_bus_sc results when I run the above code using pandas 2.14.6.

ikss_ka | skss_mw | ip_ka | ith_ka | rk_ohm | xk_ohm
37.792787 | 903.334574 | 99.527556 | 39.046183 | 0.025898 | 0.230450
1.740866 | 693.511753 | 4.657491 | 1.815276 | 7.195050 | 83.597232

My hand calculations suggest that for a fault at the HV side of the transformer (i.e., at the grid side), the generator will inject ~28 kA which will be reflected as ~1.72 kA on the HV side which I can confirm using net.res_trafo_sc. The above print out of the results indicates that the fault at bus 0, i.e., gen bus, the fault current injection from generator will be 37.79 kA. It is either wrong, or I don't know how to interpret these results. Could you please have a look at it?

Expected Behavior

As explained above.

Installed Versions

• python version: * pandas version: * networkx version: * scipy version: * numpy version: * packaging version: * tqdm version: * deepdiff version: * Operating System name/version:

Label

• Relevant labels are selected