electricpy.fault.*fault() mis-handles NumPy complex impedance values (incorrectly multiplies by 1j)

[marcostfermin]

Describe the bug

Several fault functions attempt to “ensure X-components are imaginary” using if not isinstance(Xk, complex): Xk *= 1j.

But if a user supplies NumPy complex scalars (e.g., np.complex128), isinstance(..., complex) is False, so the code incorrectly multiplies an already-complex impedance by 1j, rotating/scaling it and producing wrong fault currents.

This pattern is visible in the module code. https://electricpy.readthedocs.io/en/latest/_modules/electricpy/fault.html

Reproduction Code

# Setup
import numpy as np
import electricpy as ep

# Code which causes failure (wrong numeric result, not necessarily an exception)
Vth = 1.0 + 0.0j

# Already-complex impedances (NumPy complex scalars are common in numeric workflows)
Z0 = np.complex128(0.1j)
Z1 = np.complex128(0.2j)
Z2 = np.complex128(0.25j)

# Example: line-to-line fault
If_seq = ep.fault.phase_to_phase_fault(Vth, (Z0, Z1, Z2), sequence=True)

print(If_seq)

Expected behavior

If Z0, Z1, Z2 are already complex (including NumPy complex scalars), the function should not multiply them by 1j. Results should match the same calculation done with built-in complex types.

Screenshots
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Desktop (please complete the following information):

• OS: [e.g. Linux]
• Python Version [e.g. 3.7]
• Version [e.g. 0.2.1]

Additional context

The logic uses isinstance(Xk, complex) to decide whether to apply * 1j. That excludes NumPy complex scalars, causing incorrect math.