Fault analysis API corrupts NumPy complex impedances

[marcostfermin]

Describe the bug

Several fault analysis functions attempt to coerce impedances to imaginary values using checks like if not isinstance(Z1, complex): Z1 *= 1j. NumPy complex scalars (e.g. np.complex128) are not instances of built-in complex, so already-complex impedances are multiplied by 1j again, producing incorrect results.

Reproduction Code

# Setup
import numpy as np
import electricpy as ep

# Code which causes failure (incorrect numeric result)
Vth = 1 + 0j
Z0 = np.complex128(0.1j)
Z1 = np.complex128(0.2j)
Z2 = np.complex128(0.3j)

If = ep.fault.phase_to_phase_fault(Vth, (Z0, Z1, Z2), sequence=True)
print(If)

Expected behavior

If impedances are already complex (including NumPy complex scalars), they should not be modified. Results should be identical to using built-in complex values.

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

Type checks should use np.iscomplexobj() or isinstance(x, (complex, np.complexfloating)).