Final answer:
The Positive Sequence impedance calculation for a HV cable requires the formula Z1 = Zph - Zm, but the exact value cannot be provided without the specific formula or additional context.
Step-by-step explanation:
The student is asking about the calculation of the Positive Sequence impedance (Z1) for a high voltage (HV) cable with magnetically coupled conductors. The impedance values provided are Zph (the phase impedance), Zn (the neutral impedance), and Zm (the mutual impedance). To find the Positive Sequence impedance, we typically use the formula Z1 = Zph - Zm if the system is symmetrical and the conductors are transposed. However, without the explicit formula given in the problem statement or additional context, we can not provide an exact value for Z1.