Distance protection of multiple-circuit shared tower transmission lines with different voltages. Part I: Fault current magnitude

What is it about?

The paper deals with faults in overhead lines where two different voltage levels are installed in the same tower. These faults have an impedance different from usual faults, meaning that one is not sure that the distance relays would operate as expected. Part I does a long theoretical analysis of the phenomenon, whereas part II uses the results from part I to propose a solution and demonstrates it via hundreds of simulations based on a real line.

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Why is it important?

It proposes a straightforward solution that can be applied when designing/installing the line that assures that the distance protection operates for faults between voltage levels.