Ground-directional solution to improve selectivity in underground mining power systems protection

The trend of expanding to larger underground mining systems has motivated increases in the voltage levels used for distribution and utilisation. Such increases have caused the industry to face complexities and challenges that are not common in lower voltage systems. For high voltage levels, the mining regulations require the use of shielded cables, with a resistive grounding method for the neutral. The occurrence of a phase-to-ground fault in a power system with this arrangement causes capacitive current flows from different locations to the point of failure, which reduces the selectivity of the ground overcurrent relays. The solution proposed here for this loss of selectivity is based on the ground-directional over-current algorithm. The methodology was detailed, validated, tested, and assessed using a software test model and subsequently in a real-time hardware-in-the-loop implementation in a playback testbed. The results showed an improvement in the protection performance in the context of different failure scenarios.