Electrical Safety Considerations of Neutral Blocker Placements for Mitigating DC

Abstract

The dc in a power network might be caused by geomagnetic disturbances that result from either a geomagnetic storm or a high-altitude nuclear detonation. The augmenting trend of inverter-based resources is also acting as a source of small dc injection into the power systems. As the resultant, dc could lead toward a possible power system failure, a myriad of neutral blocking devices (NBDs) have been proposed, where, these devices are installed between the neutral and ground of wye-grounded transformers. However, the electrical safety assessment of these devices is critical prior to adding them to the grid as they might raise serious concerns both for the power equipment and the power system maintenance staff. This work is the first effort toward hazard identification and quantitative risk assessment associated with NBDs. It proposes a risk management framework for augmented electrical safety pertinent to these devices. Later, it analyzes the proposed neutral blocking strategies and highlights the associated risks to the operational safety of these installations, particularly concerning electromagnetic pulse (EMP) attacks, cyber threats, and equipment malfunction. Finally, an ideal NBD operational design is proposed incorporating a variety of risk reduction measure to avoid any hazardous situation arising from such installations. This work could provide a guideline for the electric utilities and academic researchers to consider these safety implications prior to proposing or installing these devices.