A three-phase grounding bank, also known as a grounding transformer or grounding reactor, is an electrical device used in power systems to provide a controlled path for fault currents to flow to the ground in the event of a fault. Its primary purpose is to limit the voltage rise on the un-faulted phases and ensure the safety of personnel and equipment.
Here's how a three-phase grounding bank operates:
Structure: A three-phase grounding bank consists of three individual grounding transformers or reactors, one for each phase. These transformers or reactors are typically connected in a delta configuration, with their primary windings connected to the power system's phases.
Normal Operation: Under normal operating conditions, the grounding bank remains inactive. It does not carry any significant current, and its primary function is to provide a neutral reference point for the power system. The primary windings are connected to the power lines, and the secondary windings are typically left open-circuited.
Fault Condition: When a fault occurs on one of the power system phases, such as a phase-to-ground fault, a sudden surge of fault current flows through the faulted phase. This current seeks the path of least resistance to return to the source. Without proper grounding, the faulted phase voltage could rise to dangerous levels.
Activation: The grounding bank comes into action when a fault occurs. The secondary windings of the grounding transformers or reactors are connected in a zig-zag or wye configuration. This connection creates a low