Transient Analysis of Interconnected Grounding Grids Under Physically Damaged Conditions

Grounding grids (GG) must guarantee the electrical safety to personnel during services and operations on substations. In this context, GG must provide a low-impedance path for fault currents during transient conditions, and also offer a potential reference to all equipment in normal conditions. Due to corrosion, natural phenomena and electromotive forces between conductors, the grounding electrodes may be damaged, which offers a dangerous scenario inside the electrical substation. In this paper, the Partial Element Equivalent Circuit (PEEC) is employed to model a 30 m 30m-interconnected GG subjected to two types of lightning ×currents. The frequency-independent soil electrical parameters and the propagation effects are taken into account for this GG assuming the whole and damaged condition for its conductors. Lightning currents are modeled by the first and subsequent strokes and they are injected at the corner of these GG where significant differences are obtained especially at the damaged condition. Results show that GPR distribution along the damaged GG presents a higher voltage drop around the ruptured electrodes for the subsequent lightning stroke due to the higher derivative of current associated with the high frequency content of this lightning current.