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One of the foundational defenses against atmospheric discharges in substations is the strategic deployment of lightning rods. These structures are designed not merely as conductors, but as the first line of defense against direct lightning strikes that could compromise the integrity of the entire station infrastructure. Installed atop buildings or support structures, lightning rods act as intentional targets for electrical discharges, safely channeling high-voltage currents into the ground.
They can be mounted on independent poles or integrated with the metallic frameworks of outdoor electrical installations. In some designs, lighting masts or floodlight towers double as grounding structures. However, under no circumstances should transformer portal frames be used for this purpose. Direct strikes on these frames can generate destructive overvoltages that risk catastrophic dielectric failure within the transformer windings. Ensuring that lightning does not induce such overvoltages is paramount to the long-term reliability of the substation.
The high-voltage (HV) side of a substation is a critical ingress point for lightning-induced surges, especially when transmitted via overhead lines. To mitigate this threat, the installation of metal-oxide varistor (MOV) type surge arresters or protective spark gaps near the primary terminals of power transformers is essential. These devices operate as rapid-response guardians, shunting excessive voltage transients to ground before they can traverse further into sensitive equipment.
Placement is crucial. Arresters must be mounted as close to the transformer as physically feasible. This proximity reduces inductive path impedance and minimizes residual voltage during discharge. Moreover, their grounding conductors must be interconnected with the transformer's low-voltage neutral and metallic casing to form an equipotential bonding network. This configuration ensures that all components ride the same voltage during a surge event, preventing internal potential differences that could otherwise lead to insulation breakdown or equipment failure.
In regions prone to frequent thunderstorm activity, the risk of surge intrusion through the low-voltage (LV) side of a transformer cannot be underestimated. Although often overlooked, this path can allow reflected or induced surges to back-feed into the transformer, posing a silent yet serious threat to its insulation integrity.
To address this, the installation of surge arresters or spark gaps on the LV side is recommended, particularly in high-isokeraunic zones. These devices intercept residual surges and safeguard against dielectric puncture in the secondary windings. In systems where the low-voltage neutral is ungrounded, the risk profile increases substantially. In such cases, it is imperative to equip the floating neutral with its own surge arrester or gap protection. This measure ensures balanced protection across all terminals and prevents asymmetric voltage stresses from damaging the transformer core or secondary windings.
A substation without adequate lightning protection is akin to a fortress without walls. Effective mitigation requires a multilayered strategy—starting with the interception of direct strikes via lightning rods, followed by the suppression of incoming transients at both the high- and low-voltage interfaces. Each component—whether an arrester, gap, or grounding path—must be precisely installed and interconnected to form a cohesive shield against the capricious fury of nature. Through such integrated design, the operational integrity and longevity of substation assets can be preserved even under the most electrically volatile conditions.
