Substation and Step-Up Station Lightning Protection Grounding Upgrade Plan Aligned with New Grid Safety Standards

With electricity demand surging during the summer and frequent thunderstorms increasing the risk of lightning strikes, aging grounding systems at substations have become a growing concern. Problems such as corrosion of grounding grids, excessive grounding resistance, and inadequate equipotential bonding can lead to lightning-induced line trips, transformer failures, and switchgear damage, directly affecting the reliability and stability of regional power networks.

Under the latest power-system lightning protection guidelines, the power-frequency grounding resistance of a substation’s main grounding grid must be maintained below 0.5 Ω. In addition, comprehensive equipotential bonding is required across all critical facilities, including outdoor equipment, control buildings, cable trenches, and lightning protection systems. Grounding grids made of galvanized steel that have been in service for more than ten years are generally required to undergo corrosion mitigation upgrades or complete replacement.

Traditional galvanized-steel grounding grids are often buried for decades in moist or chemically aggressive soil conditions. Over time, conductor cross-sections deteriorate due to corrosion, while welded joints may rust and fracture, creating high-resistance discontinuities within the grounding network. These defects prevent lightning currents from dissipating evenly, resulting in hazardous step and touch voltages that pose significant risks to maintenance personnel and equipment.

To address these challenges, modern grounding solutions designed specifically for substations combine copper-clad steel grounding electrodes, flexible graphite grounding conductors, and pure copper ion grounding electrodes. These materials offer superior electrical conductivity, excellent corrosion resistance, and long service life, making them well suited for large-scale grounding grid installations. Flexible graphite grounding conductors can easily conform to cable trenches, equipment foundations, and other irregular structures, minimizing installation blind spots and creating a comprehensive low-resistance current dissipation network.

For control buildings and sensitive low-voltage systems, dedicated grounding branches should be installed and interconnected with the main grounding grid to ensure a unified grounding reference. In addition, multi-stage surge protection devices (SPDs) should be deployed across both high-voltage and low-voltage systems to prevent lightning-induced electromagnetic pulses from reaching protection relays, control systems, and other secondary equipment.

Throughout June, power utilities across various regions have been conducting excavation-based inspections of substation grounding grids. Key inspection items include conductor corrosion levels, weld integrity and anti-corrosion protection, and the condition of resistance-reduction backfill materials. Substations with grounding resistance values exceeding regulatory limits are being prioritized for phased upgrades, particularly remote step-up stations in mountainous areas and aging suburban substations.

As part of these modernization projects, utilities are also deploying intelligent grounding monitoring terminals capable of continuously tracking grounding impedance and overall system performance. These devices enable real-time remote monitoring, reducing the need for frequent on-site testing and improving maintenance efficiency.

Many older substations were originally constructed with only simple ring-shaped galvanized steel grounding conductors and lacked long-term resistance-reduction materials. In regions with high soil resistivity, grounding resistance often remains above acceptable limits, leading to recurring line trips during thunderstorms and increasing emergency repair workloads.

As a critical hub within the power transmission and distribution network, a substation’s lightning protection and grounding system plays a vital role in maintaining power supply reliability. Completing grounding grid upgrades before the peak summer demand season helps establish a robust and long-lasting lightning current dissipation system that not only complies with current lightning protection standards but also significantly reduces lightning-related outages, ensuring safe and stable grid operation during periods of severe weather and peak electricity demand.