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As global energy demands rise and the integration of renewable sources accelerates, the reliability of high-voltage transmission systems becomes paramount. Shielding electrodes are critical in ensuring the efficiency and longevity of alternating current (AC) and direct current (DC) insulators.​

Understanding Shielding Electrodes

Shielding electrodes are conductive components attached to insulator strings to manage electric field distribution and mitigate adverse effects such as corona discharge and radio interference. Their application differs between AC and DC systems due to the distinct electrical characteristics of each.​

Shielding in AC Systems

In AC transmission lines, shielding electrodes serve multiple functions:​

1. Corona Suppression: By evening out the electric field, they prevent corona discharges at insulator fittings, which can lead to energy losses and material degradation.​
2. Voltage Grading: They ensure a uniform voltage distribution along the insulator string, reducing electrical stress on individual units.​
3. Radio Interference Reduction: By mitigating corona effects, they minimize electromagnetic interference with communication systems.​

Laboratory studies on 420 kV cap-and-pin insulator strings have demonstrated that the voltage drop across the first unit can be up to three times higher than average without shielding electrodes. The inclusion of grading electrodes significantly reduces this disparity, enhancing overall system reliability. ​

Shielding in DC Systems

DC systems exhibit different behavior due to the dominance of resistive currents:​Reddit

• Voltage Distribution: In clean conditions, voltage distribution is relatively uniform. However, contamination can lead to uneven distributions, necessitating the use of shielding electrodes.​
• Design Considerations: While AC and DC systems share some design principles, DC insulators require specific configurations to address issues like ion migration and surface conductivity.​

Recent projects have adopted shielding designs similar to those used in AC systems, but tailored to address the unique challenges of DC transmission. ​

Conclusion

The implementation of shielding electrodes is vital for the optimal performance of high-voltage insulators in both AC and DC systems. By addressing issues such as corona discharge, voltage imbalance, and radio interference, these components enhance the durability and efficiency of power transmission infrastructure.​

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