An alternative to Line Surge Arresters ?
High voltage transmission lines face several technical challenges, among which are lightning backflashovers. These flashovers can potentially interrupt service and damage equipment, especially in regions of high ground resistivity and high lightning density. Line Surge Arresters (LSA) are known to be effective methods to mitigate this issue. However, a new innovation, the Embedded Ground Conductor (EGC), has emerged as a promising, cost-effective, and maintenance-free alternative.
Understanding the EGC Technology
EGC technology is fundamentally an advanced method for calculating the effect of height on ground wire corona and its subsequent effect on surge impedance. This is based on the work titled "Negative Impulse Ground Wire Corona Parameters for Backflash Evaluation of High Voltage Transmission Lines" published in the IEEE Trans. on Power Delivery on September 10, 2021 by Dr. Farouk A.M. Rizk.
EGC is a ground conductor attached at a strategic location on a power transmission tower. Its placement optimizes the coupling factors to all power conductors, thereby reducing the stress on all insulator strings simultaneously. It can reduce the backflash rate by a factor of 10 or more, a significant achievement considering the costs and complexity associated with other mitigations in some cases.
Implementation and Benefits
The typical placement of the EGC is at or near the vertical axis of the power conductor system, generally above the attachment points of the lower conductors. It ensures the clearance between an EGC and any power conductor doesn't pose a problem.
For higher system voltages or towers with two circuits at different voltages, an EGC could potentially be exposed to significant induced charges. Therefore, a Streamer Inhibited Conductor or ESIGC is recommended to mitigate the risks of Radio Interference (RI) and audible noise.
Several compelling benefits make the EGC an attractive alternative to conventional mitigation methods.
Cost-effectiveness: The cost of the EGC is independent of the system voltage, making it a potential more affordable solution than some LSA installations in some high-voltage configurations.
Improved reliability: in comparison to Non-Gapped Line Arresters, EGCs offer a number of advantages, such as pollution immunity and robustness by design. The life expectancy should be compared to conventional shield wires (OHGW).
Low Maintenance: EGCs require minimal maintenance, making them attractive option long-term operations.
Improved Back Flashover Rate: EGCs improve the back flashover rate by a factor of 10 or more for 245 kV, 345 kV, and 420 kV lines (existing simulations).
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