An Externally Gapped Line Arrester (EGLA) protects transmission lines from lightning discharges and transient overvoltages by combining a series varistor unit (SVU) with metal-oxide varistor (MOV) blocks and an external series gap. This configuration prevents insulator flashovers and reduces momentary interruptions without requiring a direct line-to-ground connection or disconnector.
The series gap galvanically isolates the MOV from system voltage under normal conditions, eliminating the disconnector and ground lead required by non-gapped line arresters (NGLA). This produces a lighter, more compact design that reduces tower and conductor loads while avoiding temporary overvoltage (TOV) concerns. Energy handling is defined by charge transfer rating, and since the SVU remains isolated, thermal recovery is not a factor.
During a lightning surge, the series gap flashes over at a predetermined voltage, allowing the MOV elements to conduct surge current to ground. The MOV limits follow current and extinguishes the external power arc within milliseconds, maintaining continuous service without substation breaker operation. This mechanism controls overvoltages below the insulator’s lightning-impulse withstand level.
The EGLA’s zero watts-loss design supports energy efficiency while improving line performance by reducing lightning and switching surge outages. The compact configuration facilitates installation on various tower types, including those with short clearances in extra-high voltage (EHV) and ultra-high voltage (UHV) networks up to 765 kV, particularly in areas with high lightning activity or poor grounding conditions.
Your Trusted Supplier for High-Performance Externally Gapped Line Arresters
We are RaxPower, a trusted surge protection devices manufacturer in China specializing in manufacturing high-quality SPDs. Our Externally Gapped Line Arrester (EGLA) features an external spark gap placed in series that galvanically insulates it from the high-voltage line, providing robust surge protection for transmission systems.
These arrester assemblies can be customized for all distribution and transmission lines, leveraging our over 21 years of experience and advanced manufacturing capabilities in Hebei Province. For example, MCOV selection is based on maximum continuous voltages, such as 84 kV for 138 kV systems, ensuring optimal performance and compliance with standards.
Utilizing sophisticated hot forging technology, we produce EGLA components with greater strength and precise sizing, supported by strict quality control, including load testing and SGS certification, to deliver reliable, high-performance solutions. For more information about arrester selection, please contact your RaxPower representative.
| Parameter | Value |
|---|---|
| Voltage | 765 kV |
| Frequency | 60 Hz |
| Energy Discharge Capability | 3.6 C |
| Standards | IEC 60099-8 |
| Arc Extinction Time | ≤10 ms |
Frequently Asked Questions (FAQS)
What is an Externally Gapped Line Arrester (EGLA) and how does it work?
An Externally Gapped Line Arrester (EGLA) is a surge protection device featuring a series varistor unit (SVU) and a series gap that enhances transmission line resiliency. During a lightning strike, the gap flashes over at a predetermined voltage, allowing metal-oxide varistor (MOV) blocks to conduct surge current to ground, limit follow current, and extinguish the external power arc within milliseconds. This prevents substation breaker operation and maintains uninterrupted service without reclosing.
What are the key advantages of using EGLAs?
EGLAs improve line performance by reducing interruptions and offer a lighter design that lowers tower and conductor load. They eliminate Temporary Overvoltage (TOV) concerns, provide zero watts-loss for energy efficiency, and require no disconnector or ground lead connection that may fatigue. The series gap galvanically isolates the arrester from line voltage under normal conditions, allowing for lower rated voltage and less material than non-gapped line arresters (NGLAs). EGLAs are suitable for both retrofit and new construction applications.
What system voltages and applications are EGLAs designed for?
EGLAs can be designed for system voltages up to 800 kV and beyond, making them suitable for extra-high voltage (EHV) and ultra-high voltage (UHV) networks. RaxPower offers customizable solutions for both new construction and retrofit applications, with complete kits including insulators, clamps, and hardware for easy installation and integration into transmission lines.
How are EGLAs customized to meet specific grid requirements?
Our arresters are engineered to order based on your unique system parameters, including operating voltage, tower geometry, insulator data, lightning activity, and environmental conditions. We provide line simulation studies to ensure optimal performance and compliance with international standards such as IEC 60099-8, delivering cost-effective solutions tailored to your grid's specific needs.
What design and installation support do you provide?
We offer software analysis and simulation services to determine the optimal, cost-effective placement and quantity of arresters for your specific line parameters. Our lighter arrester design allows for easier installation on various tower types, and we provide complete kits with all necessary hardware. The elimination of disconnectors and direct ground connections simplifies installation and reduces maintenance requirements, lowering long-term costs while improving reliability.
Get A Quick Quotation Today
