Flyer · EN — Siemens Energy flyer (2021) introducing line surge arresters (LSA) for overhead power lines: why they are installed, the two available designs — non-gapped line arresters (NGLA) and externally gapped line arresters (EGLA) — with their respective benefits and applicable IEC standards, and the optional Cigré-based software simulation service used to determine the optimum number and placement of arresters along a line. Covers system voltages up to 800 kV with energy discharge capability of 3.6 C.
Line surge arresters (LSA) prevent ground faults and short circuits on power lines caused by lightning or switching overvoltages. By eliminating all lightning and switching overvoltages that exceed the insulator insulation level — the lightning-impulse withstand level (LIWL) — they prevent insulator flashovers, voltage dips and supply interruptions.
Installing LSAs at the locations recommended by a line simulation ensures enhanced overvoltage protection. Choosing the optimum arresters, particularly their quantity and installation positions, significantly improves the reliability of the whole line system and the quality of the power it delivers. The portfolio covers system voltages up to 800 kV with an energy discharge capability of 3.6 C.
Typical reasons to deploy LSAs: improve lightning protection performance; reduce outages caused by poor grounding and high lightning activity; reduce double-circuit outage rates and protect underbuild distribution lines; provide switching surge control for structural optimization and lower clearances; improve safety by preventing personal injury and equipment damage; enable line upgrading and compaction through reduced insulation levels; permit live work on the line by temporarily reducing the minimum approach distance; and achieve lower installation costs and lower losses in the line system through fewer outages.
Siemens Energy supplies line surge arresters and insulators as complete, end-to-end, technically clarified packages — compact, reliable and cost-optimized solutions.
Both designs connect directly to the overhead line. Non-Gapped Line Arresters (NGLA) offer a high degree of mounting flexibility and operational reliability: depending on tower design and the arrangement of insulators and lines, they can be installed directly on the insulators or on the tower, and they limit overvoltages to levels below the insulator withstand voltage.
Externally Gapped Line Arresters (EGLA) use an external series spark gap that galvanically isolates the active part of the arrester from line voltage under normal conditions. On a lightning strike the gap flashes over, the arrester limits the ground fault current from several kA down to a few amperes, and the arc is extinguished within 10 ms — so no circuit-breaker operation at either line end (i.e. no reclosing) is required.
| Aspect | NGLA (Non-Gapped Line Arrester) | EGLA (Externally Gapped Line Arrester) |
|---|---|---|
| Connection | Directly connected to the overhead line | Directly connected to the overhead line |
| Mounting | Most flexible solution — installation at conductor, tower, insulator etc. | Highly compact; suitable for multi-circuit towers with very small cross-arm clearances |
| Protection level | Very high protection against lightning and switching overvoltages thanks to high energy absorption capacity | Limits ground fault current from several kA to a few amperes; arc extinguished within 10 ms, no reclosing operation needed |
| Leakage current | Arrester is continuously energized | No leakage current — series gap disconnects the MOV blocks from system voltage under normal service conditions |
| Rated voltage / material | Rated for continuous energization at system voltage | Lower arrester rated voltage required (insulated by the series gap) — less material and fewer MOVs needed |
| Disconnector / ground lead | Series disconnector isolates the arrester on thermal overload, keeping the line in operation until replacement | No disconnector and no ground lead needed |
| Live installation | — | Better suited for live installation |
| Options | — | Complete EGLA solutions with polymer insulators also available |
| Standard | Designed and tested to the latest IEC 60099-4 | Designed and tested to the latest IEC 60099-8 |
As an option, Siemens Energy performs software analysis using simulation based on Cigré studies to examine customer-specific applications and carry out preliminary testing, determining the optimum and most cost-effective arrester solution.
A key benefit: outstanding protection results can be achieved while investing only a fraction of what it would cost to install the maximum amount of equipment. The flyer illustrates this with an analysis example of a double three-phase system, plotting faults per 100 km per year against tower footing resistance for different LSA deployment variants across the tower profile (phases L1-L6).
Click any figure to enlarge.