What is lightning arrester?
A lightning arrester safeguards substation equipment against voltage spikes, also known as overvoltages, which occur due to lightning hits on transmission lines and switching operations within the network.
Why Substations Require Lightning Arresters
Manufacturers design electric transformers, breakers, and busbars to operate at a particular voltage. However, lightning surges may push voltage values well above that normal range, and even several microseconds of overexposure can destroy a transformer winding.
Arresters bridge this gap by keeping voltage at the equipment terminals below the maximum withstand level, an approach engineers call insulation coordination. Without such devices, substations would need much thicker, and therefore far more expensive, insulation on every piece of equipment.
Working Principle of Lightning arrester
The latest Lightning arrester uses a MO (metal-oxide) resistor, normally zinc oxide. Under normal voltage, this material behaves like an insulator, letting only a negligible leakage current pass through.
During a voltage surge, however, the resistance drops immediately, and thousands of amperes pass safely to the earth. Engineers know this behavior as a non-linear voltage-current characteristic — the main reason modern arresters no longer need the spark gaps of older-generation silicon-carbide designs.
Once the voltage returns to normal, the arrester automatically restores its high-resistance state, and it needs no manual reset.
Parts of a Lightning Arrester
- Line terminal (connects with the overhead conductor or busbar)
- Upper sealing
- Pressure relief device
- Zinc oxide varistor elements (blocks that protect equipment from the voltage)
- Insulating spacer
- Silicone rubber housing (the exterior part of the device)
- Earthing terminal (transfers surge current to the earth)
- Mounting base
Different Types of Lightning Arresters
- Expulsion arrester (older design with spark gaps, still used in some distribution networks)
- Metal oxide (gapless) arrester (modern device)
- Horn gap arrester (earlier design based on air gap)
- Valve type arrester (uses silicon-carbide resistors with spark gaps)
- Polymer arrester (silicone rubber housing with improved contamination resistance and impact strength)
Engineers also classify arresters by installation type (indoor, outdoor, pole-mounted, substation-mounted) and by voltage class (from low voltage to ultra-high).
Locations Where Arresters Are Installed
Each arrester protects only the equipment that sits nearby, within a limited range. The farther the equipment sits from the arrester, the higher the voltage surge it may still experience. Thus, engineers install arresters as close as possible to the equipment, particularly to transformers.
The arrester’s location also depends on the length of the connecting leads, the steepness of the expected surge, and the difference between the arrester’s protection level and the equipment’s rated withstand voltage — though exact values vary by substation design, voltage class, and manufacturer recommendations.
According to a 2024 study published in IET Science, Measurement & Technology, Safaei and Niasati modeled optimal arrester placement for a full substation while accounting for environmental impacts. For instance, in a double-busbar layout, placing five arresters near the incoming lines, the main bus, and the transformer terminals considerably reduced insulation risk compared with a simpler placement strategy.
Difference Between Lightning Arrester and Surge Arrester
Both devices are actually the same thing, and engineers often use the terms interchangeably. “Surge arrester” is the general term denoting both types of protective devices, while historically, “lightning arrester” referred to lightning protection only. Modern MO arresters, however, protect the equipment from both lightning and switching surges.
Testing and Maintenance
- Visual inspection
- Insulation resistance (IR) test
- Measurement of leakage current
- Watts loss (power factor) test
- Infrared thermography (while the arrester is energized)
- Earth/ground resistance test
- AC Hipot testing
Utilities usually conduct AC Hipot testing of arresters — for instance, at around 85 kV, depending on the device rating — after installation or during regular maintenance. Meanwhile, contamination on the housing, particularly when wet, may distort voltage distribution within the device and degrade its sparkover performance. That is why technicians test external flashover and sparkover separately.
International Standards Covering Lightning Arresters
- IEC 60099-4 – testing standard for gapless metal oxide arresters
- IEC 60099-5 – application and selection guide
- IEEE C62.11 / C62.22 – similar American testing and application standards
FAQs
What is the function of a lightning arrester in a substation? Limitation of the high-voltage surges caused by lightning strikes and switching operations to the safe level.
What material is used in modern lightning arrester? Metal-oxide resistor blocks (usually zinc oxide) instead of old silicon-carbide spark-gap design.
What types of lightning arresters exist? Expulsion, metal oxide (gapless), horn gap, valve type, polymer arresters.
Where should a lightning arrester be installed? As close as possible to the protected equipment, especially transformers.
How are lightning arresters tested in the field? Visual inspection, insulation resistance, leakage current, power factor, infrared thermography, earth resistance, and AC Hipot testing.
Is a lightning arrester the same as a surge arrester? In modern usage, largely yes — one metal-oxide device typically handles both lightning and switching surges.
Final Thoughts
A lightning arrester looks like a simple gray cylinder that sits near substation equipment. But it’s doing constant, split-second work — staying silent under normal voltage and reacting instantly the moment a surge threatens the system. Understanding it is a good starting point for anyone curious about how power grids survive storms.
Sources: Volker Hinrichsen, “Metal-Oxide Surge Arresters – Fundamentals,” 2024 Seminar Edition; Safaei & Niasati, “A new method for surge arrester placement in high-voltage substations considering environmental effects,” IET Science, Measurement & Technology, 2024; industry references on arrester types and field-testing practices.