A distribution arrester, also known as a surge arrester or a lightning arrester, is a critical protective device used in overhead transmission and distribution lines. It protects electrical equipment such as transformers, insulators, and circuit breakers from overvoltage transients. These include lightning strikes, switching surges, and other voltage spikes. Its primary function is to limit overvoltages by diverting excess current to the ground. Distribution arresters are crucial for maintaining power system reliability by mitigating transient overvoltages. In rural areas with overhead power lines prone to thunderstorms, distribution arresters are vital components. A single lightning strike could cause widespread outages. Using surge arresters aids absorption and grounding to keep the lights on and equipment safe. A surge arrester is a voltage-sensitive switch that stays off under normal conditions and turns on during a surge event.
Working of a distribution arrester
In high-demand and complex electrical networks, sudden voltage spikes can cause serious damage to equipment and disrupt service. The distribution arrester is able to protect overhead transmission and distribution lines from harmful surges. It is installed in medium-voltage power systems like 2.4 kV to 34.5 kV. The arrester’s internal element (metal oxide varistor) has high resistance, and current flows normally through the power lines without interference from the arrester. The MOV detects the rise and instantly becomes conductive, which allows the surge current to be diverted away from sensitive equipment and directed safely to the ground. The MOV automatically resets, returning to its high-resistance, non-conductive state. Its internal structure of the arrester includes MOV discs, sealed housing, grading rings, and a ground terminal. Surge voltages could easily burn out transformers, damage insulators, and cause outages without distribution arresters.
Importance of using distribution arresters in overhead transmission line
Overhead transmission lines are vulnerable to transient overvoltages from lightning strikes and switching surges. Distribution arresters protect critical equipment, enhance system resilience, cut outages, and promote public and worker safety. Lightning is one of the most common causes of power outages and equipment failure in overhead lines. A distribution arrester provides a low-resistance path to the ground, safely discharging the surge and preventing insulation breakdown and flashover. The arresters limit these internal system surges to keep voltages within safe levels and protect downstream equipment. A single voltage event can lead to burnt-out transformers, damaged capacitor banks, and broken insulators. Surge arresters reduce maintenance costs, reduce system downtime, and extend the lifespan of high-value electrical assets. Grid stability depends on the operation of transmission and distribution lines. Surge arresters improve power quality, voltage regulation, and system uptime.
Key components of the distribution arresters
Distribution arresters are vital for protecting overhead transmission lines from dangerous voltages. It has various components that play a crucial role in ensuring effective, fast, and safe surge protection for overhead transmission lines. Each component has different components that ensure the effectiveness of the arrester. These components include:
- Metal oxide varistor (MOV) discs—the heart of the arrester consists of zinc oxide combined with small amounts of other metal oxides. The MOV acts as a nonlinear resistor for high resistance at normal voltage and low resistance when a surge occurs. It absorbs and safely diverts surge energy to the ground.
- Housing or enclosure—it protects the internal components and is made from porcelain or polymer. It is designed to withstand UV radiation, extreme weather, pollution, and moisture. The housing ensures insulation and durability for outdoor installations on overhead lines.
- End fittings and terminals—these are connection points for system integration. They are metal fittings attached to both ends of the arrester. It connects to the line and ground and often includes clamps or threaded studs for easy installation.
- Ground terminal—the terminal connects the arrester to the grounding system and allows excess surge energy to safely dissipate into the earth.
- Grading rings—the rings control voltage distribution along the arrester. They are metallic rings placed around housing. They reduce corona discharge and improve voltage distribution across MOV blocks.
- Pressure relief mechanisms—these are membranes that activate if internal pressure rises excessively due to an internal fault. It prevents explosion or rupture of the arrester.
Types of distribution arresters
Station-class arresters
These types function in high-voltage substations and power plants. Its voltage ranges between 69 kV and above. It has a rugged design and often includes grading rings and pressure relief devices. It functions at critical nodes in the power grid where protection of large transformers and breakers is crucial. Station class arresters are ideal for systems that demand high energy handling capability and greatest protection.
Intermediate class arresters
These arresters serve in medium-voltage and sub-transmission systems. It can handle voltage between 34.5kV 69 kV. Its design is more compact than station class but is more robust than distribution class. It is a deal in substations or industrial facilities where medium-large protection is enough.
Distribution class arresters
The arresters mostly serve on overhead distribution lines and pole-mounted transformers, between 2.4 kV and 34.5 kV. It has an energy capacity that is lower than other classes but is highly responsive. The arrester is lightweight, compact, and often polymer-housed for outdoor use. It may mount directly on poles, crossarms, or transformer bushings. Distribution classes are best for residential and commercial overhead distribution systems.
Line arresters
These are installed along the line and not just at equipment terminals. They protect long stretches of conductor from lightning-induced surges.
Porcelain-housed arresters
These have a traditional design and are very durable and weather-resistant. They are heavier and more prone to shattering under mechanical stress. These arresters are ideal for high-contamination areas where mechanical strength is crucial.
Polymer-housed arresters
These are from silicone rubber, are lightweight, UV-resistant, vandal-resistant, and safer in case of failure. They are ideal for modern overhead systems in regions with extreme weather.
Material selection for surge arresters
The material selected is crucial when designing distribution arresters for overhead transmission lines. Materials influence performance, durability, safety, and cost-effectiveness. Additionally, it affects their function, reliability, and field performance. Distribution arresters are composed of active component MOVs, insulating housing, end fittings and terminals, and sealing and bonding materials. Each component needs careful selection to ensure the arrester can survive high voltages, harsh weather, and a long service life. Here are the materials for surge arresters.
- Metal oxide varistor (MOV) discs—this acts as the core surge protection element. Under voltage it resists current flow, and under surge conditions, it becomes highly conductive to divert the surge to the ground. Zinc oxide is ideal for non-linear voltage-current behavior, high energy absorption, fast response time, and stable thermal and electrical properties.
- Housing and insulation material—this is from porcelain materials that are high-grade ceramic clay, feldspar, and silica. It has excellent mechanical durability, UV and weather resistance, and a long lifespan. They are best suited for high-contamination or mechanically demanding environments. Polymer materials include silicone rubber, EPDM, or EPR. It is lightweight, easy to handle, hydrophobic, and has high impact and vandal resistance.
- End fittings and terminals—they are from materials such as galvanized steel, stainless steel, brass, or aluminum alloys. They provide electrical connection and mechanical mounting to line and ground. It is crucial to select the materials based on their corrosion resistance, tensile strength, and compatibility with conductor material.
- Sealing and bonding materials—the materials include polymeric sealants, silicone compounds, and epoxy resins. They prevent moisture ingress, maintain internal pressure, and preserve dielectric properties.
Functions of the arresters in renewable energy expansion strategies
In the global transition towards renewable energy, power grids are becoming increasingly decentralized, complex, and exposed to new risks. Distribution arresters ensure the reliability of these evolving grids. Renewable energy systems are more vulnerable to voltage surges than traditional centralized power systems. This is mainly due to factors such as decentralized generation, frequent switching operations, and increased power electronics. Distribution arresters support renewables by protecting distributed energy infrastructure such as solar, wind, BESS, and overhead lines. The arresters also ease grid stability, off-grid renewable systems, and support renewable energy policies. Distribution arresters are more important in the new age of renewable energy. They ensure power quality and support the stability of modern and decentralized grids. Surge protection in renewable energy is crucial for the resilience and sustainability of the entire system.
Best practices for distribution arresters in overhead transmission lines
Distribution arresters are the first line of defense in protecting overhead transmission lines. This harm may be from voltage surges caused by lightning, switching operations, and other transient events. Following best practices ensures the devices perform effectively, safely, and reliably over the long term. Utility professionals and engineers can maximize system reliability, reduce equipment failure, and enhance safety by following the best practices for distribution arresters. These practices may include choosing the right type and rating of arrester, ensuring proper placement and installation, ensuring effective grounding, conducting periodic inspections, and following manufacturer guidelines and standards. Additionally, it is crucial to consider the environmental factors when installing in various regions. In conclusion, distribution arresters are crucial components in the protection of overhead transmission and distribution systems. With the rising demand for grid reliability and system resilience, distribution arresters are at the center of the demand.
