What are the Materials Used in Surge Arrester

A surge arrester is a crucial component in electrical systems, designed to protect electrical equipment from voltage spikes caused by lightning strikes, switching operations, or transient faults. The effectiveness of a surge arrester largely depends on the materials used in its construction, as they determine its ability to withstand and dissipate high voltage surges. Understanding the materials involved in the design of surge arresters is essential for professionals in electrical engineering and power systems. This article explores the various materials commonly used in surge arresters and their significance in ensuring the safety and longevity of electrical equipment.

Core Materials in Surge Arresters

Metal Oxide Varistors (MOVs):

The most crucial material used in modern surge arresters is the Metal Oxide Varistor (MOV). MOVs are semiconductors that change their electrical resistance with the applied voltage.

The primary material in MOVs is Zinc Oxide (ZnO), combined with small amounts of other metal oxides like Bismuth Oxide (Bi2O3), Cobalt Oxide (CoO), and Manganese Oxide (MnO).

These compounds enhance the varistor's non-linear voltage-current characteristics, making it highly effective in absorbing and dissipating high-energy surges.

Silicone Rubber or Porcelain for Housing:

The external housing of surge arresters is typically made from either silicone rubber or porcelain.

Silicone rubber is preferred for its excellent hydrophobic properties, resistance to UV radiation, and flexibility, which makes it less prone to damage from mechanical stress.

Porcelain, on the other hand, is known for its high dielectric strength and mechanical robustness. However, it is more susceptible to damage from environmental factors like pollution and moisture.

High-Grade Steels for Grounding Components:

Grounding components of surge arresters are usually made from high-grade steel.

Steel provides the necessary strength and durability to withstand the mechanical stresses during surge events and ensures a reliable path to the ground.

Fiber-Reinforced Plastics for Support Structures:

In some surge arresters, fiber-reinforced plastics are used for support structures.

These materials offer high strength-to-weight ratios and excellent resistance to environmental degradation.

Gas-Discharge Tubes (GDTs):

In specific types of surge arresters, like those used in telecommunications, gas-discharge tubes are employed.

GDTs usually contain a gas mixture that ionizes during a surge, creating a conducting path to divert the excess voltage.

Aluminum Oxide (Alumina) in Spark Gaps:

Spark gaps, a component in some surge arresters, often use aluminum oxide (alumina) due to its good electrical insulation properties and thermal stability.

Importance of Material Selection

The choice of materials in a surge arrester is critical for its performance. Materials like ZnO provide the necessary electrical properties to protect against surges, while silicone rubber and porcelain housings offer physical protection.

Environmental resistance is another crucial factor, as surge arresters are often exposed to harsh outdoor conditions.

The longevity and reliability of the surge arrester depend on the quality of materials used, influencing maintenance needs and overall system safety.

The materials used in surge arresters play a pivotal role in their functionality and durability. From the metal oxide varistors at their core to the external housing and support structures, each material is selected for its specific properties to ensure optimal performance. Understanding these materials is essential for those in the field of electrical engineering and power system protection, as it provides insights into the design considerations and operational capabilities of surge arresters. As technology advances, the development of new materials and composites continues to enhance the effectiveness of surge arresters in safeguarding electrical systems.