What are the functions and types of surge arresters?

We all know that surge arresters are sometimes called overvoltage protectors or overvoltage limiters. In use, surge arresters are installed near the protected equipment and connected in parallel. Under normal circumstances, the surge arrester is not conductive (at most, only a leakage current in the microampere range flows through it). When the voltage applied to the surge arrester reaches its operating voltage, the surge arrester conducts, allowing a large current to flow, releasing the overvoltage energy and limiting the overvoltage to a certain level to protect the equipment's insulation. After releasing the overvoltage energy, the surge arrester returns to its original state. Surge arresters come in various types, including protective gaps, breakdown fuses, tubular surge arresters, and valve-type surge arresters.

The function of surge arresters

A surge arrester is a crucial device in power systems that protects electrical equipment and lines from overvoltage damage. Essentially, it's a discharge device, typically connected in parallel with the protected equipment, between the conductor and ground.

When the protected equipment is operating at its normal operating voltage, the surge arrester does not trip, effectively creating an open circuit to ground.

However, if an overvoltage occurs and threatens the insulation of the protected equipment, the surge arrester immediately trips, diverting the high-voltage surge current to ground, thus limiting the voltage amplitude and protecting the equipment's insulation. Once the overvoltage dissipates, the surge arrester quickly returns to its original state, allowing the system to supply power normally.

Classification of surge arresters

Metal Oxide Surge Arrester

Core Component: Zinc Oxide (ZnO) Valves.

Working Principle: Zinc oxide vases possess extremely excellent nonlinear volt-ampere characteristics. Under normal voltage, their resistance is extremely high, and leakage current is minimal (microamperes). When the voltage exceeds a certain value, their resistance drops sharply, instantly discharging a huge surge current.

Advantages:

Gapless: Fast response speed.

Good protection performance: Low residual voltage.

Large current capacity: Can withstand powerful lightning currents.

No follow current interruption required: Automatically recovers to a high-resistance state under power frequency voltage.

Current Status: This is currently the mainstream and best-performing surge arrester, having largely replaced other types of surge arresters, and is widely used in all areas from high-voltage power grids to low-voltage power distribution.

Tube-Type Surge Arrester

Core Structure: Consists of a gas-generating tube and internal and external gaps.

Working Principle: Overvoltage breaks down the gap, generating an electric arc. The high temperature of the arc causes the gas-generating pipe wall to decompose, releasing a large amount of gas. This high-pressure gas is ejected from the pipe opening, forcefully extinguishing the arc.

Disadvantages: Significant choke point during operation, detrimental to equipment insulation; discharge characteristics greatly affected by the environment; short lifespan.

Current Status: Primarily used in transmission lines; rarely used in distribution systems.

Valve-type Surge Arrester

Core Components: Silicon carbide (SiC) valve plate + series gap.

Working Principle: Under normal conditions, the gap isolates the system voltage; during overvoltage, the gap breaks down, and the silicon carbide valve plate discharges current and limits follow current.

Disadvantages: Lower protection level than MOA; has follow current issues.

Current Status: The mainstream product before the advent of MOA; now largely obsolete and replaced.

Summary

In modern power system and electronic equipment protection, the term "surge arrester" almost always refers to metal oxide surge arresters.It is a crucial protective component in power systems and electronic equipment.

Shaanxi Huadian is a professional manufacturer of power products such as surge arresters and insulators. Please contact us if you have any needs.

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