Selection Guide for High Voltage Surge Arresters in Substations and Transmission Lines

Selection Guide for High Voltage Surge Arresters in Substations and Transmission Lines

In high-voltage power systems, surge arresters are essential protection devices used to limit lightning overvoltages and switching surges. Whether installed in substations to protect transformers, circuit breakers, busbars and cable terminations, or on transmission lines exposed to outdoor environments, surge arresters help reduce the risk of insulation breakdown and equipment damage.

As voltage levels increase, transmission distances become longer and operating environments become more complex, selecting a high voltage surge arrester requires more than matching the rated voltage. System operation, protected equipment, lightning activity, pollution level, installation position and maintenance conditions must all be considered. Proper selection improves overvoltage protection, reduces trip-out risk and extends the service life of power equipment.

Basic Function of High Voltage Surge Arresters

High voltage surge arresters usually use zinc oxide resistor blocks as the core components. These blocks have excellent nonlinear voltage-current characteristics. Under normal operating voltage, only a very small leakage current flows through the arrester. When lightning or switching overvoltage occurs, the arrester conducts quickly and releases surge energy, limiting the voltage across the protected equipment.

In substations, surge arresters are mainly used to protect transformers, switchgear, instrument transformers, cable terminations and busbar systems. On transmission lines, they are often installed in lightning-prone sections, mountainous areas, important crossing sections, line terminals and locations with weak insulation coordination.

Selection Priorities for Substation Surge Arresters

Substations contain high-value equipment and complex electrical connections. An overvoltage failure may damage transformers, switchgear or other critical assets, leading to serious outages. Therefore, substation surge arrester selection should focus on protection level, energy absorption capability, continuous operating voltage and insulation coordination.

The protection level must match the insulation withstand level of the protected equipment. If the protection level is too high, the arrester may not limit overvoltage effectively. If the parameters are selected too low, the arrester may be exposed to excessive operating stress and its service life may be reduced.

In high-voltage and extra-high-voltage substations, short-circuit current, pressure relief capability, pollution level, creepage distance and installation space should also be considered. For outdoor substations, polymer housed surge arresters are increasingly used because of their light weight, pollution resistance and impact safety.

Selection Priorities for Transmission Line Arresters

Transmission lines operate outdoors for many years and are affected by lightning, wind, rain, pollution, ice and terrain conditions. In areas with high lightning trip-out rates, properly selected line surge arresters can reduce the impact of lightning overvoltage on line insulation and improve power supply reliability.

For transmission line applications, important selection factors include line voltage level, lightning activity, tower grounding resistance, insulator string configuration, route terrain and installation method. In mountainous regions, hilly areas, long-span crossings and frequent thunderstorm zones, line arresters provide significant value.

Compared with substation arresters, line arresters require more attention to mechanical installation reliability and outdoor environmental adaptability. Mounting position, support structure, grounding connection and lead length all affect actual protection performance.

System Voltage and Continuous Operating Voltage

The maximum system voltage is the basic parameter for surge arrester selection. The continuous operating voltage of the arrester should be higher than the long-term phase-to-earth voltage that may appear in the system. This ensures that the arrester does not age too quickly under normal operating conditions.

Different neutral grounding methods can result in different voltage stress on surge arresters. Effectively grounded systems, non-effectively grounded systems, arc suppression coil grounded systems and ungrounded systems may require different rated voltages and continuous operating voltages.

Before selection, the maximum system voltage, grounding method and temporary overvoltage level should be confirmed. This helps avoid insufficient protection or excessive operating stress on the arrester.

Protection Level and Insulation Coordination

The main purpose of a surge arrester is to limit overvoltage to a level that protected equipment can withstand. A lower protection level reduces the overvoltage stress on equipment, but it may also increase the energy duty and performance requirements of the arrester.

In substations, surge arrester protection level should be coordinated with the insulation levels of transformers, GIS equipment, circuit breakers, instrument transformers and cable terminations. On transmission lines, it should be evaluated together with insulator string withstand level, line insulation design and lightning overvoltage conditions.

Proper insulation coordination is not simply selecting a product model. It requires a system-level protection design. In general, the closer the arrester is installed to the protected equipment, the better the protection effect. If the leads are too long, residual voltage and inductive voltage may reduce actual protection performance.

Discharge Capability and Energy Absorption

During overvoltage events, a surge arrester must discharge impulse current and absorb energy. Therefore, discharge capability and energy absorption are important selection factors. In areas with frequent lightning activity, long-distance transmission lines and renewable energy collection lines, impulse current withstand capability is especially important.

For substation arresters, energy absorption capability should meet the requirements of switching and lightning overvoltage protection. For transmission line arresters, lightning current capability, repeated impulse withstand and long-term outdoor service conditions should also be considered.

If the energy rating is insufficient, the arrester may degrade or fail after strong or repeated surges. In lightning-intensive regions and critical lines, a suitable arrester duty class should be selected according to project risk.

External Insulation and Creepage Distance

Outdoor surge arresters are exposed to pollution, humidity, salt fog, ultraviolet radiation and temperature variation. In coastal areas, industrial pollution zones, mining areas and high-humidity environments, creepage distance and housing material are critical.

Porcelain housed arresters have mature technology and long service experience. Polymer housed arresters use silicone rubber external insulation and offer light weight, hydrophobicity and better pollution performance. They are well suited for polluted areas, pole-mounted installations, line applications and retrofit projects.

In heavily polluted environments, creepage distance should be selected according to pollution class. Housing material, shed profile and maintenance conditions should also be evaluated together.

Installation Position and Grounding Connection

The protection effect of a surge arrester depends not only on product parameters but also on installation practice. In substations, arresters should usually be installed as close as possible to protected equipment to reduce the influence of lead inductance.

On transmission lines, installation positions should be determined based on lightning trip-out records, tower grounding conditions, route terrain and protection priorities. In lightning-prone sections, line arresters can be installed on key towers, terminal towers, tension towers or crossing towers.

Grounding connection must be reliable. High grounding resistance, loose connections or excessive lead length can reduce the actual protection effect. For important equipment and critical line sections, grounding design should be considered together with arrester selection.

Wishpower Recommendations for High Voltage Surge Arrester Selection

Wishpower believes that high voltage surge arrester selection should start from the system protection objective, not only from voltage rating. Substations and transmission lines have different operating conditions, and their requirements for protection level, discharge capability, external insulation and mechanical installation are also different.

Wishpower provides zinc oxide surge arresters for substations, transmission lines, distribution systems, renewable energy stations and industrial power equipment. The product range includes polymer housed surge arresters, high voltage surge arresters, line surge arresters and distribution surge arresters.

For project support, Wishpower can assist customers with arrester selection and technical parameter confirmation according to system voltage, grounding method, installation position, pollution level, lightning activity and equipment protection requirements. Proper selection of arrester structure and parameters can improve overvoltage protection, reduce equipment failure risk and support long-term grid reliability.