Harsh Realities About Surge Protection Devices

Surge protective devices (SPDs) and internal lightning protection systems form the basis of protection against lightning and surge overvoltages. Unfortunately, in our country, lightning protection is mostly reduced to lightning rod systems, while protection against surge overvoltages is generally not well known. However, approximately 80% of the damage to PLC, automation, and similar systems is caused by surge overvoltages. Therefore, correctly understanding and implementing surge arrester systems is of great importance for the health of our systems.

A single surge impulse can completely burn your panel. The photo was taken at a wind power plant in Adana.

1-Up Protection Level Is Very Important When Selecting a Surge Arrester

According to IEC 60634 standards, the Up protection level must be max. 2.5 kV in main distribution panels, 2.5 kV for the protection of electromechanical equipment, and 1.5 kV for the protection of electronic-based equipment. In all cases, the lower the Up level, the better the protection. Therefore, if we want to protect our equipment in a facility, we must implement cascaded protection.

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2-Selecting the Operating Voltage of Surge Arresters in Three-Phase Systems

Type 1 and Type 2 surge arresters are connected in parallel to the system. Therefore, the rated voltage of the surge arrester is the value measured between the active conductors (phase and neutral) and the earth conductor. For this reason, except for IT networks, selecting surge arresters with a Uc value of 255 V is sufficient. In IT networks, this value will be the phase-to-phase voltage. In this case, we recommend selecting surge arresters with a Uc value of 440 V.

Example surge arrester installation diagram

3-Selection of Iimp and In Values

The Iimp value is defined for Type 1 surge arresters. According to IEC 60364-5-534 standard, this value must be at least 12.5 kA. However, this may vary depending on the risk analysis defined in EN 62305-1. Our recommended values are 50 kA for maximum risk areas and 25 kA for high-risk areas with poor grounding.

The In value also depends on the risk analysis of the area where the surge arrester is used. According to standards, a minimum of 5 kA is selected. However, this value increases in high-risk areas. Increasing the In value of the surge arrester is an important factor that also increases its lifespan. In medium and high-risk areas, 10–20 kA, and in very high-risk areas, values above 20 kA should be selected.

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4-Coordination Between Surge Arresters

Surge arresters must operate in coordination to provide maximum protection. Cascaded protection and coordination ensure both sensitive and efficient protection.

5-Surge Arresters Are Not Replaced After Every Surge

The basis of surge arrester technologies is varistor technology. These systems are generally cartridge-based, and the cartridge may need to be replaced after a severe surge. VG technology surge arresters developed by RAYCAP combine varistor, gas, and spark gap technologies. These surge arresters do not become inactive after incoming surges. Therefore, we recommend using this technology in wind turbines, GSM towers, and isolated locations.