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DIN Rail Mountable Surge Protection Devices – Type 1 and Type 2

A Bolt of Lightning…

Unless you are trying to send a DeLorean through time, transient current spikes like a bolt of lightning can play havoc in your electrical equipment, costing you thousands of dollars in damage and line stoppages and even cause serious injury to your workforce. These transients can come from a host of sources; from lightning strikes to the grounding of conductors. In any case, you need to protect your investment. The best way to do that is through the use of Transient Voltage Surge Suppressors (TVSS) also known as Surge Protection Devices (SPD). These devices, if properly placed throughout your facility and grounded through a common ground reference point, will direct transient currents through low resistance grounding systems to protect your equipment.

Power Anomalies…

Transients and surges. While they can be used separately, they both indicate the same phenomenon. They refer to current, voltage, or both with peak values of over 10 kV or 10 kA. They occur very rapidly in the surge, then trail off slowly. Temporary Overvoltages (TOVs) are caused by load switching or ground impedance. They are oscillatory in nature, and can last anywhere from a few moments, to several minutes. Prolonged TOVs can cause damage to SPDs.

The NEC (National Electrical Code) and ANSI/UL 1449 break SPDs down into the groups mentioned below. There are a few more, but for the purposes of this blog, we will discuss the first two.

The first, Type 1, is intended to be connected at the point of entry for power into a building. It must be between the secondary coil of the transformer and the line side of the service disconnect overcurrent device. They are intended to be permanently connected and provide insulation from overcurrent surges from lightning strikes or power surges in the line. They are used as the primary surge arrestor for the line side.

The second, Type 2, is your second line of defense against a lightning strike. This device is connected to the load side of your service disconnect panel. Type 2s provide protection to any sensitive equipment in your system. The type 2 not only provides protection from lightning strikes, but also any motor-generated overcurrent, or internally generated surges. They are used as a surge arrestor for the load side.

Littelfuse has developed a DIN rail mounted Type 2 SPD, the SPD2 Series. The SPD2 Series is designed to protect your equipment from transient overvoltage events. They are UL Recognized and IEC Compliant, IP20 finger safe, and provide thermal protection to eliminate catastrophic failure. The SPD is offered in multiple pole configurations for different types of distribution systems. They are EN60715 Compliant and fit a 35 mm DIN rail with an interlocking tab to withstand vibration. They also feature a visual life indicator and Spark Gap and Varistor technology options.

To further protect your system, please take a look at our DIN Rail Mountable EMI filters from Schaffner EMC Inc. While the SPDs from Littelfuse will protect your system from overvoltage and current events, Schaffner’s FN 2412 and FN 3026 series Line Filters will help block line noise.

About this author

Image of Eric Halvorson

Eric Halvorson, Partnership Marketing Manager – Strategic Programs, has been with Digi-Key for over 12 years. Eric’s focus is in the Industrial Automation Market. He graduated from Northland Community and Technical College in 2011 with an AAS degree in Electronics Technology and Automated Systems. Until recently, Eric worked as a Product Manager in Electromechanical with a primary focus in Switches. Eric enjoys spending his free time woodworking, fixing things, and time out on the range.

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