SPD Type 1 & 2

Red and black cables with yellow bands plug into a white surg protective device with black switches and red detailing

Leading the Charge in Surge Protection

Boost safety and control building electrical systems by deploying smoke and heat detector, smart outlet, and LED lighting solutions from Littelfuse. We make sensors, relays for alarms, dimmers, and Type 1 and Type 2 SPDs to protect systems from lightning strikes. We also produce parts for AFCI, GFCI, and RCD outlets to prevent arc flashes and shocks.

How a Surge Protective Device (SPD) Works

SPDs limit the surge voltage amplitude to a defined level so dielectric strength of equipment is not exceeded. During voltage surge the SPD discharges the associated surge currents. An example of a circuit with common mode protection is shown in Figure.
 
When a voltage surge occurs, the SPD switch is closed as shown in Figure. Voltage surge sources can include lightning, induced power surges, industrial and switching surges, and nuclear electromagnetic pulses.
This closure only lasts for the duration of the surge voltage which is typically a few microseconds.
The equipment is safeguarded and continues to operate.
 
SPD
IEC & UL Class and Type
Electrical and electronic equipment and transients

  • IEC 61643-11 Class (EN Type)
    • Class (EN Type) defined by surge current pulse shape used to test voltage limiting SPD function
      • Class I uses 10/350 μs pulse shape
      • Class II uses 8/20 μs pulse shape
        • SPD can be classified as Class I & II
      • Class III have low discharge capacity and must be installed as supplement to Type II SPD
    • EN stands for European Norm and term “Type” is used by most European OEMs instead of Class

  • UL 1449 Types
    • Types 1, 2, and 3 defined by location
    • Type 1 are connected between service transformer and building line side
    • Type 2 are connected on load side of service disconnect or integrated in electrical panel
    • Type 3 are point of use and plug in
    • Type 4 are component assemblies with one or more Type 5 components including disconnect Examples: LST or TMOV
    • Type 5 are discrete component surge suppressors such as MOVs that may be on printed circuit board

  • IEC Class III and UL Type 3 not included in this material

SPD locations for industrial or commercial buildings
SPD locationProtected equipment examples

Main distribution protection

  • UPS
  • Motor Control Centers (MCCs)
  • Backup Power
  • Switchgear
  • Transfer switch

Sub-distribution protection

  • Local backup power
  • Switchgear
  • Generators
  • HVAC
  • Fire alarm systems
  • Security systems
  • Building management systems
  • Power Distribution
  • Unit (PDU)

Equipment level protection

  • Motor drives
  • Soft starts
  • Medical equipment
  • Life support equipment
  • Test equipment
  • Printers
  • Communication systems
  • Escalators/elevator
  • Parking lot lighting
  • Computer servers

Stacked rows of white surge protective devices

Single-Phase SPDs

Single-phase surge protective devices (SPDs) provide NEC-required protection against transient voltage surges from lightning strikes, current switching, start up, shut down, and power surges. Littelfuse makes three models of Type 1 and Type 2 single-phase SPDs that, respectively, use metal oxide varistors (MOVs), gas discharge tubes (GDTs), or MOVs, TVS diodes, and fuses to handle excess voltage.

View Block Diagram
A blue cable plugs into the corner of a red surge protective device

Three-Phase SPDs

Three-phase surge protective devices (SPDs) provide NEC-required protection against transient voltage surges from lightning strikes, current switching, start up, shut down, and power surges. Littelfuse makes three models of Type 1 and Type 2 single-phase SPDs that, respectively, use metal oxide varistors (MOVs), gas discharge tubes (GDTs), or MOVs, TVS diodes, and fuses to handle excess voltage.

View Block Diagram

SPD Type 1 & 2 Resources