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Surge Protection Tools

SPD Calculator

Choose a starting surge protective device type for AC, DC, or PV systems based on exposure, installation point, and system earthing.

Inputs
Result
Type 2 SPD

Use Type 2 protection as the starting point for normal distribution-board surge protection.

Lightning exposureLower exposure
Installation pointMain
SystemTN
Selection modeRule-based type family
Next checks
  • Check Uc against the system voltage and earthing arrangement.
  • Coordinate upstream and downstream SPDs when multiple levels are installed.
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SPD selection rule

This calculator uses a practical selection rule for the starting SPD type. It first checks whether the circuit is PV/DC, then checks lightning exposure and the installation point.

PV or DC system
T = DC/PV SPD
High lightning exposure
T = Type 1+2 SPD when LPS = yes or supply = overhead/mixed
Downstream sensitive equipment
T = upstream SPD + Type 3 local protection

where:

T
Recommended SPD type family
LPS
External lightning protection system status
supply
Incoming supply exposure, such as underground, overhead, or mixed
Type 3
Local fine protection for sensitive equipment

The result is a product-family starting point. Final SPD selection still requires Uc, Up, In/Imax, earthing system, coordination distance, and local standard checks.

Assumptions

  • Low-voltage power system
  • Preliminary product family selection only
  • Final SPD rating must match system voltage, earthing, short-circuit conditions, and installation standard

Important Warnings

  • Do not use this output as proof of IEC 61643 compliance.
  • PV and DC SPDs must be DC-rated and selected against maximum array voltage.

FAQ

Is Type 1+2 always required for overhead supply?

Not always, but overhead supply increases lightning exposure. Use the result as a prompt to check the project risk assessment and local requirements.

Can this calculator choose Uc, Up, In, or Imax?

This first version chooses the SPD type family. Voltage and discharge-current ratings still need project and product datasheet verification.

Next calculators

Continue the selection workflow.