Product Line:
Surge Protective Devices (SPD's)

Understanding Per Mode vs. Per Phase Protection Ratings:

In surge protection terminology, per mode and per phase ratings refer to different ways of expressing the capacity of a surge protective device (SPD) to handle transient overvoltages.

Per Mode Rating

• A mode refers to a specific path between two electrical conductors where surge protection is applied.
• Common modes include:
  • Line-to-Neutral (L-N)
  • Line-to-Ground (L-G)
  • Neutral-to-Ground (N-G) (less common in some SPD designs)

A per mode rating specifies the maximum surge current (in kiloamperes, kA) that the SPD can safely divert in that particular mode.

Example:

• L-N mode: 100 kA
• L-G mode: 100 kA

Each mode is rated independently.

Per Phase Rating

• A phase refers to one energized conductor in a multi-phase system (e.g., L1, L2, L3 in a 3-phase system).
• The per phase rating is the sum of the surge current ratings for all protection modes associated with that phase.

Example: If a single phase (say L1) has:

• L1-N protection rated at 100 kA
• L1-G protection rated at 100 kA

Then the per phase rating for L1 is:

• 200 kA per phase (100 kA L-N + 100 kA L-G)

This summation gives a more comprehensive view of the total surge-handling capacity for that phase.

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Why This Matters

All Schneider Electric surge protection product literature reports per phase ratings, which can appear higher than per mode ratings because they aggregate multiple protection paths.

Comparison Example:

This helps clarify that a 200 kA per phase rating doesn’t mean a single suppression component handles 200 kA, it means the combined capacity of components protecting L-N and L-G modes for that phase equals 200 kA.

Publicado para: Schneider Electric Mexico