6.13Specifying power surge protection devices#
Before specifying SPDs, ensure that the products selected are from reputable manufacturers and are suitable for the application.
The following provides typical minimum specifications for power SPDs according to their location:
Table 6.13(a) – Typical specifications for category C3–C2 surge protection devices
| Category C3–C2, high risk service entrance (MEN link) surge protection devices | |
| Nominal voltage U n | 220–240 V ac |
| Maximum continuous operating voltage U c | Max 275 V ac |
| Voltage protection level U p | Max 850 V at 3 kA / 1200 V at 20 kA |
| Maximum surge current I max | 100 kA 8 / 20 µs |
| Nominal surge current I n | 40 kA 8 / 20 µs per mode |
| Protection modes | Single mode (L1-N, L2-N, L3-N) |
| Enclosure | To suit application |
| Mounting | 35 mm DIN rail / to suit application |
| Terminals | ≤25 mm² stranded power cable ≥1.5 mm² stranded remote indication |
| Status indication | Visual, voltage free contact for remote indication |
| MOV module | None / Replaceable |
Table 6.13(b) – Typical specifications for Category C1-B surge protection devices
| Category C1-B, service entrance, sub distribution board surge protection devices | |
| Nominal voltage U n | 220–240 V ac |
| Maximum continuous operating voltage U c | Max 275 V ac |
| Voltage protection level U p | Max 850 V at 3 kA / 1200 V at 20 kA |
| Maximum surge current I max | 40 kA 8 / 20 µs |
| Nominal surge current I n | 20 kA 8 / 20 µs per mode |
| Protection modes | Single mode with MEN link (L1-N, L2-N, L3-N) Single mode no MEN link (L1-N, L2-N, L3-N, N-E) |
| Enclosure | To suit application |
| Mounting | 35 mm DIN rail / to suit application |
| Terminals | ≤25mm² stranded power cable ≥1.5mm² stranded remote indication |
| Status indication | Visual, voltage free contact for remote indication |
| MOV module | None / Replaceable |
Table 6.13(c) – Typical specifications for Category A surge protection devices
| Category A, sub-circuit surge protection devices | |
| Nominal voltage U n | 220–240 V ac |
| Maximum continuous operating voltage U c | Max 275 V ac |
| Voltage protection level U p | Max 850 V at 3 kA – electrical equipment Max 600 V at 3 kA – electronic equipment |
| Maximum surge current I max | 15 kA 8 / 20 µs |
| Nominal surge current I n | 8 kA 8 / 20 µs per mode |
| Protection modes | L-N, L-E, N-E |
| Enclosure | To suit application |
| Mounting | 35 mm DIN rail / to suit application |
| Terminals | ≤10mm² stranded power cable ≥1.5mm² stranded remote indication |
| Status indication | Visual, voltage free contact for remote indication |
| MOV module | None / Replaceable |
Table 6.13(d) – Typical specifications for Category A surge reduction filters
| Category A, sub-circuit surge reduction filters | |
| Nominal voltage U n | 220–240 V ac |
| Maximum continuous operating voltage U c | Max 275 V ac |
| Voltage protection level U p | Max 600 V at 3 kA – electronic equipment |
| Maximum surge current I max | 10 kA 8 / 20 µs |
| Nominal surge current I n | 5 kA 8 / 20 µs per mode |
| Protection modes | L-N, L-E, N-E |
| dv / dt | <50 V / uS at 20 kA (8 / 20 uS) |
| Enclosure | To suit application |
| Mounting | 35 mm DIN rail / to suit application |
| Terminals | ≤10mm² stranded power cable ≥1.5mm² stranded remote indication |
| Status indication | Visual, voltage free contact for remote indication |
The important parameters when selecting power SPDs are:
- Imax: The maximum 8 / 20 µs surge current between any one phase and neutral that the SPD can withstand for a single strike
- In: The 8 / 20 µs surge current the SPD can withstand for 15 strikes
- Up: Voltage protection level, the residual voltage after the surge has passed the SPD, and
- shunt or series connection.
Shunt – typically primary protection and some secondary applications:
- connected across L to N or L to E
- length of connection leads affects let-through voltage, and
- load current does not determine size of SPD.
Series – typically secondary protection:
- connected in circuit
- shunt connection is internal, eliminating effects of lead length, and
- load current is a factor in determining SPD.