Surge Protection Devices
Transient voltage surge suppression to safeguard sensitive downstream equipment from spikes.
About Surge Protection Devices
A surge protection device (SPD) limits transient over-voltages — from lightning strikes on or near a building, or from switching large loads and capacitor banks — by diverting the surge current to earth in microseconds and clamping the voltage that reaches connected equipment. Drives, PLCs, instrumentation, servers and LED lighting are the usual casualties when surges go unprotected.
Microtech supplies Citel surge protectors for low-voltage AC installations. Type 1+2 devices, tested with the 10/350 µs lightning current wave, go at the service entrance of buildings with a lightning protection system. Type 2 devices, rated by their 8/20 µs maximum discharge current, go at distribution boards. Type 3 or combined Type 2+3 units sit close to sensitive loads. Several Citel ranges use the maker's VG technology, which pairs gas-filled spark gaps with varistors.
We select SPDs for the earthing system, supply voltage and exposure of the site, and coordinate the types between incomer and sub-boards. They can be supplied loose or wired into panels built at our Varanasi and Lucknow facilities.
Key specifications
| Type 1+2+3 (Citel) | DS250VG and DACN1-25VGS (Iimp 25 kA), DACN1-35VGS (Iimp 35 kA), DAC1-13VGS (Iimp 12.5 kA) — VG technology |
|---|---|
| Type 1+2 (Citel) | DS250E (Iimp 25 kA, Imax 140 kA), DS500E (Iimp 50 kA, Imax 200 kA), DAC1-13S (Iimp 12.5 kA) |
| Type 2 (Citel) | DAC50S (Imax 50 kA), DAC80S (Imax 80 kA), DS40S (40 kA per module), DACF25S (Imax 25 kA, internal fuse) |
| Filtered SPDs | DS-HF Type 2+3 (single-phase) and DS40HF Type 2 (Imax 40 kA), both with RFI filtering |
| Test waveforms | 10/350 µs (Type 1, Iimp) and 8/20 µs (Type 2, In / Imax) |
| Construction | Pluggable modules or monobloc, DIN-rail mounted |
| Status indication | Remote signalling contact on most ranges |
| Product standard | IEC / EN 61643-11 |
Features & benefits
- SPD type chosen for each location: incomer, distribution board or equipment
- Coordinated Type 1 and Type 2 protection across the installation
- VG technology ranges combining gas-filled spark gaps and varistors
- Pluggable modules that can be replaced without rewiring
- Remote signalling contact for BMS or PLC alarm
- Backup fuse or breaker selected to the SPD maker's recommendation
Where it’s used
- Main LT panels of buildings with lightning protection
- Distribution boards feeding drives, PLCs and IT loads
- Data centres and telecom sites
- Hospitals and commercial buildings
- Water and wastewater pumping stations
- Street lighting and LED installations
Standards & compliance
Surge Protection Devices — FAQs
Which surge protection type do I need where?
Type 1 (or Type 1+2) at the origin of the installation where a direct lightning strike is credible — always when the building has a lightning protection system. Type 2 at distribution boards feeding sensitive equipment. Type 3 close to particularly sensitive loads. Many sites need more than one stage, coordinated by cable length.
What is the difference between Iimp and Imax?
Iimp is the impulse current a Type 1 SPD withstands with the long 10/350 µs wave that represents direct lightning current. Imax is the highest 8/20 µs current a Type 2 SPD can divert once. The two are not directly comparable, so check which test class the datasheet refers to.
How do I know an SPD needs replacing?
Check the status indication on the device, and wire its remote signalling contact — available on most Citel ranges — to a BMS or PLC alarm so a failed module is noticed. On pluggable designs, a worn-out module is replaced without disturbing the wiring.
Does an SPD replace earthing or lightning protection?
No. An SPD works only with a sound earthing system, and it complements — not replaces — the external lightning protection on the building.
