Choosing Surge Protectors
Britec’s line of AC power surge protectors is designed to cover all possible configurations in low voltage installations. They are available in many versions, which differ in:
- Type or test class (1, 2 or 3)
- Operating voltage (Uc)
- AC network configuration (Single/three-Phase)
- Discharge currents (Iimp, In, Imax, Uoc)
- Protection level (Up)
- Protection technology (varistors, spark gap, filter)
- Features (differential mode, plug-in, remote signaling, compact).
The surge protection selection must be done following the local electrical code requirements (e.g.: minimum rating for In) and specific conditions (e.g.: high lightning density).
Choosing the Type of surge protectors
The type of surge protector is based on its location and the constraints of the installation to be protected.
|Installation equipped with LPS or could be hit by lightning||
|Origin of the installation origin (Panel or main switchboard)||
|Installation without LPS||
|Secondary protection (downstream primary SPD)||
(or Type 3)
|close to protected equipment||
Choosing the operating voltages Uc and UT
The SPD Uc voltage (maximum continuous operating voltage) depends on:
- Nominal voltage of the AC network (Uo)
- Type of AC system (TN, TT, IT).
The level of resistance to temporary overvoltage (UT) is related to the Uc voltage. In addition, withstanding the “high voltage” TOV (1200 Vac, 300A, 200ms) between Neutral and PE is needed in TT AC system.
Operating voltage Uc (Line/Ground)
|Voltage Uc mini||255V||255V||440V||135V|
|Voltage UT||335/440 V||335/440 V||---||230/175 V|
|TOV N/PE||1200 V|
The impulse current Iimp is defined for Type 1 SPD. The minimum rating for Iimp is 12.5 kA by pole, following IEC 60364-5-534. This level is adapted to the real phenomenon. This value can, however, be increased according to the risk (calculation according to EN 62305-1). BRITEC proposes, in its Type 1 SPD range, 3 levels of Iimp current by pole: 12.5kA, 25kA and 50 kA.
|Very high lightning density Bad earthing||25kA||
|High, medium or low lightning density||12.5kA||BR-12.5M|
Choosing In current
The relevant nominal discharge current In for the SPD is in relation with the lightning risk in the installation area.
The minimum rating of In for a SPD connected at the installation entrance is 5 kA (8/20 μs waveform), required by standard.
Nevertheless higher ratings are advised in case of high lightning density.
Moreover higher values of In current will increase the SPD lifetime.
Imax (max. discharge current) rating is linked to In.
|Very high lightning density||> 20 kA||
|High or medium lightning density||10-20 kA||
|Low lightning density or secondary SPD||5 kA||BR-15DP|
Choosing the protection level Up
The user must select a surge protector with a protection level Up adapted to the withstand level of terminal equipment. In every case, the lower the protection level Up, the better the protection.
IEC 60364 standard calls for the minimum protection level of 2.5 kV for a SPD connected at the entrance of a 230/400 V network: this level is in compliance with the withstand of robust devices (electromechanical type).
Electronic-based terminals have lower impulse withstand and require a better protection: so, surge protectors with 1.5 kV protection are necessary to provide efficient protection.
|SPD at the installation entrance||2.5 kV max.||1.5 kV max.|
|Electromechanical protected equipment||2.5 kV||1.5 kV|
|Electronic-based protected equipment||1.5 kV||0.8 kV|
Contact Person: Macy Jin