What is difference between type 1, type 2 and type 3 surge protective devices?

What is difference between type 1, type 2 and type 3 surge protective devices?

Type 1

Type 1 Surge Protective Device (SPD)s are intended for installation between the secondary of the service transformer and the line side of the service equipment overcurrent device, as well as the load side, including watt-hour meter socket enclosures, and are intended to be installed without an external overcurrent protective device. Type 1 devices are dualrated for Type 2 applications as well, providing the highest ratings available for installation at the service entrance.

Type 1 SPD can discharge lightning current with waveform 10/350μs. This, if required, will be installed in the primary distribution board at the origin of the electrical installation. A Type 1 SPD does not in itself offer the required protection level and must be used in conjunction with co-ordinated type 2 devices. An installation with a lightning protection system will require a Type 1 SPD.

Type 2

Type 2 Surge Protective Device—Type 2 SPDs are intended for installation on the load side of the service equipment overcurrent device, including SPDs located at the branch panel.

Type 2 SPD can discharge 8/20μs current wave , they can prevent the damage of transient overvoltage in the electrical installations and protects equipment connected to it. It usually em-ploys metal oxide varistor (MOV) technology. The device would normally be installed in sub-distribution boards and in the primary distribution board if there was no requirement for a type 1 device

Type 3

These SPDs have a low discharge capacity. They must therefore only be installed as a supple-ment to Type 2 SPD and in the vicinity of sensitive loads. Type 3 SPD’s are characterized by a combination of voltage waves (1.2/50 μs) and current waves (8/20 μs).

Type 3 SPDs are normally installed right before the protected equipment.

Terminology

Iimp – Impulse current of Type 1 SPDs with 10/350 μs waveform

In – Norminal discharge current of Type 2 SPDs with 8/20 μs waveform

Imax- Maximum discharge current of Type 2 SPDs with 8/20 μs waveform

Up - The residual voltage that is measured across the terminal of the SPD when In is applied

Uc - The maximum voltage which may be continuously applied to the SPD without damage the SPD

Britec Electric offers full range of surge protective devices including Type 1, Type 1+2, Type 2 and Type 3 SPDs.