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Surge Protection

The whole nature of how electrical equipment is used in homes and at work has evolved; with everyday activities relying on electronic equipment.

Products such as computers, printers, flat screen televisions, industrial control equipment such as PLC’s, alarms, microwaves and washing machines are common place. These can all be vulnerable to transient overvoltages, which can significantly reduce the equipment’s lifespan through degradation and damage.

A transient overvoltage or surge is a short duration increase in voltage measured between two or more conductors. In short this means anything from microseconds (millionths of a second) to a few milliseconds (thousandths of a second) in duration.

Surge Protection Devices (SPD's)

SPD’s protect electrical and electronic equipment against transients, originating from lightning, switching of transformers, lighting and motors.


These transients can cause premature ageing of equipment, downtime, or complete destruction of electronic components and materials.

Selection Criteria

Surge protection devices are classified according to their functions:

Type 1
SPD which can discharge partial lightning current with a typical waveform 10/350 μs. Usually employs spark gap technology.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 coordinated type 2 devices. An installation with a lightning protection system will require a Type 1 SPD.

Type 2
SPD which can prevent the spread of overvoltages in the electrical installations and protects equipment connected to it. It usually employs metal oxide varistor (MOV) technology and is characterised by an 8/20 μs current wave.This device would normally be 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 supplement to Type 2 SPD and in the vicinity of sensitive loads. Type 3 SPD’s are characterised by a combination of voltage waves (1.2/50 μs) and current waves (8/20 μs).

Terminology

Iimp – Impulse current of 10/350 μs waveform associated with Type 1 SPD’s
In – Surge current of 8/20 μs waveform associated with Type 2 SPD’s
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 it conducting.

Maintenance

Most SPDs have an indication window that they are operational. If the indicator is green they are providing protection. If they are red then they have reached ‘end of life’ and will need replacing. Often there is a replaceable cartridge which can simply be withdrawn and replaced with a new operational device.

Surge Protection At a Glance

Available Products

Surge Protection Devices

Devices

Cat Ref.
Description
SPD 2P monobloc 12.5kA class 1 with light indicator TT + TN
SPD 4P monobloc 12.5kA class 1 with light indicator TT + TNS
SPD 4P pluggable 100kA class 1 with end of life indicator TNS
SPD 4P pluggable 100kA class 1 with end of life indicator TT
SPD 4P pluggable 100kA class 1 with end of life indicator and remote contact TNS
SPD 4P pluggable 100kA class 1 with end of life indicator and remote contact TT
SPD 1P pluggable 15kA class 2 with end of life indicator
SPD 1P pluggable 40kA class 2 with end of life indicator
SPD 2P pluggable 8kA class 2 with indicator
SPD 2P pluggable 15kA class 2 with end of life indicator
SPD 2P pluggable 40kA class 2 with end of life indicator
SPD 4P pluggable 8kA class 2 with indicator
SPD 4P pluggable 15kA class 2 with end of life indicator
SPD 4P pluggable 40kA class 2 with end of life indicator
SPD 1P pluggable 15kA class 2 with reserve + remote contact
SPD 2P pluggable 15kA class 2 with reserve + remote contact
SPD 2P pluggable 40kA class 2 with reserve + remote contact
SPD 2P pluggable 65kA class 2 with reserve + remote contact
SPD 4P pluggable 15kA class 2 with reserve + remote contact
SPD 4P pluggable 40kA class 2 with reserve + remote contact
SPD 4P pluggable 65kA class 2 with reserve + remote contact
SPD 1P+N pluggable 3kA class 3 with end of life indicator
SPD 3P+N pluggable 3kA class 3 with end of life indicator
SPD pluggable photovoltaic 25kA class 2
SPD 2P for ADSL line
SPD for VDSL2 line
Cartridge 25kA class 1 for SPN8xxx
Cartridge neutral 25kA class 1 for SPN802 and SPN802R
Cartridge 15kA 275V for pluggable SPD
Cartridge 15kA 275V for pluggable SPD with reserve
Cartridge 40kA 275V for pluggable SPD
Cartridge 40kA 275V for pluggable SPD with reserve
Cartridge neutral 40kA 255V for pluggable SPD without reserve
Cartridge 3KA 255V
Cartridge 3KA 255/440V
Cartridge 65kA 275V for pluggable SPD with reserve
Cartridge neutral 65kA 255V for pluggable SPD with reserve