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, 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.
18th Edition Requirements
The 18th edition BS 7671 now stipulates
Protection against transient overvoltages shall be provided where the consequences caused by an overvoltage could
(i) result in serious injury to, or loss of, human life, or
(ii) result in interruption of public services and/or damage to cultural heritage, or
(iii) result in interruption of commercial or industrial activity, or
(iv) affect a large number of co-located individuals.
For all other cases, a risk assessment according to Regulation 443.5 shall be performed in order to determine if protection against transient overvoltages is required. If the risk assessment is not performed, the electrical installation shall be provided with protection against transient overvoltages.
For a single dwelling unit it will be a decision for the house owner to make whether they consider the small additional cost of the surge protection device justified to protect their installation and equipment against these damaging overvoltages
Surge protection devices are classified according to their functions:
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.
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
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).
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.
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.
Frequently Asked Questions:
What does surge protection do?
A surge protection device is designed to protect electrical devices such as computers and TV's from voltage spikes. The surge protection device (SPD) attempts to lessen the voltage supplied to an electrical device by either blocking or shorting to ground any unwanted voltages above a safe standard.
Do you really need surge protection?
If electrical equipment is used then a surge protection device is definitely needed as electrical equipment comes with sensitive components that could be damaged very easily. A surge protection device will increase the longevity of electrical equipment.
How long do surge protectors last?
This will very much depend on how many surges the device will have to deal with, so there is no definitive answer.
The product standard requires the device to cope with a minimum of 15 surges at its rated value. However, a surge at the rated value would be a very large surge indeed. Most events are much smaller than the maximum, but it is these events which degrade sensitive equipment over time. Because the likely surges are smaller than the maximum, it is likely the device will last for many years.
Surge protection devices are equipped with an indication ‘window’ which will turn red when the device has reached its end of life. Usually, it is a simple case of replacing a cartridge at this time. It is recommended this window is checked from time to time especially after a lightning storm.
Can a power surge damage a TV?
Yes, electrical surges have the capacity to overload and short out any electrical equipment in a home, significantly degrading the life of the equipment. Anything that is plugged into a wall can be affected by electrical surges.
Surge Protection FilesDownload our documentations below, containing everything you need to know about Surge Protection and the 18th Edition
At a Glance | Surge ProtectionAll of the key info you need to know about Surge Protection Devices.
Bitesize Guide | 18th EditionOur small guide to everything you need to know about the 18th edition.
Residential Distribution CatalogueOur Residential Distribution Catalogue contains all of our 18th edition solutions for residential applications.
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