Surge Protection: What installers need to know

20th December 2021

Surge Protection: What installers need to know

Surge Protection is not just an integral part of electrical work, but a required one. We explain the importance of Surge Protection in public, commercial and residential systems.

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Ensuring surge protection is implemented correctly is not only required under the Wiring Regulations but is essential for the smooth running of public services and business operations.

When the current, 18th Edition of the Institution of Engineering and Technology (IET) Wiring Regulations (BS 7671) was released, a key update was to the surge protection section. The successive revisions to this section of the regulations reflect the growing importance of electrical and electronic devices in modern life. Almost any building, whether it is industrial, commercial, public sector or residential, will contain a large number of these devices and electrical equipment that must be protected from the damaging effects of power surges, also known as transient over-voltages.

Power surges can be caused by external events such as lightning strikes, utility grid switching or electrical accidents, as well as electrical switching within appliances and equipment located inside the building.

The 18th Edition introduced a simplified assessment for when Surge Protection Devices (SPD) are required and states that protection is needed where the effects of over-voltages could:

  • Result in serious injury or loss of human life
  • Cause an interruption of public services and/or damage to cultural heritage
  • Interrupt commercial or industrial activity
  • Affect a large number of individuals in the same location

Also, any commercial, industrial or public building that is supplied by overhead lines requires surge protection. However, it is not required for single residential properties if the value of the equipment does not justify the protection.

It is important to note that Overcurrent Protective Devices (OCPDs), such as circuit breakers and fuses do not provide over-voltage protection. In basic terms, OCPDs primarily protect people from the dangers of a short circuit or overload, whereas SPDs are designed to protect equipment.

There are three main types of SPD available and it is important to select the right device and install it correctly.

  • Type 1 - Provides protection against surges caused by direct lightning strikes.
  • Type 2 - Offers protection against over-voltages from switching and indirect lightning strikes.
  • Type 3 - Delivers local protection for sensitive equipment and should always be installed in addition to a Type 1 or 2 device due to the relatively low discharge capacity.

To deliver the required level of protection, the SPDs must be installed in the correct locations within the installation and in accordance with the lightning protection zones (LPZ). This includes cascading different types of devices to improve the safety of the installation and fitting devices where wiring crosses from one zone to another.

For modern buildings, surge protection is essential to prevent damage to sensitive and valuable devices and equipment. To read more about the requirements of the regulations and the options available, as well as for guidance on the installation factors to consider, download our Surge Protection guide here.

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