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Surge Protection for UK Solar PV Systems

Published: January 2024

Recent changes to the BS7671 UK Wiring Regulations 18th Edition in the form of amendment 2 have introduced requirements and considerations for surge protection on both the AC and DC side of a solar PV System. Surge protection is an interesting topic and amendment 2 to the 18th edition wiring regulations introduces some of the most significant technical changes that we've seen in recent years. In this article we take a look at surge protection, particularly in the context of the updated UK wiring regulations and how surge protection could best be incorporated into new and existing solar PV systems installed in the UK.

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The UK Wiring Regulations, 18th Edition, amendment 2

Section 443 of BS7671:2018+A2:2022 is concerned with the AC (mains) side of the PV system and requires us to consider providing protection from transient overvoltages of an atmospheric origin or due to switching. Protection from overvoltage should be provided under the following circumstances:

  • Where the overvoltage could cause a serious injury or a loss of human life
  • Where the overvoltage could result in the failure of a safety device
  • Where the overvoltage could result in significant financial or data loss

The Surge Protection device (SPD) protecting the solar inverter must be within 10m of the inverter, if this can't be achieved at the incoming mains/grid supply meter‚Äčering point or the source of the circuit, then an additional SPD should be installed close to the solar inverter.

The regulation is summarised by stating that in all other cases a Surge Protection Device (SPD) shall be provided unless the owner of the installation declines such protection.

A transient overvoltage is classed as a 10% (or more) spike in voltage over the distribution network's nominal value over a number of cycles. Of an atmospheric origin would apply to direct and indirect lightening strikes to equipment and cables on the mains power network. Damage to power lines and transformers on the mains network as well as re-energising after an outage could also be a cause of a spike in mains voltage.

Section 712 of BS7671 is dedicated to solar PV systems and states that if a surge protection device is required under section 443 (the mains/AC side of the PV system) then surge protection will also be required on the DC side.

How do surge protectors work?

Surge protection devices (SPDs) generate equipotential bonding between the connected conductors when excessive voltage is applied. This prevents voltage peaks from destroying connected devices.

A surge protector will attempt to limit the voltage available to electrical devices over a safe threshold by either blocking excess voltage or shorting it to ground.

There is a wide range of surge protection devices available of varying price and performance. The right device for each situation will be based on what a surge protection might be required to do in terms of it's clamping voltage, energy absorbtion and dissapation capabilities as well as it's response time.

A Type 1 SPD is for use alongside Lightning Protection Systems (LPS) and for overhead mains power supplies

A type 2 SPD is for use for installations not needing a type 1 SPD

Type 3 SPDs are for sensitive equipment and installations such as fire alarm / burgalar alarm panels and are supplementary to Type 1 and 2 SPDs

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Solar PV Systems & Equipment, including Electrical & Roofing Systems

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Deliveries to anywhere in the UK are quick, tracked and accurate, technical support (by phone and on site if needed) and design/product advice is available before, during and after installation. The recording and collating of serial numbers, factory and other test results, manuals any other information required for equipment warranties, add ons and extensions is included.

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Bespoke system design, equipment testing and integration support as well as on-site technical support and job/equipment specific training is available for off-grid, hybrid, larger and or more complex systems.

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Mains/Grid Isolation and Surge Protection

Mains/AC Surge Protection Solar PV Systems

A whole house surge protector is installed to provide protection from transient overvoltages originating from the mains/grid. A whole house surge protector is installed directly inline and as close as possible to the incoming mains/grid supply meter, this allows for surge protection for all circuits and equipment including solar inverters, routers, stereos and other sensitive electrical equipment within the network. The addition of a 100Amp lockable isolator also allows for safe and convenient isolation of all electrical equipment within the network including consumer units, solar inverters, battery storage units and EV chargers from the mains/grid in one place.

Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Mains/Grid Isolation and Surge Protection


Solar PV Surge Protection (DC Surge Protection)

DC Surge Protection Solar PV Systems

DC surge protection devices (SPDs) are installed between the solar panels and the solar inverter to protect both the solar inverter and the downstream electrical equipment from transient overvoltages of an atmospheric origin impacting the electrical system via the DC side of the system / the solar panels.

DC Surge protectors are in compliance with the recently updated 18th edition amendment 2 of BS7671.

Solar PV Surge Protection (DC Surge Protection)

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Articles: Further Information, Calculators & Solar Inverter Fault Codes

Lots of articles, calculators and technical information including links for further reading. Covering a range of topics related to the installation and maintenance of solar photovoltaic and electrical systems in the UK.

/Solar PV Information Articles

Engineering Recommendation G98

Grid Connections for Micro-Generators including Solar PV Systems and Elecricity Storage Systems in the UK. Under 16Amps Per Phase, grid synchronised.

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In this article we show you how to power your home using a portable diesel, petrol or LPG generator. We look at changeover switches, the importance of earthing, generator loadings, how to isolate non essential loads. We ask where to locate the generator when it's in operation, how best to safely isolate the grid/mains power supply and switch to a generator supply.

Ground Faults, Isolation (ISO) Faults, RISO Low Faults and Insulation Resistance Faults with Solar PV Systems

After a number of years exposed to wind, rain, snow, ice and sometimes animals; solar panel systems can start to develop faults. The most common faults we find related to exposure are ground faults, isolation (ISO) faults, RISO low faults and insulation resistance faults. In this article we take a look at what these faults are, the possible causes and what steps are taken to identify and resolve them.

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