Amendment 2 introduced a number of proposed changes to surge protection, with major changes to Section 712 discussing regulations related to solar photovoltaic (PV) power supply systems. Kirsty Johnson, Technical Sales Director at Surge Protection Devices, looks at how these devices work. New Regulation No. 712.443.101 states that when protection against transient overvoltage is required under Section 443, this protection must also be applied to the DC side of the PV installation. So, for example, if the solar installation is on the roof of an industrial building where the regulations in Section 443 require the installation of the SPD, then the SPD will now also need to be installed on the DC side of the installation to protect both the PV panels and the inverter. When the PV system is installed within the protected size of the LPS system, the photovoltaic system must be separated from all parts of the LPS in accordance with BSEN 62305-3, which describes the calculation of the correct separation distance. If the separation distance is not met, a Type 1 device will be required to protect the installation from lightning effects to BSEN 62305. All SPDs installed on the direct current side of PV installation shall comply with BSEN 61643-31. When the inverter includes a SPD, it is only considered to meet the requirements of the SPD if the manufacturer determines its use for the DC side for PV mounting, otherwise it will need an external SPD. Variants included in the inverter are not considered SPD. Generally speaking, it will be a Type 2 SPD, unless the building has an external lightning protection system. If the LPS does not have the correct separation distance according to BSEN 62305-3, a Type 1 device will be required. When selecting the SPD for the PV system, care must be taken to ensure that the following instructions are met: The highest SPD should not exceed Uw of the equipment to be protected (if not Not have this information, the table will provide 712.1 in BS7671 average ratings) Ucpv must be greater than or equal to Uoc max of PV matrix Type 2 SPDs should have a minimum of 5kA of type 1 SPD minimum Iimp should have 12.5kA shape 1 Figure 2 Where the inverter is located more than 10 meters from the origin of the installation, the SPD must be installed near the inverter, plus the SPD at the origin of the installation. The type of device depends on the installation. The illustration in Figure 2 will help define what is needed. SPDs should be placed on the DC side as close to the inverter as possible, and to provide protection, additional SPDs further away from the inverter may be required. Figure 3 was recreated from BS IEC 61643-32. Details of locations required for SPD devices on PV installation. AC side: SPD in Site 3 is the main input, which is required under BS 7671, Section 443 or BSEN 62305, if LPS system at present. If the SPD is at site 3 more than 10 meters away from the PV inverter, then an additional SPD should be installed at site 2. The type of this device can be determined using Figure 2. DC side: If the SPD is at site 3, then DC SPD is required on site 1. The type can be determined using Fig. 1. If the PV assembly is located more than 10 meters from the SPD at Site 1, then an additional SPD can be installed at Site 4 to provide local protection for the PV array. Obviously, at the time of writing, we are working on the “suggested” changes and there is a possibility that some elements may have changed a little by posting. We are currently expecting to publish Modification 2 in March 2022, which we all know will be here before we know it! Meanwhile, if you are interested in free CPD training on all things related to surge protection, please visit our website and register directly with the Training Academy. Get more details on free CPD training for Surge Protection Devices by clicking here
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