Surge protection for photovoltaic systems

STATE OF THE ART

Normative requirements

For the professional installation of a lightning and overvoltage protection concept for PV systems, only the pre-standard VDE V 0675-39-12 (CLC/TS 50539-12) was available to the user in addition to supplement 5 of the lightning protection standard VDE 0185-305-3 (EN 62305-3) and the information provided by the Verband der Sachversicherer e.V. in the VdS-Merkblatt 2010. Since September 2017, the new application standard IEC 61643-32 ED1 has been published on an international level, which is implemented nationally in the VDE 0675-6-32 draft. The new DIN VDE 0100-712 now also contains additional requirements for the protection of systems against overvoltages.

The new IEC 61643-32 is essentially based on the well-known VDE V 0675-39-12.
Both standards deal with selection and application principles of surge protection devices for use in photovoltaic installations. Furthermore, specifications for the selection and installation of surge protection devices on the DC and AC side are given.

The IEC 61643-32 states literally:
"The installation of SPDs on the DC and AC side of a PV system is mandatory, unless otherwise specified in a risk analysis ..."
The new IEC 61643-32 also requires the use of SPDs for data and communication lines ("When SPDs are installed to protect the PV system, it is necessary to protect all telecommunications and signal circuits that are part of the PV system ...").

The obligation to protect photovoltaic systems against overvoltages protection also results from the new DIN VDE 0100-712.
This refers first of all to Supplement 5 of the lightning protection standard VDE 0185-305-3 (EN 62305-3):
"The selection and installation of surge protection devices (SPDs) in PV systems must be carried out according to DIN EN 62305-3 Supplement 5 (VDE 0185-305-3 Supplement 5)."
This supplement 5 in turn contains the requirement:

"The need for surge protection measures on the AC side of the PV power supply system is determined according to DIN VDE 0100-443."
As is well known, this in turn makes the use of SPDs mandatory in every installation. Furthermore the DIN VDE 0100-712:
states "If transient overvoltage protection is required by DIN VDE 0100-443, section 443, such protection must also be applied on the DC side of the PV system."

Minimum requirement according to DIN VDE 0100-712 Appendix C

Further normative minimum requirements

Cross sections:

• Potential equalization conductors not carrying lightning current: At least 6 mm² copper or equivalent.
• Lightning current carrying equipotential bonding conductors: At least 16 mm² copper or equivalent.

Selection of Uc and Up:

• Uc > 1.2*Uocstc
• Up < (5*Uocstc)x0.8 or Up < Uwx0.8 (Uw: dielectric strength of the equipment)

Derivative values after:

A) DIN VDE 0100-712 and IEC 61643-32
Type 1 arrester: min. Iimp: 12.5 kA/pole (10/350)
Deviating Iimp for type 1 arresters can be depending on risk

• for DC arresters according to IEC 61643-32 Annex A,
• for AC arresters according to lightning protection class and lightning current distribution according to EN 61643-12 result in
  

Type 2 arresters (AC and DC): min. 5 kA/pole (8/20)

B) VDE 0185-305-3 Supplement 5:2014:
Type 1 arrester:

• for DC arresters according to paragraph 5.3.2, table 2 and 3:
  2.5 kA/pole (10/350) to 25 kA/pole (10/350) depending on earthing concept, plant design or plant type and arrester technology
  

• for AC arresters near:
  Inverter: min. 12.5 kA/pole (10/350).
  Feed-in point or lightning protection zone transition according to lightning protection class and lightning current distribution according to EN 61643-12 if necessary values up to 25 kA/pole (10/350).
  

Type 2 arresters (AC and DC): min. 5 kA/pole (8/20)

Cable lengths

If cable lengths >10m are reached on both the AC and DC sides, 2 surge protection devices are required.

Protection on the AC side

Installation of SPDs on the AC side with less distance between the feed point of the installation and the PV inverter (E < 10m) E: Distance between the feed point of the installation and inverter
L1 + L2 + L3: connection cable
D: SPD disconnection device (if not integrated in the SPD)

Installation of SPDs on the AC side with greater distance between the feed point of the installation and PV inverter (E > 10m) E: Distance between the feed point of the installation and inverter
L1 + L2 + L3: connection cable
D: SPD disconnection device (if not integrated in the SPD)

Protection on the DC side

Installation of SPDs on the DC side with less distance between PV generator and PV inverter (E < 10m) E: Distance between the feed point of the installation and inverter
L1 + L2 + L3: connection cable
D: SPD disconnection device (if not integrated in the SPD)

Installation of SPDs on the DC side with greater distance between PV generator and PV inverter (E < 10m) E: Distance between the feed point of the installation and inverter
L1 + L2 + L3: connection cable
D: SPD disconnection device (if not integrated in the SPD)

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SELECTION AND PLACEMENT OF SPDs

Homes

Complete protection for all areas

In practice, a distinction is made between houses with or without external lightning protection. Is there no external lightning lightning protection is required, it can be assumed that no increased There is a danger of direct lightning strike. The surge protection on the DC side of the photovoltaic system must therefore only be implemented against indirectly coupled overvoltages. In this case, an SPD type 2 (DS50VGPVS) must be provided on both the PV generator and the inverter. If the cable lengths between generator and inverter are negligible (<10m), then one of the two surge protection devices can be dispensed with. The string lines of the generator cabling may form a large induction loop in case of inductively coupling overvoltage events such as near strikes of lightning in a radius of about 2 km. In order to achieve an increased safety level beyond the normative requirements, CITEL recommends the use of a combined lightning arrester type 1+2 (DS50VGPVS/12KT1) even in buildings without external lightning protection. On the AC side, type 1+2+3 combination arresters (ZPAC or DAC1-13VGS) in the meter cabinet offer optimum protection. This protects the AC input of the inverter and the electrical installation of the building equally. For houses with external lightning protection, which is usually not mandatory, further regulations apply, about which we will be happy to provide you with detailed information if required.

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TRADE & INDUSTRY

Complete protection concep

Since commercial and industrial buildings are usually properties with high material assets and public institutions are buildings with sensitive information and data material, complete protection is particularly important here. A combination arrester T1+2+3, such as the DS250VG or the DUT250VG, guarantees the best possible protection of the AC side by a low protection level < 1500V, combined with a total lightning current discharge capacity of 100 kA (25kA/pole).

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SOLAR FARMS

Efficient protection

PV power plants today are equipped with more and more technology. In addition to monitoring systems for pure performance monitoring, this includes, above all, more and more sensor technology for recording and evaluating ambient conditions such as ambient temperature, module temperature, irradiation and wind speed. Also the currents of the individual strings are often precisely recorded. In addition, tracking systems are sometimes also used for automatic tracking of the modules according to the position of the sun. The protection of all these systems is particularly important here. Therefore, these data and control lines should be consistently included in the design of the protection concept. Open space systems have a larger spatial extension and thus a higher lightning hazard during thunderstorms than compact systems on the roof. EN 61643-32 takes this fact into account by requiring the use of type 1 surge arresters on the DC side of ground-mounted systems.

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Conclusion DC side:

If a DC type 1 arrester is required, an Iimp= 12.5kA/pole (10/350) is sufficient for almost all systems, regardless of the various standards. The DS60VG series thus offers the user a product that conforms to the standards, which in addition does not require complicated calculations in the planning stage and can be used in almost any system. If 5 smaller values are determined by a detailed calculation or by using the supplementary sheet, the DS50VGPVS-12KT1 series as a type 1+2 arrester with an Iimp= 6.25kA/pole (10/350) can be offered as a cost and space-optimised variant. The DS50VGPVS-G/51 series is used here as a DC type 2 arrester.

Conclusion AC side:

On the AC side, the DS250VG series with 25kA/pole for highest loads and the DAC1-13VG or ZPAC series with 12.5kA/pole for average loads are available as type 1+2+3 arresters. The DAC50VG series arresters round off the AC side as type 2+3.

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PRODUCT OVERVIEW

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DOWNLOADS

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