Electrical Power & Protection


Failsafe networking of photovoltaic systems

Technews Industry Guide: Sustainable Manufacturing 2022 Electrical Power & Protection

Photovoltaic systems have to play their part in ensuring high-level grid stability and supply reliability. Here, Ethernet-based networking ensures the failsafe transmission of diagnostics data and control commands between the various installed inverters, transformer stations, grid connection points and monitoring systems – whether via cable-based or wireless communication.

As a renewable energy, photovoltaics (PV) is making a considerable, sustainable contribution to meeting the globally increasing demand for energy. Planning, constructing and managing large PV systems, however, demands a huge amount of expertise and experience.

Zebotec, based in Konstanz, Germany, has established itself in this field over the last 15 years to become one of the world’s leading independent system integrators for controlling photovoltaic power stations. Zebotec is a part of the BayWa r.e. Group, which brought together various companies from within the field of renewable energies in 2009.

The Munich company’s field of activities includes the design, construction and marketing of PV power stations within the solar project management sector, among other things. Within these projects, Zebotec’s responsibilities include the systems for monitoring and control technology, among others. The range of services also includes the construction of efficient Ethernet networks that are used for networking system sections and for data exchange.

VLANs prevent unwanted communication

The Ethernet networks installed in the photovoltaic systems are used to transmit the diagnostics data recorded in the inverters, the weather stations, the temperature sensors mounted in the transformer stations, and the energy measuring devices. Forwarding the control data for grid feed-in, in particular, places high demands on the failsafe performance of this communication, because if the receiver does not receive the control values reliably, this may lead to the system feeding into the power grid without control, which would in turn put the grid’s stability at risk.

Certain special considerations have to be taken into account when networking the individual transformer stations in particular. A good example of this is the 45 MW ground-mounted system in Oosterwolde de Boer, the Netherlands, realised by Zebotec and the Dutch subsidiary of BayWa r.e., GroenLeven.

Firstly, there are large distances to be bridged between the stations in this system, and secondly, the Ethernet cables have been laid in cable ducts with very little clearance to the AC and DC cables in the system. Due to this proximity, electromagnetic interference (EMI) may arise when using classic twisted-pair copper cables and, in the worst case, can result in loss of data.

To prevent this, the copper cables would have to be equipped with special shielding or laid separately. Due to both the length of the cables and the possibility of EMI influences, Zebotec therefore decided to use fibreglass cables that, because of their immunity against EMI, proved to be an installation-friendly and error-tolerant solution.

Zebotec also installed managed switches from Phoenix Contact at the central grid connection point to further increase the stability of the network. The Ethernet transmission of the transformer stations connected in several lines comes together there. In this topology, each line is configured as a separate virtual network (VLAN). This prevents the various system sections from being able to inadvertently exchange data between each other. In turn, this prevents unnecessary data streams and improves communication efficiency.

Zebotec also sets up redundant network structures, especially in large systems, and usually in the form of a ring topology via RSTP (rapid spanning tree protocol) to achieve an even higher level of failsafe performance. This concept means that data transmission between all system sections is ensured, even in the event of a connection failure in one fibreglass line. Zebotec also uses Phoenix Contact’s FL Switchn 2200 Series managed switches here to ensure the necessary redundancy functionality.

Floating transformer stations connected via WLAN

Zebotec is also confronted with another characteristic that brings with it further requirements on the networking due to a new type of PV system. Alongside large free-standing systems, the company has recently started working together with BayWa r.e. on photovoltaic power stations on bodies of water that are not intended for tourism or ecological management purposes.

Transforming unused lakes into highly efficient photovoltaic systems brings with it considerable advantages. For example, they contribute to reducing CO2 emissions, generate high yields due to the water cooling effect, and prevent conflicts in terms of the previous necessity of taking up land. One example is the floating 27 MW system anchored to the lake bed of the Bomhofsplas gravel quarry close to the city of Zwolle in The Netherlands.

Because of the positioning on the lake, cabling the transformer stations and grid connection point would have been complex and expensive. Zebotec therefore decided upon wireless Ethernet networking: The WLAN clients installed in each transformer station establish connections with WLAN access points mounted in stations close to the shore. The transformer stations, which are themselves far from the shore, are coupled via repeaters to an access point to ensure consistent communication.

Here, the high-level reliability and robustness of the WLAN components used were a key factor. Zebotec therefore decided in favour of using the FL WLAN 5110 devices from Phoenix Contact. These industrial-grade devices can be configured as WLAN clients, as repeaters or as access points. This provided Zebotec, as the system integrator, with the flexibility to first construct the control cabinets for all transformer stations to be identical, and then to configure the final WLAN network topology once installed in the respective system.

Two omnidirectional antennas are installed on each transformer station for exchanging data between the FL WLAN 5110 devices. Due to the greater distances involved, Zebotec used directional wireless antennas for connecting the access points to an FL WLAN 5110 installed at the central grid connection point on land. All of the antenna cables are protected with surge protection equipment from Phoenix Contact to protect the photovoltaic system.

Networking concept to be adopted in future projects

To date, the Konstanz-based system integrator has had excellent experiences with both the managed and unmanaged switches, and the WLAN components from Phoenix Contact. “This was one of the reasons why we decided in favour of the infrastructure components, because the devices are industrial-grade and therefore robust enough to satisfy our high demands on high-level availability,” explains Werner Neff, CEO of Zebotec. Therefore, the company will also install the networking concepts described in future photovoltaic power stations.

As an aside, this also applies to the field of control technology. Zebotec has used AXC 3050 and ILC 191 Series controllers, as well as bus couplers, from Phoenix Contact’s Inline product family for processing the diagnostics and control data within its PV systems for years. As a Phoenix Contact solution partner in the field of renewable energies, Zebotec is also one of the first companies in the world to use the new, open PLCnext Technology control platform.


Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

High performance power distribution
Electrical Power & Protection
Hexagon Electrical plays an important role in enhancing efficiency and safety through the supply and support of a wide range of critical equipment for hazardous industrial and mining sectors in Africa.

Read more...
Navigating solar energy adoption
Electrical Power & Protection
Although South Africa’s enhanced solar tax rebate has ended, solar and energy storage solutions remain accessible and achievable. By taking a proactive and strategic approach, businesses can successfully lower their operational costs, mitigate power outages, and secure long-term energy independence.

Read more...
As wind energy gains momentum, lack of grid infrastructure remains a bottleneck
Electrical Power & Protection
Interest in wind energy has gained significant momentum in South Africa, opening up new opportunities for investment. However, lack of grid infrastructure could prove to be a stumbling block in unlocking this potential.

Read more...
Portable appliance tester
Vepac Electronics Electrical Power & Protection
The new appliance tester from Vepac is the ideal tool for testing the safety of electrical appliances in accordance with DGUV regulation 3 and BetrSichV. It enables the precise measurement of protective conductor or touch current using the equivalent leakage current method.

Read more...
Is sustainability enough any more?
Electrical Power & Protection
With the planet’s resources stretched to the brink and no signs of improvement, it is time we look beyond sustainability and explore regenerative thinking and design.

Read more...
A simple guide to understanding the importance of IP ratings
Electrical Power & Protection
When selecting electrical products for industrial, commercial or even domestic use, it is crucial to consider how well they can withstand environmental factors like dust and water. This is where ingress protection (IP) ratings come into play.

Read more...
A milestone in electrical safety
ABB South Africa Electrical Power & Protection
Celebrating a milestone in electrical safety, ABB proudly marks the 100-year anniversary of its revolutionary Miniature Circuit Breaker.

Read more...
The power of water
Editor's Choice Electrical Power & Protection
The Alpenglow Hy4 is the world’s first water-based hydrogen combustion engine, offering a convincing alternative to traditional battery-electric vehicles and established hydrogen fuel cell designs.

Read more...
Optimising purification for green hydrogen production
Parker Hannifin - Sales Company South Africa Editor's Choice Electrical Power & Protection
Parker Hannifin delivers advanced purification and thermal management components that enhance green hydrogen production.

Read more...
A new chapter in geothermal engineering
Editor's Choice Electrical Power & Protection
The town of Geretsried in southern Germany has become a focal point in the global shift toward renewable energy. While the world’s attention often turns to wind turbines and solar panels, a quieter but no less powerful force is at work deep beneath the surface, geothermal energy.

Read more...









While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.




© Technews Publishing (Pty) Ltd | All Rights Reserved