Solar power is indispensable. Almost 15 % of all the electricity generated in Germany comes from solar installations. In 2024, the figure was around 60 TWh.
A large proportion of solar power is generated in large solar power plants. The megawatt systems are mainly found in rural areas. There are hundreds in Germany alone. The largest have peak outputs of almost 190 MWp.
The number of solar parks is set to increase further. The renewable energy company BayWa r.e. also wants to build more solar power plants and upgrade existing plants to the state of the art. Proven technology from Bender is also used.
Solar power plants should generate as much electricity as possible. Downtimes should be kept to a minimum. In addition, operational safety must be guaranteed at all times.
That's not so easy. This is because solar power plants are exposed to all kinds of environmental influences 24/7/365. Sun, rain, heat, cold, dew or ice affect the systems over the course of time. In addition, there are natural ageing processes of the materials used (especially the insulation of the cables used, but also the backsheets of the PV modules used), as well as animal damage. Failures due to damage to the cabling or the solar modules are therefore only a matter of time. Identifying such damage is a major challenge.
But that's not all! As soon as light falls on the solar modules, they generate electricity. Photovoltaic systems are therefore to be regarded as permanently energised. As photovoltaic systems cannot be switched off on the DC side, there is a risk to people and material in the event of an electrical fault.
A solution is therefore needed that guarantees high availability and is secure at the same time despite these framework conditions.
More and more inverter manufacturers are now demanding that they must be operated in unearthed grids (IT system). There are various reasons for this. However, high availability and operational reliability also play an important role here.
In an earthed system (e.g. TN system), an insulation fault inevitably leads to a high residual current. However, as solar modules cannot be switched off on the DC side because they produce electricity as soon as light falls on the modules, there is an acute danger to people (electric shock) and systems (e.g. electrical fires).
Not so with an unearthed system! Since all active parts are insulated from earth, only a small residual current flows in the event of an earth fault (L1, L2 or L3 against PE), which is largely dependent on the leakage capacitance. This increases operational safety and reduces the risk of fire. An unearthed network can therefore continue to be operated in the event of an initial fault.
Unearthed networks therefore have three decisive advantages over earthed networks:
An insulation monitoring device must be used to detect faults in unearthed systems, e.g. due to moisture or animal damage.
The company BayWa r.e., a leading global developer, independent power producer, service provider and PV wholesaler, operates 94 renewable energy plants with an installed capacity of 872 MW in Germany alone.
BayWa r.e. not only builds new solar parks, but also offers technical and commercial management for photovoltaic systems as well as the marketing of the solar power produced.
BayWa r.e. had previously operated solar power plants with an earthed system (TN system). Due to the changed requirements on the part of the inverter manufacturers, existing and new solar power plants should be converted to an unearthed grid (IT system). At the same time, the operational safety (failure safety, personal and system protection) of the solar power plants should be increased overall.
BayWa r.e. at a glance:
Number of renewable energy plants in Germany: 94
Installed power: 872 MW
In the search for a suitable solution for the prescribed insulation monitoring, BayWa r.e. came across Bender, the inventor of insulation monitoring. Initially, BayWa r.e. was provided with an ISOMETER® isoPV1685DP on loan. This insulation monitoring device is designed for the special requirements of large-scale solar installations, such as the required voltage of AC 800 V / DC 1500 V, ambient temperatures of up to +70° C and the dynamic conditions in PV applications. The device also has a display which makes commissioning on site much easier.
During a test, the BayWa r.e. colleagues were very satisfied. Some specific technical queries were clarified and answered during on-site appointments. In addition, Bender provided on-site support for initial commissioning together with the technical crew, training for the project managers and instruction for the technical staff of the switchgear manufacturers.
This overall package of a suitable solution and comprehensive support convinced those responsible at BayWa r.e. All large-scale PV systems (new build and repowering projects) are now equipped with the ISOMETER® isoPV1685DP. The technical advantages, in particular the ability to control the dynamic insulation conditions and the leakage capacitances of up to 4000 µF that occur, ensure a stable and fault-free start-up phase for the systems and thus also higher yields for the solar parks.
Kai Saegebarth, Lead Concepts and Solutions Engineering Team at BayWa r.e.: "We are very satisfied and felt that we were in good hands throughout the entire process of finding a solution. The professional support was exemplary. Both: Reliability and the support from the Bender experts convinced us."
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