In a context where solar energy is one of the main renewable sources for the energy transition, efficiency and safety in photovoltaic systems are top priorities. One of the technical tools that plays a crucial role in this respect is the isolation transformer. Its integration into a photovoltaic system is not only advisable, but strategic for maximising energy quality, protecting sensitive components and ensuring grid stability.
What is an Isolation Transformer?
An isolation transformer is a device which, inserted between the photovoltaic system and the electricity grid, creates an indirect electrical connection between two circuits, guaranteeing galvanic isolation. Thanks to this physical separation, it acts as a ‘filter’ between the system and the grid, reducing the risk of disturbances and interference. But the advantages of this technology go far beyond this.
Advantages of an Isolation transformer in Photovoltaic Systems
- Optimised Efficiency: The photovoltaic system is designed to operate continuously, albeit at varying loads, while constantly maintaining the nominal voltage. Consequently, the isolation transformer must meet high efficiency criteria to minimise losses in the core and windings. With very low losses, high efficiency rates can be achieved, an indispensable requirement in any application involving renewable sources.
- Stability and advanced Safety: Typically, the type of vector connection chosen for this application is the YNyn0 type, which allows the neutral of the primary winding to be connected to earth. This results in a reduction of voltage asymmetries due to load imbalances. The safety aspect is also enhanced: in the event of faults, the earthing of the neutral creates a safe path for fault currents, minimising risk and damage. In addition, the availability of the secondary neutral increases the flexibility of the system, allowing an optimal configuration for each type of system.
- Elimination of unwanted direct current: One of the main problems with inverters is the introduction of direct current to the grid. In large power systems, this current can lead to voltage imbalances on the grid side (saturating the cores of the power transformers), compromising the quality of the energy fed in and, consequently, the overall efficiency of the system. The isolating transformer guarantees the cut-off of the DC component, ensuring voltage symmetry.
- Advanced protection against interference and overvoltage: A further advantage of the isolation transformer is the presence of a double-layer reinforced shield, which acts as a filter for interference and high-frequency harmonics injected from the inverter into the grid. This shielding prevents the transfer of interference between the PV system and the grid, helping to maintain power quality. Furthermore, in the event of lightning strikes, the shield attenuates voltage pulses, protecting the system from sudden surges that could compromise its integrity.
Isolation transformer in Photovoltaic Systems: a strategic choice
The integration of an isolation transformer in a photovoltaic system is a strategic choice for those wishing to maximise efficiency and ensure safety of the system. Through galvanic isolation, fault current control, elimination of DC components and overvoltage protection, the isolation transformer not only protects the investment, but also improves energy quality, making the photovoltaic system an even more sustainable and effective contribution to the energy landscape.
In an ever-changing sector such as renewables, a high-quality isolation transformer is not only a technical advantage, but also an added value for the overall efficiency of the system, representing a must-have solution for all photovoltaic professionals and investors.
