Voltage Transformers for Photovoltaic Systems

Voltage transformers for photovoltaic systems are designed to handle more variable operating conditions, due to the intermittent output typical of solar panels. They offer greater thermal stability, reinforced insulation, and consistent precision even in the presence of harmonics or transient overvoltages. They also comply with the requirements of the CEI-016 standard, which governs the grid connection of energy producers.

Yes, voltage transformers can be custom-designed based on system specifications. The primary and secondary voltages, accuracy class, number of windings, and terminal type can be customized. In more complex cases, separate windings for measurement and protection can be provided, as well as special configurations for residual voltage. This optimizes performance and ensures full compatibility with monitoring and protection systems.

Questi trasformatori sono destinati a installazioni indoor, in ambienti asciutti, ventilati e protetti da polveri conduttive. Tuttavia, su richiesta, possono essere forniti con resine e isolamenti rinforzati per applicazioni outdoor. Devono essere installati in posizione verticale, con spazio adeguato per la dissipazione termica e l’ispezione dei terminali. Il rispetto delle condizioni ambientali previste garantisce la stabilità del punto di misura e la durata elettrica del dispositivo.

I parametri fondamentali includono la tensione nominale primaria e secondaria, la classe di precisione, il livello di isolamento e la potenza apparente nominale. È essenziale verificare anche il fattore di tensione (tipicamente 1,2 continuo e 1,9 per 8 ore) e la frequenza operativa (50 o 60 Hz). In impianti fotovoltaici connessi in media tensione, la corretta selezione di questi valori assicura misure affidabili e protezione efficace contro sovratensioni e squilibri di fase.

Each transformer is tested according to the procedures established by IEC 60044-2 and CEI-UNEL 21007 standards. The tests include insulation verification, power frequency voltage testing, no-load loss measurement, and accuracy verification under various load conditions. Only transformers that pass all tests are certified and CE marked, guaranteeing compliance, reliability, and complete traceability of the materials used.

The CEI-016 standard defines the technical requirements for connecting power generation systems, including photovoltaic systems, to the electricity grid. Voltage transformers must ensure adequate insulation, measurement accuracy, and compatibility with grid protection equipment. It also establishes the need for compliance with complementary standards such as IEC 60044-2 and CEI-UNEL 21007, relating to construction, testing, and sizing.

The nominal insulation level represents the maximum voltage that the transformer winding can withstand without deterioration or internal discharges. Insulation up to 36 kV ensures that the transformer can be safely installed in medium-voltage switchgear, maintaining electrical integrity even in the presence of temporary overvoltages or indirect lightning strikes. This parameter is crucial for compliance with CEI and IEC regulations.

A voltage transformer (VT) is used to reduce the nominal voltage of a photovoltaic system to standardized values, compatible with measurement and protection instruments. This allows for precise monitoring of electrical parameters and the safety of the conversion and distribution system. In three-phase systems, VTs also provide the residual voltage signal necessary for monitoring asymmetries and ground fault conditions.

Photovoltaic voltage transformers use high-performance epoxy or silicone resins for insulation, combined with low-loss ferromagnetic materials for the core. These resins are self-extinguishing and resistant to UV rays and humidity, essential features for systems installed in environments with temperature fluctuations or high humidity levels. The use of tinned copper conductors also ensures long electrical and mechanical life.