Cast resin insulated Instruments transformers for distribution networks and for special applications such as current transformers with rated nominal currents up to 3.000A, ring type transformers with rated primary currents up to 20.000A and voltage transformers with insulation level phase-to-earth and phase-to-phase up to 36 kV.
The available accuracy classes are from 0,5 to 0,2s for measuring purpose. Protection voltage and current transformers are available with accuracy class from 5P10 to 5P30 (current transformers) and 3P-6P (voltage transformers). Special current transformers for differential relay protection are available on request
Voltage transformers have the purpose to provide on the secondary side a voltage level proportional to the voltage of the MV circuit on which are installed. The transformer can be designed for phase-phase or phase-earth connection. They contain only one magnet core and are designed with single or multiple secondary winding. Voltage transformers must never be short-circuited on the secondary side. The earth-side terminal of the primary winding is earthed in the terminal box.
Current transformers are designed to convert the rated current which flows through the primary winding. Current transformers can be regarded as transformers working in short-circuit, with the full normal current flowing through their primary side. Devices connected on the secondary side are series-connected. Current transformers can have several secondary windings with magnetically separated cores of the same or different characteristics. If one of the secondary windings is not used, it must be short circuited.
Thanks to high quality production processes our transformers are realized to meet the highest accuracy classes foreseen by the standard. They can be used in any application in which extreme accuracy is required, such as tariff metering or testing laboratories
The high technology employed in the manufacturing process of windings gives the product a high level of reliability.
The resin and insulating materials employed in the design and construction of Tesar transformers guarantee a high level of self-extinguishing characteristics and low emission of toxic gases.
Tesar cast resin transformers are designed in such a way as to withstand the worst climatic and environmental conditions. Preventive maintenance consists of a simple visual check.