Transformers are rated for power output in kVA or MVA based on continuous operation under specified temperature rise and cooling conditions. Nameplates show rated voltages, currents and frequency, from which apparent power is computed. For example, a three phase transformer with rated line voltage V and current I has rating S = ?3 × V × I. The rating assumes particular cooling class and ambient temperature. Some transformers also have overload or dual ratings for different cooling stages, such as ONAN and ONAF, with higher kVA when forced cooling is active.

Step-up transformers reduce current for a given power, lowering resistive losses and enabling economical long-distance transmission.

Siemens units are found in EHV substations, renewables interconnections, industrial substations, and urban distribution networks worldwide.

Same physical principle: magnetic coupling and turns ratio determine voltage and current relationships.

Power transformers can present hazards due to high voltage, high current, elevated temperature and stored energy. Risks include electric shock, arc flash, thermal burns and oil ignition in oil-filled units. Modern installations mitigate these risks through grounded enclosures, fencing, clearance zones, fire suppression, interlocks and warning signage. Condition monitoring and routine testing further reduce failure probability. With proper PPE, lock-out/tag-out procedures and safety standards, the residual risk for trained personnel remains low.

Output apparent power S_{out} = V_2 I_2, with real power P = S cdot text{pf}.

It operates on electromagnetic induction: alternating flux in a laminated core induces voltage in secondary windings proportional to turns ratio.

It enables voltage transformation between generation, transmission, and distribution segments, supporting efficient long-distance power flow and safe end-user delivery.

Infrared scans, ultrasonic testing, oil sampling, and bushing checks reveal PD activity and moisture-related insulation decay. Utilities may perform vacuum drying or oil replacement.