High Voltage Transformers

Dry-type and oil-type transformers differ in terms of insulating materials and cooling methods. Dry-type transformers are constructed with dry insulating materials, such as resin, and are suitable for indoor and environmentally sensitive locations, while oil-filled transformers utilise mineral or ester oil to effectively dissipate heat during operation, making them ideal for high-voltage applications.

A high-voltage transformer is a static electrical device that transfers electrical energy between circuits and changes the voltage between them using electromagnetic induction. High-voltage units typically handle voltages above 1000V, stepping power up for efficient transmission over long distances or stepping it down to safe, usable levels at the point of supply. They work only on AC, not DC.

A transformer has primary and secondary windings around a shared magnetic core. Alternating current in the primary winding creates a changing magnetic flux that induces a voltage in the secondary winding. The turns ratio between the two windings sets determines whether the voltage steps up or down, and by how much. Because the effect relies on a changing magnetic field, transformers operate on AC only.

The difference is the voltage they handle. High-voltage transformers handle voltages above 1000V and are used for power transmission and substation duty across the grid, while low-voltage transformers deliver safe, usable voltages — such as 415V three-phase or 230V single-phase — that site equipment runs on. Most networks use both in sequence, stepping the voltage down stage by stage.