The distribution transformer is a static electrical device which provided the last stage of voltage conversion in the electrical power delivery for end-use, by reducing the medium voltage of the distribution lines (for example, 4 kV to 35 k V) to the low voltage levels, for instance, 120V, 240V or 400V.
Distribution transformers are used on utility, industrial, commercial, and renewable energy applications. These devices function on the principle of electromagnetic induction, using the magnetic field to transfer electrical energy from the primary winding to the secondary without significant loss.
These devices are absolutely essential for every dependable power distribution. Without them, the high-tension transmission current is inedible for general load. They govern directly the grids’ stability, the system efficiency and the quality of energy for end user.
| Feature | Pole-Mounted | Pad-Mounted | Substation (Ground-Mounted) |
| Typical Rating | 10–315 kVA | 100–2500 kVA | 500–2500 kVA |
| Installation Type | Overhead line | Underground cable | Indoor/outdoor substation |
| Access for Maintenance | Bucket truck required | Ground-level access | Ground-level access |
| Best For | Rural distribution | Urban/suburban grid | Industrial & utility |
A transformer is an electrical device in a static condition that reduces high energy medium voltage distribution line voltage which usually ranges from 4 k V through to 35 k V, to low voltage suitable for use by the consumer i.e. 120V, 240V or 400V etc. This is the last stage of voltage transformation before electricity is used in the home, office or factory.
Work out your maximum demand load in kVA (total watts / pf / 1000 if single-phase, or / 1.732 if three-phase). Then allow a 20 30% headroom for growth, and choose the next standard rating from the following: 50, 100, 160, 250, 400, 630, 1000, 1600, 2000 kVA.
The former have mineral oil or ester fluid as their insulating and cooling medium. They are lower in unit cost and are the normal choice for outdoor and substation applications. The latter have insulating cast resin and no liquid. They are used when the equipment is installed in interiors within fire-sensitive environments such as hospitals, shopping malls, and tall buildings.
A well maintained oil immersed distribution transformer will usually have a life in the region of 25-35 years.The service life will relate to load factor, ambient operating temperature, oil quality & maintenance, protection from overload & lighting surges. Dry type units will have similar life span in air-conditioned indoor locations.
This varies depending on your market place. In Europe, Asia, Middle East and Africa IEC 60076 standard applies. In North America as ANSI/IEEE C57 standard will be used. Check always the grid code of your national utility or regulator before defining the final specifications.
