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How to Choose a Transformer: Dry Type vs. Oil Cooled Professional

3 weeks ago   Freebies   Napier   31 views

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Location: Napier

Types of transformer

Oil Immersed Transformer

As the name suggests the coils in this type of transformers are immersed in oil (mostly mineral oil) which helps in keeping the temperature of the transformer under control. This oil type transformer dissipates the through the radiators which are attached on the tank of the transformer and are referred to as ONAN type transformer. To further improve the cooling of the transformer the radiators are installed with fans which helps in bringing down the temperature and referred to as ONAF type transformer. This type of transformer can reach high voltage capacity, in some cases 1000kV.

Dry Type Transformer

In this type of transformer, air is used as the cooling medium. They are made using vacuum pressure impregnation in polyester or silicone varnish. Some of them are also made using VPI epoxy and cast resin for tougher environmental conditions. Since they are limited with regards to cooling aspect the maximum voltage is limited up to 35kV.


Switchgear is electrical distribution equipment: it accepts power from a source, routes it to a number of outputs and provides overcurrent protection and control functions. Of the types of distribution equipment described in the NFPA 70: National Electrical Code Article 408: Switchboards, Switchgear and Panelboards, switchgear is generally the most robustly constructed, the largest and the most expensive. It’s typically applied in high-reliability facilities, like hospitals or data centers, where continuity of power is critical to effective operation.

Switchgear is available in a wide range of voltage ratings, from below 1,000 volts to more than 200 kilovolts. Medium-voltage switchgear, rated above 1,000 volts, is manufactured by producers in a variety of configurations. Assemblies are available for exterior padmount installation, vault installation or installed in dedicated freestanding metal buildings, with air, gas, vacuum or oil as insulating media. This discussion will focus on interior low-voltage switchgear.

The alternative to switchgear is switchboard construction. Switchboards generally require less space and are less expensive. Both are typically constructed of a number of vertical sections. Each section is enclosed in sheet metal, with openings in front for overcurrent protection devices, monitoring equipment and control devices. A section may contain a main overcurrent protection device, metering devices, automatic control and monitoring systems, overcurrent protection devices for distribution feeders or a combination of these or other equipment specific to the installation. Overcurrent protection is typically accomplished with circuit breakers, with fused switches are less frequently.

Electric power substation

An assembly of equipment in an electric power system through which electrical energy is passed for transmission, distribution, interconnection, transformation, conversion, or switching. See Electric power systems

Specifically, substations are used for some or all of the following purposes: connection of generators, transmission or distribution lines, and loads to each other; transformation of power from one voltage level to another; interconnection of alternate sources of power; switching for alternate connections and isolation of failed or overloaded lines and equipment; controlling system voltage and power flow; reactive power compensation; suppression of overvoltage; and detection of faults, monitoring, recording of information, power measurements, and remote communications. Minor distribution or transmission equipment installation is not referred to as a substation.


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