By purpose
Measuring voltage transformers (or measuring windings of voltage transformers) provide grid voltage information to measuring and metering devices within the normal voltage range.
Protective voltage transformer (or protective winding of voltage transformer). Provides grid fault voltage information to devices such as relay protection in the event of grid faults.
According to the insulating medium
Dry voltage transformer. Insulating varnish is impregnated with ordinary insulating materials and used in low voltage grades below.
Cast insulated voltage transformers. It is cast from epoxy resin or other resin mixed materials and is used in the following voltage levels.
Oil immersed voltage transformer. Insulation paper and insulating oil are used as insulation. It is the most common structure type in China and is often used for the following voltage levels.
Gas insulated voltage transformer. Gas is used as the main insulation and is used at higher voltage levels.
The low-voltage transformers usually used for measurement are dry, and high-voltage or ultra-high-pressure sealed gas-insulated (such as sulfur hexafluoride) transformers are also dry. The cast type is suitable for voltage transformers of 35kV and below, and the products of 35kV or above are oil immersed.
By number of phases
Most of the products are single-phase. Because the voltage transformer has small capacity and the body size is small, the internal and external insulation requirements between the three-phase high-voltage bushings are difficult to meet, so only 3-15kV products sometimes adopt a three-phase structure.
According to the principle of voltage conversion
Electromagnetic voltage transformer. According to the principle of electromagnetic induction, the voltage is changed. The principle is completely similar to the basic structure and the transformer. Most of the voltage levels in China are used.
Capacitive voltage transformers. It consists of capacitor divider, compensation reactor, intermediate transformer, damper and carrier device protection gap. It is used in neutral point grounding system for voltage measurement, power measurement, relay protection and carrier communication.
Photoelectric voltage transformer. The voltage conversion is realized by the principle of photoelectric conversion, and is still under development.
According to the conditions of use
Indoor type voltage transformer. Installed in indoor power distribution units, generally used in the following voltage levels.
Outdoor voltage transformer. Installed in outdoor power distribution units, it is used in and above voltage levels.
According to the primary winding to ground operation status
A voltage transformer with a primary winding grounded. The end of the primary winding of the single-phase voltage transformer or the neutral point of the primary winding of the three-phase voltage transformer is directly grounded.
A voltage transformer in which the primary winding is not grounded. The single-phase voltage transformer primary winding is insulated from the ground to the ground; the parts of the primary winding of the three-phase voltage transformer, including the terminal, are insulated from the ground, and the insulation level is consistent with the rated insulation level.
According to the magnetic circuit structure
Single-stage voltage transformer. Primary winding and secondary winding (multiple secondary windings can be wound on one core as required, and the iron core is ground potential. The voltage level in China and below is single-stage.
Cascade voltage transformers. The primary winding is divided into several units of the same number of turns connected between the phase and the ground. Each unit has its own independent iron core, has multiple iron cores, and the iron core has a high voltage and a secondary winding (as needed It is assumed that a plurality of secondary windings are at the last unit connected to the ground. This type of structure is currently used in voltage levels in China.
The combined transformer is composed of a voltage transformer and a current transformer and is integrated into a transformer. It is called a combined transformer. The transformers produced with the combined electrical equipment are also called combined transformers.
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