What are measuring transformers for?

Measuring transformers are used in REA circuits to analyze the magnitude of current and voltage. This is necessary in order for the relay protection to be able to operate in time according to the settings set by the engineers when setting up the electrical equipment. As a rule, measuring transformers of current and voltage are used in RZA circuits. Consider each of the species separately.

Voltage transformers are used to orientate the protection, it is a kind of support against which the angles of phase displacement are counted, and ground-fault protection is organized with the help of windings connected by an open triangle circuit.

Measuring voltage transformers are made with several cores: one is connected according to the "star" scheme, the second one - according to the "open triangle" scheme. Today, manufacturing plants produce transformers with a third core, which is used for accounting.

Three single-phase voltage transformers are installed for RU-35-110 kV. For each connection group, separate machines are mounted. For RU-6-10 kV, three-phase VT in one housing is most often used.

Measuring current transformers are used in all RMs and are installed per phase. These transformers are made of a monolithic bus, which is the primary. Secondary windings are fixed on the bus, they can be several, and each winding (further core) is designed for a certain class of accuracy and specific power.

The cores are output for protection, accounting and measurement circuits. It is important that there is never any decayed cores left on the current transformers, otherwise the winding will burn, and the maintenance staff is exposed to the risk of being hit by an electric shock.

During installation, the current measurement transformers must be installed in accordance with the input-output voltage scheme (L1 - input, L2 - output). This determines the direction of the current vectors of each phase. According to the physical meaning, between the current vectors whose windings are connected according to the "Star" scheme, there must be 120 degrees. If, for some reason, the vectors are arranged differently, you must change the connection of the TT cores, swapping the beginning with the end.

Current transformers are used for protection against short circuits and for the organization of differential protection. Measuring current transformers are an important attribute of modern electrification, it is a certain sensor by means of which the magnitude of the current and its direction are determined.

In electrical installations, a zero-sequence transformer is used. This element is relevant for RU-0,4-6-10 kV, since the task of the transformer (in the home of a donut) protects the high voltage circuit from ground fault. His primary - this is the feeder, which is passed through a bagel. From the secondary, a quantity is measured that varies according to the change in the magnetic field of the feeder.

Thus, transformers for measuring current and voltage are the basis of protection. Thanks to them, modern microprocessors can independently calculate the power, the resistance of the circuit, the angles between current and voltage. The results obtained do not need to be checked, since modern equipment is performed using the latest technologies.

Today, quite popular devices that are a comprehensive solution and include a switch, a disconnector, as well as built-in TT and VT - it's convenient and quite profitable.