What is the difference between electronic transformers and ordinary transformers What are the main u

Electronic transformers have no core, and the output may be digital, analog, or a combination of both!

With the rapid development of optoelectronic technology, a new type of coreless transformer with simple structure, good linearity, high performance ratio, wide output range and digital output - electronic transformer came into being.

There are many types of electronic transformers, and based on different principles, there is no clear and strict definition, but they generally have the following characteristics:

Small size and light weight.

The measuring loop is electrically isolated from the measured high voltage by optical fiber, and the insulation is reliable.

There is no core, no magnetic saturation and no ferromagnetic resonance problems.

The transient response range is large, the speed is fast, the frequency response is wide, and the measurement accuracy is high.

Electromagnetic induction current transformer due to the existence of magnetic saturation problem, it is difficult to achieve a wide range of measurement, a channel can not meet the needs of measurement and protection at the same time, electronic transformer has a wide dynamic range, a measurement channel rated current of tens to thousands of amperes, overcurrent range up to tens of thousands of amperes. It can not only meet the needs of metering and protection at the same time, but also eliminate the complex structure of multiple measurement channels of traditional current transformers.

Excellent immunity to electromagnetic interference.

The secondary circuit of the electromagnetic induction current transformer can not be opened, and there is a danger of producing high voltage due to open circuit on the low-voltage side, and the primary and secondary isolation of the electronic transformer is completely isolated, and there is no danger of high voltage due to open circuit on the low-voltage side, and because there is no magnetic coupling, the impact of electromagnetic interference on the performance of the transformer is eliminated.

Easy to move digital.

Electronic transformers generally output in digital quantities, which fully adapt to the trend of digitalization, microcomputerization and automation development of power metering and protection.

Electronic transformer usually directly output digital quantity, wide frequency range, wide dynamic test range, with phase compensation and synchronous sampling interface is the core technology of electronic transformer, but also its main feature, has attracted the full attention of the power industry and began to be widely used, at present, there are more than 40 digital substations using electronic transformers in successful operation, digital, intelligent, standardized, systematic and networked has become the inevitable trend of the development of modern electric energy metering devices.

On the basis of years of frequency conversion test and research, the National University of Defense Technology and Hunan Yinhe Electric have taken the lead in developing electronic transformers suitable for motor low frequency, power frequency, medium frequency, frequency conversion, sine wave and non-sine wave testing-anyway broadband power sensor, which is widely used in well-known domestic motor enterprises and measurement and testing institutions.

The electronic transformer is completely isolated from high and low voltage, simple insulation, small size, light weight, wide dynamic range of TA, no magnetic saturation, can be counted to open circuit, does not contain iron core, eliminates the problems of magnetic saturation and ferromagnetic resonance, TV has no resonance phenomenon, and outputs digital quantity, there is no potential pollution and flammable, explosive and other dangers due to oil filling.

Current measurements are usually done with Rogowski coils. Rogowski coils are used in conjunction with integrators when they are used to measure signals of different frequencies or signals with a large harmonic content.

Because the electronic transformer does not contain an iron core, it will not be magnetically saturated, and the short-term overload capacity is very strong. Passive Qi Bimin electronic transformer generally does not contain an integrator, can only be used for fixed frequency sine wave current measurement, electronic transformer voltage measurement usually uses a capacitance voltage divider.

According to whether the high-voltage side needs to supply energy, it is divided into passive electronic transformer and active electronic transformer. Passive ECT mainly uses the Faraday magneto-optical induction principle, which can be divided into all-optical fiber type and magneto-optical glass type. Active ECT mainly uses the principle of electromagnetic induction, which can be divided into two forms: Rogowski wire high-branch coil type and "Rogowski coil + low-power coil" combination.

Passive EVT mainly applies two principles: the Bubblers effect and the inverse piezoelectric effect.

Summary. The working principle of the instrument transformer is the principle of electromagnetic induction "electricity generates magnetism, magnetism generates electricity", that is, the instrument transformer is a device that converts voltage or current proportionally. Its function is mainly to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 10A, both refer to rated values) in proportion, so as to realize the standardization and miniaturization of measuring instruments, protection equipment and automatic control equipment.

At the same time, the transformer can also be used to isolate the high-voltage system to ensure the safety of people and equipment. A device that converts voltage or current proportionally.

What principle does the transformer work on?

The working principle of the instrument transformer is the principle of electromagnetic induction "electricity generates magnetism, magnetism generates electricity", that is, the instrument transformer is a device that converts voltage or current proportionally. Its function is mainly to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 10A, both refer to rated values) in proportion, so as to realize the standardization and miniaturization of measuring instruments, protection equipment and automatic control equipment. At the same time, the transformer can also be used to isolate the high-voltage system to ensure the safety of people and equipment.

A device that converts voltage or current proportionally.

As an important part of the digital substation, the stability and reliability of the electronic transformer are the guarantee of the safe and stable operation of the power system. Compared with the traditional transformer, the electronic transformer has the advantages of large dynamic range, good transient performance, digital output, etc., and adapts to the development direction of the smart grid, so it has developed rapidly in recent years. Transformer is also known as instrument transformer, which is a general term for current transformer and voltage transformer.

Its function is mainly to convert high voltage or high current into standard low voltage (100V) or standard low current (5A or 1A, both refer to rated values) in proportion, so as to realize the standardization and miniaturization of measuring instruments, protection equipment and automatic control equipment. At the same time, the transformer can also be used to isolate the high-voltage system to ensure the safety of people and equipment.

The above is the working principle of the transformer for your reference<>

The function of the current transformer (CT) is to convert the primary current with a large value into a secondary current with a small value through a certain transformation ratio, which can be used for protection, measurement and other purposes. For example, the current transformer with a conversion ratio of 400 5 can convert the actual current of 400A into a current of 5A.

The purpose of the voltage transformer is to supply power to the measuring instrument and relay protection device, to measure the voltage, power and electrical energy of the line, or to protect the valuable equipment, motors and transformers in the line when the road fails, so the capacity of the voltage transformer is very small, generally only a few volt ampere, dozens of volt ampere, and the maximum is not more than one thousand volt ampere.

Compared with electromagnetic current transformers, electronic transformers have a series of advantages as follows:

Excellent insulation performance and low cost. The insulation structure is simple, and with the increase of voltage level, its cost advantage becomes more and more obvious.

In electronic transformers without iron cores, magnetic saturation is eliminated. ferromagnetic resonance and other issues.

There is only an optical fiber connection between the high-voltage side and the low-voltage side of the electronic transformer, and the anti-electromagnetic interference performance is good.

The output of the low-voltage side of the electronic transformer is a weak current signal, and there is no danger that the traditional transformer will produce on the low-voltage side, such as the danger that the electromagnetic current transformer will produce high voltage when the open circuit on the low-voltage side will occur.

Large dynamic range and high measurement accuracy. Due to the problem of magnetic saturation, it is difficult to achieve large-scale measurement of electromagnetic induction current transformer, and it meets the needs of high-precision measurement and relay protection. Electronic current transformers have a wide dynamic range, with rated currents ranging from hundreds of amperes to thousands of amperes, and overcurrent ranges of tens of thousands of amperes.

Wide frequency response range. Electronic current transformers have been proven to measure harmonics on high-voltage power lines, as well as transient currents, high-frequency currents, and DC currents.

There is no flammable, explosive and other dangers caused by oil filling. Electronic transformers generally do not use oil insulation to solve the insulation problem, avoiding flammable, explosive and other dangers.

Small size and light weight. The weight of the electronic transformer sensor head itself is generally relatively small. According to the 345kV optical current transformer (OCT) announced by the former Westinghouse Corporation of the United States, its height is 109kg

The oil-filled electromagnetic current transformer of the same voltage level is 61m, weighing 7718kg, which brings great convenience to transportation and installation.

It can be connected with the computer to achieve multi-functional and intelligent requirements, and adapts to the trend of large-capacity, high-voltage, miniaturization and compactness of modern power grid, digitalization, microcomputer and automation of metering and transmission and distribution systems.

The electronic sensor outputs an analog quantity. But it can be converted into a digital quantity. Zhihao Electric DOM-200 digital output module is to convert the small signal of the electronic sensor (PT CT) (e.g

Converted to the Manchester encoding format and compliant with the FT3 protocol in accordance with IEC 60870-5-1, and output to the feeder terminal FTU in accordance with the EIA RS-485 differential interface specification, the conversion module is built into the switch for use with electronic sensors. It solves the problems that the small signal transmission of traditional electronic sensors is easy to be interfered with and affects the stability and accuracy. Digital FTU, digital DTU later uses digital sensors.

1. The principle of current transformer.

1) Role. The large current of each circuit of the primary system is changed to a small current of 5A or 1A or below on the secondary side, so as to facilitate the miniaturization and standardization of measuring instruments and relays; The primary system and the secondary system are electrically isolated, and the secondary side of the transformer must be reliably grounded to ensure the safety of the secondary equipment and operating personnel; The secondary system (measuring and protection device) is separated from the primary system and becomes a stand-alone system.

2) Working status.

A current transformer is a special type of transformer, which operates in a near-short-circuit state because the load impedance value is very small when it is working normally, so it becomes a converter.

3) Structure. A current transformer is similar to a single-phase transformer and consists of:

The primary and secondary windings are composed of iron cores, but the number of turns n1 of the primary winding is very small, generally only one turn or several turns, and it is strung in the primary main circuit, while the number of turns n2 of the secondary winding is more.

4) Electrical principle.

5) Note: It is strictly forbidden to open the secondary circuit of the current transformer in operation; Pay attention to the polarity when reliably grounding and wiring one end of the secondary side.

6) Wiring method.

7) The accuracy level of the current transformer: The accuracy level of the current transformer is the percentage value of its maximum allowable current error. The accuracy level can be divided into protection level.

2. Selection of current transformer.

structure type selection; selection of rated voltage and rated current; Selection of current transformer accuracy level and rated capacity; Thermal and dynamic stability calibration.