RU196111U1 - Device for assessing the mechanical state of power transformer windings - Google Patents

Abstract

The utility model relates to the field of defectography and allows to detect defects in transformer windings during its manufacture and damage to transformer windings that occur during its operation during short circuits and during transformer electrodynamic resistance testing during short circuit. Device for assessing the mechanical state of power transformer windings allows real-time measurements and calculation of the ratio of output voltage levels to input n voltage of the power transformer and build the amplitude-frequency characteristic (AFC), through which it is concluded that there is a defect in the windings of the power transformer. The positive effect of the device is to increase the reliability of the power transformers due to the proposed diagnostic device and more accurately determine the presence of defects in its windings, and also determining the location of the damage.

Description

The utility model relates to the field of defectography and allows to detect defects in the manufacture and damage of transformer windings that occur during its operation with short circuits (SC) close to the transformer and when transformers are tested for electrodynamic resistance during short circuit. There are various methods of defectography and among all the methods currently used most often is the method of measuring short circuit resistance, by measuring which we can conclude that there are defects in the winding of the power transformer.

A device for measuring the inductance of a short circuit of a winding of a power transformer for defectography of the state of the windings (patent RU 2184999 from 04/20/2001), including a constant voltage source connected to the transformer winding, current-to-voltage converter, analog-to-digital converter, controller.

The disadvantage of this device is that the parameters of the short circuits (the number of short-circuited turns) have a large spread, which requires measuring the inductance with sufficiently high accuracy.

A device for detecting coil faults of transformer windings (patent RU 172494 U1), which allows to detect coil faults in the transformer windings in a wide range of damaged (closed) turns, due to the possibility of measuring transients in a wide range of times and to tune from the magnetization currents of the transformer by measuring the transient in the damage itself, namely in the short-circuited turns of the transformer winding.

The disadvantage of this device is that with this device it is impossible to determine other defects in the windings of power transformers, except for a short circuit, for example, twisting, unwinding, unpressing, axial and radial deformations, lodging of a winding wire.

The objective of the utility model is to develop a device for assessing the mechanical state of power transformer windings, in which the disadvantages of the above devices are eliminated.

The technical result of the proposed utility model is to improve the reliable operation of power transformers by more accurately determining the presence of defects in its windings.

The technical result is achieved by the fact that the device for assessing the mechanical state of the transformer windings (Fig. 1, pos. 1) under the control of a control device (Fig. 1, pos. 2), consisting of a controller (Fig. 1, pos. 3), a variable voltage source ( Fig. 1 pos. 4), controlled relay (Fig. 1 pos. 5), analog-to-digital converters in the amount of 2 pcs. (Fig. 1, pos. 6 and Fig. 1, pos. 7), measures the amplitude-frequency characteristic of capacitively inductive coupling between the windings of a power transformer (pos. 8)

The essence of the measurement shown in (Fig 2). The output voltage is set by the controller at a level of not more than 10 V and the frequency of the output signal in the range from 20 Hz to 2.5 MHz changes with a certain interval. Through a controlled relay, the voltage is supplied to the output of the device and then, using a coaxial cable, is supplied to one of the inputs of the power transformer. The braid of the coaxial cable from the transformer terminal is connected to the tank of the grounded power transformer. A coaxial cable is connected to the input of Meter 1, which goes to the same output of the power transformer, to which the generator output is connected, and using the ADC 1, the voltage value at the output of the power transformer is transferred to the controller. A coaxial cable connected to the other terminal of the transformer is connected to the input of Meter 2, and the voltage from the other terminal of the transformer is transmitted to the controller using ADC 2.

At each frequency step, the ratio of the output voltage level (Meter 2) to the input voltage level (Meter 1) is calculated by the formula

On the screen of the control device in the program, a characteristic is automatically built where the frequency on the abscissa is plotted on a logarithmic scale, and on the ordinate axis is the frequency response obtained at the corresponding frequency.

Comparison of the characteristics is carried out by calculating the correlation coefficient (CC) in three frequency ranges, according to which it is concluded that the winding of the power transformer is present and damaged.

,

,

и

- средние значения; x и y - наборы данных характеристик для первого и второго измерения АЧХ соответственно.where x _i and y _i - i are the values of the data sets x and y (in dB), and

and

- average values; x and y are the data sets of characteristics for the first and second measurements of the frequency response, respectively.

Changes in the characteristics in a certain frequency range correspond to specific changes in the power transformer:

up to 2 kHz - a defect in the magnetic circuit;

20-400 kHz - defect in the winding (winding, twisting / untwisting, lodging of the winding wire, radial or axial deformation);

400 kHz - 1.2 MHz - poor grounding or connection of measuring cables to the transformer inputs.

Claims (1)

A device for assessing the mechanical state of power transformer windings, consisting of a voltage source, a controlled relay, analog-to-digital converters that transmit the voltage levels of the transformer windings to a controller associated with a control device and a voltage source, characterized in that the voltage source is made in the form of a sinusoidal source voltage with a variable frequency, the voltage source output through the contact of a controlled relay is connected between the output of one of the power windings transformer and its case, the input of the first analog-to-digital converter is connected between the same output of the winding of the power transformer and its case, the input of the second analog-to-digital converter is connected between the output of the other winding of the power transformer and its case, the controller in real time at each frequency step calculates the ratio of the output voltage levels to the input voltage level of the power transformer and transfers the result to the control device, on the screen of which the amp is built cast-frequency characteristic (AFC), for calculating the correlation coefficients in three frequency ranges, by means of which the obtained AFC is compared and a conclusion is made about a defect in the windings of power transformers.

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