SU760436A1 - Analogue-digital converter - Google Patents

Description

The invention relates to measuring technique.

A analog-to-digital converter is known that contains a transducer-amplifier unit with a high-frequency sensing body in the form of an antenna installed in the body of a controlled transformer and connected to the control grid of an electronic amplifier with an actuator connected to the output; fixing its breakdown moment £ 1]. '

The disadvantage of this device is the ¹³ inability to predict the emergency stage.

A lime-analog-to-digital converter containing a generation unit for reference signals, connected to a comparators unit, a block of anti-coincidence elements, connected to a storage device, a reference voltage source, a control unit, and a pre-25 voltage-phase converter (2).

The disadvantage of the device is

inability to control the state

electrical isolation as well as prediction of the emergency stage or di2

Agnosticating the pre-emergency stage of insulation failure of transformers (autotransformers).

The aim of the invention is the implementation of continuous monitoring of the state of electrical insulation, as well as ensuring the possibility of predicting accidents.

The goal is achieved by the fact that an analog-to-digital converter containing a monitored transformer has entered a de-parametric transducer, leveled in a whole-bounding block, resonant amplifiers, a differential-amplifying block, an amplifier, an executive body, the primary windings of the parametric transducers are connected to the current terminals of the monitored transformer, the secondary windings parametric converters are connected via equalizing-limiting block-resonance amplifiers with diff inputs A potential amplifying unit whose output through an amplifier is connected to the inputs of an execution unit and an analog-to-digital converter.

760436

FIG. 1 is given a block diagram of the device; FIG. 2 shows the time diagrams of the work ”of the device.

The device contains parametric converters 1, a controlled transformer 2, a high-frequency cable 3, leveling and limiting blocks 4, resonant amplifiers 5, a differential amplifier unit 6, an amplifier 7, an actuator 8, an analog-to-digital converter 9, a differential amplifier unit 6 contains separation transformers 10, amplifier 11, the executive body contains a resistor 12, a zener diode 13, a capacitor 14, a relay 15, a relay contact 16.

The device allows you to control the state of isolation simultaneously in two ways. The first is that when a high-frequency signal passes from the primary winding to the secondary transformer or vice versa, the signal amplitude changes depending on the insulation dampening of the power transformer, since the insulation dampening changes its capacitive and active parameters.

The dependence of the resulting level ^: nya high-frequency signals on the frequency change is presented in figure 2 in the diagrams.

The characteristic of curve 1 reflects the change in the ratio of voltage levels in the windings of a power transformer versus frequency when its insulation is wetted IV,%. When wetted, this change in the ratio of stress levels is expressed by dependence II. For clarity of fixation, changes in the ratio of the levels when the moisture content of the insulation changes from M /,% to it is necessary to develop a frequency corresponding to the maximum or minimum signal level at the initial moisture content%%, as shown in FIG. 2 (frequency £ ₀ ).

To control the isolation distance of power transformers, high-frequency signals are located outside the controlled transformer, that is, in the electrical network.

These sources are inverters, electric arc furnaces, etc. A high-frequency signal can also be generated by the very non-linearity and asymmetry of the electrical network.

The spectrum of signals from the outputs of the controlled transformer 2 is reduced by parametric transducers 1, Then the signals from transducers 1 via high-frequency cable 3 go to equalizing blocks 4, and from their output to the inputs of resonant amplifiers 5, resonant amplifiers 5 filter and amplify signals of the selected frequency ^ which then arrive for summation in the differential amplifying unit 6, from the output of which the resulting signal through the amplifier 7 enters the actuator 8. When it is triggered normally With open contact 16, an alarm circuit of the category “Fault” is activated with a time delay.

In the normal state of isolation of the controlled transformer 2, the differential-amplifier unit b is summed up, and the amplifier 7 amplifies the unbalanced signal level (unbalance).

In the normal state of isolation, the executive body 8 does not work.

When the insulation state of the controlled transformer corresponds to the pre-emergency stage, for example, moisture is above the norm, the numerical values of capacitive and active conductivities of the equivalent circuit of the controlled transformer change.

In this state, the level of the signal of the selected frequency that has passed through the monitored transformer 2 will change.

The actuator 8 is triggered when the voltage level is equal to the trigger voltage, thereby closing the normally open contact 16 in the "Insulation Failure" signaling circuit.

The second way to control the state of isolation of power transformers is based on the fixation of signals arising from microdischarges ("creeping discharges") in the insulation of a controlled transformer.

Since the resonant amplifiers 5 are tuned to the frequency £ □, the signals with the frequency £ _о also come to the input of the differential-amplifier unit 6. The intensity or the number of discharges depends on the degree of moisture of the insulation of the power transformer, since when the insulation is wetted, its breakdown voltage decreases, which leads to frequent microdischarges in the insulation.

This way of control is different in that in this case the source of the high-frequency signal is located inside the controlled power transformer, torus ·

When working on the second control path, analog-to-digital converter 9 records the number of microdischarges and their intensity. When the voltage is equal to the trigger voltage, is triggered analog-to-digital Converter 9.

When finding a source of high-frequency signal outside the controlled transformer · 2 (the first way

• 760436

control, both signals coming to the inputs of the differential-amplifying unit 6 are opposite, and when the source of high-frequency signals is inside the transformer (the second control path), they are unipolar. By 5, the response of the corresponding executive body 8 or analog-digital converter 9 is determined by described ways of control. The executive unit 8 is open to simultaneous operation with the analog-digital converter 9 in time, which is rebuilt in relation to the executive unit 8 in terms of voltage. Thus, the simultaneous operation of both devices does not occur, which is based on the nature of the flow of the high-frequency signal during microdischarges and when an external generator is operating, for example, a powerful inverter in an electrical network.

Microdischarges are pulsed with a significant interval between pulses, and a powerful inverter outside the controlled power transformer 25 generates relatively longer signals. The time delay of the operation of the output relay 15, the executive body 8 is performed in a known manner 30 times, for example, as is done in electromagnetic relays.

With the help of the device, it is possible to control the insulation condition of both operating transformers and non-operating transformers. In the latter case, a high-frequency signal generator can be introduced into the device for operation according to the first monitoring method. 40

For operation according to the second method, a test increase (compared to normal) voltage is applied to any of the windings of the monitored (non-operating) transformer, and further microdischarges are regulated by the method described above.

Claims (1)

Claim An analog-to-digital converter containing a controlled transformer, an analog-to-digital converter, distinguished by the fact that, in order to exercise continuous monitoring of the state of electrical insulation, as well as to ensure the possibility of predicting accidents, parametric converters, equalizing-limiting blocks, resonant amplifiers, a differential amplifier unit, an amplifier, an actuator, the primary windings of parametric converters are connected to the terminals of the terminal controlled transformer, secondary windings, parametric converters are connected through equalizing-limiting blocks and resonant amplifiers with the inputs of the differential-amplifier unit, the output of which is connected through an amplifier to the inputs of the execution unit and the analog-digital converter.