RU2446408C1 - Device to monitor discharge voltage of liquid dielectrics - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: sawtooth oscillator 1 via a positive polarity switch 4 is connected to a primary winding of a step-up transformer 5. An increasing voltage is sent to electrodes 8 in a test cell 9 from the first secondary winding 6 of the step-up transformer 5 via a voltage doubling circuit 7, and the voltage is generated by the sawtooth generator 1 and via the positive polarity switch 4 is connected to the primary winding of the step-up transformer 5. The additional secondary winding 12 via a rectifier 13, scaling 15 memorising circuits 14 is connected to an indicator 6. Management of device operation is provided by a control circuit 2, connected to the sawtooth generator 1 and the indicator 6. The moment of electrical disruption is fixed by a circuit of electric disruption signal generation 3.

EFFECT: increased accuracy of measurements and simplified design of the device.

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Description

The invention relates to instrumentation and can be used to control the insulating properties of liquid dielectrics (ID).

The known apparatus for testing the railway AIM-90 (passport 2DE.6.040PS, manufacturer MPO "Mosrentgen", Russia). An increasing high-voltage voltage generated by an autotransformer is applied to the electrodes, between which a portion of the railway is located, and the voltage is measured at the time of breakdown of the railway.

The voltage is measured on the part of the winding connected to the power source, and increased voltage is applied to the electrodes from the entire winding of the autotransformer, which increases the measurement error of the breakdown voltage. Through the use of a test voltage of up to 100 kV, high electrical safety requirements are met.

A device for express control of the breakdown voltage of railway (RU 2220427, C2 G01R 31/12, 31/14, 2003 - adopted as a prototype).

The device contains a test cell (IJ) with electrodes, a step-up transformer, control circuits, voltage doubling, scaling, as well as a sawtooth voltage generator, two bipolar switches and an indicator. A linearly increasing voltage is supplied through the keys to the primary winding of the step-up transformer, and an alternating voltage increased by means of a doubling circuit is converted into an increasing constant voltage, which is supplied to the electrodes in the IN. At the time of electrical breakdown of the railway layer between the electrodes, the voltage of the sawtooth voltage generator is fixed. Through the scaling scheme, the recorded voltage is supplied to the indicator.

The advantage of the device is a small value of the interelectrode gap, which reduces energy consumption and increases electrical safety.

The disadvantages of the device are:

- design complexity, since bipolar switches are used, the step-up transformer must necessarily contain two identical halves of the primary winding, and the measuring circuit must be high-resistance;

- low measurement accuracy, since the circuit using the linear voltage generator does not take into account the non-linear nature of the conversion due to the step-up transformer.

The technical result is an increase in measurement accuracy and simplification of the design of the device.

The technical result is achieved by the fact that in the device for controlling the breakdown voltage of the railroad drive, containing an IN with electrodes, a step-up transformer, control circuits, generating an electrical breakdown signal, doubling the voltage, scaling, one key of positive polarity, a sawtooth voltage generator and an indicator, according to the invention are additionally introduced a memory circuit, a rectifier and a second secondary winding into a step-up transformer, which with its beginning through a rectifier, a memory circuit and scaling connected to the first input of the indicator, and the end connected to the second input of the indicator, while the output of the electric breakdown signal generating circuit is connected to the second input of the storage circuit, and the end of the primary winding of the step-up transformer is connected to the third input of the sawtooth voltage generator.

In FIG. presents a structural diagram of the device.

The device comprises a sawtooth voltage generator 1, the first input of which is connected to the first output of the control circuit 2, and the second input of the sawtooth voltage generator is connected to the output of the electric breakdown signal generation circuit 3. The output of the sawtooth voltage generator is connected to the input of the positive polarity switch 4, the output of which is connected to the beginning of the primary winding of the step-up transformer 5. The first secondary winding 6 of the step-up transformer 5 through a doubling circuit 7 is connected to one of the electrodes 8 IJ 9, and the second electrode, together with the output 10 of the first secondary winding 6 of the step-up transformer 5, is connected to the input of the electric breakdown signal generation circuit 3. A second secondary winding 12 is placed on the magnetic circuit 11 of the step-up transformer 5, the beginning of which is connected to the rectifier 13 connected in series memory 14 and the scaling circuit 15, the output of which is connected to the first input of the indicator 16, and the second input is connected to the end of the second secondary winding 12. The second input of the indicator 16 is connected to the second output row control circuit 2. The output of the signal conditioning circuit electrical breakdown 3 is connected to the second input of memory circuit 14.

The device operates as follows.

After removing the contaminant from the working volume of the IN 9, a portion of the monitored railway is placed in the 9 initial state indicator 16. As the sawtooth voltage increases with the help of a positive polarity key 4, an alternating voltage is formed on the primary winding of the step-up transformer 5, which drives an alternating voltage on the first secondary winding 6. The voltage from the first, secondary winding 6 with the help of a voltage doubling circuit 7 is converted into a variable constant voltage, which is applied to the electrodes 8 and, therefore, an increasing voltage acts on the railway layer. When the voltage reaches a value equal to the voltage of the electrical breakdown of the railway layer, an electric discharge occurs between the electrodes 8 and the electrical breakdown signal generation circuit 3 gives a signal to the second input of the sawtooth voltage generator 1 and turns it off. At the same time, the signal from the electric breakdown signal generating circuit 3 is supplied to the storage circuit 14 and the voltage on the second secondary winding 12 at the time of the electrical breakdown between the electrodes 8, after the rectifier 13 is stored by the circuit 14 and then goes to the scaling circuit 15.

In order for the indicator 16 to show the voltage in the normalized gap by the railway test procedure, the product of the transformation coefficient for the second secondary winding 12 and the conversion coefficient of the scaling circuit 15 are chosen equal to the electric breakdown voltage in the normalized gap.

Comparative analysis with the prototype shows that in the proposed device the requirements for linearity of the output voltage from the sawtooth generator are reduced, the number of elements of the device is reduced and two equal half of the primary winding are not required, which simplifies the design of the device. An increase in the measured voltage increases the accuracy of the measurement, including by reducing the influence of external factors, for example, on the characteristics of the sawtooth voltage.

In the proposed device, the measurement can be carried out after the end of electromagnetic oscillations, using the stored voltage at the time of electrical breakdown, which reduces the measurement error. In this case, it is possible to repeat the calculation procedure using the stored measured value, while in the prototype it is necessary to repeat the entire test cycle. This reduces the complexity of the test. It should also be borne in mind that in the prototype, the sawtooth voltage measures the amplitude value, and when rectifying an alternating voltage using the doubling circuit, the average voltage value is measured, which complicates the scaling scheme. To stabilize the operation of the known device in time, taking into account the small level of the measured voltage, the elements of the measuring circuit must have small leakage currents, which is realized when using elements of special design, and this additionally complicates the device. For the proposed device, reducing the ratio between the voltage applied to the electrodes of the IN and the measured voltage, as well as reducing the influence of external factors, such as ambient temperature, increases the accuracy of measurements by 10-15%, and since this also reduces the spread in readings, This increases the reliability of the test results.

Claims (1)

A device for controlling the breakdown voltage of liquid dielectrics, containing a test cell with electrodes, step-up transformer, control circuits, generating an electrical breakdown signal, doubling the voltage, scaling, one key of positive polarity, a sawtooth voltage generator and an indicator, characterized in that the circuit is additionally introduced into it memory, rectifier and a second secondary winding into a step-up transformer, which with its beginning through the rectifier, the memory circuit and scaled The is connected to the first input of the indicator, and the end is connected to the second input of the indicator, while the output of the electric breakdown signal generating circuit is connected to the second input of the storage circuit, and the end of the primary winding of the step-up transformer is connected to the third input of the sawtooth voltage generator.