SU1762276A1 - Device for sampling tests of insulation resistance - Google Patents

Abstract

Use: in measuring equipment as a device for selective control of insulation resistance of electrical networks with insulated neutral. The essence of the invention: the device contains 1 source of industrial frequency

Description

The invention relates to a measurement technique, in particular, to devices for measuring the insulation resistance of electrical networks with insulated neutral, and can be used in the shipbuilding, mining and chemical industries, and other public goods.

A device for determining the location of a ground fault, comprising a low-frequency generator, a current sensor, a narrow-band filter, a signal amplifier, and a variable capacitor, is known.

The drawback of the device is the laboriousness of the insulation resistance measurement operation associated with the need to manually adjust the variable capacitance.

It is also known to selectively monitor an insulation resistance device containing a non-industrial frequency current source, a zero sequence voltage filter, current sensors, a potentiometer, a switch, filters with rectifiers, and an indicator.

The drawback of the device lies in the low accuracy due to the approximate ratios underlying the device's work, as well as the complexity and bulkiness associated with the use of double the number of sensors on each line of the monitored network.

The aim of the invention is to improve the accuracy and simplify the design.

The goal is achieved by the fact that the device for selective control of insulation resistance, containing a source of current of non-industrial frequency, one of the outputs of which is connected to the neutral of the controlled network, the other is connected to the common

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bus, zero-sequence voltage filter, current sensors installed on each line of the monitored network and equipped with additional secondary windings connected in series, one output of which is connected to the common bus and the other to one output of the potentiometer, a switch to the inputs of which the sensor outputs are connected current and, to the output, a filter with a rectifier, and an indicator, is equipped with a phase shifter, an analog switch, an amplitude modulator, a unit for calculating the reciprocal, a peak detector, a sampling amplifier, and storage, clock pulse generator, trigger, sawtooth driver, and pulse formers on the leading and trailing edges, the output of the zero sequence voltage filter through the phase shifter, the analog switch and the amplitude modulator connected to another potentiometer output, the output of the rectifier through the calculator the return value, the peak detector and the amplifier for sampling and storage is connected with the indicator, the clock pulse generator is connected to the trigger inputs and the sawtooth ramp apr, the trigger output is connected to the control input of the analog switch and to the inputs of the pulse formers on the leading and trailing edges, the outputs of which are connected respectively to the input Reset peak detector and the input of the operation mode of the sampling and storage amplifier, and the output of the saw head voltage generator connected with the modulating input of the amplitude modulator.

Fig. 1 is a functional diagram of a device for selectively controlling insulation resistance; in fig. 2 shows time diagrams of voltages at various points of the device.

The device contains a source of 1 current of non-industrial frequency, one of the outputs of which is connected to the neutral of the monitored network, the other is connected to a common bus, a filter 2 voltage of zero-sequence voltage, sensors 3, 4, 5 current installed on lines 6, 7, 8 and provided with series-connected additional secondary windings 9, 10, 11, one output of which is connected to a common bus and the other to one output of potentiometer 12. switch 13, to the inputs of which are connected the outputs of sensors 3, 4, 5. and to the output - filter 14 with rectifier 1F, and indicator 16. The device is equipped with a phase shifter 17, an analog switch 18, an amplitude modulator 19, a block 20

calculating the reciprocal, by the peak detector 21. by the sampling and storage amplifier 22, the clock pulse generator 23, the trigger 24, the sawtooth driver 25, and the formers 26, 27 pulses on the leading and trailing edges. The output of the filter 2 through the phase shifter 17, the key 18 and the modulator 19 is connected to another output of the potentiometer 12. The output

0 rectifier 15 through block 20, detector 21 and amplifier 22 is connected to indicator 16. Generator 23 is connected to inputs of trigger 24 and driver 25. Output of trigger 24 is connected to control input of switch 18

5 and with the inputs of the formers 26, 27, the outputs of which are connected respectively to the Reset input of the detector 21 and the input of the operation mode setting of the amplifier 22. The output of the Former 25 is connected to the modulating input

0 modulator 19.

Diagrams 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38 correspond to the voltages on the outputs of the generator 23, the trigger 24. The drivers 25, 26, 27, the key 18, the modulator

5 19, rectifier 15, block 20, detector 21 and amplifier 22.

The device works as follows.

The applied current from the source 1. growing on lines 6, 7, 8 and closing through the corresponding resistance and isolation capacitances onto a common bus is detected by sensors 3, 4, 5. At the output of filter 2, a zero-sequence voltage is released common mode with active components of superimposed currents in the lines

6.7, 8. The phase shifter 17 shifts the phase of the zero sequence voltage by 90 °. Simultaneously, under the action

0 mm pulses 28 of the generator 23 overturns the trigger 24 and starts the drivers 25, 26, 27. Using the key 18. controlled by the trigger 24, the output voltage of the phase shifter 17 is converted to an intermittent voltage 33. In the modulator 19 under the action of the output voltage 30 shaper 25 produces a linearly increasing sinusoidal voltage 34, which through potentiometer 12, which regulates the amount of current, goes to additional secondary windings 9, 10. 11 sensors 3, 4, 5 Phase of current flowing through additional secondary windings 9. 10, 11, opposite phase capacitive

5 components of the superimposed current in lines x 6,

7.8. At certain values of the voltage increasing in amplitude 34, it is possible to fully compensate the capacitive components of the currents in the lines 6, 7, 8 by currents in the windings 9, 10, 11.

3, these voltage moments at the outputs of the sensors 3, 4, 5 become minimum and their magnitude is proportional to the active component of the leakage currents in the respective lines. Switch 13 provides alternate connection of sensors 3, 4, 5 to the input of filter 14, which provides for the release of a current of non-industrial frequency. In rectifier 15, the sinusoidal voltage is converted to a constant. Block 20 provides voltage inversely proportional to leakage current. In this case, the minimum input voltage 35 corresponds to the maximum output voltage 36, which is proportional to the measured insulation resistance value. The detector 21 detects the maximum voltage, and the amplifier 22 records and stores this voltage.

At the beginning of each measurement cycle that coincides with the leading edge of the output pulse 29 of the trigger 24, the detector 21 is reset to the initial state by the action of the pulse 31 at the output of the driver 26. At the end of the measurement cycle coinciding with the back edge of the pulse 29 under the action of the pulse 32 at the output of the driver 27, the amplifier 22 is set to the recording (sampling) mode, and after its termination returns to the storage mode. Indicator 16 displays the measured value of the insulation resistance.

Thus, due to the full compensation of the capacitive component of the leakage current, the proposed device provides a high accuracy measurement of the insulation resistance. The measurement process is carried out automatically and does not require the use of a variable capacitor of large capacity and double the number of current sensors on the lines of the network under control.

Claims (1)

The claims of the device for selective control of insulation resistance, containing a source of current of non-industrial frequency, one of the outputs of which is connected to the neutral of the controlled network, the other is connected to the common bus, a zero-sequence voltage filter connected to the first output of the neutral of the monitored network , current sensors installed on each line of the monitored network and equipped with additional secondary windings connected in series, one output of which is connected with the common bus, and the other with the first output of the potentiometer, the switch with the outputs of the current sensors connected to the inputs, and the output with a filter with a rectifier, an indicator characterized in that. that, in order to improve accuracy and simplify the design, it is equipped with a phase shifter, an analog key, an amplitude modulator, a reverse computation unit, a peak detector, a sampling and storage amplifier, a clock pulse generator, a trigger, a sawtooth driver, and a front-side driver and trailing edges, the third output of the zero-sequence voltage filter through the phase shifter, the analog switch and the amplitude modulator connected to the second output of the potentiometer, The rectifier is connected to the indicator via the reverse magnitude calculator, the peak detector and the amplifier of sampling and storage, the output of the clock generator is connected to the trigger input and the sawtooth driver, the trigger output is connected to the control input of the analog switch and to the inputs of the forward driver and to the leading edges, the outputs of which are connected respectively with the input of the Reset peak detector and the input of the operation mode setting of the sampling and storage amplifier, and the output of the ramp saw The voltage is connected to the modulating input of the amplitude modulator.