SU530271A1 - Device for measuring the insulation resistance of a DC network - Google Patents

Description

one

The invention relates to the field of instrumentation and can be used in devices for measuring insulation resistances.

A device for measuring the resistance of an insulated DC network under voltage, containing a meter, a switch and an auxiliary DC source, is known.

A disadvantage of this device is that it allows measuring only the total insulation resistance.

A device for measuring the insulation resistance of a DC network is known, which contains a DC source connected via a switch in series with a measuring unit between the housing and the midpoint of a voltage divider formed by a resistor and controlled by a resistance, a generator and switches. This device allows to measure both the total insulation resistance and separately the insulation resistance of the poles.

The disadvantage of this device is relatively low reliability when processing measurement results, since to determine the insulation resistance of each pole, it is necessary to perform additional operations with signals at the two outputs of the device.

The aim of the invention is to increase the reliability of information processing as a result of measurements.

The essence of the invention is that the device additionally introduces a conversion unit containing transistors of different conductivity connected via emitter followers parallel to the voltage divider arms, the collector circuits of transistors are connected to the input windings of an additional transformer with a rectangular hysteresis loop, and the output windings are connected via a differential amplifier, filter and pulse amplifier to the winding of the second additional transformer with a hister An thesis, the other windings of which are connected to the generator's outputs via the keys connected by control inputs to the outputs of the generator, and to the output of the measuring unit. The drawing shows a diagram of the proposed device. The device contains a source of direct current 1 connected through a switch 2 between the case and the midpoint of a voltage divider formed by a resistor 3 and controlled by a resistance 4, made, for example, in the form of a transistor stage, measuring element 5, generator 6, switches 7, 8 and 9, conversion unit 10, with transistors 11, 12, 13, and 14 connected, connected to the buses of the controlled network, transformer 15c with a rectangular hysteresis loop with windings 16, 17, 18, 19 and 2O. The power lines of the differential amplifier 21, made on transistors 22 and 23, are connected through a filter 24 to a pulse amplifier 25, built on a transistor 26 and resistors 27.28 and 29. The input of a pulse amplifier 25 is connected to the output winding 30 of a transformer 31 with a rectangular loop hysteresis, the primary windings 32 and 33 of which are connected to the bus controlled network. The insulation resistances of the network poles are conditionally denoted by resistors 34 and 35. The device operates as follows From the antiphase outputs of the generator 6, keys 7.9 or 2.8 are alternately opened. In the nepJiOM position, the key 2 is closed, so the diagonal of the bridge measuring circuit formed by the resistance 3, 4, 34 and 35, the voltage from source 1 is not supplied. The signal is at the output of the measuring body 5, the voltage pushes the mismatch voltage in the diagonal of the bridge circuit, through a public key 7 is fed to the control input of the controlled resistance 4, which thus changes so that the mismatch signal decreases. With a sufficiently large gain of the measuring body 5, the potential of the midpoint of the voltage divider becomes close to the potential of the housing. The voltages taken from the resistances 3 and 4 are fed to the emitter followers of the conversion unit 1, made on transistors 11 and 12 of different conductivity. The emitter follower loads are transistors 13 and 14 with the windings 16 and 17 of the transformer 15c having a rectangular hysteresis loop. Due to the positive feedback that is provided when the windings 18 and 19 of transformer 15 are wired for transamps 13, a circuit with a rectangular voltage at the output is implemented on transistors 13, 14 and transformer 1. The duration of the output reverse impulses is proportional to the voltage U and U applied to the windings 16 and 17. They are determined by relation. R is the insulation resistance between the plus and the case; T is the insulation resistance between the bus minus and the body. The pulses of duration d i and l i 2. arrive at the input of the output differential amplifier 21, opening transistors 22 and 23. Simultaneously with the balancing of the bridge circuit formed by the resistances 3,4,34 and 35, through the open key 9, the magnetization reversal to the state - In J, the core of another transformer 31 with a rectangular hysteresis loop voltage controlled network applied to the winding 32. In the next half period of the generator 6, keys 2 and 8 are open, and keys 7 and 9 are closed, the value of controlled resistance 4 remains unchanged . The voltage of the source 1 of direct current is supplied to the bridge diagonal through the switch 2. The value of the current flowing at the input of the measuring body 5 is determined by the relation where A and B are constant. - total insulation resistance. The increased voltage from the output of the measuring body 5 through the open key 8 is supplied to the winding 33 of the transformer 31. The time of magnetization reversal of the core from the state to the state is determined by the relation T КСа + Т) When the core is remagnetised by a pulse from the winding 30 of the transformer 31, the transistor 26 of the pulse amplifier opens 25. As a result of subtracting the voltage on the resistors 28 and 29 at the output of the filter 24, the supply voltage of the differential amplifier 21 is directly proportional to R from the Signal — the waveform is a sequence the difference of the opposite-polarity pulses of a length of 4. U d –t. amplitude At, K is proportional to i i and H. Significantly, over a significant range of changes 1 and T1, the sum of d -t and 12 varies slightly, so the average value of the voltage of the impulses of duration

 but

L i proportional to the magnitude of the pulses with a duration of 2.

proportional to .R

Thus, in the proposed device, a signal is obtained at one output, the parameters of which characterize the magnitude of both the total insulation resistance and the insulation resistance of each field relative to the housing. The output waveform is convenient for use in digital or analog information processing devices.

Claims (1)

Invention Formula An apparatus for measuring the insulation resistance of a DC network, comprising a DC source connected via a switch in series with a measuring device between the housing and the midpoint of a voltage divider formed by a resistor and controlled by resistance, a generator and switches, that In order to increase the reliability of information processing as a result of measurements, a conversion unit containing transistors of various conductivities is additionally introduced into the specified measuring body; via emitter followers parallel to the shoulders of a voltage divider, collector circuits of transistors are connected to the input windings of an additional transformer with a rectangular hysteresis loop, and output windings are connected through a differential amplifier, filter and pulse amplifier to the windings of a second additional transformer with a rectangular hysteresis loop, other windings which, via the keys connected by the control inputs to the generator outputs, are connected with the thickness of the monitored network and the measurement output executive body.