SU1368813A1 - Device for measuring earthing resistance - Google Patents

Abstract

The invention serves to ensure the continuity of the measurement of the value of the grounding impedance. The device contains a source of direct current 1, converters 3 and 13, a matching unit 4, a synchronous RC-filter 5, a low-pass filter 6, a broadband amplifier 7, a synchronous detector 9 and a frequency multiplier 11. The introduced comparator unit 12 and the linearly controlled phase shifter 8 form a static control system in which the value of the phase difference is kept close to zero. Thus, when the phase of the measured signal deviates due to the presence of reactive components, an error signal arises, which changes the control voltage at the input of the phase shifter 8 and compensates for the change in the phase of the measured signal. Due to this, the input and control signals of the synchronous detector 9 will become in phase. 1 il. (L

Description

U u d

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The invention relates to electrical measuring equipment and can be used to measure the grounding resistance and determine the soil resistivity on the territory of operating and commissioned electrical installations.

The aim of the invention is to improve the measurement accuracy by ensuring the continuity of the measurement of the value of the grounding impedance,

The drawing shows a block diagram of a device for measuring ground resistance.

The device contains a source of direct current 1, a switch 2, the first converter 3, a matching unit 4, a synchronous RC-filter 5, a low-pass filter 6, a broadband amplifier 7, a linearly controlled phase shifter 8, a synchronous detector 9, a measuring device 10, a multiplier 11 frequency, block 12 comparison, the second transducer 13, terminals 14-16, grounding 17, potential electrode 18, current electrode 19

The DC source 1 is connected via switch 2 to the first converter 3, the output of the first converter 3 is connected to the inputs of the frequency multiplier 11 and the second converter 13, to one of the inputs of the comparison unit 12 and to the control input of the synchronous detector 9. Matching unit 4 with its own inputs connected to terminals 14 and 15, which are connected respectively to the ground 17 and the potential electrolyte 18. A synchronous RC-filter 5, a low-pass filter 6, a broadband amplifier 7 are connected in series with the output of the matching unit 4, linear controlled phase shifter 8, synchronous detector 9, measuring device 10. Frequency multiplier 11 output is connected to control input of synchronous RC filter 5. Comparison unit 12 output is connected to control input of linearly controlled phase rotator 8, and second input block 12 is connected to the output of the linearly controlled phase shifter 8, one of the outputs of the second converter 13 is connected to terminal 16, which is connected to the current electrode, and the second output of the second converter 13 is connected to terminal 14, which is connected to 13. 2 with grounding 17 and one of the inputs of the matching unit 4.

The first converter 3 is a DC-to-AC converter of a rectangular shape, and the second converter 13 is a converter of a rectangular shape into a sinusoidal one. Matching unit 4 is a large-scale high-impedance amplifier.

The device for measuring the grounding resistance works as follows.

Turning on switch 2 energizes all units of the device. From the output of the first converter 3, a rectangular alternating current with a frequency of, for example, 80 Hz is fed to the input of frequency multiplier 11, to the second converter 13, to one of the inputs of the comparison unit 12, and also to the control input of the synchronous detector. From the output of the second transducer 13, the measuring current of a sinusoidal form with a frequency of 80 Hz is supplied to terminals 14 and 16, which are connected respectively to the earthing switch 17 and the current electrode 19. Removing the potential electrode 18 and the earthing switch 17 potential difference, which is the sum of the useful signal and noise, through terminals 14 and 15 is fed to the input of the matching unit 4 from the output of which is fed to the input of the synchronous filter 5. The useful signal allocated by the synchronous filter 5 through the low-pass filter 6 and broadband amplification s 7 is supplied to the signal input linearly controllable phase shifter 8 which provides the necessary phase shift signal. From the output of the linearly controlled phase shifter 8, the signal goes to the signal input of the synchronous detector 9, and from the output of the synchronous detector 9 to the measuring device 10. At the inputs of the comparison unit 12, the phases of the two signals, respectively, coming from the output of the first converter 3, and from the output linearly controlled phase shifter 8. The output of the comparator unit 12 produces a signal proportional to the phase difference of the input signals, which is fed to the control input of the linearly controlled phase shifter 8. Signal control Phase shifter 8,

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is present until the phase shift between the input signals of the comparison unit 12 becomes zero. As a consequence, the input signal of the synchronous detector 9 and its control signal become in-phase, and the measuring device 10 measures the voltage drop between the potential electrode 18 and the grounding conductor 17, corresponding to the impedance of the grounding conductor. The comparator unit 12 and the linearly controlled phase shifter 8 form a static control system in which the value of the phase difference is kept close to zero, i.e. when the phase of the measured signal deviates due to the presence of reactive components, an error signal occurs at the output of comparator block 12, which changes the control voltage at the control input of the phase shifter B and thus compensates for the change in the phase of the measured signal, that the input and control signals of the synchronous detector become in-phase. In this case, as in any autoregulation system, the control voltage is different from zero.

F o

rmula of invention

A device for measuring the resistance of a specimen containing a source of direct current, the output of which is connected via a switch to the input

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1 converter, serially connected matching unit, the inputs of which are connected to a terminal connected to the potential electrode, and to the terminal connected to the grounding, a synchronous RC filter, the control input of which is connected to the output of a frequency multiplier, whose input is connected to the output of the first converter, a filter a low-frequency and wide-band amplifier, as well as a synchronous detector with a measuring device at the output, the output of the first converter is connected to the control input of the synchronous detector and to the input v A transducer whose outputs are connected to a terminal connected to a current electrode and to a terminal connected to a grounding conductor, characterized in that in order to improve measurement accuracy by ensuring measurement continuity, a comparison unit and a linearly controlled phase converter are introduced the linearly controlled phase shifter is connected to the output of a wideband amplifier by its signal input, and its output to the input of a synchronous detector; one of the inputs of the comparison unit is connected to the output of the first transducer ate, and a second input coupled to an output of linearly controllable phase shifter, the output of comparator unit is coupled to a control input emog linearly controlled phase shifter.

Claims (1)

Claim A device for measuring grounding resistance, containing a direct current source, the output of which is connected via a switch to the input of the first · converter, a matching unit connected in series, the inputs of which are connected to a terminal connected to a potential electrode, and to a terminal connected to a ground electrode, a synchronous RC filter the control input of which is connected to the output of the frequency multiplier, the input of which is connected to the output of the first converter, a low-pass filter and a broadband amplifier, as well as a detector with an output measuring device, the output of the first converter is connected to the control input of the synchronous detector and to the input of the second converter, the outputs of which are connected to a terminal connected to the current electrode and to a terminal connected to the ground electrode, characterized in that in order to increase accuracy measurements by ensuring the continuity of measurement, a comparison unit and a linearly controlled phase shifter are introduced into it, and a linearly controlled phase shifter is connected to the output w by its signal input Iro-band amplifier, and with its output with the input of the synchronous detector, one of the inputs of the comparison unit is connected to the output of the first converter, and the second input is connected to the output of the linearly controlled phase shifter, the output of the comparison unit is connected to the control input of the linearly controlled phase shifter.