SU718805A1

SU718805A1 - Arrangement for measuring earthing resistance

Info

Publication number: SU718805A1
Application number: SU782608560A
Authority: SU
Inventors: Алексей Андреевич Захаров; Юрий Федорович Балабай; Юрий Васильевич Смолиговец; Иван Владимирович Тупица
Original assignee: Казахский Ордена Трудового Красного Знамени Сельскохозяйственный Институт; Завод "Мегомметр"
Priority date: 1978-04-24
Filing date: 1978-04-24
Publication date: 1980-02-29

Description

1one

Изобретение относитс к устройствам дл измерени сопротивлени заземлений, а также дл определени удельного сопротивлени грунта и измерени напр жени прикосновени на территории действующих и сдаваемых в эксплуатацию электроустановок .The invention relates to devices for measuring the resistance of grounding, as well as for determining the resistivity of the soil and measuring the voltage of touch on the territory of existing and commissioned electrical installations.

Известен измеритель сопротивлени грунта, в котором потенциальные электроды подключены непосредственно к усилителю с большим входным сопротивлением, усиленный сигнал с которого подаетс на синхронный детектор и затем на измерительный прибор. Это исключает необходимость Б непрерывном уравновешивании измер емого сигнала с падением напр жени на калибровочном реохорде при прохождении через него измерительного тока. Кроме того, прибор содержит стабилизатор измерительного тока.A soil resistance meter is known in which potential electrodes are connected directly to an amplifier with a large input resistance, the amplified signal from which is fed to a synchronous detector and then to a measuring device. This eliminates the need for B to continuously balance the measured signal with a voltage drop across the calibration rc as the measuring current passes through it. In addition, the device contains a measuring current stabilizer.

Иедостаток заключаетс в том, что в измерителе не предусмотрено никаких мер по подавлению помех на входе усилител .The disadvantage is that the meter does not provide any measures to suppress the input to the amplifier.

Известно устройство дл измерени сопротивлени заземлени , содержащее источник посто нного тока, генератор переменного тока, заградительный фильтр на частоту 50 Гц, на вход которого поступает измер емый сигнал, а к выходу последовательно подключены резонансный усилитель A device for measuring the grounding resistance is known, which contains a DC source, an alternator, a barrier filter at a frequency of 50 Hz, at the input of which a measured signal is fed, and a resonant amplifier is sequentially connected to the output.

и синхронный детектор с индикаторным прибором.and a synchronous detector with an indicator device.

Одним из недостатков прототипа вл етс низка его помехоустойчивость. Помехи на действующих подстанци х имеют, вонервых , широкий частотный спектр, во-вторых , уровень и частота помех непрерывно и резко измен ютс . Поэтому наличи заградительного фильтра на частоту 50 Гц в измерительной части прибора недостаточно дл эффективного подавлени помех. Более того, большинство из всех известных фильтров и резонансных усилителей при таком характере помех во врем переходного процесса приведут к по влению помехи на частоте измерительного тока. В результате отсчет показаний измерительного прибора становитс невозможным из-за непрерывных хаотических колебаний стрелки.One of the drawbacks of the prototype is its low noise immunity. Interference at operating substations has, firstly, a wide frequency spectrum, and secondly, the level and frequency of interference continuously and dramatically change. Therefore, the presence of a barrier filter at a frequency of 50 Hz in the measuring part of the device is not enough to effectively suppress noise. Moreover, most of all known filters and resonant amplifiers, with this type of interference during the transient process, will cause interference to the measurement current frequency. As a result, the readout of the measuring instrument becomes impossible due to the continuous random oscillations of the arrow.

Целью предлагаемого изобретени вл етс повышение помехоустойчивости устройства и повышение точности измерени .The aim of the invention is to improve the noise immunity of the device and increase the measurement accuracy.

Claims

The goal is achieved by the fact that in a device for measuring the grounding resistance, which contains a series-connected DC source, a DC-to-AC converter, the output of which through a switch is connected to the measuring terminals of the device, as well as a filter, amplifier, synchronous detector, and measuring instrument, In series, a synchronous detector, a low-pass filter, and a DC amplifier, the output of which is connected to the measuring terminals of the device, are connected via a switch. measuring device. The drawing shows a block diagram of a device for measuring ground resistance. The device for measuring the grounding resistance contains a source of direct current 1, a converter of alternating current 2 to a constant current, a transformer 3 with a primary winding 4, a secondary winding 5, 6, 7, 8, a synchronous detector 9, a low-pass filter 10, an amplifier 11 constant current meter, measuring device 12, To turn on the device, use button 13, and for switching the measuring device from measuring mode of measuring current to measuring mode of voltage drop on grounding device 14, switch 15. The device is equipped with measuring terminals 16-19 for connection to the grounding device, the current electrode. 20 and the potential electrode 21 (the second potential electrode for the case of performing vertical electrical sounding is not a knockout). The stabilization unit 22 feeds the synchronous detector 9, the low-pass filter 10 and the amplifier 11. The operation of the device is as follows. When the button 13 is turned on, the voltage of the direct current source 1 is applied to the converter 2 of the direct current in the :: variable. The alternating voltage of the secondary winding 5 of the transformer 3 is iodized on the grounding device 14 and the current electrode 20. The alternating voltage removed from the grounding device 14 and the potential electrode 21, which is the sum of the useful signal and noise, is fed to the input of the synchronous detector 9. The selected at the output of the synchronous detector 9, the constant component of the voltage, proportional to the magnitude of the useful signal, together with the alternation of the component of the interference, goes to a low-pass filter, in which it is filtered by a filter nnam component interference. A useful signal in the form of a constant voltage with the remaining insignificant variable component of the interference, not affecting the accuracy of the meter, is fed to the amplifier 11 of the direct current and nots the measuring device 12 of the magnettoelectric system that does not respond to the variable component of the voltage. Adding a DC amplifier instead of a resonant one eliminates the appearance of a parasitic signal during the transient process at the measuring current frequency, and the proposed new structural diagram of the device with the synchronous detector at the measuring path improves its noise immunity and, as a result, the measurement accuracy since the frequency of the measured current and the frequency of the control voltage of the synchronous detector are the same. Thus, the proposed device, but comparing with the known ones, allows to increase the noise immunity and, as a consequence, increase the accuracy of the measurements. Invention A device for measuring the grounding resistance, containing a series of DC power sources, a DC converter in liOpeMeHHbni, the output of which through the switch is connected to the measuring terminals of the device, as well as a filter, an amplifier. A synchronous detector and a measuring device, characterized in that, in order to increase the numbering tolerance, a serially connected synchronous detector, a low-pass filter and a DC amplifier, to the output of which the measuring device is connected, are connected to the measuring terminals of the device.

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