RU206139U1 - CURRENT MEASURING DEVICE - Google Patents

Abstract

The utility model is designed to measure discharge currents through an overvoltage arrester in the range of currents 10 kA-100 kA. The device for measuring current contains an optical current sensor (1), to which an amplifier (2), an analog-to-digital converter (3), a microcontroller (4) and a liquid crystal indicator (5) are connected in series. The optical current sensor (1) contains a source (7) of optical radiation installed on a dielectric base (6), a polarizer (8), an optically active crystal (9), an analyzer (10), a photoelectric converter (11) and a metal rod (12). The metal rod is made (12) with a diameter of 10-12 mm and a length of at least 100 mm, and its spine is located at a distance of 18-22 mm from the center of the optically active crystal (9). The current measuring device has an increased measurement accuracy. 7 p.p. f-ly, 3 dwg

Description

The utility model relates to measuring technology, namely to optical instruments and devices designed to measure medium and high currents.

A device for measuring alternating currents of a high-voltage power transmission line (see patent RU 2644574, IPC H01F 38/28, publ. 13.02.2018), containing primary and secondary conductive windings. The primary winding is made in the form of a plate bent around the circumference with L-shaped branches at the ends directed in opposite directions. The ends of the plate are bent inward to form a gap between parallel L-shaped branches. A secondary wire winding is wound on the primary winding. The end of the primary winding is connected to the end of the secondary winding. The ends of the primary winding are mounted in the cut of the power line wire, and the ends of the secondary winding are connected to the measuring device.

The known device is not intended for measuring high pulse discharge currents.

A device for remote current measurement is known (see patent RU 146741, IPC G01R 19/25, publ. 20.10.2014), containing a power supply, clock and trigger pulse shapers connected to the corresponding inputs of an analog-to-digital converter, the analog input of which is intended for connection to the sensor of the measured value, and the digital output is connected to an optical transmitter intended for fiber-optic communication with the data processing module. The digital output of the analog-to-digital converter is connected to the optical transmitter through an additionally introduced pulse-width manipulator, made with the possibility of converting binary signals into pulses of two unequal durations, the sum of which is less than the period of the clock pulses.

The disadvantages of the known device include the complexity of the design, the need to use a fiber-optic line, which are an obstacle to its widespread use.

Known device for measuring current for high-voltage lines (see patent RU 117014, IPC G02F 19/00, publ. 10.06.2012), containing a ferrite loop surrounding a current-carrying wire, with a coil of copper wire having a tap at a tenth of the turns. The output ends of the coil and the tap are connected to voltage converters into optical pulses of the infrared range with a repetition rate proportional to the current in the current-carrying wire. At a distance of (5-10) m are photodetector units with focusing lenses, selective filters and modules for converting optical pulses into electrical ones with simultaneous amplification and frequency inversion into a digital binary code, and converters into optical pulses connected to the ends of the coil and to the tap have different radiation wavelengths and pulse repetition rates.

The known device provides complete isolation of the high-voltage voltage from the low-voltage part of the equipment, but this is achieved by a significant complication of the design.

Known optoelectronic device for measuring current (see patent RU 2365922, IPC G01R 19/00, 27.08.2009), containing a primary converter, a coding unit, an optical communication channel between the high voltage side and the ground potential, a receiving unit and a power supply unit. To power the coding unit located on the high voltage side, an energy transmission channel is used from the ground potential side, consisting of a battery of light emitters, power optical channels, a battery of photodetectors and a voltage stabilizer.

The known device makes it possible to galvanically isolate high voltage circuits from the ground potential. The disadvantage of the known device is the significant complication of its design.

A device for measuring current is known (see patent RU 2608335, IPC G01R 19/00, publ. 01/17/2017), containing a primary converter, an encoding unit, a communication channel between the high voltage side and ground potential, a receiving unit and a power supply unit in the form of a channel energy transfer from the side of the earth potential. The power supply unit consists of a battery of light emitters, power optical channels, a battery of photodetectors and a voltage stabilizer. As a primary converter for the current, a shunt is used, included in the cut of the power line. The coding unit is made in the form of two analog-to-digital converters, the input of the first analog-to-digital converter is connected to the shunt, the input of the second analog-to-digital converter is connected to a low-resistance resistor. The common connection point for analog-to-digital converters is the connection point of the shunt and low-resistance resistor. The outputs of the analog-to-digital converters are connected to the inputs of the parallel digital-to-serial converters, to which the emitting LEDs are connected, supplying light signals to the fiber-optic communication channels, their other ends are connected to the corresponding receiving units.

The known device makes it possible to reduce the errors of the measured values of the current, but this is achieved by a significant complication of the design of the device.

A device for measuring current is known (see patent RU 2437106, IPC G01R 15/24, G01R 19/25, publ. 20.12.2011). The device consists of electronic and optical modules. The optical module includes a radiation source, a directional coupler, a sequentially located radiation polarizer, a radiation polarization modulator, a fiber line and a measuring sensitive fiber circuit. The electronic module includes a signal processing unit, a photodetector and a signal generator associated with a modulator. The radiation polarization modulator is made in the form of a fiber circuit located in the longitudinal magnetic field of the solenoid. The fiber line is a double bifilar fiber line. The modulator fiber circuit and double bifilar fiber line are made of magnetically sensitive optical fiber with built-in linear birefringence.

The known device makes it possible to reduce the errors in measuring the current due to external temperature and mechanical influences. The disadvantage of the known device is complex thermal stabilization, taking into account the large length of the magnetically sensitive fiber.

Known device for measuring current (see patent US 9588150, IPC G01R 15/24, G01R 19/00, publ. 03/07/2017), including at least one light input and one light output, optical fiber, Faraday rotator in the form of a magnetically sensitive optical fiber, the first and second quarter-wave plates, a polarizing separator, a light source and a signal processing circuitry including a photoelectric converter. The optical fiber has a birefringence, in which two beams of light with different rotations enter, and from which beams of light come out, which are polarized in a circle. The phase difference between the two linearly polarized light beams is compensated for in a closed light circuit between the two quarter-wave plates. The Faraday angle of rotation when the Faraday rotator is magnetically saturated is given as 22.5 + α °. In this case, the oscillation range for the relative error in the measured value of the measured current was set within ± 0.5%. The crystal axes on the optical surface of the two quarter-wave plates are set perpendicularly or in the same direction.

The disadvantages of the known device is its complicated design.

A known device for measuring current (see patent US 8957667, IPC G01R 19/00, publ. 17.02.2015), containing at least one input and output for light, an optical fiber for the sensor, a Faraday rotator in the form of a magnetically sensitive optical fiber, the first and a second quarter-wave plate, a polarizing splitter, a light source and a signal processing circuit containing a photoelectric converter. The optical fiber for the sensor has a birefringence effect and contains one end, into which two circularly polarized light beams are introduced, having different directions of rotation, and the other end, which reflects the introduced circularly polarized light beams. In addition, the phase difference between the two linearly polarized light beams in the closed light path between the two quarter-wave plates is compensated. The Faraday angle of rotation when the Faraday rotator is magnetically saturated is set to 22.5 + α ° so that the oscillation range for the relative error in the measured value of the measured current is set within ± 0.5%. In addition, the crystal axes on the optical faces of the two quarter-wave plates are set perpendicular or set in the same direction.

The disadvantage of the known device is a rather complicated optical scheme.

Known device for measuring current (see patent RU 61042, IPC G01R 29/00, publ. 10.02.2007), which coincides with the present technical solution for the greatest number of essential features and taken as a prototype. The known prototype device contains an optical radiation source connected to a polarizer by means of a fiber light guide, a magneto-optical Faraday cell in the form of an optically active crystal, an analyzer and a photoelectric converter. An amplifier, an analog-to-digital converter, a microcontroller and a liquid crystal display are connected in series with the photoelectric converter.

The known device has expanded functionality, however, the device does not directly measure the electric current, but measures the magnitude of the projection of the magnetic field strength directed parallel to the propagation of the light wave inside the magneto-optical Faraday cell, according to which the device is calibrated by performing calculations taking into account the geometry of the conductor through which the measured current flows , and the location of the conductor relative to the magneto-optical Faraday cell. However, the distribution of the magnetic field strength around the magneto-optical Faraday cell can be significantly inhomogeneous, depending on the geometry of the conductor, the medium surrounding the conductor and external magnetic influences, which negatively affects the accuracy of measurements of the electric current by the device.

The task of this technical solution was to develop a device for measuring current, in which a uniform distribution of the magnetic field strength around the magneto-optical Faraday cell is created, which increases the measurement accuracy.

The problem is solved in that the device for measuring the current contains an optical current sensor, which includes an optical radiation source, a polarizer, a magneto-optical Faraday cell in the form of an optically active crystal, an analyzer and a photoelectric converter. An amplifier, an analog-to-digital converter, a microcontroller and a liquid crystal display are connected in series with the photoelectric converter. New in the device for measuring current is that the device includes a metal rod with a diameter of (10-12) mm and a length of at least 100 mm, a metal rod, a radiation source, a polarizer, an optically active crystal, an analyzer and a photoelectric converter are installed on a dielectric base, when In this case, the metal rod is installed vertically, and its axis is spaced from the center of the optically active crystal by (18-22) mm.

The optically active crystal can be made on the basis of a crystal with a sillenite structure, for example, from Bi ₁₂ GeO ₂₀ or from Bi ₁₂ SiO ₂₀ .

The metal rod can be made of copper or aluminum.

The photoelectric converter can be made in the form of a photodiode.

The radiation source, polarizer, optically active crystal, analyzer and photodetector can be enclosed in a dielectric housing, made, for example, of plastic.

The dielectric base can be made of plexiglass or plastic, or fiberglass.

The execution of a metal rod with a diameter of (10-12) mm is due to the fact that with a diameter of less than 10 mm, the rod at high currents unacceptably overheats, and with a diameter of more than 12 mm, the measurement accuracy decreases.

Making a metal rod less than 100 mm long leads to a significant decrease in the measurement accuracy due to the inhomogeneity of the magnetic field created by the current passing through the rod.

When the distance between the axis of the metal rod and the center of the optically active crystal is less than 18 mm, the measurement accuracy is significantly reduced.

When the distance between the metal rod and the center of the optically active crystal is more than 22 mm, the sensitivity of the sensor is significantly reduced.

This utility model is illustrated by drawings, where:

in fig. 1 is a block diagram of the present device for measuring current;

in fig. 2 is a longitudinal sectional view of an optical current sensor of the present current measuring device;

in fig. 3 is a top view of the optical current sensor of the present current measuring device in section A-A shown in FIG. 2.

The present device for measuring current (see Fig. 1) contains a current sensor 1, with which an amplifier (U) 2, an analog-to-digital converter (ADC) 3, a microcontroller (K) 4 and a liquid crystal display (LCD) 5 are connected in series. 1 current (see Fig. 2-Fig. 3) includes mounted on a dielectric base 6, made, for example, of plexiglass, fiberglass, plastic, an optical radiation source (IOI) 7, made, for example, in the form of a laser or laser diode, polarizer (P) 8, optically active crystal (OAK) 9, made, for example, from Bi ₁₂ GeO ₂₀ or from Bi ₁₂ SiO ₂₀ , analyzer (A) 10, photoelectric converter (PEC) 11, for example, in the form of a photodiode connected in the photovoltaic mode, and a metal rod (MS) 12, made, for example, of copper or aluminum. IOI 7, P 8, OAK 9, A 10 and FEP 11, which make up the optical part 13 of the sensor 1, are placed in the housing 14 to be protected from the external environment. MC 12, fixed on a dielectric base 6, is provided at the ends with cylindrical threaded protrusions 15, 16 and nuts 17 made of non-magnetic material. The threaded protrusion 15 is connected to ground with the nut 17, and the threaded protrusion 16 is connected with the nut 17 to the lower point of the surge arrester (SPD), which is connected, in turn, to the high-voltage line (not shown). MC 12 with a diameter (10-12) mm and a length of at least 100 mm is located at a distance (18-22) mm from the center of OAK 9. The length L ₀ OAK 9 and the angle α ₀ between the optical axes P 8 and A 10 are chosen so that The deviation from the temperature of the value of the Verdet constant ΔV / Δt will be compensated by the deviation from the temperature of the coefficient of intrinsic circular birefringence ΔΘ / Δt while ensuring the maximum modulation depth of the signal.

The device for measuring current operates as follows.

MC 7 of the calibrated sensor 1 is connected between the point of the lower flange of the arrester and the earthing point. Include IOI 2, for example, the visible and near infrared range, the radiation of which, when passing through P 8, is linearly polarized. When current passes through MS 12, linearly polarized radiation, when passing through OAK 9, experiences a rotation of the plane of polarization due to the Faraday effect and its own optical activity θа OAK 9. The radiation emerging from A10 is recorded by the FEC 11, the current value of which determines the amount of current passing through the MS 12. The electrical signal from FEP 11 enters U 2. The analog signal amplified in U 2 enters the ADC 3, where it is converted into a digital code, which can be stored and processed in K 4 and is presented on the LCD 5 by the result of measuring the electric current.

Example. A prototype device for measuring discharge currents through a surge arrester in the current range of 10 kA-100 kA was manufactured. Structurally, the device is installed in an enclosure. The dimensions of the sensor without the rod were (135 × 56 × 65) mm ³ . The optically active crystal was made from bismuth germanate (BGO). The choice of the crystal length of 4.7 mm with an aperture of (5 × 5) mm ² made it possible to simplify the assembly of the BGO crystal with a polarizer and an analyzer with dimensions (5 × 5 × 5) mm ³ without additional adjustment of the polarizer-analyzer system by choosing the operating point at zero magnetic field inside the crystal. The electrical components have been selected to minimize the power consumed by the device. The gain of the amplifier was about 10. The functions of the ADC and digital processing of the measuring signals are performed by a low-power microcontroller of the STM32L476RCT6 type manufactured by ST Microelectronics. The processor has a 32-bit Cortex-M4 core, 128KB built-in RAM and 1024KB flash memory. All components are powered by a linear NCP1117ST33 regulator from On Semiconductors. The speed of the device is up to 10 ^-7 s, the measurement accuracy is less than 5%.

The present current measuring device differs from the prototype device in increased accuracy.

Claims (8)

1. A device for measuring current, containing an optical current sensor, including an optical radiation source, a polarizer, a magneto-optical Faraday cell in the form of an optically active crystal, an analyzer and a photoelectric converter, in series with which an amplifier, an analog-to-digital converter, a microcontroller and a liquid crystal indicator are connected. in that the device includes a metal rod with a diameter of 10-12 mm and a length of at least 100 mm, a metal rod, a radiation source, a polarizer, an optically active crystal, an analyzer and a photoelectric converter are installed on a dielectric base, while the metal rod is installed vertically on the dielectric base, and its axis is spaced from the center of the optically active crystal by 18-22 mm. 2. A device according to claim 1, characterized in that the optically active crystal is based on a crystal with a sillenite structure. 3. The device according to claim 2, characterized in that the optically active crystal is made of Bi ₁₂ GeO ₂₀ . 4. A device according to claim 2, characterized in that the optically active crystal is made of Bi ₁₂ SiO ₂₀ . 5. The device according to claim 1, characterized in that the metal rod is made of copper. 6. The device according to claim 1, characterized in that the photoelectric converter is made in the form of a photodiode. 7. A device according to claim 1, characterized in that the radiation source, polarizer, optically active crystal, analyzer and photoelectric converter are enclosed in a dielectric housing. 8. The device according to claim. 7, characterized in that the dielectric body is made of plastic.

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