RU2648020C1 - Device for measuring ac voltage and voltage with galvanic distribution - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to electrical equipment for measuring (scaling) the values of alternating current and voltage. Device for measuring alternating current and voltage with galvanic isolation contains an electromagnetic current transformer, a current transformer with an air core or with a core of a ferromagnet with a concentrated or dispersed non-magnetic gap, an analog-to-digital converter with an optical output of the converted signal, power supply unit, optical glass fiber (fiber optic cable) or optical communication channel, power supply unit, digital-to-analog converter with optical input, voltage divider, output matching device with transformer galvanic isolation. To power the analog-to-digital converter, a photo converter, a light emitter and light guides, or a receiving coil together with a power transmission coil with a generator are used to create a resonance frequency.

EFFECT: extending the range of measured currents from zero to 40–60 times of the nominal range, simplifying the device, increasing reliability, the ability to operate the device as part of circuit protection systems against short-circuit currents.

1 cl, 2 dwg

Description

The invention relates to electrical equipment for measuring (scale conversion) of alternating current and voltage values, not suitable for measurement by standard electrical measuring instruments, to current and voltage values, respectively, suitable for measuring by standard electrical measuring instruments, and also for providing galvanic isolation between an electric circuit, which is measured, and output circuits.

As electrical equipment for measuring (large-scale conversion) of AC and voltage values, with galvanic isolation, classical electromagnetic current and voltage transformers are widely used today. Their descriptions can be found in the following sources:

1. Barzilovich V.M. High voltage current transformers. L .: Gosenergoizdat, 1962

2. Bachurin N.I. Current transformers. L .: "Energy", 1964

3. Vavin V.N. Current transformers. M .: "Energy", 1966

4. Vavin V.N. Voltage transformers and their secondary circuits. 2nd ed. - M .: "Energy", 1977

5. Current transformers / V.V. Afanasyev, N.M. Adonyev, V.M. Kibel et al. - 2nd ed., - L .: Energoatomizdat. Leningra. Sep., 1989

More modern electrical equipment for measuring (scale conversion) of AC and voltage and voltage and voltage is known as converters with current and voltage measurements based on the Faraday and Pockels effects, Hall. Converters are also known that convert current or voltage with primary high-precision sensors, located near the measured circuit, and in some cases having the same potential with it, with further conversion of the measured current or voltage into a magnetic, electromagnetic or optical signal, the distance between the transmitter and receiver signal serves as a galvanic isolation. This electrical equipment is known from the following sources:

6. Converter type NXVCT manufactured by NxtPhase T&D Corporation: http://pro-ln.ru/en/production_services/nxvct.html (link on the Internet).

7. Sensors of types NCS or ES manufactured by ABB: http://fmccgroup.ru/products/protecting_measuring/sensors (link on the Internet).

8. Golodolinsky GV Electro-optical methods and apparatus for measuring currents and voltages // "Electricity", 1963, No. 4, pp. 24-27.

9. Martsenyuk S.I. Optoelectronic current and voltage transformer // Energoekspert, 2012 No. 4 (44), pp. 42-45.

10. USSR author's certificate No. 099753 "Device for measuring electrical voltages in high-voltage networks", ed. Golodolinsky GV, priority 10.02.1953

11. USSR author's certificate No. 110607 "Device for measuring electrical voltages in high-voltage networks", ed. Golodolinsky G.V., priority 10.05.1956

12. RF patent for the invention No. 2166218 "Measuring current transformer."

13. RF patent for the invention No. 2171996 "Current sensor".

14. RF patent for the invention No. 2176799 "Method of non-contact digital measurement of current and device for its implementation."

15. RF patent for the invention No. 2222021 "Method for measuring alternating electric current or voltage and a device for its implementation."

16. RF patent for the invention No. 2223512 "Method of optoelectronic current measurement."

17. RF patent for the invention No. 2261450 "Method for measuring high voltage".

18. RF patent for the invention No. 2346285 "High-voltage optoelectronic device for measuring current."

19. RF patent for the invention No. 2365922 "Optoelectronic current sensor".

20. RF patent for the invention No. 2368906 "High-voltage digital device for measuring current."

21. RF patent for the invention No. 2371729 "Current and voltage sensor".

22. RF patent for the invention No. 2408891 "Device for measuring current in a high voltage network, a method of measuring alternating current."

23. RF patent for the invention No. 2437106 "Fiber-optic current sensor."

24. RF patent for the invention No. 2438138 "Fiber optic current transformer."

25. RF patent for the invention No. 2451941 "Fiber-optic measuring current transducer".

26. RF patent for the invention No. 2482502 "Device for measuring current in a high voltage circuit with remote transmission of information."

27. RF patent for the invention No. 2482503 "Device for measuring voltage in a high voltage circuit with remote transmission of information."

28. RF patent for the invention No. 2508554 "Combined electrical measuring device."

29. RF patent for the invention No. 2516034 "Device for measuring current and voltage in a high voltage network."

30. RF patent for the invention No. 2525581 "Electronic sensor of current and voltage at high potential."

31. RF patent for the invention No. 2531040 "Isolated current sensor."

32. RF patent for the invention No. 2555524 "Electronic current transformer."

33. RF patent for utility model No. 100284 "Device for measuring and processing electrical quantities in circuits with full galvanic isolation."

34. RF patent for utility model No. 166063 "Device for measuring current and voltage in a high-voltage network."

The closest in technical essence to the patented device should be considered the devices described in sources [9], [29], [33] and [34].

These devices contain a primary current transducer (in particular, an electromagnetic current transformer or a current shunt), a primary voltage transducer (in particular, a voltage divider), scaling the current and voltage to values suitable for processing by electronic circuits, with further signal coding by an analog-to-digital converter and transmitting it via optical communication channels (optical fibers) to digital-to-analog converters, with the subsequent issuance of an analogue scaled signal. The optical communication channel serves as galvanic isolation, and the current sensor (current transformer or current shunt), located directly next to the circuit in which the current is measured, together with digital processing and signal transmission guarantees the specified measurement accuracy (scale conversion). The power for operation of an analog-to-digital converter located on the potential side of the circuit in which the measurement is carried out is carried out using optical communication channels, with the conversion of the light flux into electric current using a photoconverter, or from a rapidly saturable current transformer working in conjunction with a power supply, or from a transformer operating from the current of a high voltage voltage divider.

The disadvantages of these devices are:

- a small range of measured currents - due to the presence of an electromagnetic current transformer operating as a primary converter, current measurement in a small specified range of currents is provided - as a rule, up to 120% of its rated current value. Transformers that provide large measuring ranges (up to 40-60 times of the nominal current value) cannot measure current with high accuracy at low current values (up to 120% of the nominal);

- the inability to work as devices for protection against short circuit currents (for devices according to the sources [29], [34]), due to the fact that for protection devices it is necessary to constantly be in operation - even with a prolonged absence of voltage and current in the circuit in which measurement is performed (scale transformation). The analog-to-digital converters and power supplies of the devices described in sources [29] and [34], with a long absence of current and voltage in the circuit, will not be able to quickly start and transmit the measured (scaled) signal about the current in the measured circuit;

- excessive complexity of the device - due to the presence of 2 analog-to-digital converters and 2 digital-to-analog converters located on the potential side of the circuit in which the measurement is made. In the case of analog-to-digital conversion of the voltage value at the potential of the circuit in which the measurement is carried out, there is a sense of such an isolation (device by source [29]), and in analog-digital conversion of voltage on the side of the measurement devices (device by source [34]), the meaning of double The conversion loses its meaning, adds an excessive error to the measurement (large-scale conversion) and makes the device unreliable due to its complexity. The presence of a rapidly saturable transformer and a power supply as a power source for an analog-to-digital converter without additional sources (device by source [34]) located on the potential side of the measured circuit limits the measurement of currents from scratch, since the fast saturable transformer also starts to work from a certain minimum current values.

The invention solves the problem of expanding the range of measured currents from zero to 40-60 times the nominal, simplifying the device, increasing its reliability and giving a new quality to the device — the ability to work as part of a circuit protection system against short circuit currents.

As an implementation, two versions of the new device are proposed for patenting. The layout of the new device, option 1, is shown in FIG. 1. The patented device contains (numbers in Fig. 1):

1 - electromagnetic current transformer for measuring (scale conversion) of the circuit current with high accuracy in the range up to 120% of the rated current;

2 - a current transformer with an air core (Rogowski belt) or with a ferromagnet core with a concentrated or dispersed non-magnetic gap for measuring (scale conversion) of current with high accuracy in the range from 1 to 60 of the rated current;

3 - analog-to-digital Converter with the optical output of the converted signal, for converting the current signal into a digital code and issuing it in the form of an optical signal;

4 - optical glass fiber (fiber optic cable) or optical communication channel to provide galvanic isolation;

5 - power supply to provide a stabilized voltage analog-to-digital Converter with optical output;

6 - a photoconverter for converting the light flux directed on the other side of the galvanic isolation into electrical energy and supplying it to the power supply;

7 - emitter of light flux, to create a light flux;

8 - optical fibers for transmitting the light flux to the potential side of the circuit in which the measurement is made, and creating a galvanic isolation;

9 - digital-to-analog converter with optical input;

10 - voltage divider;

11 - output matching device with transformer galvanic isolation.

Instead of a set of devices that transmit energy to power an analog-to-digital converter on the potential side of the circuit in which the measurement is performed (photoconverter 6, light emitter 7 and light guides for transmitting light flux 8), a no less efficient circuit with energy transfer through an alternating current can also be applied sinusoidal magnetic field of interconnected inductive coils tuned to resonance.

The device diagram, option 2, with energy transfer through an alternating sinusoidal magnetic field of interconnected inductive coils tuned to resonance, is shown in FIG. 2.

The device contains (numbers in Fig. 2):

1 - electromagnetic current transformer for measuring (scale conversion) of the circuit current with high accuracy in the range up to 120% of the rated current;

2 - a current transformer with an air core (Rogowski belt) or with a ferromagnet core with a concentrated or dispersed gap for measuring (scale conversion) of the circuit current with high accuracy in the range from 1 to 60 of the rated current;

3 - analog-to-digital Converter with the optical output of the converted signal to convert the current signal into a digital code and output it in the form of an optical signal;

4 - optical glass fiber (fiber optic cable) or optical communication channel to provide galvanic isolation;

5 - power supply to provide a stabilized voltage analog-to-digital Converter with optical output;

9 - digital-to-analog converter with optical input;

10 - voltage divider;

11 - device matching output with transformer galvanic isolation;

12 - receiving coil located on the potential of the circuit;

13 - power transmission coil located on the potential of the outputs;

14 - generator to create a resonant frequency at which the energy transfer system will work with maximum efficiency.

By introducing a current transformer and a current transformer with an air core (Rogowski belt) or with a ferromagnet core with a concentrated or dispersed gap for primary current conversion, it will be possible to measure (scale) currents in the normal range (from 1 to 120% of the nominal value) and currents short circuit (up to 40-60 times the nominal value), and the use of an energy transmission system through galvanic isolation (device option 1) or through an alternating magnetic field (device option 2), gives Device completely new quality - work as a primary sensor for the protection systems from short circuit currents. In addition, the elimination of one analog-to-digital and one digital-to-analog converters, a rapidly saturable transformer simplifies the device and thereby increases its reliability.

The patented device, option 1 and option 2 works as follows (Fig. 1 and Fig. 2). When the measured current flows through current transformer 1 and simultaneously through a current transformer with an air core 2, a large-scale current conversion occurs, the signal from the conversion is transmitted to an analog-to-digital converter with optical output 3. In analog-to-digital converter 3, the current scaling signal is converted to digital form and is converted into an optical form, and transmitted via optical glass fiber (fiber optic cable), or optical communication channel 4 to a digital-to-analog converter with optical Kim inlet 9, wherein the signal is received in an optical form, is converted into an electrical and decrypted, converted to analog form, identical to the original current signal with a particular scaling factor. The voltage is measured by a voltage divider 10, at the output of which there is a signal identical to the original voltage signal, with a certain scaling factor. For the voltage scaling coefficient to be unchanged depending on the load, an output matching device with transformer galvanic isolation 11 is introduced between the high-resistance voltage divider 10 and the output circuit, which is a high-precision analog voltage amplifier with a transformer output, whose input resistance is constant from the output load, which is not changes the resistance and capacitance of the lower arm of the voltage divider 10, and thereby ensures the stability of the scale factor voltage. The power of the analog-to-digital Converter with optical output 3 is carried out in two versions of the patented device in different ways.

In embodiment 1 of the device, the power is supplied from a power supply unit 5 with a photoconverter 6, which is a low-power solar battery, to which the light flux is directed through the light guides 8 from the light flux emitter 7, which is several super bright LEDs. The optical fibers 8 are made of non-conductive material, and thereby provide galvanic isolation of the power circuits and the circuit in which the measurement takes place. The source [9] describes the practical implementation of this method of energy transfer with positive results - to power an analog-to-digital converter, enough power over bright LEDs with a total power of 3 W, which is a worthy result.

In embodiment 2 of the device, the analog-to-digital converter 3 is powered from the power supply 5 with the receiving coil 12. In the coil 12, the voltage is induced by an alternating magnetic field created by the energy transfer coil 13 located on the potential of the output circuits. Due to the distance between the receiving coil 12 and the energy transfer coil 13, a galvanic isolation is created between the measurement circuit and the output circuits. Additionally, in order to transfer energy more efficiently, to power the energy transfer coil 13, a generator has been introduced into the energy transfer system to create a resonant frequency 14, at which the energy transfer system through the coils will operate with maximum efficiency.

As a result, a device was created that has a new quality - the ability to work as part of a circuit protection system against short-circuit currents, the range of measured currents has been expanded, the device is simpler and more reliable than analogs.

Claims (1)

An alternating current and voltage measuring device with galvanic isolation, containing an electromagnetic current transformer and an analog-to-digital converter on the potential of the circuit in which the measurement is made, a digital-to-analog converter on the side of the output circuits, a voltage divider, characterized in that it is used together with an electromagnetic current transformer current transformer with an air core, or with a ferromagnetic core with a concentrated or dispersed non-magnetic gap, and power supply a digital converter on the potential of the circuit in which the measurement is carried out, is either from a photoconverter receiving the light flux from the emitter of the light flux located on the side of the potential of the output circuits, or from a coil with an induced voltage located on the potential of the circuit in which the measurement is made, from alternating the magnetic field created by the coil located on the potential side of the output circuits, and the voltage measurement is performed by a voltage divider having low-voltage output leads and potential side output circuits connected between a voltage divider output and a high-precision analog voltage amplifier.

Images