WO2019160437A1

WO2019160437A1 - Combined current and voltage transformer

Info

Publication number: WO2019160437A1
Application number: PCT/RU2018/000102
Authority: WO
Inventors: Николай Иванович СТАРОСТИН; Александр Алексеевич СОКОЛОВСКИЙ; Алексей Александрович ДИКЕВИЧ; Максим Анатольевич ЯНИН; Петр Николаевич КУРОВИЧ
Original assignee: Общество с ограниченной ответственностью "Научно-Производственный центр "Профотек"; Акционерное общество "Профотек"
Priority date: 2018-02-16
Filing date: 2018-02-21
Publication date: 2019-08-22

Abstract

The technical solution relates to electrical engineering and can be used for commercial electrical power metering in high-voltage networks, for measuring electrical power quality, and in protection systems. A combined current and voltage transformer comprises a high-voltage tubular supporting insulator having a voltage divider, a current transformer, a measurement and conversion module, and a fiber optic communication link to a base unit, wherein the current transformer is a fiber loop made of an magnetosensitive optical fiber that encircles a current busbar, and the fiber optic communication link is laid in a pipe that is disposed inside of the high-voltage tubular supporting insulator, the end faces of said pipe being hermetically embedded in the upper and lower flanges of the high-voltage tubular supporting insulator. The technical result consists in increasing the reliability of a combined current and voltage transformer and increasing the precision of measurements.

Description

COMBINED CURRENT AND VOLTAGE TRANSFORMER

FIELD OF TECHNOLOGY

The technical solution relates to electrical engineering and can be used for commercial metering of electricity in high-voltage networks, measuring the quality of electricity and protection systems.

BACKGROUND

Known combined, that is, structurally implemented on the basis of a single high-voltage column, current and voltage transformers (CTN) based on traditional (inductive) current transformers and voltage transformers. Such transformers (EJOF, EJGF) are produced by many companies, for example, Pfiffner (http://www.pfiffner-group.com) Kopsag (www.koncar-mjt.hr), ABB, etc. The disadvantage of such combined transformers is:

• low accuracy of measurements in transient conditions associated with the inherent phenomenon of inductive transformers ferroresonance phenomenon, magnetization and core saturation

• small dynamic and frequency range of inductive transformers

• the need for galvanic isolation of a current transformer at high potential from recording devices at zero potential

• a large volume of insulating oil, which complicates the design of the transformer (large expansion bellows are required) and significantly increases the weight of the transformer (550-660 kg).

Also known is a combined single-phase device for measuring current, voltage and providing RF communications (RU 2337480 C1, publ. 10/27/2008)

This device relates to electrical engineering and can be used in measuring transformers of current, voltage and high-frequency and ultra-high voltage RF capacitors. A combined device for measuring current, voltage, and providing RF communications includes a high voltage capacitor, a high voltage unit with a current transformer and a transmitter under high voltage potential, a base unit with a receiver at zero potential, and the high voltage unit transmitter is connected to the receiver of the base unit through a high voltage capacitor and is galvanically connected to one of the high voltage bushings. A capacitor voltage transformer incorporates a high voltage capacitor, a high voltage unit with a current transformer and a transmitter that is completely at high voltage potential, and a base unit with a receiver that is at zero potential, while the transmitter is connected to the receiver using a high voltage capacitor, which serves as for HF communication, and for transmitting a signal about the magnitude of the measured current. The current value is measured on the high voltage side by a current transformer, the measured current value is converted by a transmitter located on the high voltage side into an encoded signal. The receiver converts the received encoded signal into a current value. To exclude the influence of current, voltage, and RF transformers on each other, each device uses a high-voltage capacitor in its frequency range. A high voltage voltage transformer operates at an industrial network frequency of 50 hertz, a range of 50-600 kilohertz is used for RF communications, and a current meter operates in the megahertz range. Thus, working at different frequencies, the three devices can use one high-voltage capacitor, while not interfering with each other. An independent power source is used to power the transmitter or the necessary power is transmitted from the base unit with a high-frequency signal via a high-voltage capacitor.

The disadvantage of this technical solution is the use of inductive transformers for measuring current, which are characterized by the disadvantages mentioned above. In addition, the disadvantage of this device is the transmitter power system, which, when using an autonomous power source, has a limited time resource, and when powered by a high-frequency signal, it will require a powerful RF signal generator.

Closest to the claimed device is a combined fiber-optic voltage and current transformer (RU 145064 U1, publ. 09/10/2014)

This combined fiber-optic voltage and current transformer contains a hollow insulating column with a voltage divider, a measuring and conversion module located at its high-voltage end connected to the sensor of the measured current and the basic signal processing module under zero potential. The measuring and conversion module is connected by a two-wire fiber optic line to the base module. The basic module is equipped with a data photodetector, an optical power transmitter and a network digital data transmitter, and the measurement and conversion module is equipped with an optical data transmitter and a photovoltaic power receiver. The measuring and converting module and the base module are connected by a two-channel fiber-optic line, through one channel of which the optical power necessary for powering the measuring and converting module is transmitted, and data on the measured current and voltage are transmitted through the other channel.

At the same time, a clock source is introduced into the base module, the output of which is connected to the optical power transmitter and the synchronization input of the network data transmitter, and the measurement and conversion module contains a clock generator, whose input is connected to the photovoltaic power receiver, and the output - to the start input of the measurement and conversion module .

The utility model has a refinement development, which consists in the fact that:

- the sensor of the measured current can be made in the form of a current transformer with a resistor load, a current shunt or Rogowski belt, loaded on an integrating circuit;

- the divider may be voltage resistive or capacitive;

- to the measuring-conversion module, an additional sensor of the measured current can be connected;

The disadvantage of this combined current / voltage transformer is the need to place electronic devices at high potential and provide them with power in ways that provide high-voltage galvanic isolation. Another disadvantage of this CTN is that the duplex fiber optic communication line runs inside a high voltage column that is filled with insulating oil. This requires quite sophisticated methods of sealing the internal volume of the column, which are not always effective when operating the CTN in a wide temperature range. The consequence of these disadvantages is the low accuracy of the measurement and the reliability of the device.

The claimed current and voltage transformer can significantly overcome these disadvantages inherent in both existing analogues and the prototype.

DISCLOSURE OF TECHNICAL SOLUTION

The technical problem that the proposed technical solution solves is the creation of a reliable and accurate current and voltage transformer.

The technical result consists in increasing the reliability of the combined current and voltage transformer with increasing measurement accuracy.

The technical result is achieved due to the fact that the combined current and voltage transformer contains a high voltage support tubular insulator with a voltage divider, a measured current sensor (current transformer), measuring and converting module, fiber-optic communication line with the base unit, while the current transformer is made in the form of a fiber circuit of a magnetically sensitive optical fiber covering the current bus, and the fiber-optic communication line is laid in a tube located inside the high-voltage supporting tubular insulator, the ends which is hermetically sealed in the upper and lower flanges of the high-voltage supporting tubular insulator.

The magnetically sensitive optical fiber is made in the form of a fiber with a built-in spiral structure of the axes of linear birefringence and a radiation reflector at the end.

The tube is made of an insulating material inert to oil.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 - General view of a combined current / voltage transformer;

Figure 2 is a sectional view of a combined current / voltage transformer.

IMPLEMENTATION OF THE TECHNICAL SOLUTION

The combined current and voltage transformer contains a high voltage support tubular insulator 1, on the upper flange of which a measured current sensor (current transformer) is installed, which is a fiber sensing element 3 covering the current bus 4 in a protective casing in the form of a loop of a magnetically sensitive optical fiber, capacitive (or resistive ) a voltage divider 2, located inside the high-voltage supporting tubular insulator 1, a fiber-optic communication line 6 with the base unit, passing through without a tube 5 of insulating material located inside the high-voltage supporting tubular insulator 1, the ends of which are hermetically sealed in the upper and lower flanges of the high-voltage supporting tubular insulator 1, the base (stand) 7 for accommodating the measuring-transducer module 8.

The use of a tube 5 of insulating material located inside a high-voltage supporting tubular insulator passing through a volume filled with oil, the ends of which are hermetically sealed in the upper and lower flanges of the high-voltage supporting tubular insulator 1, provides long-term protection of the fiber cable passing in this tube 5 from destructive exposure to the oil in which the capacitive divider is located, and also solves the problem of tight insulation of the cable input / output from the output of the magnetically sensitive fiber a contour of the internal volume of the high-voltage insulator filled with insulating oil, simplifying the sealing of the capacitive divider, increasing reliability of operation while maintaining high accuracy of measurement of the combined transformer. In addition, the presence of a tube reduces the required volume of insulating oil.

The tube 5 for the cable passing inside the tubular insulator can be made of the same material as the carrier tube of the insulator, for example, fiberglass. The tube can also be made of another material inert with respect to oil, for example, fluoroplastic. If the coefficients of thermal expansion of the carrier pipe of the insulator and the tube for the cable are different, the latter can be installed with an excess in length.

The use of an optical current transformer, which is a fiber sensitive element covering the current bus in the protective casing in the form of a loop of magnetically sensitive optical fiber, made it possible to ensure the reliability and accuracy of measurements. The optical current transformer does not contain a saturable core, and the range of the measured phase difference can be several orders of magnitude.

A magnetically sensitive optical fiber can be made in the form of a fiber with a built-in spiral structure of linear birefringence axes and a radiation reflector at the end, additionally providing the possibility of measuring with high accuracy and reliability of electric current in a wide range of operating conditions and the use of sensitive contours of reduced dimensions

Description of the combined current and voltage transformer.

The principle of measuring the current of a combined current and voltage transformer is based on two physical laws: the law of the total current and the Faraday effect. The device measures the current as follows. In the fiber circuit of a sensitive current element (magnetically sensitive optical fiber), two light waves are generated in the forward and reverse directions, formed at the input of the fiber circuit. The magnetic field of the measured electric current induces a phase shift between the light waves in the fiber circuit, which is directly proportional to the magnitude of the current (Faraday effect). The information signal from the circuit through the connecting fiber-optic communication line enters the base unit (electron-optical unit). Up to three multi-turn sensitive circuits (measuring and protective) can be in the casing of the fiber sensor. The fiber-optic communication line runs in a tube of insulating material inside the high-voltage column, which allows you to separate the volume filled with oil (in which the capacitive divider is located) and the transmission channel of the fiber-optic communication line. The base unit measures the phase shift, converts it to a current value, and outputs the measured current value in the form of digital data packets according to the IEC standard 61850-9-2 to secondary devices.

The principle of voltage measurement is based on the large-scale conversion (division) of AC voltage using a capacitive divider and its subsequent digitization of the ADC. Voltage measurement is carried out using a measuring and conversion module placed in the base of the tubular insulator of the capacitive divider and connected to its midpoint. The measuring and conversion module is connected by a duplex fiber cable to the base unit, contains an ADC, an FPGA for controlling a laser, and an optical transmitter based on a semiconductor laser. The device measures the voltage as follows. A high-voltage capacitive divider connected to an electric line reduces the measured voltage to a value compatible with the input of the analog-to-digital converter installed in the measuring-conversion module. The digital signal from the ADC output is fed to the optical transmitter and, then, via the fiber communication line to the electron-optical voltage measuring unit, which, similarly to the one described above, provides the measured voltage value in the form of digital data packets according to IEC 61850-9-2 to the secondary devices. The digital unit generating the output data packets is common to current and voltage.

Signal transmission from the sensitive element to the base unit can be carried out via a fiber optic cable at a distance of 20 to 1200 m, which allows you to place the electron-optical unit in a room with the required operating conditions.

To increase the electric strength of the capacitive divider, the capacitors of the divider are located in an oil bath through which a tube of insulating material passes, inside which the output optical cable of the fiber sensing element passes. The ends of the tube are hermetically sealed in the upper and lower flanges of the high-voltage column and separate the transport channel for the fiber from the volume filled with oil.

The base unit of the combined transformer can have a built-in self-diagnosis system that allows real-time assessment of the state of the main elements that affect the metrological characteristics. Diagnostic results are displayed on the display screen of the device, indicator lights and serial port for remote online monitoring of diagnostic data.

By combining in one device a fiber-optic current transformer and a capacitive voltage divider, the implementation of an optical current transformer based on the Faraday effect with a fiber circuit covering a conductor with a measured current and thereby eliminating the metal windings of classical current transformers and voltage transformers, onto which electrodynamic forces act in the process of short circuit, which can lead to the destruction of structures due to the location of the fiber-optic communication line in a hermetically sealed insulating tube inside the high-voltage insulator, which separates the volume occupied by the oil in which the capacitive divider is located, and the passage of the fiber path, it is possible to measure electric current in a non-contact way, increases the accuracy of measurement, provides the possibility of reliable sealing of the volume, in which contains an oil-filled capacitive (or resistive) divider, which increases the accuracy of measurements and the reliability of the current transformer and voltage in general, and also increases the safety of maintenance.

Claims

CLAIM

1. A combined current and voltage transformer containing a high voltage support tubular insulator with a voltage divider, a current transformer, a measuring and converting module, a fiber optic communication line with a base unit, characterized in that the current transformer is made in the form of a fiber circuit from a magnetically sensitive optical fiber, covering the current bus, and the fiber-optic communication line is laid in a tube located inside the high-voltage supporting tubular insulator, the ends of which are adic embedded in the upper and lower flanges of the tubular support high voltage insulator.

2. The combined current and voltage transformer according to claim 1, characterized in that the magnetically sensitive optical fiber is made in the form of a fiber with a built-in spiral structure of linear birefringence axes and a radiation reflector at the end.

3. The combined current and voltage transformer according to claim 1, characterized in that the tube is made of an insulating material inert with respect to oil.