RU2804266C1 - Multichannel distributed sensor for monitoring location of lightning strike in ground wire of power transmission line - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to devices for real-time monitoring of the location of lightning strikes in the ground wire of power lines. The device comprises a source (1) of polarized optical radiation, a bidirectional optical communication channel (2), a computer (3), a device (4) for receiving and measuring optical radiation parameters, an optical splitter (9), an output optical amplifier (10), an input optical amplifier (11). The device (4) for receiving and measuring optical radiation parameters comprises a balanced photodetector (12), a bandpass amplifier (13), a frequency detector (14), an analogue-to-digital converter (15), a signal processing unit (16) and a threshold device (17). The bidirectional optical communication channel (2) includes optical fibres (5) connected on one side by a reverse loop (8), and on the other side forming the input (6) and output (7) of optical radiation.

EFFECT: expanding the range of measured values.

1 cl, 1 dwg

Description

The invention relates to devices for distributed monitoring in real time of the location of lightning strikes in the ground wire of power lines. The length of power lines can be hundreds and even thousands of kilometers, for example, for lines with a voltage of 220 kV, the distance between supports (spans) reaches 400 meters, and power lines can be located in hard-to-reach areas. It is known that high-voltage power lines are equipped with lightning protection systems. For overhead power lines to protect against lightning strikes, it is typical to use lightning cables stretched between the supports. One of the passport parameters characterizing a lightning cable is the maximum current that it can withstand without destruction for a certain time. Structurally, specially designed lightning cables consist of individual metal conductors twisted in a certain way and are equipped with optical fiber, which serves to transmit information. The design of such ground wires can be viewed on the websites of manufacturers of ground wires with optical fiber, for example, an OPGT type cable manufactured by Incab (Incab.ru), [Electronic resource]. - Access mode: https://incab.ru/useful-information/ documents/#doc_0, free entry - (06/07/2023).

A lightning strike into a ground wire causes current to flow through it, which, if the current exceeds the rated value, can lead to its damage - melting of part of the conductors and, as a result, permissible currents. Possible damage to a lightning cable with optical fiber from a lightning strike is discussed in detail on the website of the Alfa EMS company (Alfa EMS (alfa-ems.ru) [Electronic resource] in the Information section - Lightning protection cable with optical fiber. Thermal resistance to direct lightning strike. - Access mode : https://alfa-ems.ru/info/grozozashhimyiy-tros-s-opticheskim-voloknom, free admission - (06/07/2023).

An urgent task is to determine the location of damage to the ground wire when it is struck by lightning. Determining the possible location of damage to the ground wire is based on the Faraday effect, which consists of changing the polarization of the light flux in an optical fiber under the influence of a magnetic field when a current begins to flow in the ground wire, creating a strong longitudinal magnetic field. A lightning strike is characterized by a rapid increase in current, which, in turn, leads to a rapid rotation of the polarization vector of the optical signal. In the sources (see, for example, the website of the ELKON company, [Electronic resource]. - Access mode: http://electro-control.ru/info/5l-priroda-molnii-grozozashchita.html, free admission - (06/07/2023 ) the stages of development of a lightning discharge and the parameters characterizing a lightning discharge are described. For example, the recorded amplitude values of the lightning current in the ground wire can reach 200...300 kA with the front duration of the lightning current pulse from fractions of a microsecond to several tens of microseconds.

The LM-S lightning current monitoring system is known, designed for recording and analyzing lightning strikes in real time (NEW TECHNOLOGIES (www.phoenix.nt-rt.ru), [Electronic resource]. - Access mode: https://phoenix.nt -rt.ru/images/manuals/zashita_molnii_lms.pdf, free entry - (05/17/2023) This system is focused on recording lightning currents for structures located in an open unprotected area, such as: wind farms in coastal areas, radio towers, complexes recreation or tall buildings. It transmits data on the impact force online, based on typical lightning parameters. Due to data on the operating parameters of the equipment and the measurements taken, the system provides the ability to find the optimal solution for performing inspection and maintenance tasks. The disadvantage of such a system is the fact that it is essentially intended for installation at one site and is practically not suitable for long power lines.

The “System, method and device for detecting the location of lightning” is known (RF patent No. 2662457 C1, published on July 26, 2018). The lightning detection system includes a lightning location detection database and an analysis unit configured to receive, from a plurality of portable communication devices over a communication network, data indicating the locations of the portable communication devices and distances between the lightning strike and the portable communication devices; detecting the location of the lightning strike based in part on data indicating distances from the lightning strike to the locations of the portable communications devices and storing the location of the lightning strike in a lightning location detection database. The known technical solution has low accuracy and does not allow determining the fact and location of a lightning strike from a lightning strike into a ground wire, which makes the use of such a system problematic for long power lines.

The closest to the claimed technical solution - the prototype - is a multi-channel distributed sensor for monitoring the location of a lightning strike in the ground wire of a power line, containing a source of polarized optical radiation, a device functionally connected to a computer for receiving and measuring the parameters of optical radiation, and two mutually parallel optical fibers placed in the ground wire, combined on one side, a reverse loop with the formation of a forward and reverse channel, and on the other side, forming the input and output of optical radiation, respectively (Optica Publishing Group, [Electronic resource]. - Access mode: https://opg.optica.org/oe/fulltext .cfm?uri=oe-25-9-9689&id=363200, free entry - (06/06/2023). The prototype allows you to detect the location of the transient process of the state of polarization of the optical process (SOP) along the cable path. Thanks to the reverse loop, each transient process of the SOP is registered , as a pair of transient processes (one from each direction of propagation), which allows you to determine the place or multiple places (which essentially makes the sensor multichannel) of the occurrence of the transient process. In the prototype, transients are recorded by a Novoptel PM-500 polarimeter, which samples the Stokes vector at a rate of 100 MHz with an analog Stokes parameter bandwidth of 35 MHz. The longest arc that can occur between any two Stokes vector samples for a finite volume sample must have a length less than or equal to π, which limits the maximum measurable angular velocity of rotation of the polarization vector to 19.6 Mrad/s. Thus, the prototype has a limited area application, since it has a limitation of the maximum measurable angular velocity of 19.6 Mrad/s, which does not allow recording changes in the angular velocity of rotation of the polarization vector exceeding this value by large values of currents arising in the ground wire when a lightning discharge hits it, which can cause its mechanical damage due to fast local heating.

Thus, the identified problem is ensuring the possibility of estimating large values of currents in the ground wire when it is hit by lightning discharges, characteristic of values of the angular velocity of rotation of the polarization vector above 19.6 Mrad/s.

The technical result is an increase in the technological capabilities of a multi-channel distributed sensor for monitoring the location of a lightning strike in a power line ground wire by expanding the measurement range.

The problem is solved, and the claimed technical result is achieved by the fact that a multi-channel distributed sensor for monitoring the location of a lightning strike in the ground wire of a power line, containing a source of polarized optical radiation, a device for receiving and measuring the parameters of optical radiation functionally connected to a computer, and two mutually parallel optical fibers placed in the ground wire, combined on one side by a return loop to form a forward and reverse channel, and on the other side forming, respectively, the input and output of optical radiation, equipped with a polarization-preserving optical splitter, and the device for receiving and measuring the parameters of optical radiation is made in the form of a functionally interconnected balanced photodetector, a bandpass amplifier, frequency detector, analog-to-digital converter, threshold device and signal processing unit, wherein the output of the optical radiation of the reverse channel is connected to the signal input of the balanced photodetector, the output of the balanced photodetector is connected through a series-connected bandpass amplifier and frequency detector to the information inputs of the analog-to-digital converter and a threshold device, the information outputs and control inputs of which are connected to the corresponding inputs and outputs of the signal processing unit, the output of which is connected to a computer, and the output of the source of polarized optical radiation is connected to the input of a polarization-preserving optical splitter, the first output of which is connected to the input of the optical radiation of the direct channel, and the second output is connected to the heterodyne input of the balanced photodetector.

The invention is illustrated by an image that schematically represents the claimed multi-channel distributed sensor for monitoring the location of a lightning strike in a power line ground wire.

The digital positions in the presented image mean the following:

1 - source of polarized optical radiation;

2 - bidirectional optical communication channel;

3 - computer;

4 - device for receiving and measuring parameters of optical radiation;

5 - optical fiber;

6 - optical radiation input;

7 - optical radiation output;

8 - reverse loop;

9 - optical splitter that maintains polarization;

10 - output optical amplifier;

11 - input optical amplifier;

12 - balanced photodetector;

13 - bandpass amplifier;

14 - frequency detector;

15 - analog-to-digital converter;

16 - signal processing unit;

17 - threshold device.

The claimed multi-channel distributed sensor for monitoring the location of a lightning strike in the ground wire of a power line (hereinafter also referred to simply as the “sensor”) contains a source of polarized optical radiation 1, a device for receiving and measuring the parameters of optical radiation 4, functionally connected to a computer 3, and two mutually parallel located in the ground wire optical fibers 5 (the specified optical fibers 5 must be part of the bidirectional optical communication channel 2 placed in the lightning cable) and, combined on one side by a reverse loop 8 to form a forward and reverse channel, and on the other side forming, respectively, the input 6 and output 7 of optical radiation (for coordination of the levels of optical signals of the bidirectional optical communication channel 2 with the device for receiving and measuring parameters of optical radiation 4, it is advisable to provide for the presence of output 10 and input 11 optical amplifiers). The sensor is equipped with a polarization-preserving optical splitter 9. The device for receiving and measuring parameters of optical radiation 4 is made in the form of a functionally interconnected balanced photodetector 12, a bandpass amplifier 13, a frequency detector 14, an analog-to-digital converter 15, a threshold device 17 and a signal processing unit 16. The output 7 of the optical radiation of the return channel (through the input optical amplifier 11) is connected to the signal input of the balanced photodetector 12, the output of the balanced photodetector 12 through a series-connected bandpass amplifier 13 and the frequency detector 14 is connected to the information inputs of the analog-to-digital converter 15 and the threshold device 17, information the outputs and control inputs of which are connected to the corresponding inputs and outputs of the signal processing unit 16, the output of which is connected to the computer 3, and the output of the source of polarized optical radiation 1 is connected to the input of the polarization-preserving optical splitter 9, the first output of which is connected (via an output optical amplifier 10) with input 6 of optical radiation of the direct channel, and the second output is connected to the heterodyne input of balanced photodetector 12.

The sensor, whose operation is based on the Faraday effect, which consists in changing the polarization of the light flux under the influence of a magnetic field, works as follows. The optical radiation of the polarized radiation source 1, passing through the polarization-preserving optical splitter 9, arrives at the input 6 of the bidirectional optical communication channel 2 (hereinafter referred to as communication channel 2). Communication channel 2 is located in a ground wire equipped with standard single-mode fiber 5 (for example, G.652). The optical radiation of the polarized radiation source 1, having passed through the optical fiber 5 in the forward direction, is looped through the reverse loop 8 and propagates in the opposite direction. The length of a bidirectional optical communication channel 2 can be hundreds or even thousands of kilometers. Bidirectional optical communication channel 2 contains optical amplifiers, such as in the considered prototype (the configuration of communication channel 2 is not considered, since it is not the subject of the present invention). It is necessary that the fibers 5 of forward and backward propagation of optical radiation be structurally placed in the ground wire of the bidirectional optical communication channel 2 in close proximity to each other (placed in parallel), which is ensured by the design of the cable. As a result of a lightning strike into a lightning cable, a rapid increase in current occurs in it in a very short time from fractions to units of microseconds. The current creates a strong magnetic field, which causes rotation of the polarization vector. The rotation speed of the polarization vector of optical radiation can reach 200 Mrad/sec or more. At the output 7 of the bidirectional communication channel 2, as discussed in the prototype, first a signal appears, propagating in the opposite direction and characterizing a lightning strike, and then a signal appears, traveling in the forward and reverse directions. The optical radiation passed through the bidirectional communication channel 2 enters the device for receiving and measuring the parameters of optical radiation 4, in which the rotation speed of the polarization vector of the optical radiation passing through the bidirectional communication channel 2 is analyzed. The principle based on on heterodyne reception of optical radiation with direct frequency conversion (transfer to the “zero” frequency) and subsequent analysis of the electrical signals obtained as a result of the conversion. This implementation of a device for receiving and measuring the parameters of optical radiation, instead of the polarimeter used in the prototype, makes it possible to record (as shown by the experiments described below) significantly higher rotation rates of the polarization vector, and in the stated totality, significantly higher values of lightning discharge currents affecting the lightning rod.

Optical radiation from output 7 of communication channel 2 is supplied (via amplifier 11) to the signal input of the balanced photodetector 12 of the device for receiving and measuring the parameters of optical radiation 4, and the heterodyne input of the balanced photodetector 12 receives optical radiation from the polarized radiation source 1 from the second output, which maintains the polarization of the optical splitter 9. During operation, an alternating signal is present at the output of the balanced photodetector 12, caused by the difference in frequencies at its inputs, due to the mismatch between the instantaneous frequency of the optical radiation source 1 and the frequency of the optical radiation passing through the communication channel 2. Also, the polarization state of the optical radiation passing through the channel connection 2 changes under the influence of external factors (such as temperature, vibration and others). Under these “quiet” conditions, in the absence of lightning strikes, there is an “interfering” signal at the output of the balanced photodetector 12, the frequency of which usually does not exceed kilohertz. In essence, these rotation frequencies of the polarization vector reflect a certain natural background state of the line - in our case - interfering signals. Next, the alternating signal from the output of the balanced photodetector 12 is supplied to the input of the bandpass amplifier 13, in which selective amplification and limitation of the signal occurs. The frequency range of the bandpass amplifier 13 is determined based on the rejection of interfering signals and the need to isolate possible frequencies of rotation of the polarization vector caused by a lightning strike into the ground wire. Limiting the signal is necessary in order to eliminate the influence of amplitude changes in the signal during subsequent processing on the result of detecting the rotation frequencies of the polarization vector, which characterize a lightning strike into a ground wire. As a result of a lightning strike, a high-frequency alternating signal is received from the output of the bandpass amplifier 13 to the input of the frequency detector 14, which, as a result of detection at its output, is converted into a unipolar signal, the magnitude of which is proportional to the frequency value at its input. This signal, being properly calibrated, fully reflects the nature of the rate of increase in the change in current flowing through the ground wire and the assessment of the current value; the higher the rotation speed of the polarization vector, the greater the current value. The signal from the output of the frequency detector 14 is supplied to the information inputs of the analog-to-digital converter 15 and the threshold device 17. In the analog-to-digital converter 15, the unipolar signal from the output of the frequency detector 14 is converted into a digital code, which is supplied to the first information input of the signal processing unit 16, the second information input of which receives a signal from the information output of the threshold device 17 indicating that the current in the ground wire exceeds the permissible value. The first control output of the signal processing unit 16, connected to the control input of the analog-to-digital converter 15, ensures mutual synchronization of their operation, its second control output sets the threshold of the threshold device 17. The signal processing unit 16 ensures mutual synchronization, pre-processing and transmission of the received data over the communication channel information to computer 3. Computer 3 also sets the initial data via the communication channel to configure the operating mode of the signal processing unit 16.

An example of the implementation of the proposed sensor. The performance of the claimed sensor was assessed by the method of semi-natural modeling of the claimed technical solution in order to confirm the possibility of estimating the rotation of the polarization vector with angular rotation frequencies exceeding 19.6 Mrad/s. In the experimental bench, laser radiation, as in the prototype, was created using an unmodulated Ciena transponder with a performance of 10G, which through polarization-preserving optical splitter 9, for example, type RMTS-15-RM-TAR, was fed to the input of the simulator of communication channel 2, consisting of two sections of fiber, each 10 kilometers long, between which a Novoptel EPC1000 scrambler was connected, allowing to change the optical polarization at a speed of up to 50 Mrad/s. Using a scrambler, a lightning “strike” was simulated by creating a rotation of the polarization vector of optical radiation propagating in the optical line. By changing the speed of rotation of the polarization vector over time, it is possible to simulate a standard pulse of lightning voltage currents (tests are regulated by GOST 1516.2-76). The output of communication channel 2 was connected to the input of balanced photodetector 12, the heterodyne input of which was supplied with optical radiation from laser radiation source 1 (transponder) from the output of optical splitter 9. As a balanced detector 12, a balanced photodetector of the LSM-DET-BHS-W1-150M type with a bandwidth of up to 150 MHz was used. A two-stage bandpass amplifier with a bandpass filter with cutoff frequencies of 1 MHz and 150 MHz connected between the stages. High-speed operational amplifier microcircuits of type K1432UD11/12 were used as amplification elements. The total transmission coefficient was chosen in such a way as to ensure limitation of the signal in the passband. As a frequency detector 14, a standard solution was used that implements the principle of digital frequency detection and makes it possible to obtain an almost linear dependence of the output voltage on frequency in the range of input frequencies that interests us (see, for example, Digital frequency detector. [Electronic resource]. - Access mode: https://vikidalka.ru/2-118561.html?ysclid=li30yti4qf196676859 (07.062023). The threshold device 17 is implemented on a high-speed operational amplifier, for example, type K1432UD6. The basis for the implementation of the analog-to-digital converter 15 is a microcircuit of the AD9265BCPZ-125 type, operating with a conversion frequency of 100 MHz, which, in accordance with Kotelnikov's theorem, allows converting frequencies up to 50 MHz. The signal processing unit 16 is implemented on the basis of programmable matrices, for example, the FPGA ICE40HX8K type. In the process of testing the proposed technical solution, rotation was carried out using a Novoptel EPC1000 scrambler polarization vector with speeds of 10 Mrad/s, 20 Mrad/s, 30 Mrad/s and 40 Mrad/s. The proposed technical solution made it possible to record these values.

Thus, the foregoing allows us to conclude that the identified problem - ensuring the possibility of assessing large values of currents in a ground wire when a lightning discharge hits it, characteristic for values of the angular velocity of rotation of the polarization vector over 19.6 Mrad/s - has been solved, and the declared technical The result - increasing the technological capabilities of a multi-channel distributed sensor for monitoring the location of a lightning strike in a power line ground wire by expanding the measurement range - has been achieved.

Claims (1)

Multi-channel distributed sensor for monitoring the location of a lightning strike into a power line ground wire, containing a source of polarized optical radiation, a device functionally connected to a computer for receiving and measuring optical radiation parameters, and two mutually parallel optical fibers placed in the ground wire, connected on one side by a return loop to form a forward and return channel , and on the other side forming, respectively, the input and output of optical radiation, characterized in that it is equipped with a polarization-preserving optical splitter, and the device for receiving and measuring the parameters of optical radiation is made in the form of a functionally interconnected balanced photodetector, a bandpass amplifier, a frequency detector, an analogue a digital converter, a threshold device and a signal processing unit, wherein the output of the optical radiation of the return channel is connected to the signal input of the balanced photodetector, the output of the balanced photodetector is connected through a series-connected bandpass amplifier and frequency detector to the information inputs of the analog-to-digital converter and the threshold device, information outputs and control the inputs of which are connected to the corresponding inputs and outputs of the signal processing unit, the output of which is connected to the computer, and the output of the source of polarized optical radiation is connected to the input of a polarization-preserving optical splitter, the first output of which is connected to the input of the optical radiation of the direct channel, and the second output is connected to the heterodyne input balanced photodetector.

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