RU2474831C1 - Method to detect area of power transmission and communication lines damage and device for its realisation - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: method consists in sending probing voltage pulses into a line, reception of reflected signals and determination of a distance to irregularities and areas of line damage by time delays of reflected pulses relative to probing ones. Probing is carried out at two opposite ends of line sections in turns. Information on distances to irregularities is sent to a single centre. The damaged section is determined by comparison of produced and stored information from one source. Confirmed distance to the area of section damage is calculated on the basis of data received from its both ends. Sequence of sending and receiving pulses, and also transfer of information into a single centre is synchronised by sync packages received from this centre. For this purpose the device is equipped with a subunit of sync packages decoding.

EFFECT: unambiguity and high accuracy for detection of damage areas in non-uniform branched lines of arbitrary configuration, automation of line diagnostics process, reduced time for damage detection.

6 cl, 9 dwg

Description

The group of inventions relates to electrical engineering and diagnostic tools and can be used to determine the distance to the places of damage to power lines and communications, in particular for branched power cable lines of arbitrary configuration.

To improve the quality of customer service, particular importance is the speed, accuracy and unambiguity of determining the location of damage, especially when visual inspection of lines is difficult or impossible, for example, with underground dislocation of communication or power cables.

A known method of determining the distance to the place of damage in the distribution power networks [1], which is based on measuring the time between the moment of sending a probe electric pulse to the line and the moment of arrival of the pulse line reflected from the place of damage at the beginning. Sending an impulse to the line, measure the interval Δt - the double travel time of this impulse to the place of damage. The distance to the place of damage is found as L = V · Δt / 2, where V is the pulse propagation velocity along the line. (To ensure the integrity of the presentation, the following notation is used in the following text: L is the line length, the length of the line section, Lx is the distance to the place of damage, Δt is the time interval between sending the probing signal and returning the reflected signal, τ is the duration of the probing signal, V is the propagation velocity electromagnetic wave in this section of the line, δ is the measurement error, q is the signal-to-noise ratio, T _s is the signal delay time, A is the amplitude.)

Currently, the location-based method for determining the location of damage to power lines and communications is the most common [2]. Continuous improvement over several decades of this method, in relation to isolated lines, made it possible to achieve location accuracy unattainable by other methods (see, for example, patents RU 2269789 C1, RU 2398244 C2, class G01R 31/11). The disadvantages of these methods is that they are applicable only to unbranched lines; for branched lines of complex topology, the accuracy of these methods is insufficient.

For such lines, the determination of the location of damage is significantly more complicated. In this case, a simple location does not give an unambiguous indication of the branch in which the damaged area is located (localization of the place of damage), since all responses to the probing effect are formed on a single time (or frequency) axis without separation along the branches. For such lines, modifications of the location method are used, which make it possible to judge with some certainty the location of the damage.

A known method for determining the presence of damage to cable systems with a branched topology, based on the use of reflectometry data (see Soraghan JJ et al., Automatic fault location in cabling systems. Patent US No .: 6385561 Bl, Int. Cl ⁶ : G01M 11/00, G01R 31/11; Date 05/07/2002).

This method compares a composite signal reflected from inhomogeneities in an intact cable with a similar signal in a damaged one. The accuracy of the OTDR interpretation is improved by using a priori information about the network topology and responses in the intact state. Based on these a priori data, adaptive filtering and sequential comparison of the composite reflected signal are carried out.

The disadvantage of this method is that only by changing the responses to the probing signals it is impossible to eliminate the localization ambiguity in lines with an arbitrary topology and, as a result, the accuracy of the method will be low in cases of constant switching of loads and branches.

There is also a method of determining the location of damage in networks with a branched topology (Patent RU 2386974 C1; CL G01R 31/11; publ. 04/20/2010), in which the master device performs a preliminary collection of information about the integrity of the sections of the controlled network, sending slaves over the same network, an encoded information message (scanning marker or "CM frame"), which, in turn, change in a certain way the contents of the information field of the CM frame and passes it to the next slave in the link, up to the ends on the slave link or to the first damaged network section. Based on the information received by the master device after the CM frame is returned to it, a conclusion is made about the serviceability or malfunction of a particular part of the network and its pulse sensing is carried out. According to the data obtained, a conclusion is made about the localization of the fault area and the distance to the place of damage is calculated.

This method is applicable to a network with homogeneous, perfectly coordinated at the boundaries of the sections, the lengths of which L are significantly greater than half the product of the duration τ of the transmitted information message (SM) by the speed of its propagation V across the section:

moreover, the same restriction also applies to the distance to the heterogeneity of the line section closest to the transmitter.

If this condition is violated, then the frame of the information message at the entrance to the receiving device, reflected from any heterogeneity, or from the boundaries of the section, can add up to itself, which will lead to distortion of the information transmitted in the information message, up to its complete destruction. Even the advanced methods of modulating the signal and the methods of its input filtering do not protect against distortion of the transmitted information resulting from the addition of two (or more) identical frames with an arbitrary temporal shift of the latter.

The real line of the distribution network consists of many different types of air and / or cable sections (sections), that is, significantly heterogeneous, and the lengths of the network sections can be less than in the specified restriction. The signal propagating along the lines is strongly distorted at the inhomogeneities associated with the taps and loads of the lines, as well as the presence of couplings along the route. Moreover, each heterogeneity gives rise to multiple reflections of the sent informational message, which makes decrypting this message doubtful, and sometimes completely impossible.

Thus, the disadvantages of this method include the fact that in relation to real lines of arbitrary configuration, this method can lead to incorrect identification of the damaged area or not to identify it at all.

The closest in technical essence to the claimed solution, the known method for determining the location of damage to power lines and communications and a device for its implementation (Patent RU 2400765 C2, class G01R 31/11, publ. 09/27/2010), adopted in this application for the prototype .

The method consists in sending voltage probes with time-frequency modulation to the line, receiving the reflected pulses and measuring the time delays of the reflected pulses relative to the probing ones. At the same time, an array of demodulated reflected signals received from the undamaged line is recorded in the form of an electronic image of the line. Carry out autocorrelation processing, spectral analysis and determine the frequencies corresponding to the pulses reflected from natural inhomogeneities. The values of the frequencies and the corresponding distances to the natural inhomogeneities are recorded in the form of reference points. To detect damage, the reflected demodulated pulses from natural inhomogeneities and heterogeneity arising from damage to the line are subtracted from the lines recorded in the electronic image. The conclusion about the damage to the line is made in the presence of differential signals. The difference signal is subjected to autocorrelation processing and spectral analysis and the frequency corresponding to the damage coordinate is determined, and the distance to the damage site is determined by this frequency and reference points. Measurements of the time delays of the reflected signals are based on the frequency shift of the reflected signal relative to the reference. The method provides for the transfer of information about the damage and the distance to it in the dispatch center.

The main advantage of this method, which predetermined its choice as a prototype, is the presence of cyclic sensing operations on an undamaged line, storage and continuous updating of line images, as well as comparing the received image with the stored one, with the subsequent identification of significant differences in this case when damage occurs. The transfer of the received data to the control room implies the possibility of their subsequent analysis on the computer of the site and surgical intervention to restore the operability of the line.

The main disadvantages of this method, as well as previously discussed, include difficulties in unambiguously determining the damaged section of a branched line in the presence of parallel sections in it, that is, the accuracy of localizing the malfunction and determining the distance to damage with respect to branched lines in this method is insufficient. (The authors of the method use the term “branched lines” in the description, but they use this term in the sense of lines with branches, and malfunctions of the branches themselves are completely excluded from consideration.)

Other disadvantages of this method include:

The limited application (as well as the method according to patent RU 2386974) is where the doubled travel time in the area with heterogeneities of the sent signal is comparable with its duration. The use of linear time-frequency modulation involves the use of a probe pulse of considerable duration and therefore, in uncoordinated sections of a length shorter than that specified in restriction (1), the ambiguity in determining the distance to the damage that has arisen is lost.

We illustrate this statement. The time interval between the probe and reflected signal in this method is determined indirectly by measuring their frequency shift. In case of violation of condition (1), at the input of the receiver there will be simultaneously signals reflected from at least two inhomogeneities - from the existing natural and from the resulting line damage. In this case, the difference frequencies will arise not only in the interaction of reflections with the reference signal, but also due to the interaction of the reflected signals with each other, that is, in the short section with inhomogeneities when damage occurs, not one additional difference frequency occurs, but a whole spectrum of these frequencies. Moreover, additional frequencies, depending on the relationship between the natural and the arising inhomogeneities, can be located on the frequency response of the site both further and closer to the origin, than the frequency corresponding to the damage. The values of the additional frequencies are a difference function of the distances to the damage and to the reference points and are therefore not known in advance. And since the image of the site is built on the basis of the amplitude-frequency characteristics and there is no explicit time parameter in it, it seems difficult to judge which signal came earlier, in this case. Therefore, the difference frequency resulting from the interaction of two reflections and located, for example, closer to the origin along the frequency axis, can be taken as the damage frequency.

Thus, if this condition is violated, a situation is possible when the distance to damage by the prototype method will be determined inaccurately, which limits its use in heterogeneous lines with sections of small length, which, as already mentioned, include power distribution cable lines.

In addition, lines of this kind have a relatively narrow bandwidth (of the order of 2 MHz), which also seriously limits the possibility of using a signal with time-frequency modulation.

There is another problem, the solution of which is difficult when using time-frequency modulation of the probe signal. When probing a “hot” (that is, energized) damaged line, a situation cannot occur that an arc discharge may occur at the site of damage, which, together with the reactivity of the line itself, can generate frequencies from the range of the same sounding signal [3]. These frequencies are unpredictable in spectrum. Having reached the receiver, they will “smear” the entire spectral picture of the line segment, not matching the previously recorded frequency image of the undamaged line, located on the frequency axis not only after, but also to the actual location of the frequency of the damage site. This will lead to incorrect analysis and unpredictable results when calculating the distance to the place of damage to the line.

In other words, the use of this method for lines under operating voltage limits the ability to identify certain types of damage, limiting or completely eliminating damage in the form of short circuits, which negatively affects the accuracy of determining the location of damage to the line.

A device is known for implementing the known method (Patent RU 2269789 C1, class G01R 31/11, publ. 2006), which comprises interconnected probe pulses, a computing unit, a receiver, and an indication unit. In this case, the probe pulse generator has a memory unit, a digital-to-analog converter (DAC) and a power amplifier, and the receiver contains a mixer, a low-pass filter, and an analog-to-digital converter.

This device has insufficient ambiguity and accuracy in determining the location of damage to branched lines of complex topology.

There is also known a device for implementing the known method for determining the location of damage to power lines and communications (patent RU 2400765 C2, class G01R 31/11, publ. September 27, 2010), which contains a probe pulse generator, a computing unit comprising a processor , a receiver equipped with an analog-to-digital converter, a switch, a directional coupler and an information transmission unit, the input of which is connected to the output of the computing unit.

Its main drawback is the lack of synchronization and the ability to control the device from the control center, which is the center for analysis and processing of incoming information about the operation of the line and related systems. This disadvantage leads to the autonomous operation of the device, which cannot be remotely affected in an emergency. Therefore, the efficiency and reliability of the received data on damage is reduced, up to a long neglect of the fact of its occurrence, if the frequency of sensing the line given to the device is insufficient.

The lack of synchronization from a single center does not allow the use of two or multilateral sounding, which in the conditions of branched lines of complex configuration increases the degree of uniqueness of localization of the damage site and increases the accuracy of determining the distance to it. In the absence of synchronization, the processors of autonomous devices will disperse in time, which can lead to the simultaneous sending of two probe pulses from different directions to the line and to obtain inaccurate and unreliable results.

In addition, the control room stores information not only about the operation of the monitored line, but also about the state of the system as a whole. Therefore, when the first signs of abnormal operation of the system occur (such as, for example, network overvoltages or malfunctions of neighboring devices), the possibility of operational control of the device (for example, a command to change the frequency of sensing) can contribute to the positive development of the situation. In this case, repeated duplication of measurements and their comparison often allows you to see the process in dynamics and makes it possible to accurately identify still developing damage that is invisible in a single measurement.

There are other disadvantages of this device, associated mainly with the time-frequency nature of the modulation of the signal. Some of them appear at lengths of line sections commensurate with the time it takes for the probe pulse to travel along them, while others occur when the line is probed in the “hot mode”. So, in the first case, the superposition of the signal reflections on themselves significantly reduces the accuracy and unambiguity of determining the location of the damage, in the second case, as a result of the occurrence of an arc discharge, the spectral composition of the reflected signal is greatly distorted.

In addition, with time-frequency modulation, the input filters of the receiver must pass a broadband signal, which makes it difficult to use effective noise filtering and reduces the reliability of localization and the accuracy of determining the location of damage.

The above analysis of the prior art indicates that the above methods and devices, including the method and device according to patent RU 2400765, do not provide the necessary accuracy in localizing the location and determining the distance to damage of a branched line of arbitrary configuration.

The objective of this group of inventions is to increase the accuracy of localization of the damaged area and determine the distance to the place of damage in relation to heterogeneous branched power lines and communication of arbitrary configuration, in particular to distribution power lines.

The technical result that can be obtained by implementing the claimed group of inventions is to achieve high accuracy of measuring the distance to the place of damage of complex heterogeneous branched lines of arbitrary configuration, as well as the ability to automate the process of diagnosing such lines and reducing the time of detection and elimination of their malfunctions.

The problem is solved in that in the proposed method for determining the locations of damage to power lines and communications, probing voltage pulses are sent to the line, reflected pulses are received, followed by their filtering, analysis and measurement of time delays of reflected pulses relative to the probing ones, based on which the distances to inhomogeneities are determined, fixed an array of reflected signals received from an undamaged line in the form of an electronic image of the line, perform autocorrelation processing, dist Strengths to natural heterogeneities are recorded in the form of reference points, this information is transferred to a single center, and if line damage is detected, the distance to the damage site is calculated, the process of sending probing voltage pulses and receiving reflected pulses is carried out alternately from two opposite ends of the line sections. An array of reflected signals is fixed for sections of the line, and the distances to heterogeneities are recorded for sections of the line in the form of digital information, which is provided with labels unique to each of the possible sources of this information, and alternately transferred to a single center, where it is stored at least until updated information from the same source, and in order to detect a damaged area, the obtained information about the distance to natural inhomogeneities and to the heterogeneity that arose during damage to a line section, Overcome autocorrelation comparison with previous information from the same source. In the presence of non-correlating distances, the damaged area and preliminary distances to the place of damage Lx ₁ and Lx ₂ are determined, determined from two ends of this section, and the specified distance to the place of damage Lx ' _K from any of the ends, K = 1 ÷ 2, the area is calculated by the formula :

,

,

where L is the known total length of this section of the line, m, and the sequence of sending and receiving pulses from the ends of the sections of the line and transmitting information to a single center is synchronized in sync packets that are received from this center.

The advantage of the method is the use of two-sided location of the line sections and the transfer of the results, marked with the information source labels, to a single processing center, where the state of the controlled line is analyzed. To eliminate the mutual overlapping of signals from different sources, a certain sequence of the process of sending probe pulses and information transfer, which is synchronized from a single center, is established for them.

This method of sensing the line completely eliminates the ambiguity of damage localization, since according to the information received from both ends of the damaged area, this area is uniquely identified, including for branched heterogeneous lines with a loopback. The proposed method also improves the accuracy of determining the distance to the place of damage.

The error in determining the range when locating the place of damage depends on the errors in measuring the propagation speed of the signal and its delay time, therefore, increasing the accuracy of distance measurement is directly related to eliminating the influence of inaccuracies in determining the phase velocity of the wave in the line and reducing errors in measuring the delay time.

. To есть эти ошибки можно представить как

и

, полагая δ погонной ошибкой измерения, связанной с неточным определением скорости распространения. Подставляя предварительные, ошибочные значения длин

и

в приведенную выше формулу, после группировки и сокращения получим:Suppose that we do not know the exact value of the phase velocity of propagation of an electromagnetic wave in a given region during this period, and therefore the preliminary distances to the damage site obtained from the two opposite ends of the damaged section Lx ₁ and Lx ₂ were measured with errors - δLx ₁ and δLx ₂ respectively. Note that due to the equality of the wave propagation velocities in two branches of the line section (the section, as a rule, is not performed from conductors with different characteristics), the length measurement errors will be proportional to the true value of this length

. To eat these errors can be represented as

and

, assuming δ the linear measurement error associated with inaccurate determination of the propagation velocity. Substituting preliminary, erroneous lengths

and

in the above formula, after grouping and reduction we get:

.

.

, после сокращения получаем тождество, которое доказывает, что даже при большой неточности определения скорости распространения волны в данном участке линии, в случае использования предложенного способа, можно получить точное расстояние до места повреждения. Обобщая, заметим, что при использовании данного способа вообще нет необходимости в определении скоростей распространения зондирующего импульса в участках контролируемой линии, а предварительные длины до места повреждения могут быть определены в любых (но одинаковых) единицах измерения.Given that

, after reduction, we obtain an identity that proves that even with a large inaccuracy in determining the wave propagation velocity in a given section of the line, in the case of using the proposed method, it is possible to obtain the exact distance to the place of damage. Summarizing, we note that when using this method, there is no need at all to determine the propagation velocity of the probe pulse in sections of the monitored line, and preliminary lengths to the place of damage can be determined in any (but identical) units of measurement.

Extending the above reasoning to all systematic measurement errors (for example, errors in measuring time intervals), it can be stated that errors proportional to the measured value itself (for example, the inaccuracy of the used reference time units) do not affect the accuracy of the results obtained. The only thing that can have a negative impact on the accuracy of the measurements is unsystematic errors inherent in each measuring instrument individually. But when using a single technique, the same equipment and when measuring with a small interval (fractions of milliseconds), it is difficult to expect that the parameters of the line and equipment will change any significantly. Therefore, when the equipment is in good working order, we have the right to assume the insignificance of the influence of non-systematic errors on the result obtained and their incommensurability with the errors discussed earlier.

That is, it can be argued that the use of the proposed method significantly reduces the level of measurement errors, thereby increasing the accuracy of determining the distance to the place of damage of heterogeneous lines of complex and branched topology.

Improving the accuracy of determining the distance to the place of damage and the uniqueness of localization of a portion of non-uniform lines of arbitrary configuration is also achieved by the fact that in the indicated method, the array of reflected signals for sections of the line is subjected to an amplitude lower limit on the level that is preset with an excess of the average noise level in the line section, but below the minimum the level of reflections from natural inhomogeneities, then the array is transferred to a packet of unipolar pulses of a fixed amplitude, and the distance to the natural idents inhomogeneities and preliminary distance to the fault is determined based on the time interval from the sending probe pulse and before the arrival of the leading edge of the next pulse packet.

The essence of this addition to the main method is that for lines with relatively short sections, for the above reasons, the use of extended probe pulses, the transit time of which along the section (or to its inhomogeneities) is commensurate with the duration of the pulse itself (see restriction (1 )).

The root-mean-square error of measuring the delay time δ, according to [4], is associated with the duration of the probe pulse τ and the signal-to-noise ratio q:

.

.

The decrease in error in this case is associated with a decrease in the duration of the probe pulse. Therefore, in lines with relatively short sections, one should strive to reduce the pulse duration to a limit determined by the capabilities of the equipment and the line capacity (especially since when locating areas of short length, there is no need to use powerful probe pulses). That is, for lines of this configuration, the achievement of the result stated in the method excludes the possibility of applying time-frequency modulation of the probe signal and involves the use of unmodulated pulses of short duration. The latter requires alternative actions when processing the reflected signals and measuring the delay time, which are described in addition to the proposed method.

In addition, as follows from the above expression, an increase in the accuracy of determining the distance to the fault is associated with an increase in the signal-to-noise ratio in the receiving device. For sections of the mid-noise line, this increase can be obtained by restricting the array of reflections from below, even before it is transferred to a packet of unipolar pulses, so that the signal reflected from inhomogeneities and damage after the limitation is largely eliminated from noise. For each section of the line, the limit level can be set individually based on test measurements. In addition, when probing with an unmodulated pulse, it is possible to use input narrow-band filtering of the signal, which also helps to increase the mentioned ratio.

As follows from the foregoing, the use of time-frequency modulation limits the accuracy of measuring the distance to damage when sensing a live line. The arising arc can distort the frequency characteristics of the reflection array and lead to unreliable results of measuring distances in such a line. In this case, preference should be given to sensing a line section with a short unmodulated pulse. The likelihood of a surge in the arc discharge, similar to the probe pulse, is relatively small, and all other arc manifestations in the received signal can be reduced by band pass filtering.

Thus, for lines with short sections and lines that are energized, the application of this addition to the claimed method leads to an increase in the accuracy of determining the location of damage to the line, which corresponds to the task.

Improving the uniqueness of localization and accuracy of determining the location of damage is facilitated by the fact that in the inventive method at least two pulses are sent to one probe sending process, separating their sending by a time interval T _s that is known to be longer than twice the transit time of the probe pulse along the longest section of the line, receive reflected signals from each of the sent n probe pulses, counting the beginning of each of the arrays as the sending time of the next probe pulse 1≤i≤n, and received Siva reflected signals below limit of the preset level and is converted into packets unipolar pulse of fixed amplitude, and delay packets depending on the number of probe pulse i, reflections which they are at the time T _zi, determined according to the expression:

T _zi = (ni) · T _s,

all packets are summed in amplitude into one packet, which is limited from below by an amount calculated according to the formula

A _o = A · (n-0.9),

where A is the fixed amplitude of the initial pulse packets, and the distances to inhomogeneities and preliminary distances to the damage site are determined based on the time intervals from sending the last of the probe pulses to the leading edge of the next pulse of the total packet.

For lines with a high degree of noise, using only the aforementioned restriction from the bottom of the array of reflected signals at a predefined level may not give a sufficient degree of detuning from the noise of the line. In this case, sending two or more probe pulses in series, followed by the addition of the received reflection packets, makes it possible to almost completely get rid of any noise or other irregular component of the incoming signals. For correct addition, the bulk of the noise is first cut out from the arrays of reflected signals, and the result is transferred to packets of unipolar pulses of the same amplitude. Then the packets are delayed so that their addition coincides at the beginning. Given the static nature of natural heterogeneities and damage, we can expect that their reflections will add up, giving a total signal amplitude equal to the product of the amplitude of the packets by their number. But noises, due to their irregularity, will be placed differently in different packets, therefore, in the total signal, their amplitude will be less than the amplitudes of static inhomogeneities. Cutting the resulting total signal from below by the value of A _o = A · (n-0.9), as a result we obtain only pulses reflected from static inhomogeneities (a coefficient of 0.9 instead of unity prevents random fluctuations from entering the final signal). The required number of probe pulses in one packet depends on the intensity and density of the noise component of the line. Since a decrease in the noise level in the signal entails an increase in the accuracy of the location, it can be argued that the proposed addition to the method helps to increase the accuracy of determining the distance to the place of damage of a very noisy line.

The solution of the problem of the invention is directed and clarification to the two previous additions of the claimed method. In the proposed method, the probe pulse is inverted, transformed in amplitude, and simultaneously with the initial probe pulse from the line is fed to the receiving device, where these pulses are summed in amplitude, and the inverted pulse is transformed so that the sum of these pulses in the receiving device is smaller in amplitude than the pulses reflected from heterogeneities.

The essence of the proposal is to compensate for the probe pulse in the receiving device so that it does not "interfere" with the identification of reflections from the nearest inhomogeneities. The commonly used technique of completely blocking the receiver for the duration of the probe pulse leads to the fact that reflections from the inhomogeneities close to the beginning of the line will also be blocked, which reduces the likelihood of detecting damage falling into this zone. For lines of short length, which, for example, include distribution power networks, the latter leads to a decrease in the reliability and accuracy of determining the location of damage. The proposed method allows to reduce the voltage surge for the duration of the probe pulse along the receiver circuits, without resorting to the complete blocking of its input. Against the background of the residual signal, reflections from close inhomogeneities become resolvable, which increases the accuracy of the method as applied to sections of the line of small length.

Thus, the application of the proposed method provides a solution to the problem for all the above types of power lines and communications.

The proposed method can be implemented using a device including a probe pulse generator having an input and two outputs, a receiver containing an analog-to-digital converter and equipped with two inputs and an output, a computing unit containing a processor and equipped with at least two outputs and an input , an information transmission unit equipped with an input, one of the inputs of the receiver connected to the line, and the second with the second output of the generator, the input of the information transmission unit connected to one of the outputs of the computing unit And the output of the receiver is the output of analog-to-digital converter. The computing unit of the device is equipped with a sub-block for decrypting sync packets, the output of which is connected to an additional second input of the processor, and the input is the second input of the computing block, while the information transfer unit is configured to receive sync packets and is equipped with an output connected to the second input of the computing block.

The main disadvantage of the prototype noted above — the lack of synchronization and the ability to remotely control the operation of the device — is eliminated in the claimed invention by the fact that the device information transmission unit is equipped with an additional function of receiving sync packets from a single center, which, as a rule, is a control center. The computing unit of the claimed device is equipped with a subunit of decryption of sync packets, the task of which is to decrypt information messages transmitted in these sync packets. In addition to the main task - synchronizing the work of the computing unit (and with it the entire device) according to a single schedule formed in the center - the decryption subunit decrypts and sends control commands to the computing unit, which may be contained in sync packets. Thus, it becomes possible to synchronize all devices of the monitored line and remotely control them, which allows to increase the accuracy of determining the location of damage to the line and eliminate the ambiguity in its localization.

The proposed method with additions can be implemented using a device in which the receiver of the device contains a bandpass filter, an inverter amplifier, each of which includes an input and an output, respectively, a signal delay unit equipped with two inputs and m outputs, a first adder including two inputs and an output, a second adder including m inputs and an output, and two comparators, each of which contains an input connected to the output of the corresponding adder, and an output. The inputs of the bandpass filter and amplifier-inverter are the first and second inputs of the receiver, respectively, and the outputs of the bandpass filter and amplifier-inverter are the first and second inputs of the first adder, the second input of the signal delay unit is the third additional input of the receiver, which is connected to the additional output of the computing unit, and m outputs of the signal delay unit are m inputs of the second adder, which is connected through the second comparator to the input of the analog-to-digital converter of the receiver.

As the analysis of the prototype showed, for lines with relatively short sections, as well as for lines under voltage and very noisy lines, the use of time-frequency modulation of the probe pulse is not an optimal solution and entails a decrease in the accuracy of determining the location of damage. The latter is due to the contradiction between the pulse duration with time-frequency filling and the lengths of the probed sections, between the spectral compositions of the probing signal and the noise filling of the damaged line.

The technical contradiction noted above is eliminated in the proposed device, all units of which are optimized for operation with short probe pulses and are equipped with modules that reduce the noise level in the final signal, which fully corresponds to the objective of the invention.

The method and device, according to the present group of inventions, is illustrated by the example of a preferred embodiment with reference to the accompanying drawings.

Figure 1 presents the device that implements the proposed method; figure 2 presents an example of the execution of the computing unit; figure 3 presents an embodiment of the device, figure 4 presents an example implementation of the receiver according to a variant of the device; figure 5 shows a fragment of a city distribution power network, figures 6-9 explain the operation of the proposed device.

The device (Fig. 1) includes a probe pulse generator 1 (consisting of a memory unit 2, a digital-to-analog converter 3 and a power amplifier 4), a directional coupler (BUT) 5, a switch 6, a receiver 7, a computing unit 8 (for example, a microcomputer), a unit receiving and transmitting information 9.

The first input of the receiver 7 through the directional coupler 5 and the switch 6 is connected to the controlled line, the second input of the receiver 7 is connected to the second output of the generator 1, and the output of the receiver 7 is connected to the input of the computing unit 8.

Computing unit 8 (Fig. 2), in the general case, can be a microcomputer containing an address, data, control bus 10, processor 11, keyboard control device 12, memory module 13, and sync packets decryption subunit 14, the output of which is connected to the second input processor 11, and the input, which is the second input of the computing unit 8, is connected to the output of the information transmitting and receiving unit 9.

The embodiment of the device (Fig. 3) includes all of the above blocks, but in it the receiver 7 is provided with an additional third input connected to the additional output of the computing unit 8. In this embodiment, the receiver 7 contains (Fig. 4) a bandpass filter 15, an amplifier-inverter 16, a first adder 17, a first comparator 18, a signal delay unit 19, a second adder 20, a second comparator 21, and an analog-to-digital converter (ADC) 22.

The input of the bandpass filter 15 and the input of the amplifier-inverter 16 is, respectively, the first and second inputs of the receiver 7, and the outputs of the bandpass filter 15 and the amplifier-inverter 16 are connected to two inputs of the first adder 17, the output of which, through the first comparator 18, is connected to the first the input of the delay unit of the signal 19, the second input of which is the third additional input of the receiver 7, connected to the additional output of the computing unit 8.

The delay unit of the signal 19, in the General case, may be a set of m artificial delay lines made with the ability to switch by the command of the computing unit 8. Each of the m outputs of the delay unit of the signal 19, which is simultaneously the output of the same delay line, is connected to the corresponding input of the second the adder 20, the output of which through the second comparator 21 is connected to the analog-to-digital Converter 22. The output of the ADC 22 is the output of the receiver 7.

The inventive method is implemented in the work of the proposed device, which we will consider as an example of its implementation for a power line of a city power distribution network of 6.3 kV (a fragment of a network diagram of a distribution substation RP-7 of the Engelsky branch of Oblkommunenergo is shown in Fig. 5) when modeling the damage that a section of an underground cable line occurs. The whole set of devices of this network bush is located at transformer substations (TP), which are the boundaries of the sections of the monitored line (in Fig. 5 TP are indicated by circles, inside which TP numbers are located). Underground power cables in the diagram are indicated by dashed lines, next to which data on the type of cable and the length of the plot are placed. The set of all probing devices of the monitored line forms an information network and is subordinate to a single information processing center, which in this case is a control center. Such an information network can function both independently and as part of a distribution network monitoring system (for example, such as in the source [5]).

Sounding of lines can be carried out continuously, including for live lines, since the spectrum of sounding signals (0.4-1 MHz) does not coincide with the frequency of the power network. Transmission and reception of information can be arranged in a wireless channel. In this case, information from all network devices is transmitted directly to the control room.

The devices of this network bush are preliminarily (that is, before the start of work) an individual number is assigned and the sequence and frequency (for example, every 10 s) of their connection with the center and sensing of the line are established (at the command of the center, in a critical situation, the frequency can be significantly reduced) . The power amplifier 4 of the probe pulse generator 1 (Fig. 3) of each network bush device presets the probe pulse level so that the minimum level of reflections from natural inhomogeneities exceeds the average noise level of the tested section of the line. It is also desirable to set for each of the bush devices its own allowed time interval (time slice), which determines in which part of the current second this device can perform external operations (sensing, data transfer). The position of the quantum within a second is determined by the adopted sequence and the estimated time of activity of the device. The activity time (not more than 0.015 s) includes the process of sensing, receiving and transmitting data from one device. Installation of time quanta does not allow devices of the same bush to influence each other's work even in extreme conditions. The network bush accounts for 12-17 sites, that is, the total activity time of devices in one bush does not exceed 0.3 s.

To cut off the main volume of the noise component of the signal on all devices, the restriction level of the array of reflected signals is also pre-set (based on test tests). Based on the values of the density and amplitude of the noise component of a given section of the line, the number of probe pulses "n" in one process is set for devices (when the noise level changes, this number can be adjusted).

For definiteness, let us consider the operation of devices restricting a portion of a cable line 655 m long that runs between TP-55 and TP-48 (Fig. 5). The sections of the line adjacent to this have lengths of 1012 m (for the section on the right) and 835 m (on the left) and are made of the same type of cable. Suppose that the preset noise restriction level in the devices is 17 V, counting from the lower cutoff of the amplified and rectified signal, and for these devices it is optimal to send 2 probe pulses in one process. This bush of the power network does not contain sections longer than 1.5 km, therefore, for its devices, a sufficient delay interval is T _s = 100 μs, which is 1.4 times longer than the double pulse propagation time along the longest cable section of this type.

In the normal mode of operation of the network, the substation TP55 device in its quantum of time with a given frequency produces a sounding line. Under the influence of the control signals of the computing unit 8 (assembled on the basis of the ATmega128 microcontroller), the DAC 3 of the generator 1 generates a probe pulse of a given shape, which is amplified by a power amplifier 4 and sent to the probed line (Fig. 3). Information about the shape of the probe signal is stored in the memory unit 2 of the generator 1. At the same time as sending a probe pulse to the second input of the receiver 7 from the second output of the generator 1, a reference pulse is supplied. The reference pulse passes through the amplifier inverter 16 (figure 4), where it is transformed in amplitude and inverted, and then fed to the first adder 17. At the first input of the adder 17, simultaneously with the reference, a probe pulse is received.

The diagram in Fig.6 "a" shows the waveform at the first input of the receiver 7. The letter "A" on it indicates the probing pulse received at the input of the receiver. As can be seen from the diagram, despite the presence in the circuits of the receiver 7 and the generator 1 (Fig. 3) of decoupling devices in the form of a directional coupler 5, the probe pulse, however, passes to the input of the receiver. However, after summing and amplification, the signal takes the form shown in diagram b (Fig.6), where it is noticeable that the difference between the probe and reference pulses (letter A) no longer interferes with the identification of other reflections.

The noisy signal reflected from the line inhomogeneities passes through a narrow-band filter 15 (Butterworth active bandpass filter of the 4th order based on the LM6172IM), which significantly reduces the level and limits the spectral composition of noise, passes through the adder 17 to the input of the first comparator 18, where it is amplified, rectified, and passed the restriction on the cutoff level of the signal and turns into a packet of unipolar pulses, with an amplitude of 1 V. The subsequent stages of the signal processing are shown in the diagrams of Fig.6, 7 "a" and "b", where the letters "B" indicate the distance from the opposite end of the test section, the letters "C" are the reflection from the adjacent section located between TP55 and TP113 (Fig. 5), and the letter "D" is the noise remaining after signal restriction (for convenience, all diagrams are scaled in units of distance ) Upon exit from the first comparator 18, the signal is fed to the input of the delay unit of signal 19 (assembled on the basis of a set of artificial M-type delay lines, the inputs of which are switched by the command of computing unit 8). The first incoming packet of unipolar pulses in block 19 is delayed by a time T _s = 100 μs. (The signal delay unit, depending on the required delay value, can be made on the basis of controlled digital lines (for example, TDA4665 microcircuits) or using household ultrasonic lines (for example, ULZ64-8 or ULZ128-2B). In the latter case, adopted for the device the delay time must be a multiple of 64 or 128 μs.) At the end of the delay, the generator sends a second probe pulse to the line, the reflections of which undergo the same processing as the first, except that the second packet of unipolar pulses is not delayed And directly supplied to the second input of the second adder 20 (Figure 4). For clarity, in the diagrams of Fig. 7 "a" and "b" the reflections of the second probe pulse and the resulting packet of unipolar pulses are shown in lighter tone.

With the start of the second probe pulse, a delayed packet arrives at the first input of the second adder 20, and a second reflection packet arrives at the second input. Reflections from natural inhomogeneities (in particular, from opposite ends of adjacent sections) are added up and the total signal becomes equal to 2 V (the signal at the output of the second adder 20 is conditionally shown in dashed line in Fig. 7), and the noise, due to their irregularity , do not coincide in time, their amplitudes do not add up, therefore remain equal to 1 V. From the output of the second adder 20, the signal is fed to the input of the second comparator 21, where it passes the second lower limit from the level A _o = 1 · (2-0.9) = 1.1 AT.

The result of the restriction turns into a packet of pulses with an amplitude of 1 V. This packet contains information on the location of static inhomogeneities of two adjacent sections of the line (as can be seen from the diagram in Fig. 7 "b", one of the marks is approximately 650 m from TP55; this mark is reflection of the opposite end of the test section, and the second mark is removed at a distance of ~ 1010 m and is a reflection of the end of the left adjacent section).

In the form of pulses with an amplitude of 1 V (the leading edge of which contains information about the distance to the inhomogeneity), the packet arrives at the input of the ADC 22 (for example, a microcircuit like PCF8591P), where it is digitized and fed to the input of computing unit 8 (Fig. 3).

Computing unit 8 using an internal fast counter (crystal oscillator with a clock frequency of 20 MHz) measures the time intervals from sending a second pulse to the arrival of units corresponding to the leading edges of the reflection pulses. The data obtained for the entire package are stored in the memory module 13 of the processor 11 (Fig.2). Of these, the processor 11 forms a frame of information to which a unique device number and CRC are added.

Via the data bus 10, the generated information at the corresponding time is transmitted to the transmit-receive unit 9 (Fig. 3), from where it is transferred to the control room.

The control room computers have a powerful computing resource that is incomparable with the limited capabilities of microcontrollers, so the control room has the ability to analyze and compare the data received with the previous data received from the same device in the previous probe cycle in real time. In addition, control room computers can memorize and store information from many network sensing cycles, which makes it possible to analyze the dynamics of changes and, to some extent, predict the occurrence of an emergency. When working in conjunction with the monitoring system of the computer network of a control center, they can detect damage by other methods (or damage to adjacent systems) and can give devices a command to change the operating mode. It can be shown that using the proposed method and device, damage of any type can be classified and determined, and with the use of switch 6 (Fig. 3), damage to individual phase wires of a multiphase power line can also be determined.

If the differences between the newly received and stored data are within the acceptable range, the control room machines replace the previous information with the newly received and continue to operate normally. A sign of normal operation for devices is the starting sync packet transmitted from the control center, which begins a new line sensing cycle.

Sync packets coming from the control room can be of two types: broadcast and address. Broadcast sync packets are addressed to all devices in the network bush. As a rule, they contain a command to synchronize devices by the timer of the control room machines (starting the sync packet), but they can also contain other commands common to the devices in this bush. At the synchronization command, the internal counters of all devices are reset. The synchronization command is issued at the beginning of each of the sounding cycles of the line of a given network bush, therefore, the quartz processor counters cannot disperse by more than one clock cycle (0.1 μs), which ensures synchronous and accurate operation of all the bush devices.

The address command can relate to one of the devices of the network bush and, in addition to the center code number, contains the recipient code number, command, and CRC. The unit of transmitting and receiving information of the device 9 (Fig. 3) all the time, except for the moment of data transmission from this device, is in the listening mode of the communication channel. Received messages from the information transmitting and receiving unit 9 are transmitted to the subunit of the sync packet decoder 14 (Fig. 2), which after decryption (from whom the message was received, what type it belongs to, to whom it is addressed, which command it contains, etc.) transmits the corresponding a command to the processor 11, which implements this command, controlling the operation of the device.

The operation of the device in the mode of detecting damage, we consider the example of the same section of the distribution power network (Fig. 5), in which damage in the form of a line break was modeled by opening two phases on a coupler located at a distance of 190 m from TP55.

The entire sequence of operation of the TP55 device when the network is damaged is completely identical to that described above. Diagrams of the received signal at different stages of its processing are shown in Fig. 8. Visually comparing the same stages of the signal processing in Fig. 8 and Fig. 6, 7, the following can be noted:

- increased density of the noise component of the received signal;

- there was an additional outlier (letter "E1", Fig. 8), located at a distance of 200 m from TP55;

- the outburst disappeared (letter “B”, Figs. 6, 7), corresponding to the reflection from the opposite end of the test section (more precisely, it didn’t completely disappear, but sharply decreased in amplitude and went beyond the limits of identification, which is quite natural when two phases are broken);

- the voltage spike corresponding to the reflection from the end of the adjacent section remained in the same place (letters "C" in Fig.6, 7 and letter "C1" in Fig.8).

After passing through all the stages of processing, the data is transmitted to the control room, where comparing them with previously received data from the TP55 device shows that there is a significant difference between them.

The operation of the TP48 device is identical to the operation of the TP55 device, so there is no need to describe it separately. Differences similar to those described above can be found by comparing damaged diagrams (Fig. 9) with intact line diagrams obtained by the TP48 device. The difference lies only in the distance to the newly appeared outlier (letter "E2", Fig. 9), which is about 470 m, and in the position of the remaining frame (letter "C2"), which is a reflection from the end of the right adjacent section with a length of 835 m. In turn, the TP48 device sends the received data to the control room, where, similarly to the first case, the difference with the previous state is recorded. The difference in data from all other devices in the network bush does not go beyond the permissible difference, therefore, based on autocorrelation comparison, a damaged section of the line concluded between TP55 and TP48 is uniquely identified.

According to the data received from devices that limit the damaged area, uncorrelated distances are identified at the control room by the exclusion method, that is, preliminary distances to the place of damage Lx ₅₅ and Lx ₄₈ are determined (in whatever units they are presented). In the case under consideration, these distances are presented in measures of the internal counters of two devices and are respectively Lx ₅₅ = 44 cycles, Lx ₄₈ = 107 cycles. Substituting the preliminary distances in the above formula, you can get:

Thus, the estimated distance from TP55 to the site of the simulated damage is 190.86 m, which is less than 0.5% different from its true value. (The above error is mainly related to the discreteness of the count. With an increase in the measured lengths, the relative error will decrease, but for underground cable lines a further increase in accuracy does not seem to make sense, since the size of the overburden works still exceed the absolute value of the error.)

The given implementation example showed the effectiveness and prospects of using the inventive device and method for determining the location of damage to power lines and communication of arbitrary configuration, including lines under load, in particular cable lines of the urban power distribution network 6.3 kV.

The application of the proposed method and the device implementing it in distribution networks makes it possible to automatically, remotely and quickly determine the location of damage to underground cable lines, which, compared with the existing level of technology, significantly reduces the time for detection and elimination of malfunctions. According to the PUE [6], the site of damage should be detected within two hours. However, in practice, even with good organization, the site of damage can be detected within 6-10 hours. Particular difficulties in finding the place of damage appear in underground cable lines with insulated neutral. Visual inspection of them is difficult and the determination of the place of damage sometimes takes several days, and due to significant neutral displacements arising from short circuits, such lines must be disconnected and must remain in the disconnected position until the damage is detected and eliminated. With the current level of technology, the detection of a specific location of damage is usually carried out by portable equipment, moreover, on sections of lines completely disconnected from all connections, which also entails considerable time costs. In a relatively short time (4-6 hours), if there is a sufficient amount of portable equipment, the place of damage can be determined only with the simultaneous operation of several teams. The time to find and repair the damage and the number of teams taking part in this can be significantly reduced if the site and the distance to the place of damage to the underground cable line are established with sufficient accuracy. This is the technical result achieved by the application of the invention.

Information sources

1. Measurement of distances to places of damage on overhead and cable power and communication lines / V.L. Bakinovsky, A.P. Osadchy, N.I. Sosthenov, V.K. Spiridonov. - TSNIEL, 1954, issue 2.

2. Shalyt G.M. Determination of places of damage in electrical networks. - M.: Energoizdat, 1982, 312 p.

3. SONG, Y.H., AGGARWAL, R.K. and JOHNS, A.T., "Digital simulation off fault arcs on long distance compensated transmission systems with particular reference to adaptive autoreclosure", European Trans. on Electrical Power Engineering, Vol.5, No.5, pp. 315-324 (September / October 1995).

4. Theoretical foundations of radar. Ed. Shirmana Y.D. Textbook for high schools. - M.: Soviet Radio, 1970, p. 192.

5. Kadomskaya K.P., Kachesov V.E., Lavrov Yu.A., Ovsyannikov A.G., Sakhno V.A. Diagnostics and monitoring of cable networks of medium voltage classes // Electrical Engineering, 11, 2000.

6. Rules for the installation of electrical installations. M .: Energoatomizdat, 1985 .-- 640 p.

Claims (6)

1. The method of determining the location of damage to power lines and communications, in which probing voltage pulses are sent to the line, reflected pulses are received, followed by filtering, analysis and measurement of time delays of reflected pulses relative to the probing ones, based on which distances to inhomogeneities are determined, an array of reflected signals is recorded received from an undamaged line in the form of an electronic image of the line, produce autocorrelation processing, the distance to natural inhomogeneities beyond write in the form of reference points, transmit this information to a single center, and if line damage is detected, calculate the distance to the place of damage, characterized in that for lines, including branched ones, consisting of many sections, the process of sending sounding voltage pulses and receiving reflected pulses from two opposite ends of the line sections in turn, the array of reflected signals is fixed for the line sections, and the distances to the inhomogeneities are recorded for the line sections in the form of a digital the formation, which is provided with labels that are unique for each of the possible sources of this information, and is alternately transferred to a single center, where it is stored, at least until updated information is received from the same source, and information on the distance to natural inhomogeneities and to the heterogeneity that occurred when the line section is damaged, are subjected to autocorrelation comparison with previous information from the same source, and in the presence of non-correlating distances, stated failures portion and preliminary distance to the damage Lx ₁ and Lx _2, defined at the two ends of this portion, the refined distance to fault

from any of the ends K = 1 ÷ 2 sections are calculated by the formula:

where L is the known total length of this section of the line, m,
and the sequence of the process of sending and receiving pulses from the ends of the line sections and transmitting information to a single center is synchronized by sync packets that are received from this center. 2. The method according to claim 1, characterized in that the array of reflected signals for sections of the line is subjected to an amplitude limit from below in terms of a level that is preinstalled with an excess of the average noise level in the section of the line, but below the minimum level of reflections from natural inhomogeneities, then the array is transferred into a packet unipolar pulses of a fixed amplitude, and the distances to natural inhomogeneities and preliminary distances to the place of damage are determined on the basis of time intervals from sending a probe pulse and before the arrival of the leading edge of the next pulse of the packet. 3. The method according to claim 1, characterized in that at least two pulses are sent to the same probe sending process, dividing their sending by a time interval T _s that is known to be longer than twice the transit time of the probe pulse along the longest section of the line; signals from each of the sent n sounding pulses, counting the beginning of each of the arrays as the sending time of the next sounding impulse 1≤i≤n, and the received arrays of reflected signals limit from below the preset level and translation at the packets of unipolar pulses of fixed amplitude, and the packets are delayed depending on the number of the probe pulse i, the reflections of which they are, for a time T _zi , determined according to the expression:
T _zi = (ni) · T _s,
all packets are summed in amplitude into one packet, which is limited from below by an amount calculated according to the formula:
A _o = A · (n-0.9),
where A is the fixed amplitude of the initial pulse packets, and the distances to heterogeneities and preliminary distances to the damage site are determined based on the time intervals from sending the last of the probe pulses to the leading edge of the next pulse of the total packet. 4. The method according to claim 2 or 3, characterized in that the probe pulse is inverted, transformed in amplitude and simultaneously with the original probe pulse from the line is fed to the receiving device, where these pulses are summed in amplitude, and the inverted pulse is transformed so that the sum of these the amplitude of the pulses in the receiver was less than the pulses reflected from inhomogeneities. 5. A device for determining the location of damage to power lines and communications, including a probe pulse generator having an input and two outputs, a receiver containing an analog-to-digital converter and equipped with two inputs and an output, a computing unit containing a processor and equipped with at least two outputs and an input, an information transmission unit equipped with an input, one of the inputs of the receiver connected to the line, and the second to the second output of the generator, the input of the information transmission unit connected to one of the outputs will calculate unit, and the output of the receiver is the output of an analog-to-digital converter, characterized in that the computing unit of the device is equipped with a subunit for decrypting sync packets, the output of which is connected to an additional second input of the processor, and the input is the second input of the computing unit, while the information transfer unit is configured to receiving sync packets and is equipped with an output connected to the second input of the computing unit. 6. The device according to claim 5, characterized in that the receiver of the device comprises a bandpass filter, an amplifier-inverter, each of which includes an input and an output, respectively, a signal delay unit equipped with two inputs and m outputs, a first adder including two inputs and an output , a second adder including m inputs and an output, and two comparators, each of which contains an input connected to the output of the corresponding adder, and an output, while the inputs of the bandpass filter and the inverter-amplifier are the first and second inputs of the receiver, respectively, the outputs of the bandpass filter and the inverter-amplifier are the first and second inputs of the first adder, the second input of the signal delay unit is the third additional input of the receiver, which is connected to the additional output of the computing unit, am the outputs of the signal delay unit are m inputs of the second adder, which is connected through the second comparator with the input of the analog-to-digital converter of the receiver.

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