RU97831U1 - DEVICE FOR ASSESSING QUANTITATIVE AND STATISTICAL CHARACTERISTICS OF INTERNAL INHOMOGENEITIES OF ELECTRIC CABLES - Google Patents

Abstract

 1. A device for evaluating the quantitative and statistical characteristics of internal heterogeneities of electric cables, containing a probe pulse generator and a matching device, output coupled to a receiver containing an amplifier and ADC, a computing unit containing a processor connected to the input / output by a memory unit, with corresponding input and output the computing unit is associated respectively with the output and the corresponding inputs of the receiver and the input of the display unit, characterized in that it contains a unit for connecting made with at least two separate inputs / outputs on the side of the cable, which are the corresponding inputs / outputs of the said matching device, which is included in the connection unit, which also contains a differential system, the input connected to the output of the probe pulse generator, and the input / output - with the output / input of the matching device, the trace memory unit is inserted into the receiver, the corresponding input is connected to the ADC output, the corresponding input is connected to the output of the amplifier, the th block further comprises a series-connected distortion corrector, an amplitude corrector, a statistical processing unit, the corresponding inputs / outputs of which are connected to the outputs / inputs of the correlator and the processor, the control output of which is connected to the control inputs of the amplitude corrector, distortion corrector, trace memory unit and receiver amplifier, a probe pulse generator and a matching device of the connection unit, the output of the differential system and the corresponding output of the devices

Description

The utility model relates to pulsed technology and electrical measurements and can be used to estimate the quantitative and statistical characteristics of the internal inhomogeneities of symmetric and coaxial cables, as well as to compare cable circuits according to the criterion of “uniformity”.

Known devices for determining places of damage to power lines and communications, called reflectometers, which are based on sounding the line with voltage pulses created by a probe pulse generator and registering by the receiver a reverse flow arising from the reflection of probe pulses from internal cable inhomogeneities, which can be interruptions , short circuits, etc. The time to the damage is determined by the time delay of the reflected signal relative to the probing one.

One such device (see US Patent No. 6448781, M. CL G01R 31/11, published September 10, 2002) contains an OTDR connected to the cable and connected to a backflow analysis system. The analysis principle is based on dividing the received trace into separate segments, after which the slope of the impulse response in individual segments is used to judge the nature of the heterogeneity in certain places of the cable corresponding to this segment on the characteristic. To implement such an analysis, the device contains interconnected processor, memory blocks, in one of which information on various types of heterogeneities is stored, and in the other, information about the impulse response in individual segments of the trace is recorded. The impulse characteristics in individual segments are compared with the characteristics of the cable inhomogeneities in the first memory unit, and the result of the comparison is displayed on the display device (printer).

The advantage of this device is the ability to automatically determine the location and type of cable inhomogeneities. At the same time, the device does not allow one to judge the quality of cable manufacture by analyzing the quantitative and statistical characteristics associated with its internal structural heterogeneities.

A device is also known for determining the locations of damage to power lines and communications (see RF patent for invention No. 2073253, M. cl.

G01R 31/11, publ. 02/10/1997), containing a probe pulse generator, consisting of a series-connected probe pulse generator and a control unit for the output impedance of the generator, necessary to ensure that the output impedance of the generator matches the wave resistance of the line under study.

The output of the control unit of the output resistance of the generator is connected to the corresponding input of the receiver, which includes a mixer and an ADC connected in series with each other with controlled amplification. The input of the control unit of the output resistance of the generator is connected to the corresponding output of the computing unit (microcomputer), the other output of which is connected to another corresponding input of the receiver, the input / output of which is connected to the corresponding output / input of the computing unit, the other outputs of which are connected respectively to the inputs of the display unit and the unit synchronization, the corresponding outputs of which are connected to the synchronization input of the probe pulse generator and the synchronization input of the receiver.

In this device, voltage pulses at the output of the probe pulse generator enter the control unit of the output impedance of the generator, where, to exclude spurious reflections from the input line, the output impedance is cyclically matched with the line impedance. In this case, in the first cycle, half the amplitude of the probe pulse is memorized when the line is turned off. In the second cycle, the amplitude of the probe pulse is measured at an arbitrarily set value of the output resistance at the input of the connected line, the value stored in the first matching cycle is subtracted from it, and the sign and value of the subtraction result are stored. In the third cycle, according to the results of measurements of the first and second cycles, the wave impedance value is calculated, and the output impedance of the probe pulse generator is set using its digital code with a given accuracy.

This allows you to increase the accuracy and reliability of measurements when determining the location of damage to the lines. At the same time, the time dependence of the reverse flow is observed on the display device (display unit), and the operator judges the location of the damage by the greatest reflection.

However, this device, like the previous analogue, does not allow the assessment of quantitative and statistical characteristics of internal structural heterogeneities of transmission lines, i.e. judge its quality.

In addition, in both analogues, no measures were taken to separate probe pulses and reverse flow. As a result of this, the fluctuations in the reflection coefficient in the near field are indistinguishable, this portion of the trace is called the "dead zone". In the last analogue, a probe pulse, falling into the receiver, causes a transient process that distorts the trace, called the “ski effect”.

The presence of a "dead zone" and distortions caused by the "ski effect" in devices for determining the location of line inhomogeneities are acceptable, but are unacceptable for assessing the quantitative and statistical characteristics of internal structural heterogeneities of cables.

In addition, when measuring the characteristics of internal inhomogeneities of symmetrical cables, it is necessary to provide symmetrical input / output so as not to disrupt the operation of the cable circuit. Failure to comply with this condition leads to unreliable results. For devices for locating faults, this requirement is not critical, therefore devices with an unbalanced input can be used both for measurements on symmetric and asymmetric circuits.

In addition, in the case of a study of balanced cables, it is desirable to determine the location and magnitude of the concentrated energy transitions between adjacent pairs of balanced cables, which cannot be done in known analogues.

The device according to the patent of the Russian Federation for the invention No. 2073253 is selected as a prototype.

The technical result of the claimed device is to provide an opportunity to assess the quantitative and statistical characteristics of internal structural inhomogeneities of cables, such as laws and moments of distribution of reflection coefficients, as well as the location and magnitude of inhomogeneities of concentrated energy transitions between adjacent pairs of balanced cables while increasing the reliability of measurements and expanding the range of studied cables.

The achievement of the specified technical result is provided in the proposed device for assessing the quantitative and statistical characteristics of the internal heterogeneities of electric cables, containing a probe pulse generator and a matching device, output connected to a receiver containing an amplifier and ADC, a computing unit containing a processor connected to the memory block by input / output, moreover, the corresponding input and output computing unit is connected respectively with the output and the corresponding inputs nickname and the input of the display unit, characterized in that it contains a connection unit made with at least two separate inputs / outputs from the cable side, which are the corresponding inputs / outputs of the said matching device, which is included in the connection unit, which also contains a differential system input connected to the output of the probe pulse generator, and input / output - with the output / input of the matching device, the receiver has a trace memory unit corresponding to the input connected to the output m ADC, the corresponding input connected to the output of the amplifier, the computing unit further comprises a series-connected distortion corrector, amplitude corrector, statistical processing unit, the corresponding inputs / outputs of which are connected to the outputs / inputs of the correlator and the processor, the control output of which is connected to the control inputs of the amplitude corrector, distortion corrector, trace memory unit and receiver amplifier, probe pulse generator and device for matching the connection unit moreover, the output of the differential system and the corresponding output of the matching device of the connection unit are connected to the corresponding inputs of the amplifier, which are the inputs of the receiver, the output of the trace memory block, which is the output of the receiver, is connected to the input of the computing unit, which is the input of the distortion corrector, and the output of the computing unit, which is the output of the statistical processing unit is connected to the input of the display unit.

Moreover, to ensure the input of necessary information by the operator, the input of the processor can be connected to the output of the keyboard.

The matching device can be configured to match the output impedance of the probe pulse generator with the wave impedance of the cable.

The matching device can be performed balancing.

The presence in the connection block of a differential system allows you to separate the probe pulses from the reverse flow and prevent the probe pulses from passing into the receiver amplifier, which eliminates the trace portion called the “dead zone”, as well as eliminates the transient process called the “ski effect” that distort the trace, which increases the reliability of measurements.

The implementation of the matching device in the connection unit with the possibility of matching the output impedance of the probe pulse generator with the wave impedance of the cable also improves the reliability of the measurements.

The implementation of the matching device in the connection block symmetrical and its implementation with at least two separate inputs / outputs on the cable side makes it possible to expand the range of the studied cables by providing measurements of the characteristics of balanced cables, as well as determine the magnitude and location of the concentrated energy transitions caused by inhomogeneities between adjacent pairs of balanced cables.

The introduction of reflectograms into the memory block allows the accumulation (averaging) of the recorded reverse flow during multiple sensing, increasing the signal-to-noise ratio, which increases the reliability of measurements and allows the accumulation of statistics of the reflection coefficient distribution over the cable.

Introduction to the computational unit of the distortion corrector, amplitude corrector, statistical processing unit, correlator allows you to get a histogram of the distribution of reflection coefficients, statistical characteristics and auto and cross-correlation functions, i.e. it becomes possible to assess the quantitative and statistical characteristics of internal structural inhomogeneities of the cable.

The proposed utility model is illustrated by drawings, where figure 1 shows a structural diagram of a device for assessing the quantitative and statistical characteristics of internal heterogeneities of electric cables,

figure 2. a schematic diagram of the connection unit 2 is shown, FIG. 3a shows a trace of a cable chain showing the “dead zone” section (1), reflections from internal cable inhomogeneities (section 2) and reflection from the far end of the cable (section 3).

on figb shows a plot of the trace with distortion "ski effect" (1) and the transition process (2).

on fig 3c. the trace portion is shown after elimination of the “ski effect” distortions, at the input of the amplitude corrector (1) and after the amplitude correction (2),

on fig. a histogram of the distribution of reflection coefficients from internal cable inhomogeneities (1) and a Gaussian curve approximating it (2) are presented.

figure 4 shows the block diagram of the algorithm of the program installed in the processor 15 of the computing unit 10.

According to figure 1, the proposed device contains a probe pulse generator 1, a connection unit 2, including a differential system 3 and a matching device 4, with an output / input connected to the input / output of the differential system 3. Moreover, the input of the differential system 3, which is the input of the connection unit 2, connected to the output of the probe pulse generator 1, and the matching device is made with at least two separate inputs / outputs for connecting the cable 5, including a balanced one.

It should be noted that the matching device 4 can be made balancing and with the possibility of matching the output impedance of the probe pulse generator 1 with the wave impedance of cable 5.

The device also contains a receiver 6, including a series-connected amplifier 7, ADC 8 and the trace memory unit 9, and the outputs of the differential system 3 and the matching device 4 are connected to the corresponding inputs of the amplifier 7, which are the inputs of the receiver 6, and the output of the trace memory unit 9, which is the output of the receiver 6, is connected to the input of the computing unit 10, which is the input of the corrector 11 distortion.

The computing unit 10 also contains a series-connected amplitude corrector 12, a statistical processing unit 13, the output of which is the output of the computing unit 10, and the output of the distortion corrector 11 is connected to the input of the amplitude corrector 12, the corresponding inputs / outputs of the statistical processing unit 13 are connected respectively to the outputs / inputs correlator 14 and processor 15, the other outputs / inputs of which are connected to the inputs / outputs of the memory unit 16.

The output of the statistical processing unit 13 is connected to the input of the indication unit 17, and the processor 15 is connected to the keyboard 18 by the input and the control output to the control inputs of the amplitude corrector 12, distortion corrector 11, trace memory unit 9, amplifier 7, matching device 4, and generator 1 probe pulses.

The work of the proposed device is as follows. The probe pulse generator 1 generates a voltage pulse, which can have a rectangular shape, and the amplitude and shape of the pulse can be set by the operator through the keyboard 18 or by the control commands of the processor 15. The pulse repetition period is determined by the doubled pulse propagation time from the beginning to the end of the cable under investigation 5. Then through the block 2 connections, the pulses enter the two-wire circuit of the test cable 5.

The connection unit 2 includes a matching device 4, which serves to coordinate the output impedance of the probe pulse generator 1 and the wave impedance of cable 5, while it has at least two inputs / outputs, which allows operating in the common and separate inputs mode . In the common input mode, the reverse flow of one cable circuit is analyzed, and in the mode with separate inputs, the reverse flow is received, formed by the transition of the probe pulses between the circuits of the cable under test 5. Moreover, the implementation of the balancing device 4 makes it possible to work with symmetrical cables and allows you to determine the size and location of the cables heterogeneities of concentrated energy transitions between adjacent pairs of balanced cables.

The differential system 3 included in the connection unit 2 ensures separation of the probe pulses and the reverse flow so that the probe pulses do not pass into the amplifier 7 of the receiver 6. If probe pulses get into the amplifier 7, it is saturated, which leads to distortion of the trace. The need to use differential system 3 occurs when working in the common input mode.

The probe pulses propagating through cable 5 are partially reflected from inhomogeneities, forming a reverse flow, which, through the connection block 2, enters the receiver 6, the amplifier 7 of which amplifies the reverse flow signal, and the ADC 8 converts it to digital form. The samples of the return flow signal are recorded in the block 9 memory traces. The proposed device can carry out multiple sensing of the cable 5, while the block 9 of the memory of the trace is the accumulation (averaging) of the recorded stream, which increases the signal-to-noise ratio. As a result, a trace 5 of the cable 5 is formed at the output of the receiver (Fig. 3a).

The registered trace then goes to the computing unit 10 - to the input of the corrector 11 distortions, which serves to eliminate distortions of the type “ski effect”, while this block can be performed in such a way that eliminates distortion either on the basis of regression analysis, or by approximation methods ( figb). Then the trace goes to the amplitude corrector 12, where the distortion distortion caused by the attenuation and dispersion of the pulses during propagation along the cable circuit is eliminated. Correction is made taking into account the shape, duration of the probe pulse and the impulse response of cable 5. (Fig. 3c) For this, not only shortening factors (as is done in known devices for detecting places of cable inhomogeneities) are recorded in the memory unit 16, but also the parameters of the impulse response of the studied cable 5. After that, the corrected pulses are sent to the statistical processing unit 13, in which the amplitude of the trace is converted to the reflection coefficient. In addition, the initial and final sections are excluded from the trace, since there are reflections of inconsistency from the end heterogeneities in them, and the trace is represented by a variational series of reflection coefficients, which determine the statistical characteristics of cable 5 (Fig. 3d).

In the correlator 14, the auto and cross-correlation functions of the variational series of reflection coefficients and transition coefficients are calculated to identify dependencies characterizing the internal heterogeneities of cable 5.

The recorded trace and calculation results (histogram of the distribution of reflection coefficients, statistical characteristics, auto and cross-correlation functions) are displayed on the display unit 17.

The functioning of the device is carried out by the processor 15, under the control of a program recorded in the memory unit 16.

As mentioned above, measurements can be performed in a multiple cycle to obtain greater reliability. At the same time, on the basis of the measurement results, the processor 15 sets the parameters of the probe pulses (for example, the duration or the repetition period), selects the best matching with the line, sets the optimal gain and correction factors, monitors the signal-to-noise ratio of the recorded trace.

A keyboard 18 may be used to enter the initial settings and control the device. In addition, the device may have an interface for communication with an external computer for transmitting reflectograms and processing results to it.

Consider an example of the execution of the blocks of the proposed device.

As the generator 1 of the probe pulses, a digital functional generator of the ANR-3122 type (manufacturer Aktakom) can be used.

As the receiver 6, a digital oscilloscope can be used, with the function of transmitting the registered signals to a personal computer, for example, the ASK-3107 oscilloscope (manufactured by Aktakom). The generator and the oscilloscope have ports for communication with the computer, their work is controlled by the program downloaded to the computer.

The connection unit 2 can be performed on specialized operational amplifiers, for example AD815, AD8056 (manufacturer Analog Device) according to the circuit shown in figure 2. To organize the second input / output of the connection unit 2 (input / output of the matching device 4), it is necessary to use two circuits of Fig. 2 connected at the input. The circuit has a symmetrical input / output, while the tunable resistor (R11) available in it ensures matching the output impedance with the wave impedance of the connected cable 5.

As the computing unit 10 can be used a personal computer connected to a generator and an oscilloscope.

In our device, as the processor 15 of the computing unit 10, a processor of a personal computer can be used on which a program is installed, the block diagram of which is shown in FIG. 4. Under the control of the program, a computer connected to the generator and the oscilloscope can perform the functions of a computing unit: control the generator, distortion correction, amplitude correction, statistical and correlation processing of samples of the backflow signal recorded by the oscilloscope, storing and displaying the results. The display unit 17 and the keyboard 18 in this case are respectively the monitor and keyboard of a personal computer. As a personal computer, you can use a computer such as Foxconn 6627 MA, Celeron 3066, 512 Mb, HDD 80, GeForce 7300 GS.

The structural diagram of the claimed device can also be implemented on the basis of commercially available reflectometers, for example, Flight-205 (manufacturer Stell), Ri-20 m (manufacturer Oersted). OTDRs are connected to the test cable through the connection unit (figure 2) and register reflectograms of the tested cable circuits. With such an implementation, an OTDR performs the functions of a generator 1, a receiver 6, and part of the functions of a computing unit 10. Registered OTDRs in the form of sample files are transmitted to a computer, where distortion correction and amplitude correction are performed under program control, statistical characteristics of inhomogeneities are calculated, and correlation processing is performed. The calculation results are displayed on the monitor and saved in the report file.

Claims (4)

1. A device for evaluating the quantitative and statistical characteristics of internal heterogeneities of electric cables, containing a probe pulse generator and a matching device, output coupled to a receiver containing an amplifier and ADC, a computing unit containing a processor connected to the input / output by a memory unit, with corresponding input and output the computing unit is associated respectively with the output and the corresponding inputs of the receiver and the input of the display unit, characterized in that it contains a unit for connecting made with at least two separate inputs / outputs on the side of the cable, which are the corresponding inputs / outputs of the said matching device, which is included in the connection unit, which also contains a differential system, the input connected to the output of the probe pulse generator, and the input / output - with the output / input of the matching device, the trace memory unit is inserted into the receiver, the corresponding input is connected to the ADC output, the corresponding input is connected to the output of the amplifier, the th block further comprises a series-connected distortion corrector, an amplitude corrector, a statistical processing unit, the corresponding inputs / outputs of which are connected to the outputs / inputs of the correlator and the processor, the control output of which is connected to the control inputs of the amplitude corrector, distortion corrector, trace memory unit and receiver amplifier, a probe pulse generator and a matching device of the connection unit, the output of the differential system and the corresponding output of the device the coordination of the connection block is connected to the corresponding inputs of the amplifier, which are the inputs of the receiver, the output of the trace memory block, which is the output of the receiver, is connected to the input of the computing unit, which is the input of the distortion corrector, and the output of the computing unit, which is the output of the statistical processing unit, is connected to the input of the block indication. 2. The device according to claim 1, characterized in that the input of the processor is connected to the output of the keyboard. 3. The device according to claim 1, characterized in that the matching device is configured to match the output impedance of the probe pulse generator with the wave impedance of the cable. 4. The device according to claim 1, characterized in that the matching device is made symmetrical.