CN108333476A - A kind of cable fault TDR localization methods and system considering cable attenuation characteristic - Google Patents
A kind of cable fault TDR localization methods and system considering cable attenuation characteristic Download PDFInfo
- Publication number
- CN108333476A CN108333476A CN201810136168.3A CN201810136168A CN108333476A CN 108333476 A CN108333476 A CN 108333476A CN 201810136168 A CN201810136168 A CN 201810136168A CN 108333476 A CN108333476 A CN 108333476A
- Authority
- CN
- China
- Prior art keywords
- cable
- pulse signal
- tdr
- fault
- amplitude
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 56
- 230000004807 localization Effects 0.000 title claims abstract description 7
- 238000012545 processing Methods 0.000 claims abstract description 8
- 238000004364 calculation method Methods 0.000 claims abstract description 7
- 230000005540 biological transmission Effects 0.000 claims description 45
- 238000012360 testing method Methods 0.000 claims description 12
- 239000011810 insulating material Substances 0.000 claims description 6
- 238000010187 selection method Methods 0.000 claims description 2
- 230000015556 catabolic process Effects 0.000 abstract 2
- 230000008569 process Effects 0.000 description 8
- 230000008859 change Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000003321 amplification Effects 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 230000002238 attenuated effect Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 238000003199 nucleic acid amplification method Methods 0.000 description 3
- 230000008054 signal transmission Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000035699 permeability Effects 0.000 description 2
- 238000001028 reflection method Methods 0.000 description 2
- 238000002310 reflectometry Methods 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012774 insulation material Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 239000003595 mist Substances 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/083—Locating faults in cables, transmission lines, or networks according to type of conductors in cables, e.g. underground
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/088—Aspects of digital computing
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/11—Locating faults in cables, transmission lines, or networks using pulse reflection methods
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Mathematical Physics (AREA)
- Theoretical Computer Science (AREA)
- Locating Faults (AREA)
Abstract
Considering that the cable fault TDR localization methods of cable attenuation characteristic and system, localization method include the following steps the invention discloses a kind of：Selected transmitting pulse signal amplitude, emits and acquires reflected impulse signal, carries out breakdown judge according to reflected impulse signal, judges the reasonability of possible breakdown point, terminates cable fault positioning；System using this method includes display module, processing module and TDR modules.Using the localization method and system, the influence of " false-alarm " is not only can effectively avoid, the accurate positioning for completing failure；And the amplitude of transmitting pulse signal can be determined according to result of calculation, it thoroughly solves the problems, such as to bring due to determining signal emission parameter because by rule of thumb in the past various.
Description
Technical Field
The invention relates to the technical field of cable fault testing, in particular to a cable fault TDR positioning method considering cable attenuation characteristics, and further relates to a system for performing TDR positioning on cable faults by using the method.
Background
The cable is a hub for connecting power supply and electric equipment and connecting the equipment, and is responsible for tasks such as power transmission, signal transmission and distribution. As power is used more and more widely in various devices, the impact of a cable fault (such as a short circuit or an open circuit) is more and more serious. For example, cables on airplanes are distributed all over the airplanes, and are easily subjected to short circuit, open circuit and other faults due to long-term influence of factors such as water vapor, ultraviolet rays, vibration, salt mist corrosion and the like. The cable fault of the airplane affects the flight performance if the cable fault is slight, and endangers the flight safety if the cable fault is serious, even causes flight accidents. Because cables in airplanes and ships are often arranged in narrow spaces, the traditional visual inspection method cannot be adopted to complete fault positioning.
At present, for the positioning of cable faults in airplanes and ships, a mature method is used as a TDR method, namely a time domain pulse reflection method. The method comprises the steps of injecting a pulse signal into a cable, reflecting the pulse signal when the pulse signal passes through an impedance mismatching point on the cable, and calculating the product of the time difference between a transmitted pulse signal and a reflected pulse signal and the propagation speed of the pulse signal in the cable to obtain the fault distance so as to complete the positioning of the cable fault. For cables in an airplane and a ship, one cable may pass through impedance change points (i.e., impedance mismatching points) in various forms such as plug connectors, hinge points, welding points and the like in the wiring process, and when fault location is performed by using a TDR method under the condition, a fault reflection pulse signal is formed at a fault point (such as short circuit or open circuit), and a non-fault reflection pulse signal is also formed at the impedance change point, so that large interference is formed on cable fault location, a 'false alarm' signal is given, the cable fault location accuracy is affected, even misjudgment is caused, and the maintenance cost is increased. Moreover, when the TDR method is used to locate a cable fault, a low-voltage pulse signal is usually injected into the cable for detection, but because the actual attenuation characteristic of the signal in the cable is not considered, the transmission parameter (mainly, the voltage of the signal) of the signal can only be determined empirically, and without theoretical guidance, the fault location cannot be detected at all when the transmission parameter setting is low, and the problem that the implementation is difficult or the implementation cost is high when the transmission parameter setting is high occurs.
Disclosure of Invention
The invention provides a cable fault TDR positioning method and system considering cable attenuation characteristics, and aims to solve the problems that fault misjudgment is easy to occur in the existing cable fault positioning, signal emission parameters are determined only by experience, and the like.
The invention discloses a cable fault TDR positioning method considering cable attenuation characteristics, which comprises the following steps:
step S1, according to the characteristic of the tested cable, selecting the amplitude V of the TDR emission pulse signalin(ii) a The characteristic of the tested cable mainly refers to the attenuation characteristic of the cable, and the following influence factors are mainly considered: length l of cable to be testedHEquivalent resistance R of the cable to be testedLCharacteristic impedance Z of the cable to be tested0Equivalent conductance G of the cable to be testedLAnd the like.
Step S2, generating a transmitting pulse signal, injecting the transmitting pulse signal into the tested cable, and then collecting a reflected pulse signal at the position where the impedance is not matched; in the TDR positioning method, a pulse signal generator generates a transmitting pulse signal, and a signal collector collects a reflected pulse signal.
Step S3, judging the fault according to the reflected pulse signal; specifically, the waveform of the reflected pulse signal needs to be analyzed, and the fault type can be determined according to the amplitude and phase relationship between the reflected pulse signal and the transmitted pulse signal. But due to the external environment and internal influences generated when passing through the connector (including the plug connector, the hinge point, the welding point, etc.), a "false alarm" phenomenon or a false judgment may occur. In order to improve the accuracy of fault judgment, the following method is adopted for judging the fault:
(1) when the absolute value | V (td) | of the amplitude of the reflected pulse signal is more than or equal to 1V, judging that the tested cable has a fault, and determining the fault type and the fault point distance L; the fault point distance L can be determined according to the TDR positioning method.
(2) When the absolute value of 0.5V is less than or equal to absolute value V (td) is less than 1V, the possibility of fault of the tested cable is judged, and then the distance l of a possible fault point d is calculateddWhere the distance l of the possible fault points ddAlso determined according to the TDR positioning method.
(3) When | V (td) | < 0.5V, it is determined that there is no fault in the measured cable, and the process proceeds to step S5.
Step S4, judging whether the amplitude V (td) of the reflected pulse signal of the possible fault point d is reasonable or not according to the attenuation characteristic of the cable; if reasonable, L ═ LdI.e. the distance l of the possible fault point ddNamely the distance L of the fault point; if not, the possible fault point d is a false alarm, and the process goes to step S5.
And step S5, ending the cable fault location.
Preferably, in step S4, when determining whether the amplitude v (td) of the reflected pulse signal at the possible fault point d is reasonable according to the attenuation characteristic of the cable, the following method is specifically adopted:
step S41, assuming that the tested cable is a uniform cable, calculating an absolute value | V (d) | of the theoretical amplitude of the reflected pulse signal of the possible fault point d, namely calculating the absolute value | V (d) | of the theoretical amplitude of the reflected pulse signal of the position corresponding to the possible fault point d when the tested cable is the uniform cable;
step S42, if | V (td) | > | V (d) |, the amplitude V (td) of the reflected pulse signal at the possible fault point d is not reasonable; otherwise, it is reasonable.
Preferably, the method for calculating | v (d) | in step S41 specifically includes:
wherein ldDistance of possible fault points d, RLIs the equivalent resistance, Z, of the cable under test0Is the characteristic impedance of the cable to be tested, GLIs the equivalent conductance of the cable under test.
Preferably, the amplitude V of the transmitted pulse signal in step S1inThe selection method specifically comprises the following steps:
wherein, V1(d) Limit value of interference noise in tested cable,/HThe length of the tested cable; by determining VinThe problem that the transmission parameters of the signals can be determined only according to experience in the past can be solved, and various problems caused by the problem are avoided.
Preferably, V1(d) Is 0.5V. According to a large number of experimental tests, for a common cable, the amplitude of various noises acting on the common cable is about 0.5V at most, wherein the noises comprise external noises, noises introduced by a connector and the like, the amplitude of a transmitting pulse signal is gradually attenuated when the transmitting pulse signal is transmitted through the tested cable, and the TDR positioning method cannot identify the transmitting pulse signal when the transmitting pulse signal is attenuated to the range, so that 0.5V is selected as a judgment threshold value.
Preferably, the method for calculating the distance L between the fault points in step S4 is replaced by:
wherein,c is the speed of light, εrAnd delta t is the time difference between the transmitted pulse signal and the reflected pulse signal, which is the relative dielectric constant of the insulating material of the tested cable.
In order to better realize the cable fault TDR positioning method considering the attenuation characteristic of the cable, the invention also provides a system for positioning the cable fault by using the TDR positioning method.
The positioning system comprises a TDR module, a processing module and a display module; the TDR module is used for generating a transmitting pulse signal and receiving a reflected pulse signal; the processing module is used for analyzing the waveform of the reflected pulse signal, judging whether a fault point and a possible fault point d exist or not, analyzing the rationality of the possible fault point d, and determining the fault type and the fault point distance L; the display module is used for displaying the selected parameters, the possible fault points d and the information of the fault points; the display module, the processing module and the TDR module are electrically connected in sequence, and the TDR module is electrically connected with a tested cable.
Preferably, the TDR module in the positioning system is electrically connected to the cable to be tested via an impedance matching connector. By providing impedance matching connectors, the impact of the connection location on fault location can be reduced.
Preferably, the TDR module in the positioning system is composed of a pulse signal generator and a signal collector, the pulse signal generator is configured to generate a transmission pulse signal, and the signal collector is configured to collect a reflection pulse signal at the impedance mismatch position.
Preferably, the amplitude of the pulse signal generator to generate the transmission pulse signal is adjustable, so as to realize the step S1 of selecting the amplitude V of the TDR transmission pulse signal according to the characteristics of the cable to be tested in the aforementioned positioning methodinThe problems associated with empirically determining the transmit parameters of a signal are reduced.
The TDR positioning method and system for cable faults considering the attenuation characteristics of the cable can effectively remove the influence of false alarms and accurately complete the positioning of the faults; and the amplitude V of the transmitted pulse signal can be determined according to the calculation resultinThe method thoroughly solves various problems caused by determining the signal transmission parameters by experience in the past.
Drawings
Fig. 1 is a flow chart of a cable fault TDR locating method taking into account cable attenuation characteristics.
Fig. 2 is a schematic structural diagram of a positioning system.
FIG. 3 is a schematic view of the TDR module assembly and the connection between the TDR module and the tested cable.
Fig. 4 is a waveform diagram of a transmission signal and a reflection signal of a cable with an open fault at test 87m when the amplitude of the transmission pulse signal is 5.5V.
Fig. 5 is a waveform diagram of a transmission signal and a reflection signal of a cable with an open fault at a test 87m when the amplitude of a transmission pulse signal is 3.3V.
FIG. 6 is a waveform diagram of the transmitted signal and the reflected signal of the 100m cable tested when the amplitude of the transmitted pulse signal is 5.5V.
Detailed Description
The following describes an embodiment of the present invention with reference to fig. 1 to 6.
As shown in fig. 1, a method for TDR location of cable fault considering attenuation characteristic of cable according to the present invention mainly includes five steps: and selecting the amplitude of the transmitted pulse signal, transmitting and collecting the reflected pulse signal, judging the fault according to the reflected pulse signal, judging the rationality of a possible fault point, and finishing the cable fault positioning. Where it is justified to judge a possible point of failure an optional step, which may be omitted when there is no possible point of failure and is therefore indicated by a dashed line in fig. 1.
To better illustrate a cable fault TDR locating method of the present invention that considers the attenuation characteristics of a cable, the following describes in detail how the attenuation characteristics of a cable are analyzed in the present invention.
The frequency of the high-frequency pulse signal is basically unchanged in the process of propagating along the tested cable; the waveform is distorted due to external signal interference and the characteristics of the transmission line; the amplitude of the signal may have some attenuation due to dielectric loss, wire loss, radiation loss, etc., and the attenuation of the signal may be more severe as the frequency of the signal is higher and the propagation distance is longer.
Attenuation is a characteristic of lossy transmission lines and is a direct result of solving a second-order lossy RLCG distributed parametric circuit model, commonly used at αnThe attenuation in unit length, given in neper/meter, is defined as follows:
wherein: rLIs the equivalent resistance of the transmission line, in Ω; gLIs the equivalent conductance of the transmission line, in units S; l isLIs the equivalent inductance of the transmission line, unit H; cLIs the equivalent capacitance of the transmission line, unit F; ω is the frequency of the signal on the transmission line.
In a uniform lossy transmission line, it can be expressed as:
in the formula: z0Which is the characteristic impedance of the transmission line, in omega.
When a signal propagates along a uniform cable, the influence of the wire loss on the signal is mainly to attenuate the signal amplitude. If the signal amplitude is V for the transmit pulseinThe amplitude of the signal is not linearly reduced along with the increase of the distance, but exponentially reduced along with the change of the distance, and the amplitude relation of the input signal and the output signal on the transmission line is as follows:
in the formula, VinRepresents the amplitude of the transmitted pulse signal, in units V; v (d) represents the voltage amplitude of the point d on the transmission line in the unit V; a. thenRepresents total attenuation, in neper; ldDistance d, in meters, from the signal input to point d αnIs the attenuation of a transmission line in units of length, in units of neper/meter.
Since decibel usage is more common and calculation is more convenient, α can be obtained by using the conversion relation in the following formula (4)nConversion to decibel form:
from the above equation, the relationship between the input voltage and the output voltage expressed in decibels is obtained:
if equation (2) is converted to dB form by the conversion relation of equation (4), the attenuation dB/length per unit length of the transmission line is obtained as:
the formula of the attenuation characteristic of the transmission signal along the transmission line can be known from the formulas (5) and (6):
the above is an analysis process of the cable attenuation characteristic, and a relationship between the amplitude and the propagation distance of the high-frequency pulse signal on a certain cable is obtained on the basis of the frequency and the amplitude of the given high-frequency pulse signal according to the cable attenuation characteristic model.
The theory of cable fault location based on TDR (i.e. time domain pulse reflection method) is briefly described below. The TDR basic theory is the transmission line theory; in the transmission line principle, a cable is used as a distributed parameter element, and in a uniform transmission line, the characteristic impedance on the transmission line is a certain value, wherein the characteristic impedance of the cable can be represented by equation (8):
in the formula, LL1Inductance per unit length of cable, CL1Is the capacitance per unit length of cable.
In the transmission line theory, in the process of transmitting an electric pulse signal in a cable, if a transmission medium is uniform, the signal can be transmitted all the time along the cable, and if the cable has a fault (open circuit or short circuit), the transmission medium is not uniform, and the pulse signal can be reflected at a position with changed impedance. The reflection coefficient at the impedance mismatch on the transmission line is the ratio of the reflected voltage to the transmitted voltage:
in the formula, VreFor reflecting the amplitude of the pulse signal voltage, ZlInput impedance, Z, for points of cable route obstruction0Is the characteristic impedance of the cable. The following three characteristics can be obtained from the formula (9):
(1) when the cable is normal, Z0＝Zlρ is 0, the transmitted signal will eventually be absorbed by the load without reflection;
(2) when the cable is broken, Zl→ infinity, ρ 1, where the reflected electrical pulse is the same amplitude and phase as the initial transmitted pulse;
(3) when the cable is short-circuited, Zl→ 0, ρ ═ 1, the reflected electrical pulse is the same amplitude as the initial pulse, but opposite in phase.
In transmission line theory, signals propagate in the form of electromagnetic waves on a transmission line; after a voltage is applied to one end of the cable, a certain time is required for signal transmission due to inertia of capacitance in distribution parameters of the cable. The propagation velocity v of the signal in the cable is then:
in the formula, epsilon0In order to have a dielectric constant in a vacuum,μ0is a vacuum permeability, mu0＝4π×10-7，εrIs the relative dielectric constant, mu, of the insulating materialrThe relative permeability of the insulating material is generally 1. Will epsilon0、μ0、μrSubstituting the value of (2) into the formula (10) to obtain:
wherein c is the speed of light, c is 3 × 108；
From the equation (11), the propagation speed of the signal in the cable is only related to the relative dielectric constant of the insulating material, and is not related to other factors. The signals have the same speed in the cables of the same insulating material;
the time domain reflectometry determines the fault distance by measuring the time difference delta t between the transmitted pulse and the reflected pulse at the impedance mismatch position and calculating the propagation speed of the signal in the cable according to the formula (11), wherein the fault distance is as follows:
wherein L is the distance between the test end and the fault point, v is the propagation speed of the signal in the cable, and delta t is the time difference between the transmitted pulse and the reflected pulse.
By analyzing the waveform of the reflected pulse signal, when the reflected pulse signal is obvious (as mentioned above, because the noise level in the cable is about 0.5V, when the absolute value of the amplitude of the reflected pulse signal is more than or equal to 1V, the noise level is more exceeded, the reflected pulse signal is considered to be obvious), the existence of a fault in the tested cable is directly judged; when the reflected pulse signal is not obvious (when the absolute value of the amplitude of the reflected pulse signal is between 0.5V and 1V, the reflected pulse signal is considered to be not obvious), the possibility of fault of the tested cable is judged, the amplitude of the reflected pulse signal when the reflected pulse signal is not obvious is measured, then the fault distance is obtained according to the product of the time difference between the transmitted pulse signal and the reflected pulse signal and the propagation speed of the pulse signal in the cable, finally the theoretical amplitude of the reflected pulse signal at the position is calculated by combining the attenuation characteristic of the cable, and the fault diagnosis result is obtained through comprehensive judgment.
As shown in fig. 2, a cable fault TDR locating system considering cable attenuation characteristics according to the present invention includes a TDR module, a processing module, and a display module.
When the cable is connected with a tested cable, the impedance matching connector is used for connection, and the impedance matching connector is specifically shown in fig. 3; the pulse signal generator in the TDR module sends a transmitting pulse signal to the tested cable through the impedance matching connector, and when the impedance mismatching position exists in the tested cable, the reflecting pulse signal is collected by the signal collector of the TDR through the impedance mismatching connector.
Example 1:
the following describes how to select the amplitude of the transmitted pulse using a cable fault TDR locating method of the present invention that takes into account the attenuation characteristics of the cable.
The tested cable is a section of cable in the airplane, and the characteristic impedance Z of the tested cable050 Ω, equivalent resistance RL0.0062 Ω, equivalent conductance GL0.00046S, insulation material of tested cableRelative dielectric constant of ∈r2.25, length lhAt a position of 87 meters of the cable, an open circuit fault is artificially produced, and two transmitting pulse signals with different amplitudes and 100MHz frequencies are respectively selected for TDR positioning. The amplitude of the transmission pulse signal in fig. 4 is 5.5V, and the amplitude of the transmission pulse signal in fig. 5 is 3.3V.
As shown in fig. 4 and 5, there is a transmission pulse signal 1 in both figures. However, in fig. 4, there is a reflected pulse signal 2, and the corresponding position is determined as a fault point according to a conventional TDR positioning method; whereas in fig. 5 no reflected pulse signal 2 is present.
As can be seen from the comparison of the two graphs, when the amplitude of the transmitted pulse signal is 3.3V, the fault cannot be located. In the conventional TDR positioning method, the amplitude of the transmitted pulse signal is determined according to previous experience. As mentioned above, when the amplitude of the selected transmission pulse signal is low, the definition of the fault cannot be realized; when the amplitude of the selected transmitting pulse signal is high, the cost of the TDR component is increased, and when the amplitude is too high, the TDR component cannot be realized even in engineering.
The working voltage of chips such as an FPGA (field programmable gate array) and the like which are commonly used for generating TDR (time domain reflectometry) transmission pulse signals is 3.3V, and the pulse signals generated by a core chip can be subjected to amplitude amplification and output through an operational amplification circuit. For the amplification of the high-frequency pulse signal, the slew rate of the operational amplifier is considered (the slew rate refers to an average value of the output voltage time change rate of the closed-loop amplifier when the input is a step signal, and simply means a key index for determining the rising speed of the signal), if the slew rate is too small, the rising edge of the generated pulse signal is not steep enough and does not meet the requirement of the TDR test, and a device with a large slew rate is relatively expensive. By the above example, the amplitude of the transmitted pulse signal can be selected to help us to design a circuit better, and a relatively cheap device is selected, so that the circuit has a great economic value.
According to the method for selecting the amplitude of the transmitted pulse signal in the cable fault TDR positioning method considering the attenuation characteristic of the cable, the method is knownDetermining the amplitude V of a transmitted pulse signalin。
Wherein V1(d) In this embodiment, 0.5V is selected as the threshold V for determining the interference noise in the cable to be tested1(d) The value of (1) is that the signal is considered to be attenuated to 0.5V in the cable propagation process and then is considered to be unidentifiable.
According to the above calculation method and V1(d) Is calculated to obtain VinIs about 5.06V, the cable fault location can be carried out on the tested cable with the length of 100 meters by using the TDR technology. It can also be seen from this analysis that when V isinAt 3.3V, cable fault localization is not possible at all because the reflected pulse signal is completely drowned in noise.
Example 2:
the following describes how to use the cable fault TDR positioning method and system considering the cable attenuation characteristic to perform the complete process of TDR positioning on the cable fault.
In this embodiment, the parameters of the tested cable are exactly the same as those in embodiment 1, and the frequency of the transmitted pulse signal is 100 MHz.
Step S1, selecting the amplitude of the transmitted pulse signal
Calculated as in example 1, VinIs about 5.06V, the cable fault location can be carried out on the tested cable with the length of 100 meters by using the TDR technology. In order to make the reflected pulse signal more noticeable with respect to noise, V is appropriately increased in the present embodimentinAmplitude of (2), in particular Vin＝5.5V。
Step S2, emitting and collecting reflected pulse signals
As shown in fig. 6, the amplitude of the transmission pulse signal 1 is 5.5V, the frequency is 100MHz, and the time difference between the transmission pulse signal and the reflection pulse signal is Δ t equal to 500 ns; the amplitude of the reflected pulse signal 2 collected by the signal collector is V (td) ═ 0.99V.
Step S3, according to the reflected pulse signal, making fault judgment
According to the method of the invention, since 0.5V ≦ V (td) | < 1V, this point is a possible failure point.
Step S4, judging the rationality of possible fault points
According toAnd calculating the theoretical amplitude | V (d)) | of the reflected pulse signal of the possible fault point, and calculating to obtain | V (d)) | 1.73V.
If the amplitude v (td) of the reflected pulse signal at the possible fault point is reasonable, the possible fault point is determined to be a fault point. Further analysis of the reflected pulse signals reveals that the fault type at the fault point is "open circuit".
To further improve the accuracy of the calculation of the distance to the fault point, based onAnd Δ t, fromAnd calculating the distance L between the fault point and the test end to be 50 meters, namely the distance between the fault point and the test end is 50 meters.
And step S5, ending the cable fault location.
Finally, it should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and are not intended to limit the present invention, and although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications and equivalents can be made in the technical solutions described in the foregoing embodiments, or some technical features thereof can be replaced. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A cable fault TDR positioning method considering cable attenuation characteristics is characterized by comprising the following steps:
step S1, according to the characteristic of the tested cable, selecting the amplitude V of the TDR emission pulse signalin；
Step S2, generating a transmitting pulse signal, injecting the transmitting pulse signal into the tested cable, and then collecting a reflected pulse signal at the position where the impedance is not matched;
step S3, judging the fault according to the reflected pulse signal;
when the absolute value | V (td) | of the amplitude of the reflected pulse signal is more than or equal to 1V, judging that the tested cable has a fault, and determining the fault type and the fault point distance L;
when the absolute value of 0.5V is less than or equal to absolute value V (td) is less than 1V, the possibility of fault of the tested cable is judged, and then the distance l of a possible fault point d is calculatedd；
When | V (td) | < 0.5V, it is determined that there is no fault in the measured cable, and go to step S5;
step S4, judging whether the amplitude V (td) of the reflected pulse signal of the possible fault point d is reasonable or not according to the attenuation characteristic of the cable; if reasonable, L ═ Ld(ii) a If not, the possible fault point d is a false alarm, and the step S5 is executed;
and step S5, ending the cable fault location.
2. The TDR localization method of cable fault considering cable attenuation characteristic according to claim 1, wherein in step S4, when determining whether the amplitude v (td) of the reflected pulse signal at the possible fault point d is reasonable according to the attenuation characteristic of the cable, the following method is adopted:
step S41, assuming that the cable to be tested is a uniform cable, calculating the absolute value | V (d) | of the theoretical amplitude of the reflected pulse signal of the possible fault point d;
step S42, if | V (td) | > | V (d) |, the amplitude V (td) of the reflected pulse signal at the possible fault point d is not reasonable; otherwise, it is reasonable.
3. The TDR locating method for cable fault considering the attenuation characteristic of the cable according to claim 2, wherein the calculation method of | v (d) | in step S41 is specifically:
wherein ldDistance of possible fault points d, RLIs the equivalent resistance, Z, of the cable under test0Is the characteristic impedance of the cable to be tested, GLIs the equivalent conductance of the cable under test.
4. The TDR positioning method for cable faults considering cable attenuation characteristics as claimed in any one of claims 1 to 3, wherein the amplitude V of the transmitted pulse signal in step S1inThe selection method specifically comprises the following steps:
wherein, V1(d) Limit value of interference noise in tested cable,/HIs the length of the cable to be tested.
5. The TDR positioning method for cable faults considering the attenuation characteristics of cables as claimed in claim 4, wherein V1(d) Is 0.5V.
6. The TDR localization method of cable fault considering attenuation characteristic of cable according to claim 1, wherein the calculation method of fault point distance L in step S4 is replaced by:
wherein,c is the speed of light, εrAnd delta t is the time difference between the transmitted pulse signal and the reflected pulse signal, which is the relative dielectric constant of the insulating material of the tested cable.
7. A system for cable fault location using the TDR location method of any one of claims 1 to 6, comprising a TDR module, a processing module, a display module;
the TDR module is used for generating a transmitting pulse signal and receiving a reflected pulse signal;
the processing module is used for analyzing the waveform of the reflected pulse signal, judging whether a fault point and a possible fault point d exist or not, analyzing the rationality of the possible fault point d, and determining the fault type and the fault point distance L;
the display module is used for displaying the selected parameters, the possible fault points d and the information of the fault points;
the display module, the processing module and the TDR module are electrically connected in sequence, and the TDR module is electrically connected with a tested cable.
8. The TDR locating system for cable faults considering attenuation characteristics of the cable as claimed in claim 7, wherein the TDR module is electrically connected to the cable to be tested through an impedance matching connector.
9. The TDR locating system for cable faults considering the attenuation characteristics of the cable as claimed in claim 7 or 8, wherein the TDR module is composed of a pulse signal generator for generating the transmission pulse signal and a signal collector for collecting the reflection pulse signal at the impedance mismatch position.
10. The TDR locating system for cable faults considering the attenuation characteristics of the cable as claimed in claim 9, wherein the amplitude of the pulse signal generated by the pulse signal generator is adjustable.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810136168.3A CN108333476A (en) | 2018-02-09 | 2018-02-09 | A kind of cable fault TDR localization methods and system considering cable attenuation characteristic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810136168.3A CN108333476A (en) | 2018-02-09 | 2018-02-09 | A kind of cable fault TDR localization methods and system considering cable attenuation characteristic |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN108333476A true CN108333476A (en) | 2018-07-27 |
Family
ID=62928732
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201810136168.3A Pending CN108333476A (en) | 2018-02-09 | 2018-02-09 | A kind of cable fault TDR localization methods and system considering cable attenuation characteristic |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN108333476A (en) |
Cited By (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109116215A (en) * | 2018-08-10 | 2019-01-01 | Oppo（重庆）智能科技有限公司 | A kind of test method, test device and the storage medium of line reflection resonance point |
| CN109342880A (en) * | 2018-10-23 | 2019-02-15 | 东莞市慧眼数字技术有限公司 | A kind of cable fault detection method and system |
| CN109639345A (en) * | 2018-11-22 | 2019-04-16 | 成都飞机工业（集团）有限责任公司 | A kind of cable bandwidth test method based on time domain reflectometry TDR technology |
| CN110069027A (en) * | 2019-03-28 | 2019-07-30 | 深圳市联讯通讯技术有限公司 | A kind of cable Measuring error system and its application method with intelligent distributing frame |
| CN110261739A (en) * | 2019-07-29 | 2019-09-20 | 哈尔滨工业大学 | A kind of cable soft fault positioning device and localization method |
| CN110687396A (en) * | 2019-09-30 | 2020-01-14 | 山东信通电子股份有限公司 | Method and system for improving cable fault measurement precision |
| CN110763955A (en) * | 2019-12-04 | 2020-02-07 | 国网江苏省电力有限公司南通供电分公司 | Cable fault detection system and method based on high-voltage pulse signal injection |
| CN110763954A (en) * | 2019-12-04 | 2020-02-07 | 国网江苏省电力有限公司南通供电分公司 | Power cable fault detection system and method based on signal injection |
| CN110940896A (en) * | 2019-12-19 | 2020-03-31 | 苏州裕太车通电子科技有限公司 | Damage diagnosis method for ultra-long cable |
| CN111090022A (en) * | 2019-11-25 | 2020-05-01 | 国网山西省电力公司大同供电公司 | TDR-based water seepage defect accurate positioning method |
| WO2020104124A1 (en) * | 2018-11-21 | 2020-05-28 | Siemens Aktiengesellschaft | Method and measuring assembly for detecting faults on electrical lines |
| CN111352004A (en) * | 2020-03-26 | 2020-06-30 | 成都飞机工业（集团）有限责任公司 | Cable fault detection method, device, system and readable storage medium |
| CN112557823A (en) * | 2020-12-04 | 2021-03-26 | 国网浙江省电力有限公司绍兴供电公司 | Power transmission line fault positioning qualitative method based on time domain reflection technology |
| CN112630598A (en) * | 2020-12-30 | 2021-04-09 | 南方电网科学研究院有限责任公司 | Method and device for detecting fault degree of long-distance high-voltage cable |
| CN112731046A (en) * | 2020-12-04 | 2021-04-30 | 国网浙江省电力有限公司绍兴供电公司 | Power transmission line fault positioning qualitative system based on time domain reflection technology |
| CN113567801A (en) * | 2020-04-28 | 2021-10-29 | 南宁富桂精密工业有限公司 | Wire detection device and wire detection method |
| CN113759204A (en) * | 2021-11-10 | 2021-12-07 | 成都高斯电子技术有限公司 | Power line loss testing device and method |
| CN114994467A (en) * | 2022-05-26 | 2022-09-02 | 海南电网有限责任公司乐东供电局 | Cable fault double-end positioning method based on long test pulse |
| CN115128405A (en) * | 2022-06-22 | 2022-09-30 | 重庆长安新能源汽车科技有限公司 | Vehicle-mounted video line fault on-site diagnosis method and system |
| CN115356597A (en) * | 2022-10-20 | 2022-11-18 | 石家庄科林电气股份有限公司 | Power distribution network cable breakpoint distance measuring method and device and terminal equipment |
| CN116500500A (en) * | 2023-04-25 | 2023-07-28 | 内蒙古建升电气工程有限公司 | Rapid detection method and detection device for lightning protection device of wind generating set based on high-frequency pulse technology |
| CN117129798A (en) * | 2023-08-28 | 2023-11-28 | 中南大学 | Fault power module positioning method and system based on time domain reflection method |
| CN117739825A (en) * | 2023-12-14 | 2024-03-22 | 国网江苏省电力有限公司南通供电分公司 | Method for realizing cable length measurement |
| CN117970031A (en) * | 2024-02-28 | 2024-05-03 | 杭州欣美成套电器制造有限公司 | Cable monitoring and early warning system and method based on stress wave |
| CN117970031B (en) * | 2024-02-28 | 2024-10-29 | 杭州欣美成套电器制造有限公司 | Cable monitoring and early warning system and method based on stress wave |
Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA944431A (en) * | 1970-10-01 | 1974-03-26 | Michael A. Mcferrin | Tdr cable fault location |
| US6437578B1 (en) * | 2000-11-14 | 2002-08-20 | Tektronix, Inc. | Cable loss correction of distance to fault and time domain reflectometer measurements |
| US20030052694A1 (en) * | 2001-07-26 | 2003-03-20 | Gokhan Dindis | Identification of a distribution of transformers and fault location in primary underground loop systems |
| US20150253370A1 (en) * | 2012-10-24 | 2015-09-10 | Wirescan As | Method and system for monitoring a condition of electrical cables |
| CN105445624A (en) * | 2015-11-26 | 2016-03-30 | 重庆大学 | Cable fault positioning method according to combination of wavelet transformation and curve fitting |
| US20160139194A1 (en) * | 2013-06-11 | 2016-05-19 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Reflectometry method for identifying soft faults affecting a cable |
| CN106443359A (en) * | 2016-11-11 | 2017-02-22 | 南京工程学院 | Short-distance cable fault ranging system and ranging method with low-voltage pulse method |
| CN206638771U (en) * | 2017-03-29 | 2017-11-14 | 烟台中正新技术有限公司 | A kind of Anti-interference cable fault test system based on TDR |
-
2018
- 2018-02-09 CN CN201810136168.3A patent/CN108333476A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA944431A (en) * | 1970-10-01 | 1974-03-26 | Michael A. Mcferrin | Tdr cable fault location |
| US6437578B1 (en) * | 2000-11-14 | 2002-08-20 | Tektronix, Inc. | Cable loss correction of distance to fault and time domain reflectometer measurements |
| US20030052694A1 (en) * | 2001-07-26 | 2003-03-20 | Gokhan Dindis | Identification of a distribution of transformers and fault location in primary underground loop systems |
| US20150253370A1 (en) * | 2012-10-24 | 2015-09-10 | Wirescan As | Method and system for monitoring a condition of electrical cables |
| US20160139194A1 (en) * | 2013-06-11 | 2016-05-19 | Commissariat A L'energie Atomique Et Aux Energies Alternatives | Reflectometry method for identifying soft faults affecting a cable |
| CN105445624A (en) * | 2015-11-26 | 2016-03-30 | 重庆大学 | Cable fault positioning method according to combination of wavelet transformation and curve fitting |
| CN106443359A (en) * | 2016-11-11 | 2017-02-22 | 南京工程学院 | Short-distance cable fault ranging system and ranging method with low-voltage pulse method |
| CN206638771U (en) * | 2017-03-29 | 2017-11-14 | 烟台中正新技术有限公司 | A kind of Anti-interference cable fault test system based on TDR |
Non-Patent Citations (3)
| Title |
|---|
| A. HAMEL: "Attenuation of sound and temperature caused by faulted distribution cable joints" * |
| 何光华: "脉冲波形对脉冲反射法的电缆故障定位影响的研究" * |
| 刘晓琳: "基于低压脉冲反射法的飞机导线故障诊断与定位" * |
Cited By (32)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109116215A (en) * | 2018-08-10 | 2019-01-01 | Oppo（重庆）智能科技有限公司 | A kind of test method, test device and the storage medium of line reflection resonance point |
| CN109342880A (en) * | 2018-10-23 | 2019-02-15 | 东莞市慧眼数字技术有限公司 | A kind of cable fault detection method and system |
| WO2020104124A1 (en) * | 2018-11-21 | 2020-05-28 | Siemens Aktiengesellschaft | Method and measuring assembly for detecting faults on electrical lines |
| US11867742B2 (en) | 2018-11-21 | 2024-01-09 | Siemens Aktiengesellschaft | Method and measuring assembly for detecting faults on electrical lines |
| CN109639345A (en) * | 2018-11-22 | 2019-04-16 | 成都飞机工业（集团）有限责任公司 | A kind of cable bandwidth test method based on time domain reflectometry TDR technology |
| CN109639345B (en) * | 2018-11-22 | 2021-02-26 | 成都飞机工业（集团）有限责任公司 | Cable bandwidth testing method based on Time Domain Reflectometry (TDR) technology |
| CN110069027A (en) * | 2019-03-28 | 2019-07-30 | 深圳市联讯通讯技术有限公司 | A kind of cable Measuring error system and its application method with intelligent distributing frame |
| CN110261739A (en) * | 2019-07-29 | 2019-09-20 | 哈尔滨工业大学 | A kind of cable soft fault positioning device and localization method |
| CN110687396A (en) * | 2019-09-30 | 2020-01-14 | 山东信通电子股份有限公司 | Method and system for improving cable fault measurement precision |
| CN110687396B (en) * | 2019-09-30 | 2022-01-28 | 山东信通电子股份有限公司 | Method and system for improving cable fault measurement precision |
| CN111090022A (en) * | 2019-11-25 | 2020-05-01 | 国网山西省电力公司大同供电公司 | TDR-based water seepage defect accurate positioning method |
| CN110763954A (en) * | 2019-12-04 | 2020-02-07 | 国网江苏省电力有限公司南通供电分公司 | Power cable fault detection system and method based on signal injection |
| CN110763955A (en) * | 2019-12-04 | 2020-02-07 | 国网江苏省电力有限公司南通供电分公司 | Cable fault detection system and method based on high-voltage pulse signal injection |
| CN110940896A (en) * | 2019-12-19 | 2020-03-31 | 苏州裕太车通电子科技有限公司 | Damage diagnosis method for ultra-long cable |
| CN111352004A (en) * | 2020-03-26 | 2020-06-30 | 成都飞机工业（集团）有限责任公司 | Cable fault detection method, device, system and readable storage medium |
| CN113567801A (en) * | 2020-04-28 | 2021-10-29 | 南宁富桂精密工业有限公司 | Wire detection device and wire detection method |
| CN112731046A (en) * | 2020-12-04 | 2021-04-30 | 国网浙江省电力有限公司绍兴供电公司 | Power transmission line fault positioning qualitative system based on time domain reflection technology |
| CN112557823A (en) * | 2020-12-04 | 2021-03-26 | 国网浙江省电力有限公司绍兴供电公司 | Power transmission line fault positioning qualitative method based on time domain reflection technology |
| CN112630598A (en) * | 2020-12-30 | 2021-04-09 | 南方电网科学研究院有限责任公司 | Method and device for detecting fault degree of long-distance high-voltage cable |
| WO2022142615A1 (en) * | 2020-12-30 | 2022-07-07 | 南方电网科学研究院有限责任公司 | Long-distance high-voltage cable fault degree detection method and device |
| CN113759204A (en) * | 2021-11-10 | 2021-12-07 | 成都高斯电子技术有限公司 | Power line loss testing device and method |
| CN114994467A (en) * | 2022-05-26 | 2022-09-02 | 海南电网有限责任公司乐东供电局 | Cable fault double-end positioning method based on long test pulse |
| CN114994467B (en) * | 2022-05-26 | 2024-06-07 | 海南电网有限责任公司乐东供电局 | Cable fault double-end positioning method based on long test pulse |
| CN115128405A (en) * | 2022-06-22 | 2022-09-30 | 重庆长安新能源汽车科技有限公司 | Vehicle-mounted video line fault on-site diagnosis method and system |
| CN115356597A (en) * | 2022-10-20 | 2022-11-18 | 石家庄科林电气股份有限公司 | Power distribution network cable breakpoint distance measuring method and device and terminal equipment |
| CN116500500B (en) * | 2023-04-25 | 2024-05-17 | 内蒙古建升电气工程有限公司 | Rapid detection method and detection device for lightning protection device of wind generating set based on high-frequency pulse technology |
| CN116500500A (en) * | 2023-04-25 | 2023-07-28 | 内蒙古建升电气工程有限公司 | Rapid detection method and detection device for lightning protection device of wind generating set based on high-frequency pulse technology |
| CN117129798A (en) * | 2023-08-28 | 2023-11-28 | 中南大学 | Fault power module positioning method and system based on time domain reflection method |
| CN117129798B (en) * | 2023-08-28 | 2024-02-06 | 中南大学 | Fault power module positioning method and system based on time domain reflection method |
| CN117739825A (en) * | 2023-12-14 | 2024-03-22 | 国网江苏省电力有限公司南通供电分公司 | Method for realizing cable length measurement |
| CN117970031A (en) * | 2024-02-28 | 2024-05-03 | 杭州欣美成套电器制造有限公司 | Cable monitoring and early warning system and method based on stress wave |
| CN117970031B (en) * | 2024-02-28 | 2024-10-29 | 杭州欣美成套电器制造有限公司 | Cable monitoring and early warning system and method based on stress wave |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN108333476A (en) | A kind of cable fault TDR localization methods and system considering cable attenuation characteristic | |
| CN209590197U (en) | A kind of cable fault positioning device based on time-domain pulse reflection method | |
| RU2650717C2 (en) | Method and system for monitoring condition of electrical cables | |
| Song et al. | Detection and location of multiple wiring faults via time–frequency-domain reflectometry | |
| Sheng et al. | Partial discharge pulse propagation in power cable and partial discharge monitoring system | |
| US20170199235A1 (en) | Cable fault diagnosis method and system | |
| KR101570506B1 (en) | Apparatus and method for detecting cable fault location and impedance using linear chirp reflectometry | |
| US10048309B2 (en) | Method and device for automatically measuring physical characteristics of a cable, in particular the propagation velocity | |
| Tang et al. | A frequency-domain location method for defects in cables based on power spectral density | |
| CA2742667A1 (en) | Systems and methods employing time domain reflectometry | |
| CN109932614A (en) | A kind of cable fault investigation method and device | |
| CN106556782A (en) | A kind of Partial Discharge Sources location determining method and system | |
| US8570049B2 (en) | Method and apparatus for measuring AC shield continuity for shielded twisted pair structured datacomm cable link | |
| CN104406509A (en) | HHT (Hilbert Huang transform))-based electric cable length measuring method | |
| CN107576884A (en) | The online Fault Locating Method of deformation of transformer winding based on empirical mode decomposition and neutral net | |
| KR20180124570A (en) | system and method detecting reliability for cable fault localization | |
| CN110261739B (en) | Cable soft fault positioning device and positioning method | |
| Lee et al. | Contactless monitoring technique for live shielded cable via stepped-frequency waveform reflectometry and inductive coupler | |
| CN117434386A (en) | High-voltage cable sheath defect positioning method based on sheath grounding loop broadband impedance spectrum | |
| Thayoob et al. | Analysis of wave propagation in Time Domain Reflectometry circuit simulation model | |
| Horan et al. | A novel pulse echo correlation tool for transmission path testing and fault finding using pseudorandom binary sequences | |
| Hernandez-Mejia | Time Domain Reflectometry (TDR) | |
| Fantoni et al. | Wire system aging assessment and condition monitoring using line resonance analysis (LIRA) | |
| US20180372789A1 (en) | A method of locating a fault in a power transmission medium | |
| Alam et al. | Rod Insertion TDR for Detecting Corrosion Damage in Vertical Grounding Electrodes |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| WD01 | Invention patent application deemed withdrawn after publication | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20180727 |