CN209590197U - A kind of cable fault positioning device based on time-domain pulse reflection method - Google Patents

Abstract

The utility model discloses a cable fault location device based on a time-domain pulse reflection method. The device includes a display module, a processing module and a TDR module; in addition, a parameter input module can also be selected; a display module and a parameter input module Both the TDR module and the TDR module are electrically connected to the processing module. When the positioning device is used for cable fault location, the amplitude of the transmitted pulse signal can be determined according to the calculation results, which completely solves various problems caused by determining the signal transmission parameters based on experience in the past.

Description

A cable fault location device based on time domain pulse reflection method

This application is a divisional application of a patent application with an application date of February 9, 2018, an application number of 201820236603.5, and an invention titled "A cable fault location device based on time domain pulse reflection method".

technical field

The utility model relates to the technical field of cable fault testing, and mainly relates to a cable fault location device based on a time-domain pulse reflection method, in particular to a cable fault TDR location device considering cable attenuation characteristics.

Background technique

The cable is the hub of the connection between power supply and electric equipment, as well as the connection between various equipment, and is responsible for the transmission of power, transmission and distribution of signals and other tasks. As electricity is used more and more widely in various devices, the impact of cable failures (such as short circuits or open circuits) has become more and more serious. For example, the cables on the aircraft are all over the aircraft. Due to the long-term influence of water vapor, ultraviolet rays, vibration, salt spray corrosion and other factors, the cables are prone to short circuit and open circuit failures. Aircraft cable faults can affect flight performance in the slightest, endanger flight safety in severe cases, and even cause flight accidents. Since the cables in aircraft and ships are often arranged in a narrow space, traditional visual inspection methods cannot be used to complete fault location.

At present, for the location of cable faults in aircraft and ships, the more mature method is the TDR method, which is the instant domain pulse reflection method. When using this method to locate a fault, a TDR positioning device is required to inject a pulse signal into the cable through the TDR positioning device. The pulse signal is reflected when it passes through the impedance mismatch point on the cable. By calculating the time difference between the transmitted pulse signal and the reflected pulse signal The product of the propagation speed of the pulse signal and the pulse signal in the cable can be used to obtain the fault distance, and the cable fault location can be completed. For cables in aircraft and ships, a cable may pass through various forms of impedance change points (ie, impedance mismatch points) such as connectors, hinge points, and welding points during the wiring process. In this case, TDR is used When the locating device and method perform fault location, in addition to forming a fault reflection pulse signal at the fault point (such as a short circuit or an open circuit), a non-fault reflection pulse signal will also be formed at the above-mentioned impedance change point, which will form a greater impact on the location of the cable fault. Interference, giving a "false alarm" signal, affecting the accuracy of cable fault location, even causing misjudgment and increasing maintenance costs. Not only that, when using the TDR positioning device and method for cable fault location, the TDR positioning device usually injects a low-voltage pulse signal into the cable and detects it, but because the actual attenuation characteristics of the signal in the cable are not considered, the signal can only be determined based on experience The transmission parameters (mainly refer to the voltage of the signal), but lack of theoretical guidance, when the transmission parameters are set low, it is impossible to detect the fault location at all, and when the transmission parameters are set high, it will be difficult or costly to implement high question.

Utility model content

In order to solve the problem of determining signal transmission parameters only by experience in the existing cable fault location, the utility model proposes a cable fault location device based on the time-domain pulse reflection method.

A cable fault location device based on the time-domain pulse reflection method of the utility model, the device includes: a TDR module, a processing module, a display module; the TDR module is used to generate a transmission pulse signal and receive a reflected pulse signal; the processing module is used Analyze the waveform of the reflected pulse signal, judge whether there is a fault point and possible fault point d, analyze the rationality of the possible fault point d, and determine the type of fault and the distance L of the fault point; the display module is used to display the selected parameters, possible fault point d and fault point information; the aforementioned display module, processing module and TDR module are electrically connected in sequence, and the TDR module is electrically connected to the cable under test.

Preferably, the TDR module in the positioning device is electrically connected to the cable under test through an impedance matching connector. By setting the impedance matching joint, the influence of the connection position on the fault location can be reduced.

Preferably, the TDR module in the positioning device is composed of a pulse signal generator and a signal collector, the pulse signal generator is used to generate the transmitted pulse signal, and the signal collector is used to collect the reflected pulse signal at the position where the impedance does not match.

Preferably, the pulse signal generator produces an adjustable amplitude of the transmitted pulse signal, so as to realize the selected TDR transmitted pulse signal amplitude V _in according to the characteristics of the cable under test, and reduce the transmission parameters caused by empirically determining the signal. The problem.

Preferably, a parameter input module is also provided in the positioning device. The parameter input module is used to input the amplitude V _in of the TDR transmitted pulse signal or the measured cable parameters required for calculating V _in . The parameter input module is electrically connected to the processing module. When V _in is selected or calculated in advance according to the characteristics of the cable under test, V _in can be input directly through the parameter input module, and the processing module will control the amplitude of the transmitted pulse signal generated by the TDR module according to the input V _in ; When the measured cable parameters are known and the V _in size is not calculated in advance, the measured cable parameters required for calculating _Vin can be directly entered into the parameter input module, and V _{in is calculated by the processing module, and according to the calculated V in size} , to control the amplitude of the transmit pulse signal generated by the TDR module. By setting the parameter input module, various problems caused by determining the signal transmission parameters by experience in the past.

Preferably, the parameters of the tested cable specifically refer to the length _{l H} of the tested cable, the equivalent resistance _RL of the tested cable, the characteristic impedance Z ₀ of the tested cable, and the equivalent conductance GL of the tested cable.

Preferably, when inputting the measured cable parameters to calculate V _in , the processing module calculates V _in by the following method,

Among them, V ₁ (d) is the limit value of interference noise in the tested cable.

Preferably, the value of V ₁ (d) is 0.5V. According to a large number of experimental tests, for common cables, the maximum amplitude of various noises acting on it is about 0.5V. The noise here includes external noise and noise introduced by the connector. When the pulse signal is transmitted When propagating through the tested cable, its amplitude will gradually attenuate. When the attenuation reaches this range, the TDR positioning method will not be able to identify it. Therefore, 0.5V is selected as the judgment threshold.

In order to more clearly illustrate the composition and connection relationship of a cable fault location device based on the time-domain pulse reflection method of the present invention, the method for using the location device for fault location is introduced below. The method mainly includes the following five steps:

Step S1, according to the characteristics of the cable under test, select the amplitude V _in of the TDR emission pulse signal; the characteristics of the cable under test mainly refer to the attenuation characteristics of the cable, mainly considering the following influencing factors: the length l of the cable under test _H , the equivalent resistance _RL of the tested cable, the characteristic impedance _{Z 0} of the tested cable, the equivalent conductance GL of the tested cable, etc.

Step S2, generate a transmission pulse signal and inject it into the cable under test, and then collect the reflected pulse signal at the position where the impedance does not match; in the TDR positioning method, the transmission pulse signal is generated by the pulse signal generator and collected by the signal collector reflected pulse signal.

Step S3, perform fault judgment according to the reflected pulse signal; specifically, it is necessary to analyze the waveform of the reflected pulse signal, and determine the fault type according to the amplitude and phase relationship between the reflected pulse signal and the transmitted pulse signal. However, due to the influence of the external environment and the internal influence generated when passing through the connector (including connectors, hinge points, welding points, etc.), "false alarm" phenomenon or misjudgment may occur. In order to improve the accuracy of fault judgment, the following methods are used for fault judgment:

(1) When the absolute value of the reflected pulse signal amplitude |V(td)|≥1V, it is determined that there is a fault in the cable under test, and the fault type and the distance L of the fault point are determined; the distance of the fault point can be determined according to the TDR positioning method L.

(2) When 0.5V≤|V(td)|<1V, it is determined that there may be a fault in the cable under test, and then calculate the distance l d of the possible fault point d, where the distance l _d of the possible fault point _d is also located according to TDR The method is determined.

(3) When |V(td)|<0.5V, it is determined that there is no fault in the cable under test, and go to step S5.

Step S4, according to the attenuation characteristics of the cable, judge whether the reflected pulse signal amplitude V(td) of the possible fault point d is reasonable; if it is reasonable, then L=ld, that is to say, the distance l _d of the possible fault point _d is the fault point distance L; if it is unreasonable, it is possible that fault point d is a false alarm, and go to step S5.

Step S5, end cable fault location.

Preferably, in step S4, according to the attenuation characteristics of the cable, when judging whether the reflected pulse signal amplitude V(td) of the possible fault point d is reasonable, the following method is specifically adopted:

Step S41, assuming that the cable under test is a uniform cable, calculate the absolute value |V(d)| of the theoretical amplitude of the reflected pulse signal at the possible fault point d, that is, calculate the reflection at the corresponding position of the possible fault point d when the cable under test is a uniform cable The absolute value of the theoretical amplitude of the pulse signal |V(d)|;

In step S42, if |V(td)|>|V(d)|, the amplitude V(td) of the reflected pulse signal at fault point d may be unreasonable; otherwise, it is reasonable.

Preferably, the calculation method of |V(d)| in step S41 is specifically:

Among them, l _d is the distance of the possible fault point d, _RL is the equivalent resistance of the tested cable, _{Z 0} is the characteristic impedance of the tested cable, and GL is the equivalent conductance of the tested cable.

Preferably, the method for selecting the amplitude V _in of the transmitted pulse signal in step S1 is specifically:

Among them, V ₁ (d) is the limit value of the interference noise in the cable under test, and l _H is the length of the cable under test; by determining V _in , the problem that the transmission parameters of the signal can only be determined based on experience in the past can be solved, and it can also avoid various problems arising from this.

Preferably, the value of V ₁ (d) is 0.5V. According to a large number of experimental tests, for common cables, the maximum amplitude of various noises acting on it is about 0.5V. When the transmitted pulse signal propagates through the cable under test, its amplitude will gradually attenuate. When it reaches this range, the TDR positioning method will not be recognized, so 0.5V is selected as the judgment threshold.

Preferably, the calculation method of the fault point distance L in step S4 is replaced by:

in, c is the speed of light, ε _r is the relative permittivity of the cable insulation material under test, and Δt is the time difference between the transmitted pulse signal and the reflected pulse signal.

A cable fault location device based on the time-domain pulse reflection method of the utility model can determine the amplitude V _in of the transmitted pulse signal according to the characteristics of the tested cable, which completely solves the problems caused by determining the signal transmission parameters based on experience in the past. various problems.

Description of drawings

Figure 1 is a schematic diagram of the structure of the positioning device.

Figure 2 is a schematic diagram of the composition of the TDR module and the connection between the TDR module and the cable under test.

Fig. 3 is a flow chart of cable fault location using the location device of the present invention.

Fig. 4 is a schematic structural diagram of a positioning device with a parameter input module.

Fig. 5 is the wave form diagram of the transmitted signal and reflected signal when the amplitude of the transmitted pulse signal is 5.5V, and there is an open circuit fault cable at 87m.

Fig. 6 is a waveform diagram of the transmitted signal and reflected signal when the transmitted pulse signal amplitude is 3.3V when testing the cable with an open circuit fault at 87m.

Figure 7 is a waveform diagram of the transmitted signal and reflected signal when the transmitted pulse signal amplitude is 5.5V when testing a 100m cable.

Detailed ways

Below in conjunction with accompanying drawing 1 to accompanying drawing 7, introduce the specific embodiment of the utility model.

As shown in Figure 1, a cable fault location device based on the time domain pulse reflection method of the present invention mainly includes a TDR module, a processing module, and a display module; in addition, a parameter input module can be selected as required.

In order to better illustrate the composition and working principle of a cable fault location device based on the time-domain pulse reflection method of the present invention, how to consider the cable attenuation characteristics in the present invention is specifically explained below.

During the propagation of the high-frequency pulse signal along the cable under test, its frequency basically does not change; the waveform will be distorted due to external signal interference and the characteristics of the transmission line itself; the amplitude of the signal is due to dielectric loss, wire loss and radiation loss, etc. The reason is that there will be a certain attenuation, and as the frequency of the signal is higher and the distance of propagation is longer, the signal will be attenuated more seriously.

Attenuation is a characteristic of lossy transmission lines, which is a direct result of solving a second-order lossy RLCG distributed parameter circuit model. Usually _αn is used to represent the attenuation per unit length, and its unit is Neper/meter, which is defined as follows:

Among them: R _L is the equivalent resistance of the transmission line, the unit is Ω; G _L is the equivalent conductance of the transmission line, the unit is S; L _L is the equivalent inductance of the transmission line, the unit is H; C _L is the equivalent capacitance of the transmission line, the unit is 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: Z ₀ is the characteristic impedance of the transmission line, the unit is Ω.

When a signal propagates along a uniform cable, the effect of wire loss on the signal is mainly to attenuate the signal amplitude. If the signal with the amplitude of the transmitted pulse signal V _in propagates on the transmission line, the signal amplitude does not decrease linearly with the increase of distance, but decreases exponentially with the change of distance, the input signal and output signal amplitude on the transmission line The relationship is:

In the formula, V _in represents the amplitude of the transmitted pulse signal, unit V; V(d) represents the voltage amplitude at point d on the transmission line, unit V; A _n represents the total attenuation, unit Neper; l _d is the distance of point d , specifically the distance from the signal input terminal to point d, in meters; α _n is the attenuation per unit length of the transmission line, in Neper/meter.

Since the use of decibels is more common and the calculation is more convenient, the conversion relationship in the following formula (4) can be used to convert α _n into decibels:

From the above formula, the relationship between the input voltage and the output voltage expressed in decibels is obtained:

Converting formula (2) into decibel form by the conversion relationship of formula (4), then the attenuation dB/length per unit length of the transmission line is obtained as:

From formula (5) and formula (6), it can be known that the attenuation characteristic formula of the transmitted signal along the transmission line is:

The above is the analysis process of the cable attenuation characteristics. According to the cable attenuation characteristic model and given the frequency and amplitude of the high-frequency pulse signal, the relationship between the amplitude and the propagation distance of the high-frequency pulse signal on a certain cable is obtained.

The cable fault location theory based on TDR (time-domain pulse reflection method) will be briefly described below. The basic theory of TDR is the transmission line theory; in the transmission line theory, the cable is used as a distributed parameter element, and in a uniform transmission line, the characteristic impedance of the transmission line is a certain value, and the characteristic impedance of the cable can be expressed by formula (8):

In the formula, L _L1 is the inductance of the cable per unit length, and C _L1 is the capacitance of the cable per unit length.

In the transmission line theory, when the electric pulse signal is transmitted in the cable, if the transmission medium is uniform, the signal will be transmitted along the cable. If the cable fails (open circuit or short circuit), the transmission medium is uneven, and the pulse signal will be in the impedance change Where reflections occur. The reflection coefficient at an impedance mismatch on a transmission line is the ratio of the reflected voltage to the emitted voltage:

In the formula, V _re is the voltage amplitude of the reflected pulse signal, Z _l is the input impedance of the obstacle point of the cable line, and Z ₀ is the characteristic impedance of the cable. The following three characteristics can be obtained from formula (9):

(1) When the cable is normal, Z ₀ =Z _l , ρ=0, the transmitted signal will be absorbed by the load without reflection;

(2) When the cable is disconnected, Z _l → ∞, ρ = 1, at this time the reflected electric pulse has the same amplitude and phase as the initial transmitted pulse;

(3) When the cable is short-circuited, Z _l → 0, ρ = -1, the reflected electric pulse has the same amplitude as the initial pulse, but the phase is opposite.

In the transmission line theory, the signal propagates in the form of electromagnetic waves on the transmission line; after the voltage is applied to one end of the cable, due to the inertia of the capacitance in its distribution parameters, the signal transmission takes a certain amount of time. Then the propagation velocity v of the signal in the cable is:

where _ε0 is the vacuum permittivity, μ ₀ is the vacuum magnetic permeability, μ ₀ =4π×10 ^-7 , ε _r is the relative permittivity of the insulating material, and μ _r is the relative magnetic permeability of the insulating material, which is generally 1. Substituting the values of ε ₀ , μ ₀ , and μ _r into formula (10), we get:

In the formula, c is the speed of light c=3×10 ⁸ m/s;

It can be known from (11) that the propagation speed of the signal in the cable is only related to the relative dielectric constant of its insulating material, and has nothing to do with other factors. Signals have the same speed in cables of the same insulation material;

The time domain reflection method measures the time difference Δt of the reflected pulse at the place where the transmitted pulse does not match the impedance, and calculates the propagation speed of the signal in the cable according to (11) to determine the fault distance. The fault distance is:

In the formula, L is the distance between the test end and the fault point, v is the propagation speed of the signal in the cable, and Δt 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 earlier, because the noise level in the cable is about 0.5V, when the absolute value of the reflected pulse signal amplitude is greater than or equal to 1V, the noise level is exceeded. If the reflected pulse signal is considered obvious), it is directly judged that there is a fault in the cable under test; when the reflected pulse signal is not obvious (when the absolute value of the reflected pulse signal amplitude is between 0.5V and 1V, the reflected pulse signal is considered not obvious) , it is judged that there may be a fault in the cable under test, and the amplitude of the reflected pulse signal is measured when the reflected pulse signal is not obvious, and then 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, " Fault distance", and finally calculate the theoretical amplitude of the reflected pulse signal at this position in combination with the cable attenuation characteristics, and comprehensively judge to obtain the fault diagnosis result.

As shown in Figure 2, when the positioning device of the present invention is connected to the cable under test, it is connected through an impedance matching joint; the pulse signal generator in the TDR module sends a transmission pulse signal to the cable under test through an impedance matching joint, and when it is tested When there is an impedance mismatch position in the test cable, the reflected pulse signal is collected by the TDR signal collector through the impedance mismatch connector.

When the utility model is used to locate cable faults, the specific method is shown in FIG. 3 . Judging the rationality of possible fault points is an optional step. When there is no possible fault point, this step can be omitted, so it is represented by a dotted line in FIG. 3 .

Example 1:

The following introduces how to use a cable fault location device based on the time-domain pulse reflection method of the present invention to select the amplitude of the transmitted pulse signal.

As shown in FIG. 4 , a parameter input module is provided in the positioning device, and the parameter input module is electrically connected to the processing module. In this embodiment, the parameter input module is used to input the measured cable parameters required for calculating V _in and the fault point distance L.

Assuming that the cable under test is a section of the cable inside the aircraft, the characteristic impedance of the cable under test Z ₀ =50Ω, the equivalent resistance R _L =0.0062Ω, the equivalent conductance G _L =0.00046S, the relative permittivity of the cable insulation material ε _r = 2.25, length l _h = 100 meters, artificially create an open-circuit fault at the 87-meter position of the cable, and select two different amplitude but 100MHz transmitting pulse signals for TDR positioning. The amplitude of the transmitted pulse signal in FIG. 5 is 5.5V, and the amplitude of the transmitted pulse signal in FIG. 6 is 3.3V.

As shown in Fig. 5 and Fig. 6, there is a transmit pulse signal 1 in both figures. However, there is a reflected pulse signal 2 in Figure 5, and the corresponding location is determined to be the fault point according to the traditional TDR positioning method; while there is no reflected pulse signal 2 in Figure 6 .

By comparing the two figures, it can be seen that when the amplitude of the transmitted pulse signal is 3.3V, the fault cannot be located. In the traditional TDR positioning method, the amplitude of the transmitted pulse signal is determined based on past experience. As mentioned earlier, when the amplitude of the selected transmission pulse signal is low, the definition of the fault cannot be realized; and when the amplitude of the selected transmission pulse signal is high, the cost of the TDR component is bound to be increased. When the amplitude Too high is not even possible engineering.

The operating voltage of FPGA and other chips commonly used to generate TDR transmission pulse signals is 3.3V, and the pulse signal generated by the core chip can be amplified and output through an operational amplifier circuit. For the amplification of high-frequency pulse signals, the slew rate of the operational amplifier should be considered (the slew rate refers to the average value of the time change rate of the output voltage of the closed-loop amplifier when the input is a step signal, which is simply a key to determine the rising speed of the signal Index), if the slew rate is too small, the rising edge of the generated pulse signal is not steep enough to meet the TDR test requirements, and the device with a high slew rate is relatively expensive. From the above examples, we can know that selecting the amplitude of the transmitted pulse signal can help us better design the circuit, and choose relatively cheap devices, which have greater economic value.

In order to reasonably select the amplitude of the transmitted pulse signal, in this embodiment, the length l _H of the cable under test, the equivalent resistance R _L of the cable under test, the characteristic impedance Z ₀ of the cable under test, and The equivalent conductance _GL input of the measuring cable. V _in is calculated by the processing module, specifically by Calculate the size of V _in , where V ₁ (d) is the noise amplitude in the tested cable, select 0.5V as the value of the judgment threshold V ₁ (d) in the present embodiment, that is, it is considered that the signal attenuates to 0.5V is considered unrecognizable.

According to the above calculation method and the value of V ₁ (d), when the amplitude of _Vin is calculated to be about 5.06V, the TDR technology can be used to locate the cable fault of the aforementioned 100-meter-long cable under test. It can also be known from this analysis that when _Vin = 3.3V as shown in FIG. 6 , cable fault location cannot be realized at all, because the reflected pulse signal is completely submerged in the noise.

Example 2:

The following describes how to use a cable fault location device based on the time-domain pulse reflection method of the present invention, how to judge the rationality of the fault, and complete the fault location.

In this embodiment, the parameters of the cable under test are exactly the same as those in Embodiment 1, and the frequency of the transmitted pulse signal is 100 MHz. The following will introduce in detail in conjunction with the aforementioned methods.

Step S1, select the amplitude of the transmitted pulse signal

As calculated in Embodiment 1, when the amplitude of _Vin is about 5.06V, the TDR technique can be used to locate the cable fault of the aforementioned 100-meter-long cable under test. In order to make the reflected pulse signal more obvious than the noise, in this embodiment, the amplitude of _Vin is appropriately increased, specifically, _Vin =5.5V. In this embodiment, the calculation of V _in is carried out in advance, and the calculated V _in is directly entered through the parameter input module to control the amplitude of the transmitted pulse signal generated by the TDR module, and the entered V _in will be displayed on the display module.

Step S2, transmit and collect reflected pulse signal

As shown in Figure 7, the amplitude of the transmitted pulse signal 1 generated by the pulse signal generator in the TDR module is 5.5V, and the frequency is 100MHz; and the time difference between the transmitted pulse signal and the reflected pulse signal is Δt=500ns; the signal collector collects The received reflected pulse signal 2 has an amplitude of V(td)=0.99V.

Step S3, perform fault judgment according to the reflected pulse signal

According to the aforementioned method introduced in the utility model, the processing module performs related processing and judgment. Since 0.5V≤|V(td)|<1V, this point is a possible fault point.

Step S4, judging the rationality of possible failure points

according to The theoretical amplitude V(d) of the reflected pulse signal at the possible fault point is calculated by the processing module, and V(d)=1.73V is obtained through calculation.

Since |V(td)|<|V(d)|, the reflected pulse signal amplitude V(td) of the possible fault point is reasonable, and the possible fault point is judged as the fault point. Further analysis of the reflected pulse signal shows that the fault type of this fault point is "open circuit".

In order to further improve the calculation accuracy of the fault point distance, according to and Δt, given by Calculate the fault point distance as L=50 meters, that is, the distance between the fault point and the test end is 50 meters.

The possible fault point d and the information of the fault point will also be displayed on the display module, and the specific information includes the size of V(td) and V(d) of the possible fault point d, and the rationality judgment result of the possible fault point; in addition, when judging When the possible fault point is the fault point, the fault point distance, fault type, etc. should also be displayed.

Step S5, end cable fault location.

Finally, it should be noted that the above is only a preferred embodiment of the utility model, and is not intended to limit the utility model. Although the utility model has been described in detail with reference to the foregoing examples, for those skilled in the art, It is still possible to modify the technical solutions described in the foregoing embodiments, or to perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present utility model shall be included in the protection scope of the present utility model.

Claims (6)

1. A cable fault positioning device based on a time domain pulse reflection method is characterized by comprising a TDR module, a processing module and a display module; 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;

the TDR module consists of a pulse signal generator and a signal collector, wherein the pulse signal generator is used for generating a transmitting pulse signal, and the signal collector is used for collecting a reflected pulse signal at an impedance mismatch position; the pulse signal generator generates the amplitude V of the transmitted pulse signal_inIs adjustable.

2. The cable fault location device based on the time domain pulse reflection method as claimed in claim 1, wherein the TDR module is electrically connected with the tested cable through an impedance matching connector.

3. The cable fault location device based on the time domain pulse reflection method as claimed in claim 1, wherein the location device is further provided with a parameter input module, the parameter input module is used for inputting the amplitude V of the TDR transmission pulse signal_inAnd frequency or calculation V_inThe parameter input module is electrically connected with the processing module according to the required parameters of the tested cable.

4. The cable fault location device based on the time domain pulse reflection method as claimed in claim 3, wherein the measured cable parameter specifically refers to the length l of the measured cable_HEquivalent resistance R of the cable to be tested_LCharacteristic impedance Z of the cable to be tested₀Equivalent conductance G of the cable to be tested_LRelative dielectric constant ε of insulation material of cable to be tested_r。

5. The cable fault location device based on time domain pulse reflection method as claimed in claim 4, wherein V is calculated when the parameter of the tested cable is inputted_inThe processing module calculates V by the following method_in，

Wherein, V₁(d) Is the limit value of interference noise in the tested cable.

6. The time-domain pulse reflectometry-based cable fault localization arrangement of claim 5 wherein V₁(d) Is 0.5V.