Secondary cable on-line length detection system and detection method

Abstract

The invention discloses a secondary cable on-line length detection system and a detection method, and belongs to the technical field of power cable detection, the secondary cable on-line length detection system comprises a signal emission module, a signal acquisition module, a processing and analysis module and a display and output module, the signal is transmitted in the cable and is reflected at a characteristic impedance change part, the signal acquisition module receives the reflected signal and transmits data to the processing and analysis module, and the processing and analysis module calculates the time and the intensity of the signal, so that the position and the distance of a characteristic point on the cable are determined, namely the length of the cable is obtained. The problem that a live cable cannot be tested is solved, and various data of the cable can be acquired in real time.

Description

Technical Field

[0001] The present invention relates to the technical field of power cable detection, and in particular to a secondary cable online length detection system and detection method. Background Art

[0002] The main function of power cables is to transmit electricity from power stations to substations, and then from substations to various user ends, such as factories, commercial buildings and residences. For example, in the power supply network of a city, high voltage electricity is transmitted from large substations in the suburbs to various buildings in the city center through underground power cables. This transmission method can effectively reduce the loss of electricity during transmission. Compared with overhead lines, cables are less affected by external environment (such as bad weather, birds, etc.) due to the protection of the insulation layer, and can ensure stable and continuous transmission of electricity.

[0003] The length and resistance of the substation secondary equipment cable are one of the key parameters for circuit design and maintenance in the secondary profession. The cable length is proportional to the resistance, and the heat generated by the cable is also proportional to the resistance. This means that for cables of the same specification, the longer the cable, the more heat it generates, shortening the service life of the cable. Currently, the cable length can only be measured before installation, and it cannot be tested with power on. For running equipment, it can only be identified by the cable's own markings. The test accuracy is not high, which may cause test errors and cannot achieve high-precision length testing and low-resistance testing. Summary of the invention

[0004] The main purpose of the present invention is to provide a secondary cable online length detection system and detection method to solve the above problems and to detect the length of the cable while acquiring various data of the cable in real time.

[0005] To achieve the above object, the present invention proposes a secondary cable online length detection system, comprising:

[0006] A signal transmitting module is used to send a short pulse signal into the cable, and the signal propagates in the cable and is reflected at a point where a characteristic impedance change is encountered;

[0007] A signal acquisition module, used for acquiring the reflected signal and converting it into a digital signal;

[0008] The processing and analysis module amplifies, filters, and digitizes the collected signals to extract the location of the fault point. After receiving the reflected pulse signal, the processing module calculates the time between the two pulse transmissions and the length of the cable.

[0009] The display and output module transmits and stores the received signals, and can intuitively display the test results, the distance of the characteristic impedance change point and the waveform diagram.

[0010] Optionally, the secondary cable online length detection system also includes an auxiliary module, which includes a power supply, a path meter, a probe and a connecting line. The power supply provides a stable power supply for the instrument to ensure the normal operation of the instrument. The path meter is used to help the user determine the path of the cable to facilitate fault location. The probe and connecting line are used to connect the test object to ensure effective transmission of the signal.

[0011] Optionally, the signal transmitting module includes a pulse generator and a high-voltage power supply. The pulse generator generates a high-frequency pulse signal and injects it into the cable to be tested. The pulse signal propagates in the cable and generates a reflected wave when encountering a fault point. The fault location is determined by analyzing the reflected wave. The high-voltage power supply is electrically connected to the pulse generator to provide high-voltage power to the pulse generator.

[0012] Optionally, the signal acquisition module includes a sampling box and a sensor network, the sampling box collects the reflected signal and converts it into a digital signal, and the sensor network is arranged along the line.

[0013] Optionally, the processing and analysis module includes a signal processing unit, a control unit and a positioning algorithm unit. The signal processing unit processes the received signal and outputs it to the control unit. The control unit sets control parameters, stores data and outputs results. The positioning algorithm unit calculates the time when two pulses are emitted.

[0014] Optionally, the positioning algorithm unit calculates the cable length specifically by the following formula:

[0015] L=(Δt×C×VF) / 2

[0016] Where L is the cable length, in meters; Δt is the time difference, in seconds; C is the speed of light, which is approximately equal to 300,000 km / s, which is converted to meters / second as 3×10^8 meters / second; VF is the cable velocity factor, which is dimensionless, and the cable length L is calculated.

[0017] Optionally, the display and output module includes a display screen, a storage unit, a printing unit and an alarm unit. The storage unit can store a large amount of field waveforms and data, and can be called up for use at any time to facilitate subsequent viewing and comparison. The printing unit can print and archive the test results to facilitate paper records and report writing. When a fault is detected, the alarm unit can sound an alarm and can also send the fault information to the terminal device of relevant personnel.

[0018] A method for detecting the length of a secondary cable online, using the secondary cable online length detection system as described above, comprises the following steps:

[0019] S1. Install sensors on the clamps along the line;

[0020] S2. Use a pulse generator at the beginning of the cable to send a high-speed edge pulse signal to the cable. The signal will propagate along the cable. If the other end of the cable is disconnected, the signal will be reflected back after reaching the end of the cable, forming an echo signal.

[0021] S3. After receiving the pulse signal, the sensor transmits another pulse signal back to the processing module. The processing module calculates the time between the two pulse transmissions and the frequency of the two pulses, and calculates the length of the clamped cable.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention sends a short pulse signal to the cable through a signal transmitting module. The signal propagates in the cable and is reflected at a location where the characteristic impedance changes. The signal acquisition module receives the reflected signal and transmits data to the processing and analysis module. The processing and analysis module calculates the time and intensity, thereby determining the position and distance of the characteristic points on the cable, that is, obtaining the length of the cable. This solves the problem of being unable to test live cables and can obtain various data of the cable in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0025] Figure 1 This is the module composition diagram of the secondary cable online length detection system;

[0026] Figure 2 The figure is a flow chart of the method for online detection of length of secondary cables.

[0027] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0030] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0031] In one embodiment of the present invention, a secondary cable online length detection system is provided, the secondary cable online length detection system comprising:

[0032] A signal transmitting module is used to send a short pulse signal into the cable, and the signal propagates in the cable and is reflected at a point where a characteristic impedance change is encountered;

[0033] A signal acquisition module, used for acquiring the reflected signal and converting it into a digital signal;

[0034] The processing and analysis module amplifies, filters, and digitizes the collected signals to extract the location of the fault point. After receiving the reflected pulse signal, the processing module calculates the time between the two pulse transmissions and the length of the cable.

[0035] The display and output module transmits and stores the received signals, and can intuitively display the test results, the distance of the characteristic impedance change point and the waveform diagram.

[0036] In this embodiment, the signal transmitting module includes a pulse generator and a high-voltage power supply. The pulse generator generates a high-frequency pulse signal and injects it into the cable to be tested. The pulse signal propagates in the cable and generates a reflected wave when encountering a fault point. The fault location is determined by analyzing the reflected wave. The high-voltage power supply is electrically connected to the pulse generator to provide high-voltage power to the pulse generator.

[0037] Among them, the pulse generator can be a pulse generator model TT535-4Z produced by Times Mountain Peak, with a measurement range of impulse discharge during cable fault testing at voltage levels of 35kV and below, a voltage accuracy of level 1.5, and can meet the DL / T846-2004 "High Voltage Test Equipment" standard.

[0038] In order to ensure that the pulse signal has enough energy, the stability of the high-voltage power supply directly affects the accuracy of the test results. The high-voltage power supply can be the XG-2131 high-voltage power supply produced by Wuhan Xigao Huadian Electric Co., Ltd., which is a high-frequency high-voltage power supply for ultra-light cable fault testing. Output voltage ≮35KV, working current ≮40mA, display voltage value error <±2%, discharge energy ≮2450J / 5S, minimum discharge cycle 3 seconds, weight only 11kg, with voltage regulation and automatic voltage stabilization function, open circuit short circuit automatic protection function, etc., using engineering plastic insulation material, safe operation, simple wiring, can work continuously for more than 4 hours.

[0039] In one embodiment of the present invention, the signal acquisition module includes a sampling box and a sensor network. The sampling box collects the reflected signal and converts it into a digital signal. The sensor network is arranged along the line.

[0040] In this embodiment, the sampling box can be a CYH type sampling box produced by Xi'an Everbright Baina Electronic Technology Co., Ltd., with a measurement range of 30KM, a measurement accuracy of ±1%, ABS material, a size of 1007040mm, a weight of 0.3kg, and receives the reflected signal to ensure the accuracy of data collection. The sensor network is composed of a variety of sensors, such as temperature sensors, current sensors, vibration sensors, etc., which collect various state parameters of the cable in real time. The electromagnetic environment around the cable is complex and there are various interference signals. The sampling box can remove some unnecessary high-frequency or low-frequency interference components through filtering operations, retain only the effective signal frequency band related to the fault, and convert the analog signal into a digital signal for digital signal processing and analysis to achieve online detection.

[0041] In one embodiment of the present invention, the processing and analysis module includes a signal processing unit, a control unit and a positioning algorithm unit. The signal processing unit processes the received signal and outputs it to the control unit. The control unit sets control parameters, stores data and outputs results. The positioning algorithm unit calculates the time when two pulses are emitted.

[0042] In this embodiment, the processing and analysis module is a ME-6000W three-level pulse distance meter and a central control unit, which adopts a three-level pulse advanced arc reflection pre-positioning technology to achieve a change in arc short-circuit time from a few microseconds to 350 milliseconds, so that the test waveforms all appear as low-voltage pulse waveforms, which can realize automatic distance judgment. The central control unit can automatically control the first-level high-voltage breakdown fault, the second-level active arc continuation, and the third-level pulse sampling.

[0043] The cable length is measured based on the principle of TDR technology: a high-speed edge pulse signal is sent to a cable of unknown length, and the signal will propagate along the cable. If the other end of the cable is disconnected, the signal will be reflected back after reaching the end of the cable, forming an echo signal. By measuring the time difference (Δt) from the pulse signal being transmitted to being reflected back, combined with the speed of light (C) and the cable velocity factor (VF), the length of the cable can be calculated.

[0044] Determine the cable velocity factor VF based on the cable type.

[0045] Substitute Δt, C and VF into the calculation formula L = (Δt×C×VF) / 2 (where L is the cable length, unit: meter; Δt is the time difference, unit: second; C is the speed of light, approximately equal to 300,000 km / s, converted to meters / second is 3×10^8 meters / second; VF is the cable speed factor, dimensionless), and calculate the cable length L.

[0046] In one embodiment of the present invention, the display and output module includes a display screen, a storage unit, a printing unit and an alarm unit. The storage unit can store a large amount of field waveforms and data, and call them out for use at any time to facilitate subsequent viewing and comparison. The printing unit can print and archive the test results to facilitate paper records and report writing. When the alarm unit detects a fault, it can sound an alarm and can also send the fault information to the terminal device of the relevant personnel.

[0047] In this embodiment, the display screen can intuitively display the test results, including fault distance, waveform diagram, etc., to facilitate analysis by operators. When the alarm unit detects a fault, the system can issue an alarm through an audible and visual alarm, a vibration alarm, etc., so that timely measures can be taken.

[0048] In one embodiment of the present invention, the secondary cable online length detection system also includes an auxiliary module, which includes a power supply, a path meter, a probe and a connecting line. The power supply provides a stable power supply for the instrument to ensure the normal operation of the instrument. The path meter is used to help the user determine the path of the cable to facilitate fault location. The probe and the connecting line are used to connect the test object to ensure the effective transmission of the signal.

[0049] In this embodiment, the auxiliary module may further include a grounding device to ensure safety during the test and prevent electric shock to operators and damage to the instrument.

[0050] The present invention also proposes a method for online detection of the length of a secondary cable, using the above-mentioned online detection system for the length of a secondary cable, comprising the following steps:

[0051] S1. Install sensors on the clamps along the line;

[0052] S2. Use a pulse generator at the beginning of the cable to send a high-speed edge pulse signal to the cable. The signal will propagate along the cable. If the other end of the cable is disconnected, the signal will be reflected back after reaching the end of the cable, forming an echo signal.

[0053] S3. After receiving the pulse signal, the sensor transmits another pulse signal back to the processing module. The processing module calculates the time between the two pulse transmissions and the frequency of the two pulses, and calculates the length of the clamped cable.

[0054] The system receives the reflected signal and calculates its time and strength to determine the position and distance of the characteristic point on the cable, that is, the length of the cable.

[0055] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A secondary cable online length detection system, characterized in that: include: A signal transmitting module is used to send a short pulse signal into the cable, and the signal propagates in the cable and is reflected at a point where a characteristic impedance change is encountered; A signal acquisition module, used for acquiring the reflected signal and converting it into a digital signal; The processing and analysis module amplifies, filters, and digitizes the collected signals to extract the location of the fault point. After receiving the reflected pulse signal, the processing module calculates the time between the two pulse transmissions and the length of the cable. The display and output module transmits and stores the received signals, and can intuitively display the test results, the distance of the characteristic impedance change point and the waveform diagram.

2. The secondary cable online length detection system according to claim 1, characterized in that: The secondary cable online length detection system also includes an auxiliary module, which includes a power supply, a path meter, a probe and a connecting line. The power supply provides a stable power supply for the instrument to ensure the normal operation of the instrument. The path meter is used to help the user determine the path of the cable to facilitate fault location. The probe and the connecting line are used to connect the test object to ensure the effective transmission of the signal.

3. The secondary cable online length detection system according to claim 1, characterized in that: The signal transmitting module includes a pulse generator and a high-voltage power supply. The pulse generator generates a high-frequency pulse signal and injects it into the cable to be tested. The pulse signal propagates in the cable and generates a reflected wave when encountering a fault point. The fault location is determined by analyzing the reflected wave. The high-voltage power supply is electrically connected to the pulse generator to provide high-voltage power to the pulse generator.

4. The secondary cable online length detection system according to claim 1, characterized in that: The signal acquisition module includes a sampling box and a sensor network. The sampling box collects the reflected signal and converts it into a digital signal. The sensor network is arranged along the line.

5. The secondary cable online length detection system according to claim 1, characterized in that: The processing and analysis module includes a signal processing unit, a control unit and a positioning algorithm unit. The signal processing unit processes the received signal and outputs it to the control unit. The control unit sets control parameters, stores data and outputs results. The positioning algorithm unit calculates the time when two pulses are emitted.

6. The secondary cable online length detection system according to claim 5, characterized in that: The positioning algorithm unit specifically calculates the cable length by the following formula: L=(Δt×C×VF) / 2 Where L is the cable length, in meters; Δt is the time difference, in seconds; C is the speed of light, which is approximately equal to 300,000 km / s, which is converted to meters / second as 3×10^8 meters / second; VF is the cable velocity factor, which is dimensionless, and the cable length L is calculated.

7. The secondary cable online length detection system according to claim 1, characterized in that: The display and output module includes a display screen, a storage unit, a printing unit and an alarm unit. The storage unit can store a large amount of field waveforms and data, and can be called up for use at any time to facilitate subsequent viewing and comparison. The printing unit can print and archive the test results to facilitate paper records and report writing. When a fault is detected, the alarm unit can sound an alarm and can also send the fault information to the terminal device of relevant personnel.

8. A method for detecting the length of a secondary cable online, using the system for detecting the length of a secondary cable online as claimed in any one of claims 1 to 7, comprising the following steps: S1. Install sensors on the clamps along the line; S2. Use a pulse generator at the beginning of the cable to send a high-speed edge pulse signal to the cable. The signal will propagate along the cable. If the other end of the cable is disconnected, the signal will be reflected back after reaching the end of the cable, forming an echo signal. S3. After receiving the pulse signal, the sensor transmits another pulse signal back to the processing module. The processing module calculates the time between the two pulse transmissions and the frequency of the two pulses, and calculates the length of the clamped cable.

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