An online monitoring device and monitoring method for disconnection of copper shield of medium voltage cable

Abstract

The present invention discloses an online monitoring device and monitoring method for the disconnection of copper shielding of medium voltage cables, comprising: a main control module, an audio signal transmitting module, an audio signal collecting module, a pulse signal transmitting module, a pulse signal collecting module, a display module and a setting module; the audio signal transmitting module couples the composite audio signal to the copper shielding of the cable through a caliper, the audio signal collecting module collects the current of the composite audio signal, when the current is less than the set threshold, the main control module determines that the copper shielding of the cable is disconnected, the pulse signal transmitting module generates a pulse, and couples the pulse to the cable core wire through a thin film electrode, the pulse signal collecting module collects the pulse reflection signal, and locates the position of the disconnection of the copper shielding by calculating the time difference between the pulse transmitting signal and the reflection signal. The present invention realizes the abnormal online monitoring of the copper shielding of the cable when the cable is energized and gives the positioning distance in time, thereby improving the detection efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of medium voltage cable copper shield monitoring, and in particular to an online monitoring device and a monitoring method for disconnection of a medium voltage cable copper shield. Background Art

[0002] Electric energy has been widely transmitted by power cables in cities. Medium-voltage cables are generally three-core turnkey cables. Since the three-phase turnkey cables are balanced, there is basically no induced voltage to the outside. Therefore, the copper shield and steel armor of the three-core turnkey cables are basically not monitored at present. However, with the increasing use of cables, the copper shield of the cables is often stolen and cut, resulting in cable failures, power outages, and even fires. When the cable is in operation, the surrounding environmental factors will also damage the cable itself, which may cause the copper shield to be disconnected. Cable outer sheath faults, including breakage and short circuits, will cause abnormal operation of the cable. At present, traditional methods cannot locate cable sheath faults under power. The focus of monitoring medium-voltage cables is mainly on the monitoring and early warning of main insulation faults. Therefore, it is necessary to design an online monitoring technology for the disconnection of copper shield of medium-voltage cables. Before the cable fails, the disconnection of copper shield is monitored, and the distance of copper shield disconnection is monitored online, so as to carry out planned power outages and maintenance to avoid power outages. Summary of the invention

[0003] In order to overcome the defects and shortcomings of the prior art, the present invention provides an online monitoring device and a monitoring method for the disconnection of the copper shield of a medium-voltage cable. The device and a monitoring method are used to determine whether the copper shield has a disconnection point by detecting the current size of the audio signal coupled to the copper shield of the cable, and then the disconnection point is determined by combining the method of coupling the pulse signal. The audio signal is coupled to the copper shield of the cable in a non-contact manner, which does not affect the normal operation of the cable. The pulse signal is coupled to the cable core wire through a thin film electrode, and has no direct contact with the high voltage, which does not affect the normal operation of the cable. The technical problem of monitoring whether the copper shield of the cable is disconnected when the cable is energized is solved, and the technical effect of not affecting the normal power supply of the cable and timely providing the positioning distance of the cable with abnormal copper shielding is achieved.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides an online monitoring device for disconnection of copper shield of medium voltage cable, comprising: a main control module, an audio signal transmitting module, an audio signal collecting module, a pulse signal transmitting module, a pulse signal collecting module, a display module and a setting module;

[0006] The main control module is respectively connected to the audio signal transmitting module, the audio signal collecting module, the pulse signal transmitting module, the pulse signal collecting module, the display module and the setting module, and is used to control each module;

[0007] The audio signal transmitting module is used to generate a composite audio signal and clamp-couple the composite audio signal to the copper shield of the cable;

[0008] The audio signal acquisition module is used to collect the current of the composite audio signal on the copper shield. When the current is less than the set threshold, the main control module determines that the cable copper shield is disconnected.

[0009] The pulse signal transmitting module is used to generate a positioning pulse signal. One end of the pulse signal output line is connected to a thin film electrode installed on the main insulation surface of the cable core wire, and the other end is connected to the cable copper shield. A capacitor is formed between the cable core wire and the thin film electrode to couple the emitted pulse signal to the cable core wire.

[0010] The pulse signal acquisition module is used to collect the pulse reflection signal of the cable copper shield, calculate the time difference between the pulse transmission signal and the pulse reflection signal, and locate the position where the copper shield is disconnected;

[0011] The display module is used to display the audio signal current and the positioning result, and the setting module is used to set the pulse transmission parameters.

[0012] As a preferred technical solution, the composite audio signal uses two synthetic signals of different frequencies. After the audio is superimposed, the collected signal is subjected to FFT transformation in the audio signal collection module to separate the two frequency signals.

[0013] As a preferred technical solution, the composite audio signal adopts a synthetic signal with frequencies of 512 Hz and 1024 Hz.

[0014] As a preferred technical solution, the pulse signal transmitting module is used to generate a positioning pulse signal, the pulse width of the pulse signal is adjustable between 100ns and 5us, and the pulse amplitude is 30V.

[0015] As a preferred technical solution, the time difference between the pulse transmission signal and the pulse reflection signal is calculated to locate the position where the copper shield is disconnected. The specific calculation formula is:

[0016] L=1 / 2*V*t

[0017] Among them, L represents the distance, V represents the wave speed of the pulse transmission signal, and t represents the time difference between the pulse transmission signal and the pulse reflection signal.

[0018] As a preferred technical solution, the positioning result is presented by the collected pulse transmission signal and pulse reflection signal.

[0019] The present invention provides a monitoring method of an online monitoring device for disconnection of copper shield of a medium-voltage cable. The online monitoring device for disconnection of copper shield of a medium-voltage cable is provided with a main control module, an audio signal transmitting module, an audio signal collecting module, a pulse signal transmitting module, a pulse signal collecting module, a display module and a setting module;

[0020] The specific steps of the monitoring method include:

[0021] The main control module controls the audio signal transmitting module to couple the composite audio signal to the cable copper shield through the clamp, and the main control module controls the audio signal collecting module to collect the composite audio signal current;

[0022] The main control module determines the state of the cable copper shielding according to the current of the collected composite audio signal. When the current is less than the set threshold, the main control module determines that the cable copper shielding is disconnected.

[0023] When the copper shield is disconnected, the main control module controls the pulse signal transmitting module to generate pulses, and couples the pulses to the cable core through the thin film electrode. At the same time, the main control module controls the pulse signal acquisition module to collect the pulse reflection signal, and locates the position where the copper shield is disconnected by calculating the time difference between the pulse transmission signal and the reflection signal.

[0024] The pulse emission parameters are adjusted through the setting module, and the display module displays the audio signal current and positioning results.

[0025] As a preferred technical solution, the composite audio signal uses two synthetic signals of different frequencies. After the audio is superimposed, the collected signal is subjected to FFT transformation in the audio signal collection module to separate the two frequency signals.

[0026] As a preferred technical solution, the composite audio signal adopts a synthetic signal with frequencies of 512 Hz and 1024 Hz.

[0027] As a preferred technical solution, the position where the copper shield is disconnected is located by calculating the time difference between the pulse transmission signal and the reflection signal. The specific calculation formula is:

[0028] L=1 / 2*V*t

[0029] Among them, L represents the distance, V represents the wave speed of the pulse transmission signal, and t represents the time difference between the pulse transmission signal and the pulse reflection signal.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] The present invention determines whether the copper shielding has a disconnection point by detecting the current size of the audio signal coupled to the copper shielding of the cable, and then performs positioning in combination with the method of coupling pulse signals. The audio signal is coupled to the copper shielding of the cable in a non-contact manner, which does not affect the normal operation of the cable. The pulse signal is coupled to the core wire of the cable through a thin film electrode, and has no direct contact with the high voltage, which does not affect the normal operation of the cable. The technical problem of monitoring whether the copper shielding of the cable is disconnected when the cable is energized is solved, and the technical effect of not affecting the normal power supply of the cable and timely providing the positioning distance for the cable with abnormal copper shielding is achieved, thereby improving the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the framework structure of an online monitoring device for disconnection of copper shielding of a medium voltage cable according to the present invention;

[0033] Figure 2 This is a connection diagram of the audio signal transmitting module of the present invention;

[0034] Figure 3 It is a connection diagram of the pulse signal transmitting module of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides an online monitoring device for disconnection of copper shield of medium voltage cable, including: a main control module, an audio signal transmitting module, an audio signal collecting module, a pulse signal transmitting module, a pulse signal collecting module, a display module and a setting module;

[0038] In this embodiment, the main control module is respectively connected to the audio signal transmitting module, the audio signal acquisition module, the pulse signal transmitting module, the pulse signal acquisition module, the display module and the setting module, and is used to control each module. The audio signal transmitting module is used to generate a composite audio signal and couple the composite audio signal clamp to the copper shield of the cable. The audio signal acquisition module is used to collect the current of the audio signal on the copper shield. The pulse signal transmitting module is used to generate a pulse signal for positioning, and the pulse width is adjustable between 100ns and 5us, and the pulse amplitude is 30V. The main function of the pulse signal acquisition module is high-speed data acquisition of pulse signals, and the data sampling frequency is not less than 50M. The display module is used to display the audio signal current and positioning results. The positioning results are presented by the collected transmission pulse and reflection pulse waveforms. The setting module is used to set the pulse transmission parameters; the audio signal transmission parameters of this embodiment can adopt fixed parameters.

[0039] In this embodiment, the online monitoring device monitors the copper shielding status of the cable in real time. The copper shielding at both ends of the cable is directly grounded, and the copper shielding forms a signal loop with the ground. The monitoring device couples the audio signal to the copper shielding of the cable through a caliper. In order to avoid interference with a single frequency, a composite frequency is selected for the audio signal frequency, that is, a superposition signal of two frequencies. This embodiment preferably uses a composite signal of 512Hz and 1024Hz. After the audio is superimposed, the two frequency signals can be separated by performing an FFT transformation on the collected signal in the audio signal acquisition module;

[0040] like Figure 2 As shown, when the copper shield is in good condition, current flows through the signal loop between the copper shield and the earth. When the copper shield is disconnected, the copper shield and the earth cannot form a signal loop, and no current flows through the signal loop between the copper shield and the earth. The main control module controls the current in the acquisition loop of the audio signal acquisition module. At this time, the current is very small. When the current is less than the set threshold (basically zero), the main control module determines that the cable copper shield is disconnected;

[0041] In this embodiment, the audio signal is only used to determine whether the copper shielding of the cable is disconnected, and does not locate the disconnection position. When the device determines that the copper shielding is disconnected, the disconnection position is located by pulse reflection.

[0042] like Figure 3As shown, when the monitoring device detects that the copper shield of the cable is disconnected, the main control module controls the pulse signal transmitting module to generate pulses, and at the same time starts the pulse signal acquisition device to collect data. One end of the pulse signal output line is connected to the thin film electrode installed on the main insulation surface of the cable core wire, and the other end is connected to the copper shield of the cable. Since the thin film electrode is installed on the main insulation surface, a capacitor will be formed between the cable core wire and the thin film electrode, and this capacitor can couple the emitted pulse signal to the cable core wire. The pulse signal propagates in the cable, and when it is transmitted to the place where the copper shield is disconnected, the pulse signal is reflected, and the reflected signal will be transmitted to the monitoring device. The reflected signal will be collected by the pulse signal acquisition device. By calculating the time difference between the pulse transmission signal and the reflected signal, the position where the copper shield is disconnected can be located.

[0043] In this embodiment, the pulse transmission signal will be transmitted in the cable, and total reflection will occur at the place where the copper shielding is disconnected, that is, the pulse signal will be transmitted to the monitoring device. There is a fixed wave velocity V during pulse transmission. The time difference t between the pulse transmission signal and the reflected signal can be obtained by the device, and the distance L can be calculated according to the formula L=1 / 2*V*t.

[0044] In this embodiment, when the copper shield is detected to be disconnected, a pulse with an amplitude of 30V is emitted to the cable core wire through the thin film electrode. The pulse propagates in the cable. When it is transmitted to the place where the copper shield is disconnected, the pulse will be reflected due to the change in the cable wave impedance. The device can locate the place where the copper shield is disconnected by collecting the transmitted pulse and the reflected pulse.

[0045] Example 2

[0046] This embodiment provides a monitoring method of an online monitoring device for disconnection of copper shielding of a pressure cable, comprising the following steps:

[0047] S1: The main control module controls the audio signal transmitting module to couple the composite audio signal to the cable copper shield through the clamp. Since the cable copper shield and the ground form a loop, the main control module controls the audio signal acquisition module to collect the composite audio signal current.

[0048] S2: The main control module determines the status of the cable copper shield according to the current of the collected composite audio signal. When the current of the detected composite audio signal is very small and less than the set threshold, it is determined that the copper shield is disconnected. When the copper shield is disconnected, a pulse signal is used to locate the position where the copper shield is disconnected;

[0049] S3: The main control module controls the pulse signal transmitting module to generate pulses, and couples the pulses to the cable core wire through the thin film electrode. At the same time, the main control module controls the pulse signal acquisition module to collect the pulse reflection signal. By calculating the time difference between the pulse transmission signal and the reflection signal, the position where the copper shield is disconnected can be located.

[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An online monitoring device for disconnection of copper shield of medium voltage cable, characterized in that: include: Main control module, audio signal transmitting module, audio signal collecting module, pulse signal transmitting module, pulse signal collecting module, display module and setting module; The main control module is respectively connected to the audio signal transmitting module, the audio signal collecting module, the pulse signal transmitting module, the pulse signal collecting module, the display module and the setting module, and is used to control each module; The audio signal transmitting module is used to generate a composite audio signal and clamp-couple the composite audio signal to the copper shield of the cable; The composite audio signal uses two synthetic signals of different frequencies. After the audio is superimposed, the collected signal is subjected to FFT transformation in the audio signal collection module to separate the two frequency signals. The composite audio signal adopts a composite signal with frequencies of 512 Hz and 1024 Hz; The audio signal acquisition module is used to collect the current of the composite audio signal on the copper shield. When the current is less than the set threshold, the main control module determines that the cable copper shield is disconnected. The pulse signal transmitting module is used to generate a positioning pulse signal. One end of the pulse signal output line is connected to a thin film electrode installed on the main insulation surface of the cable core wire, and the other end is connected to the cable copper shield. A capacitor is formed between the cable core wire and the thin film electrode to couple the emitted pulse signal to the cable core wire. The pulse signal acquisition module is used to collect the pulse reflection signal of the cable copper shield, calculate the time difference between the pulse transmission signal and the pulse reflection signal, and locate the position where the copper shield is disconnected; The display module is used to display the audio signal current and the positioning result, and the setting module is used to set the pulse transmission parameters.

2. The online monitoring device for disconnection of copper shield of medium voltage cable according to claim 1 is characterized in that: The pulse signal transmitting module is used to generate a positioning pulse signal. The pulse width of the pulse signal is adjustable between 100ns and 5us, and the pulse amplitude is 30V.

3. The online monitoring device for disconnection of copper shield of medium voltage cable according to claim 1, characterized in that: The time difference between the pulse transmission signal and the pulse reflection signal is calculated to locate the position where the copper shield is disconnected. The specific calculation formula is: L=1 / 2*V*t Among them, L represents the distance, V represents the wave speed of the pulse transmission signal, and t represents the time difference between the pulse transmission signal and the pulse reflection signal.

4. The online monitoring device for disconnection of copper shield of medium voltage cable according to claim 1, characterized in that: The positioning result is presented through the collected pulse transmission signal and pulse reflection signal.

5. A monitoring method for an online monitoring device for disconnection of copper shield of a medium voltage cable, characterized in that: The online monitoring device for disconnection of copper shield of medium voltage cable is provided with a main control module, an audio signal transmitting module, an audio signal collecting module, a pulse signal transmitting module, a pulse signal collecting module, a display module and a setting module; The specific steps of the monitoring method include: The main control module controls the audio signal transmitting module to couple the composite audio signal to the cable copper shield through the clamp, and the main control module controls the audio signal collecting module to collect the composite audio signal current; The composite audio signal uses two synthetic signals of different frequencies. After the audio is superimposed, the collected signal is subjected to FFT transformation in the audio signal collection module to separate the two frequency signals. The composite audio signal adopts a composite signal with frequencies of 512 Hz and 1024 Hz; The main control module determines the state of the cable copper shielding according to the current of the collected composite audio signal. When the current is less than the set threshold, the main control module determines that the cable copper shielding is disconnected. When the copper shield is disconnected, the main control module controls the pulse signal transmitting module to generate pulses, and couples the pulses to the cable core through the thin film electrode. At the same time, the main control module controls the pulse signal acquisition module to collect the pulse reflection signal, and locates the position where the copper shield is disconnected by calculating the time difference between the pulse transmission signal and the reflection signal. The pulse emission parameters are adjusted through the setting module, and the display module displays the audio signal current and positioning results.

6. The monitoring method of the online monitoring device for the disconnection of the copper shield of a medium voltage cable according to claim 5 is characterized in that: The copper shield disconnection position is located by calculating the time difference between the pulse transmission signal and the reflection signal. The specific calculation formula is: L=1 / 2*V*t Among them, L represents the distance, V represents the wave speed of the pulse transmission signal, and t represents the time difference between the pulse transmission signal and the pulse reflection signal.

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