A method and system for monitoring the insulation condition of a cable intermediate joint

Abstract

The application relates to the technical field of power equipment monitoring, and discloses a cable intermediate joint insulation state monitoring method and system. The method collects insulation state data of a target cable intermediate joint, extracts insulation state characteristic quantities from the insulation state data, packs the insulation state characteristic quantities into data packets, encodes and modulates the data packets and matches the impedance, obtains high-frequency signals, performs bidirectional transmission of the high-frequency signals along a carrier channel of a transmission line corresponding to the target cable intermediate joint to two adjacent device nodes at two ends of the target cable intermediate joint, demodulates the high-frequency signals, obtains corresponding insulation state characteristic quantities and a destination address, judges whether the destination address is consistent with a preset address, determines whether the device nodes are master stations, and then, the master stations evaluate the insulation state of the target cable intermediate joint according to the insulation state characteristic quantities in the data packets, so that the carrier communication improves the efficiency and accuracy of the insulation state monitoring of the cable intermediate joint.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power equipment monitoring, and particularly relates to a cable intermediate joint insulation state monitoring method and system. BACKGROUND

[0002] With the rapid development of China's economy, the level of urban modernization is continuously improved, and the demand for electricity is increasing year by year. Cable lines gradually replace overhead lines as an important carrier for transmitting electric energy in urban power distribution networks due to high reliability and small land occupation. However, most cable lines are concentrated in cable trenches, cable wells or directly buried underground. Both the cable body and the cable accessories are in a closed and compact distribution. Once a failure occurs, the loss is much more than that of overhead lines. Previously, State Grid Corporation of China has counted the operation failure of power cable equipment. The results show that more than 70% of the operation failure of power cable lines is caused by cable accessory failure, and the most important one is joint failure. Therefore, the insulation state monitoring of cable intermediate joints has become one of the key concerns in the industry.

[0003] The working environment of cable intermediate joints is special, the number of joints is large, and the distribution is wide. In the use process, it is necessary to stop production and power supply for maintenance and repair regularly, but it is still impossible to avoid the occurrence of cable joint failure accidents. Therefore, how to effectively monitor the insulation state of each cable intermediate joint to prevent accidents and further expansion is the key to ensure the safe and stable operation of the power system. Data communication is one of the key problems that must be considered in system work.

[0004] A kind of power cable intermediate joint insulation state on-line detection device is disclosed in Chinese patent with patent No.CN201910328593.7, which is composed of ultrasonic sensor, ross coil, conditioning circuit A, conditioning circuit B, A / D conversion module, ARM processor, communication module and host computer, and the position of cable intermediate joint partial discharge is determined by acoustic-electric comprehensive detection method. The communication module adopts wired transmission mode with optical fiber model GYXTW-4A1b, which avoids the problem of inaccurate information transmission that may occur in wireless transmission, and provides convenience for cable intermediate joint fault positioning detection. However, 4-core multimode optical cable is used as data transmission channel, which requires re-laying of line and high construction cost. Once a failure occurs, the maintenance engineering quantity is huge and it is not convenient for large-area use.

[0005] The utility model discloses a CN202021099943.1 of Chinese utility model patent proposes a kind of power cable intermediate joint state on-line monitoring system, it is designed to include multiple monitoring terminal, and be located in the mobile communication module receiving end and host computer system of indoor, monitoring terminal includes acoustic sensor, vibration sensor, temperature and humidity sensor, high voltage power coil and main control module etc., communication module utilizes mobile wireless public network to carry out wireless communication, realize the remote real-time monitoring of cable intermediate joint partial discharge state and environmental parameter.But for the data communication of cable intermediate joint, lack of universal applicability.Wireless communication mode is limited by topographical environment, in the area where wireless public network is not comprehensive, data transmission efficiency is poor, and cable intermediate joint generates partial discharge signal simultaneously also accompanied by the generation of other signals, such as electromagnetic wave etc., will produce interference to wireless signal, so that communication accuracy reduces.

[0006] The utility model discloses a CN201910039775.2 of Chinese invention patent proposes a kind of wireless cable trench cable intermediate joint operating state monitoring device, it is designed to include sensor unit, single-chip microcomputer unit, wireless communication unit, fire extinguisher unit and on-line energy taking unit's state monitoring device.Utilize the wireless communication unit that GSM / GPRS module and LoRa (Long Range Radio, long distance radio) module are composed to realize the monitoring of cable trench inner cable operating environment and operating state, and when meeting failure and fire, can timely send alarm signal and automatically start fire extinguishing function.But, it has an inherent problem that needs to build base station or to the existing base station is upgraded, so that monitoring is more complex.

[0007] In summary, the communication mode of the insulation state of the cable intermediate joint in the prior art is relatively complex, resulting in low monitoring efficiency and low accuracy of the insulation state of the cable intermediate joint. SUMMARY

[0008] The present application provides a cable intermediate joint insulation state monitoring method and system, which solves the technical problem of the communication mode of the insulation state of the cable intermediate joint in the prior art being relatively complex, resulting in low monitoring efficiency and low accuracy of the insulation state of the cable intermediate joint.

[0009] Therefore, the first aspect of the present application provides a cable intermediate joint insulation state monitoring method, comprising the following steps:

[0010] S1, collecting the insulation state data of the target cable intermediate joint, the insulation state data including partial discharge state quantity, temperature state data and humidity state data;

[0011] S2, extracting insulation state features from the insulation state data, the insulation state features including partial discharge amount, average discharge amount, partial discharge times, partial discharge amount maximum, relative temperature rise and relative humidity;

[0012] S3, packing the insulation state features into a data packet;

[0013] S4, encoding and modulating the data packet and impedance matching to obtain a high-frequency signal, and transmitting the high-frequency signal along a carrier channel of a transmission line corresponding to the target cable intermediate joint to two adjacent device nodes at both ends of the target cable intermediate joint;

[0014] S5, demodulating the high-frequency signal through the device node to obtain corresponding insulation state features and a destination address, and judging whether the address preset in the device node is consistent with the destination address, if the address preset in the device node is consistent with the destination address, determining that the device node is a master station, and executing step S6; if the address preset in the device node is not consistent with the destination address, determining that the device node is not a master station, and returning to step S4 until the data packet is transmitted to the master station;

[0015] S6, evaluating the insulation state of the target cable intermediate joint according to the insulation state features in the data packet through the master station to obtain a corresponding insulation state monitoring result.

[0016] Preferably, step S4 further comprises:

[0017] S40, detecting whether the carrier channel of the transmission line corresponding to the target cable intermediate joint is in an idle state, if the carrier channel of the transmission line corresponding to the target cable intermediate joint is in an idle state, sending a data blocking message to the cable intermediate joints closest to both ends of the target cable intermediate joint, executing step S4, if the carrier channel of the transmission line corresponding to the target cable intermediate joint is not in an idle state, continuing to wait for the carrier channel until an idle state appears.

[0018] Preferably, step S1 specifically comprises:

[0019] S101, collecting insulation state data of the target cable intermediate joint according to a preset collection time, the insulation state data including partial discharge state amount, temperature state data and humidity state data, wherein the preset collection time of each cable intermediate joint is different.

[0020] Preferably, the method further comprises:

[0021] determining whether the receiving ends on both sides of the main station receive the data packet transmitted by the target cable intermediate joint, and if it is determined that the receiving ends on both sides of the main station do not receive the data packet transmitted by the target cable intermediate joint, an alarm is given.

[0022] Preferably, the method further comprises:

[0023] S10, sending a monitoring message to the target cable intermediate joint along the transmission line by the main station, receiving a response message returned by the target cable intermediate joint, and if the response message is not received within a preset time length, performing step S11;

[0024] S11, sending a monitoring message to the target cable intermediate joint along the transmission line by the main station again, receiving a response message returned by the target cable intermediate joint, and if the response message is not received within a preset time length, sending a fault early warning, and if the response message is received within a preset time length, sending a short-term drop-out early warning.

[0025] In a second aspect, the present application also provides a cable intermediate joint insulation state monitoring system, comprising a data acquisition unit, a feature extraction unit, a data packet unit, a communication unit, a main control unit and an evaluation unit.

[0026] The data acquisition unit is configured to acquire insulation state data of a target cable intermediate joint, and the insulation state data comprises partial discharge state data, temperature state data and humidity state data.

[0027] The feature extraction unit is configured to extract insulation state feature quantities from the insulation state data, and the insulation state feature quantities comprise partial discharge quantity, average discharge quantity, partial discharge frequency, maximum partial discharge quantity, relative temperature rise and relative humidity.

[0028] The data packet unit is configured to package the insulation state feature quantities into a data packet.

[0029] The communication unit comprises a carrier wave communication module, an impedance matching module and an inductive coupler.

[0030] The carrier wave communication module is configured to encode and modulate the data packet to obtain a high-frequency signal.

[0031] The impedance matching module is configured to perform impedance matching on the high-frequency signal.

[0032] The inductive coupler is installed at the connection between the transmission line and the target cable intermediate joint at both ends of the target cable intermediate joint, and is configured to perform bidirectional transmission of the high-frequency signal along the carrier wave channel of the transmission line corresponding to the target cable intermediate joint to the adjacent device nodes at both ends of the target cable intermediate joint.

[0033] The main control unit is configured to demodulate the high-frequency signal by the device node to obtain a corresponding insulation state characteristic quantity and a destination address, and determine whether the address preset in the device node is consistent with the destination address; if the address preset in the device node is consistent with the destination address, it is determined that the device node is a master station; if the address preset in the device node is not consistent with the destination address, it is determined that the device node is not a master station.

[0034] The evaluation unit is configured to evaluate the insulation state of the target cable intermediate joint according to the insulation state characteristic quantity in the data packet to obtain a corresponding insulation state monitoring result.

[0035] Preferably, the system further comprises:

[0036] The channel detection module is configured to detect whether a carrier channel of a transmission line corresponding to the target cable intermediate joint is in an idle state; if the carrier channel of the transmission line corresponding to the target cable intermediate joint is in the idle state, a data blocking message is sent to the cable intermediate joints closest to the two ends of the target cable intermediate joint; if the carrier channel of the transmission line corresponding to the target cable intermediate joint is not in the idle state, the carrier channel is continuously waited for until the idle state appears.

[0037] Preferably, the data acquisition unit is specifically configured to acquire the insulation state data of the target cable intermediate joint according to a preset acquisition time, and the insulation state data includes a partial discharge state quantity, temperature state data and humidity state data, wherein the preset acquisition time of each cable intermediate joint is different.

[0038] Preferably, the system further comprises:

[0039] The receiving detection module is configured to determine whether the receiving ends on both sides of the master station have received the data packet transmitted by the target cable intermediate joint; if it is determined that the receiving ends on both sides of the master station have not received the data packet transmitted by the target cable intermediate joint, an alarm is given.

[0040] Preferably, the master station comprises a message detection module, the message detection module is configured to send a monitoring message to the target cable intermediate joint along the transmission line, receive a response message returned by the target cable intermediate joint, if the response message is not received within a preset time length, send the monitoring message to the target cable intermediate joint again along the transmission line, receive the response message returned by the target cable intermediate joint, if the response message is not received within the preset time length, send a fault early warning, if the response message is received within the preset time length, send a short-term drop-out early warning.

[0041] From the above technical solutions, the present application has the following advantages:

[0042] The application collects insulation state data of the target cable intermediate joint, extracts insulation state characteristic quantities from the insulation state data, packs the insulation state characteristic quantities into data packets, encodes and modulates the data packets and impedance matches to obtain high-frequency signals, transmits the high-frequency signals along the carrier channels of the transmission lines corresponding to the target cable intermediate joint to the two ends of the target cable intermediate joint, demodulates the high-frequency signals to obtain corresponding insulation state characteristic quantities and destination addresses, judges whether the destination addresses are consistent with preset addresses to determine whether the device nodes are master stations, and then evaluates the insulation state of the target cable intermediate joint according to the insulation state characteristic quantities in the data packets through the master stations, thereby improving the efficiency and accuracy of the cable intermediate joint insulation state monitoring by using carrier communication. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A flowchart of a cable intermediate joint insulation state monitoring method provided for an embodiment of the application is shown in the figure.

[0044] Figure 2 A transmission structure diagram of a cable intermediate joint provided for an embodiment of the application is shown in the figure.

[0045] Figure 3 A structure diagram of a cable intermediate joint insulation state monitoring system provided for an embodiment of the application is shown in the figure.

[0046] Figure 4 A circuit diagram from the sending end to the receiving end of a cable intermediate joint provided for an embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0047] In order for those skilled in the art to better understand the application scheme, the technical solutions in the embodiments of the application will be described clearly and completely below with reference to the accompanying drawings of the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0048] For easy understanding, please refer to Figure 1 The application provides a cable intermediate joint insulation state monitoring method, which comprises the following steps:

[0049] S1, collecting insulation state data of the target cable intermediate joint, the insulation state data comprising partial discharge state quantities, temperature state data and humidity state data.

[0050] It can be understood that the partial discharge state quantity, the temperature state data and the humidity state data are all related to the insulation state of the cable intermediate joint.

[0051] S2, extracting insulation state characteristic quantities from the insulation state data, the insulation state characteristic quantities including a partial discharge quantity, an average discharge quantity, a partial discharge frequency, a maximum partial discharge quantity, a relative temperature rise and a relative humidity.

[0052] Due to problems in materials, construction, installation quality and operation and maintenance of the cable, the insulation performance gradually deteriorates, partial discharge phenomenon is easily generated at the cable joint, thereby causing operation failure, the temperature of the cable joint and the terminal part is easily increased under the long-term operation of the power cable in a high-voltage and strong-current environment, which may cause explosion accidents and fires, and the cable intermediate joint is often placed on a cable trench or a cable well support after being completed, and if drainage is not timely in a thunderstorm, the cable head will be soaked in water for a long time, thereby causing a decrease in insulation performance and a breakdown accident is easily generated after power-on. Therefore, the partial discharge signal, the temperature signal and the humidity signal of the cable intermediate joint are state quantities that can represent the insulation state of the cable intermediate joint, obtaining the insulation state quantity of the cable intermediate joint can effectively monitor the insulation condition of the cable intermediate joint and prevent failure.

[0053] Among them, by collecting the partial discharge state quantity of the cable intermediate joint, filtering and denoising, attenuating amplification and A / D conversion and other pretreatments are performed, so that the waveform of the partial discharge signal can be obtained more clearly, and according to the waveform, the partial discharge quantity, the average discharge quantity, the partial discharge frequency and the maximum partial discharge quantity in a certain time period can be extracted, which can represent the insulation state of the cable intermediate joint.

[0054] At the same time, by collecting the temperature state data and the humidity state data of the cable intermediate joint, the relative temperature rise and the relative humidity can be easily obtained.

[0055] In addition, the pulse phase width and the discharge power can also be included.

[0056] S3, packaging the insulation state characteristic quantities into a data packet.

[0057] Among them, in one example, the data packet is also compressed, and by extracting the insulation state characteristic quantities from the insulation state data, the transmission pressure is reduced and the transmission efficiency is improved.

[0058] S4, encoding and modulating the data packet and impedance matching to obtain a high-frequency signal, and bidirectionally transmitting the high-frequency signal along the carrier channel of the transmission line corresponding to the target cable intermediate joint to the two adjacent device nodes at the two ends of the target cable intermediate joint.

[0059] It can be understood that the data packet is transmitted along the carrier channel of the transmission line corresponding to the target cable intermediate joint in both directions, so that the data packet can be received by both ends of the master station, and the transmission efficiency can be improved through carrier communication relay transmission.

[0060] Wherein, assuming that the transmission rate of data on the transmission line is v, the length of the transmission line is l1 and l2 respectively, and the time for data processing in the lower machine is T H , then a data packet forwarding period T r is:

[0061]

[0062] S5, demodulate the high-frequency signal through the device node to obtain the corresponding insulation state characteristic quantity and the destination address, judge whether the preset address in the device node is consistent with the destination address, if the preset address in the device node is consistent with the destination address, determine that the device node is the master station, execute step S6; if the preset address in the device node is inconsistent with the destination address, determine that the device node is not the master station, return to step S4 until the data packet is transmitted to the master station.

[0063] It can be understood that the data packet needs to be transmitted to the master station for processing, so that each device node is judged whether it is the master station, if the destination address is consistent with the preset address, it is determined that the device node is the master station, if the destination address is inconsistent with the preset address, it is determined that the device node is not the master station, but other cable intermediate joints.

[0064] Wherein, a data packet can contain destination address, source address, data length, data part, check, etc., and the insulation state characteristic quantity is only the data part. The destination address, source address, data length and check are set in the program.

[0065] S6, the master station evaluates the insulation state of the target cable intermediate joint according to the insulation state characteristic quantity in the data packet, and obtains the corresponding insulation state monitoring result.

[0066] Wherein, the insulation state of the target cable intermediate joint can be evaluated according to the insulation state characteristic quantity by using the evaluation scheme in the prior art.

[0067] For example, the partial discharge signal is selected as the input parameter to evaluate the insulation state of the cable joint. The number of partial discharges N, the maximum discharge quantity Q max , the pulse phase width and discharge power P are selected as the basic input parameters, and the state evaluation method based on BP neural network can be used.

[0068] The number of partial discharges N, the maximum discharge quantity Q max , the pulse phase width and The discharge power P is taken as the input layer of the neural network, and the output is used to judge the severity of the partial discharge, i.e. normal, general (attention), more serious (abnormal) and serious (warning).

[0069] The average value of each feature parameter in different partial discharge severity classification stages is taken as the standard value representing the severity of the partial discharge. Considering that the partial discharge signal is a random non-steady signal, the signal standard value is in a certain range, as shown in Table 1:

[0070] Table 1

[0071]

[0072] The selected feature quantity reflecting the insulation deterioration degree of the cable intermediate joint is a smaller-is-better type parameter, i.e. as the feature parameter value increases, the severity of the partial discharge increases, and the insulation state of the cable intermediate joint is worse.

[0073] The embodiment provides a cable intermediate joint insulation state monitoring method. Insulation state data of a target cable intermediate joint is collected, insulation state feature quantities are extracted from the insulation state data, the insulation state feature quantities are packaged into data packets, the data packets are encoded and modulated and impedance matched, high-frequency signals are obtained, the high-frequency signals are bidirectionally transmitted along a carrier channel of a transmission line corresponding to the target cable intermediate joint to two adjacent device nodes at both ends of the target cable intermediate joint, the high-frequency signals are demodulated, corresponding insulation state feature quantities and a destination address are obtained, it is judged whether the destination address is consistent with a preset address, so as to determine whether the device node is a master station, then the insulation state of the target cable intermediate joint is evaluated by the master station according to the insulation state feature quantities in the data packets, and therefore the efficiency and accuracy of the cable intermediate joint insulation state monitoring are improved by using carrier communication.

[0074] In one specific embodiment, step S4 further includes:

[0075] S40, detecting whether the carrier channel of the transmission line corresponding to the target cable intermediate joint is in an idle state, if the carrier channel of the transmission line corresponding to the target cable intermediate joint is in an idle state, sending a data blocking message to the cable intermediate joints closest to both ends of the target cable intermediate joint, and executing step S4, if the carrier channel of the transmission line corresponding to the target cable intermediate joint is not in an idle state, continuing to wait for the carrier channel until the idle state appears.

[0076] Wherein, by introducing CSMA / CA, i.e. carrier sense multiple access with collision avoidance, a collision avoidance mechanism is provided, and before data transmission, the state of the power line is listened to, if there is a carrier on the communication medium, the channel is occupied, i.e. the medium is busy, otherwise the medium is idle.

[0077] If the carrier channel of the transmission line corresponding to the target cable intermediate joint is in an idle state, a data blocking message is sent to the cable intermediate joints closest to the two ends of the target cable intermediate joint, and after the adjacent cable intermediate joints receive the data blocking message, data transmission is stopped to avoid channel blocking and be ready to receive data packets at any time.

[0078] In one specific embodiment, step S1 specifically comprises:

[0079] S101, collecting insulation state data of the target cable intermediate joint according to a preset collection time, the insulation state data including partial discharge state data, temperature state data and humidity state data, wherein the preset collection time of each cable intermediate joint is different.

[0080] Wherein, the main control unit of each cable intermediate joint controls each data collection unit to complete 5 times of data collection lasting 5 minutes within 24 hours, the data collection time of each cable intermediate joint is staggered, and the same transmission line is used for transmission at different time periods to avoid data conflict.

[0081] In one specific embodiment, the method further comprises:

[0082] Determining whether the receiving ends on both sides of the main station have received the data packets transmitted by the target cable intermediate joint, and if it is determined that the receiving ends on both sides of the main station have not received the data packets transmitted by the target cable intermediate joint, an alarm is given.

[0083] In one example, if the main station can only monitor the data information of a certain cable intermediate joint on one side, the main station immediately starts a blue pre-warning, and the staff immediately checks whether the cable intermediate joint device closest to the other side is malfunctioning, and checks whether the data information of other cable intermediate joints on the other side is abnormal, and determines the location of the malfunctioning device after checking one by one.

[0084] In one specific embodiment, the method further comprises:

[0085] S10, sending a monitoring message to the target cable intermediate joint along the transmission line through the main station, receiving a reply message returned by the target cable intermediate joint, and if the reply message is not received within a preset time length, step S11 is performed.

[0086] S11, sending a monitoring message to the target cable intermediate joint along the transmission line again through the master station, receiving the response message returned by the target cable intermediate joint, if the response message is not received within a preset time length, sending a fault early warning, if the response message is received within a preset time length, sending a short-term drop-out early warning.

[0087] The double fault monitoring mechanism of the master station is a protection mechanism for ensuring effective data transmission. The insulation state data of the cable intermediate joint collected by each cable intermediate joint is transmitted on the transmission line, and the data transmission is bidirectional relay transmission. During the transmission process, a cable intermediate joint may fail to transmit data, thereby losing part of the insulation state data of the cable intermediate joint. The double fault monitoring mechanism started by the master station can better detect the operating conditions of each cable intermediate joint, maintain the fault lower machine system in time, and ensure reliable data transmission of the entire cable intermediate joint online monitoring.

[0088] The following is a specific example provided by the application:

[0089] As shown in Figure 2 If the insulation state data of the cable intermediate joint n is collected, the insulation state data is feature extracted, the amount of transmission data is reduced, and whether the transmission line of the adjacent cable intermediate joint section is idle is listened to. When the transmission line is idle, first, data blocking messages are sent to the nearest intermediate joint n-1 and intermediate joint n+1, and the intermediate joint n-1 and the intermediate joint n+1 stop data transmission after receiving the data blocking messages.

[0090] Then, after the processed data packet is encoded, modulated, filtered and amplified, and impedance matched, the data is coupled to the transmission line through the two clamping type inductive couplers of the intermediate joint n for bidirectional transmission.

[0091] After the data transmission is completed, the intermediate joint n-1 and the intermediate joint n+1 receive the data packet sent by the intermediate joint n;

[0092] The data is demodulated and processed, the destination address obtained by demodulation is verified, if the address matches, the data is analyzed and processed, if the address does not match, the device does not respond, and the received data packet is re-encoded and modulated.

[0093] If the device addresses of the intermediate joint n-1 and the intermediate joint n+1 are both non-destination addresses, it is necessary to listen to whether the transmission line of the adjacent cable intermediate joint section is idle, when the transmission line is idle, data blocking messages are sent to the nearest cable intermediate joint, and the intermediate joint n-2, the intermediate joint n and the intermediate joint n+2 stop data transmission after receiving the data blocking messages.

[0094] Then, the processed data packet is encoded and modulated by the carrier device, filtered and amplified, and impedance matched, and then coupled to the transmission line in the form of electromagnetic coupling through intermediate joint n-1 and intermediate joint n+1 to perform relay transmission, after the data transmission is completed, the intermediate joint n-2 and the intermediate joint n receive the data packet sent by the intermediate joint n-1, and the intermediate joint n discards the data packet; the intermediate joint n+2 and the intermediate joint n receive the data packet sent by the intermediate joint n+1, and the intermediate joint n discards the data packet, and the above steps are repeated until the data is transmitted to the main station, so that the data can be finally transmitted to the main station for state evaluation, data storage and terminal display.

[0095] The above is a detailed description of an embodiment of the cable intermediate joint insulation state monitoring method provided by the application, and the following is a detailed description of an embodiment of a cable intermediate joint insulation state monitoring system provided by the application.

[0096] For the convenience of understanding, please refer to Figure 3 The application provides a cable intermediate joint insulation state monitoring system, which comprises a data acquisition unit 100, a feature extraction unit 200, a data packet unit 300, a communication unit 400, a main control unit 500 and an evaluation unit 600.

[0097] The data acquisition unit 100 is used for acquiring insulation state data of the target cable intermediate joint, and the insulation state data comprises partial discharge state quantity, temperature state data and humidity state data.

[0098] The feature extraction unit 200 is used for extracting insulation state characteristic quantities from the insulation state data, and the insulation state characteristic quantities comprise partial discharge quantity, average discharge quantity, partial discharge frequency, maximum partial discharge quantity, relative temperature rise and relative humidity.

[0099] The data packet unit 300 is used for packing the insulation state characteristic quantities into data packets.

[0100] The communication unit 400 comprises a carrier communication module 401, an impedance matching module 402 and an inductive coupler 403.

[0101] The carrier communication module 401 is used for encoding and modulating the data packet to obtain a high-frequency signal.

[0102] The impedance matching module 402 is used for impedance matching the high-frequency signal.

[0103] The inductive coupler 403 is installed at the connection between the two ends of the target cable intermediate joint and the transmission line, and is used for bidirectional transmission of the high-frequency signal along the carrier channel of the transmission line corresponding to the target cable intermediate joint to the adjacent device nodes at the two ends of the target cable intermediate joint.

[0104] The main control unit 500 is used for demodulating the high-frequency signal through the device node to obtain the corresponding insulation state characteristic quantity and the destination address, judging whether the address preset in the device node is consistent with the destination address, if the address preset in the device node is consistent with the destination address, determining that the device node is the main station, if the address preset in the device node is not consistent with the destination address, determining that the device node is not the main station.

[0105] The evaluation unit 600 is used for evaluating the insulation state of the intermediate joint of the target cable according to the insulation state characteristic quantity in the data packet to obtain the corresponding insulation state monitoring result.

[0106] The carrier communication module 401 contains a serial communication interface, receives data from the main control unit 500, is encoded and modulated by the carrier communication module 401, impedance matching is performed by the impedance matching module 402, so that the internal resistance of the lower computer side is as equal as possible to the characteristic impedance of the transmission line, the refraction and reflection attenuation of the signal caused by the impedance mismatch is reduced, and then is coupled to the transmission line by the inductive coupler 403; an impedance matching circuit needs to be arranged between the power line carrier module and the inductive coupler.

[0107] In one example, the inductive coupler adopts a clamping type inductive coupler, utilizes the principle of electromagnetic induction, couples the high-frequency signal to the cable shielding layer for transmission, and the cable shielding layer is grounded outside the coupler. For any cable intermediate joint data sending end, the primary side is the system side, and the secondary side is the cable side; for any cable intermediate joint data receiving end, the primary side is the cable side, and the secondary side is the system side. The magnetic core material of the coupler is selected to be ferrite material, the shape of the magnetic core is selected to be a CC type annular magnetic core which is easy to disassemble and install, the inner diameter of the coupler should be as close as possible to the outer diameter of the cable to reduce the loss, the smaller the magnetic resistance of the coupler, the smaller the loss of the carrier signal through the magnetic ring, and the magnetic resistance of the coupler magnetic ring is calculated as follows:

[0108]

[0109] In the formula, R is the magnetic resistance of the magnetic ring, a is the inner diameter of the magnetic ring, b is the outer diameter of the magnetic ring, h is the height of the magnetic ring, μ is the magnetic permeability of the magnetic ring, and l is the distance from the magnetic ring to the center of the cable.

[0110] The clamping type inductive coupler does not need to change the original grounding mode of the cable, does not need to operate without power, is simple and convenient to operate, and is the currently popular coupling mode for power cables.

[0111] The characteristic impedance of the transmission line is only related to the structure, material and frequency of the transmission line, and determines the voltage and current characteristics on the transmission line. The characteristic impedance of a general power cable is about 50Ω. When a high-frequency signal is transmitted on the transmission line, it is easy to cause refraction and reflection of the wave when encountering an impedance discontinuity point, forming a standing wave, so that the transmission power of the signal cannot reach the maximum, thereby affecting the stability of the output power and frequency of the signal source. Therefore, in order to make the system have better transmission performance and reduce the attenuation of the transmission line as much as possible, it is necessary to design an impedance matching circuit to improve the transmission efficiency of data.

[0112] Considering that the data transmission and reception are both carried out by using the same size type of card joint type inductive coupler, the structure diagram from the data transmission end to the receiving end has strong symmetry, therefore, the embodiment uses the Smith circle diagram theory as an auxiliary tool for impedance matching design, and selects a T-type or Π-type impedance matching circuit to design the impedance matching circuit according to the actual situation of the transmission line. The principle diagram of the middle joint of the cable from an arbitrary sending end to a receiving end is shown in Figure 4 .

[0113] In one specific embodiment, the system further comprises:

[0114] The channel detection module is configured to detect whether the carrier channel of the transmission line corresponding to the target cable middle joint is in an idle state, and if the carrier channel of the transmission line corresponding to the target cable middle joint is in an idle state, send a data blocking message to the two nearest cable middle joints at both ends of the target cable middle joint, and if the carrier channel of the transmission line corresponding to the target cable middle joint is not in an idle state, continue to wait for the carrier channel until an idle state appears.

[0115] In one specific embodiment, the data acquisition unit is specifically configured to acquire the insulation state data of the target cable middle joint according to a preset acquisition time, and the insulation state data includes partial discharge state data, temperature state data and humidity state data, wherein the preset acquisition time of each cable middle joint is different.

[0116] In one specific embodiment, the system further comprises:

[0117] The receiving detection module is configured to determine whether the receiving ends on both sides of the main station have received the data packet transmitted by the target cable middle joint, and if it is determined that the receiving ends on both sides of the main station have not received the data packet transmitted by the target cable middle joint, an alarm is performed.

[0118] In one specific embodiment, the master station comprises a message detection module, the message detection module is used for sending a monitoring message to the target cable intermediate joint along the transmission line, receiving a reply message returned by the target cable intermediate joint, if the reply message is not received within a preset time length, sending the monitoring message to the target cable intermediate joint again along the transmission line, receiving the reply message returned by the target cable intermediate joint, if the reply message is not received within a preset time length, sending a fault early warning, if the reply message is received within a preset time length, sending a short-term drop-out early warning.

[0119] The system adopts the CT+ backup battery combination power taking mode, when there is a large current flowing through the system, the CT coil takes power from the high voltage side and supplies power to the system after surge protection and rectification filtering processing, and charges the battery, when the current is too small due to system failure, the backup battery is used as a supplement to supply power to the system.

[0120] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, device and unit described above can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0121] In several embodiments provided by the present application, it should be understood that the disclosed device and method can be implemented by other ways. For example, the device embodiments described above are only schematic, and the division of units is only a logical function division, and there can be another division way in actual implementation, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0122] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they can be located in one place, or can be distributed on a plurality of network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0123] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware, or in the form of software functional unit.

[0124] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for monitoring the insulation condition of a cable joint, characterized in that, Includes the following steps: S1. Collect insulation status data of the intermediate joint of the target cable, including partial discharge status data, temperature status data and humidity status data; S2. Extract insulation state feature quantities from the insulation state data. The insulation state feature quantities include partial discharge quantity, average discharge quantity, number of partial discharges, maximum partial discharge quantity, relative temperature rise, and relative humidity. S3. Pack the insulation state characteristics into a data packet; S4. Encode, modulate, and impedance match the data packet to obtain a high-frequency signal, and transmit the high-frequency signal bidirectionally along the carrier channel of the transmission line corresponding to the intermediate joint of the target cable to the adjacent device nodes at both ends of the intermediate joint of the target cable. S5. Demodulate the high-frequency signal through the device node to obtain the corresponding insulation state characteristic quantity and destination address. Determine whether the preset address in the device node is consistent with the destination address. If the preset address in the device node is consistent with the destination address, the device node is determined to be the master station, and step S6 is executed. If the preset address in the device node is inconsistent with the destination address, the device node is determined not to be the master station, and the process returns to step S4 until the data packet is transmitted to the master station. S6. The insulation status of the target cable intermediate joint is evaluated by the main station based on the insulation status characteristic quantity in the data packet, and the corresponding insulation status monitoring result is obtained. Step S4 is preceded by: S40. Detect whether the carrier channel of the transmission line corresponding to the target cable intermediate joint is idle. If the carrier channel of the transmission line corresponding to the target cable intermediate joint is idle, send a data blocking message to the cable intermediate joints at both ends of the target cable intermediate joint and execute step S4. If the carrier channel of the transmission line corresponding to the target cable intermediate joint is not idle, continue to wait for the carrier channel until it becomes idle.

2. The method for monitoring the insulation status of cable joints according to claim 1, characterized in that, Step S1 specifically includes: S101. Collect insulation status data of the target cable intermediate joint according to the preset collection time. The insulation status data includes partial discharge status, temperature status data and humidity status data. The preset collection time is different for each cable intermediate joint.

3. The method for monitoring the insulation status of cable joints according to claim 1, characterized in that, Also includes: Determine whether both receiving ends of the master station have received the data packet transmitted by the target cable intermediate connector. If it is determined that both receiving ends of the master station have not received the data packet transmitted by the target cable intermediate connector, an alarm is triggered.

4. The method for monitoring the insulation status of cable joints according to claim 1, characterized in that, Also includes: S10. The master station sends a monitoring message to the target cable intermediate joint along the transmission line and receives the response message returned by the target cable intermediate joint. If the response message is not received within a preset time, step S11 is executed. S11. The master station sends a monitoring message to the target cable intermediate joint along the transmission line again, and receives the response message returned by the target cable intermediate joint. If the response message is not received within a preset time, a fault warning is sent. If the response message is received within a preset time, a short-term disconnection warning is sent.

5. A cable joint insulation condition monitoring system, characterized in that, include: The system comprises a data acquisition unit, a feature extraction unit, a data packet unit, a communication unit, a main control unit, and an evaluation unit. The data acquisition unit is used to acquire insulation status data of the target cable intermediate joint, including partial discharge status data, temperature status data and humidity status data. The feature extraction unit is used to extract insulation state feature quantities from the insulation state data. The insulation state feature quantities include partial discharge quantity, average discharge quantity, number of partial discharges, maximum partial discharge quantity, relative temperature rise, and relative humidity. The data packet unit is used to package the insulation state characteristic quantities into a data packet; The communication unit includes a carrier communication module, an impedance matching module, and an inductive coupler; The carrier communication module is used to encode and modulate the data packets to obtain high-frequency signals; The impedance matching module is used for impedance matching of the high-frequency signal; The inductive coupler is installed at the connection points between the two ends of the target cable intermediate joint and the transmission line, respectively, and is used to transmit the high-frequency signal bidirectionally along the carrier channel of the transmission line corresponding to the target cable intermediate joint to the adjacent device nodes at both ends of the target cable intermediate joint. The main control unit is used to demodulate the high-frequency signal through the device node to obtain the corresponding insulation state characteristic quantity and destination address, and to determine whether the preset address in the device node is consistent with the destination address. If the preset address in the device node is consistent with the destination address, the device node is determined to be the master station. If the preset address in the device node is inconsistent with the destination address, then the device node is determined not to be the master station. The evaluation unit is used to evaluate the insulation status of the target cable joint based on the insulation status characteristic quantity in the data packet, and obtain the corresponding insulation status monitoring result. The channel detection module is used to detect whether the carrier channel of the transmission line corresponding to the target cable intermediate joint is idle. If the carrier channel of the transmission line corresponding to the target cable intermediate joint is idle, a data blocking message is sent to the nearest cable intermediate joint at both ends of the target cable intermediate joint. If the carrier channel of the transmission line corresponding to the target cable intermediate joint is not idle, the module continues to wait for the carrier channel until it becomes idle.

6. The cable joint insulation condition monitoring system according to claim 5, characterized in that, The data acquisition unit is specifically used to acquire insulation status data of the target cable intermediate joint according to a preset acquisition time. The insulation status data includes partial discharge status, temperature status data and humidity status data. The preset acquisition time is different for each cable intermediate joint.

7. The cable joint insulation condition monitoring system according to claim 5, characterized in that, Also includes: The receiving detection module is used to determine whether both receiving ends of the master station have received the data packet transmitted by the target cable intermediate connector. If it is determined that both receiving ends of the master station have not received the data packet transmitted by the target cable intermediate connector, an alarm is triggered.

8. The cable joint insulation condition monitoring system according to claim 5, characterized in that, The master station includes a message detection module, which is used to send monitoring messages along the transmission line to the target cable intermediate joint and receive response messages returned by the target cable intermediate joint. If the response message is not received within a preset time period, the monitoring message is sent again along the transmission line to the target cable intermediate joint and the response message is received. If the response message is not received within the preset time period, a fault warning is sent. If the response message is received within the preset time period, a brief disconnection warning is sent.

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