CN103575415B - A kind of underground cable Joint Temperature on-line monitoring system and monitoring method thereof - Google Patents

Abstract

The invention relates to an on-line monitoring system and a monitoring method for the temperature of a power cable, in particular to an on-line monitoring system and a monitoring method for the temperature of an intermediate joint of an underground cable. The monitoring system is composed of wireless sensor nodes, thermoelectric generators (TEG), wireless temperature measurement concentrators and monitoring centers. The intermediate joints of buried cables are located under the cable wells, and the wireless sensor nodes and thermoelectric generators are installed on the outer surface of the cable joints. Above; the wireless temperature measurement concentrator is installed in the switching station, ring network cabinet or cable branch box at the cable terminal or branch joint, and its antenna is extended to the cable channel to collect the monitoring data of wireless sensor nodes, and transmit it through GPRS or The optical fiber is sent to the monitoring center. The present invention uses a thermoelectric generator and an energy collector to convert the temperature difference into electric energy to supply power to the wireless sensor, and at the same time collect monitoring data wirelessly; the wireless sensor node works in a low-power mode, thereby reducing the overall monitoring system. power consumption.

Description

An on-line monitoring system and monitoring method for the temperature of the intermediate joint of buried cables

technical field

The invention relates to an on-line monitoring system and a monitoring method for the temperature of a power cable, in particular to an on-line monitoring system and a monitoring method for the temperature of an intermediate joint of an underground cable.

Background technique

With urbanization and the development of urban power grids, power cables have been widely used, and the average annual growth rate in my country has reached 35%. With the increase in the number of cables used and the increase in power transmission capacity, once a fault occurs, the damage will be serious, so the operational reliability of power cables has received more and more attention. Through the investigation of the failure rate of power cables in major cities across the country, it is found that within 1 to 5 years of the initial operation of the cable and 5 to 25 years after it is put into operation, the failure of power cable accessories (including branch joints, terminal joints and intermediate joints) rate is always the highest. In particular, the production process of the cable intermediate joint is high, and there is a greater possibility of potential accidents. Therefore, online monitoring of its temperature is of great significance.

Existing on-line monitoring methods for cable temperature include point-type temperature measurement method and line-type temperature measurement method. 1) The traditional point temperature measurement method uses temperature sensors such as thermocouples, thermal resistors, and thermistors to measure the temperature of local points on the outer surface of the protective shell of the intermediate joint or the surface of the outer sheath of the cable body. The monitoring device generally uses batteries or electromagnetic induction to take power The device is powered. If a battery is used for power supply, it is easy to burst at high temperature, and the battery needs to be replaced regularly, resulting in a large maintenance workload. When the electromagnetic induction power taking device is used for power supply, if the current in the cable is small, the electric energy cannot be taken out, and the monitoring device stops working; if the cable current is large, the monitoring device is easy to burn out. When monitoring the three-core cable, the electromagnetic induction power-taking device cannot work. 2) The linear temperature measurement method generally uses temperature-sensing cables, distributed optical fiber temperature sensors, and optical fiber grating temperature sensors to be bound on the surface of the outer sheath of the cable (or embedded inside the cable) along the cable line to measure the temperature of the entire cable. This method is suitable for measuring the temperature trend of the entire cable and the thermal bottleneck area, but the cost of long-distance laying is high and the installation project is huge.

Contents of the invention

In view of the problems of the existing on-line monitoring system for cable intermediate joints such as high cost, difficulty in power supply, and difficulty in installation and maintenance, the purpose of the present invention is to provide an on-line monitoring system for the temperature of buried cable intermediate joints, and another purpose is to provide a buried The online monitoring method for the temperature of the cable intermediate joint, the invention uses a wireless sensor to measure the temperature of the outer skin of the cable intermediate joint, transmits the monitoring data in a wireless manner, and uses a thermoelectric generator and an energy collector to convert the temperature difference into electric energy to supply power to the wireless sensor, with low cost , maintenance-free, easy installation, high degree of safety and so on.

The object of the present invention is to adopt following technical scheme to realize:

The invention provides an on-line monitoring system for the temperature of the intermediate joint of buried cables. The system includes N wireless sensing nodes, a thermoelectric generator, a wireless temperature measuring concentrator and a monitoring center arranged above the cable well. The improvement That is, the cable intermediate joint is arranged under the cable well, and a single wireless sensor node and a thermoelectric generator are installed side by side on the outer surface of the cable intermediate joint in sequence; In the station, ring network cabinet or cable branch box, the antenna is extended to the cable channel to collect monitoring data of wireless sensor nodes, and the wireless temperature measurement concentrator performs data interaction with the monitoring center through GPRS or optical fiber.

Preferably, the high temperature side of the thermoelectric generator is pasted on the outer skin of the cable intermediate joint, and the low temperature side diffuses the heat flow into the air through the radiator; the distance between adjacent cable intermediate joints is 100 to 400 meters .

Preferably, the single wireless sensor node includes an energy harvester, a microcontroller, and a first wireless transceiver connected in sequence, the semiconductor temperature sensor is connected to the microcontroller, and the semiconductor temperature sensor and the first wireless transceiver are connected through the microcomputer in FIG. 2 The VOUT pin of the controller gets power; there is no signal connection between the two.

More preferably, the energy harvester includes an energy harvesting management chip, a microtransformer, a supercapacitor, and a capacitor; the microtransformer, supercapacitor, and capacitor are all connected to the energy harvesting management chip;

The energy harvester converts the voltage output by the thermoelectric generator into the operating voltage of the microcontroller, the first wireless transceiver and the semiconductor temperature sensor, and outputs an effective PGOOD signal to the microcontroller when the output voltage reaches 93% of the preset value, At the same time, the supercapacitor is charged; when the voltage output by the thermoelectric generator is lower than 20mV, the supercapacitor starts to discharge, and supplies power to the microcontroller, the first wireless transceiver and the semiconductor temperature sensor through the energy collection management chip.

More preferably, the semiconductor temperature sensor adopts a TMP36 type sensor, and when it works in the normal mode, the working current is less than 50 μA; when it is in the off mode, the working current is less than 0.5 μA.

More preferably, the microcontroller internally integrates on-chip peripherals such as analog-to-digital converters, timers, general-purpose I/O, and interrupt controllers;

The microcontroller is connected to the first wireless transceiver through the serial peripheral SPI interface, and uses the general I/O output shutdown or shutdown signal SDN (SDN signal refers to the Shutdown signal, shutdown or shutdown signal) to control the first wireless transceiver Power-on reset and working power;

The microcontroller starts the analog-to-digital converter regularly to convert the temperature analog signal into a digital signal, and sends the monitoring data through the first wireless transceiver; when the analog-to-digital conversion is not performed, the microcontroller outputs the shutdown signal #SHDN to the temperature sensor (the signal is output through a pin on the microcontroller) to low, and at the same time disable the first wireless transceiver transmit function;

The microcontroller uses the monitoring mode to receive data;

When the microcontroller is idle, it enters sleep mode, reducing its operating current to 1µA and allowing a timer interrupt to wake up the device.

More preferably, a thermoelectric generator and an energy collector are used to convert the temperature difference between the intermediate joint of the cable and the environment into electrical energy to supply power to the wireless sensor nodes.

Preferably, the wireless temperature measurement concentrator is powered by the mains, PT power supply or battery in the switching station, ring network cabinet or cable branch box, including a microprocessor, a second wireless transceiver (the model of the wireless transceiver The same as in the wireless sensor node, all are SI4463), GPRS module/optical Ethernet interface, LCD display, radio frequency circuit and antenna; the second wireless transceiver, GPRS module/optical Ethernet interface and LCD display are respectively It is connected with the microprocessor, and the antenna is connected with the second wireless transceiver through a radio frequency circuit.

More preferably, the wireless temperature measurement concentrator is used to collect temperature data uploaded by wireless sensor nodes in the cable channel, local display and alarm parameters of temperature data, and parameters for configuring wireless sensor nodes; receive and execute commands from the monitoring center and upload monitoring data.

Preferably, the frequency band of the wireless communication between the wireless sensor node and the wireless temperature measurement concentrator is 433MHz, the communication protocol is IEEE802.15.4g, and the authentication is performed through a key.

The present invention provides a method for on-line monitoring of the temperature of the intermediate joint of buried cables based on another purpose. The improvement is that the method includes the following steps:

(1) The thermoelectric generator converts the temperature difference on both sides into a voltage signal, and outputs it to the energy harvester of the wireless sensor node;

(2) The energy harvester converts the voltage output by the thermoelectric generator into the working voltage of the microcontroller, the first wireless transceiver and the semiconductor temperature sensor, and the wireless sensor node enters the working mode;

(3) The wireless sensor nodes upload monitoring data to the wireless temperature measurement concentrator in a point-by-point manner;

(4) After the wireless temperature measurement concentrator receives the data sent by the wireless sensor node, it displays it locally, and uploads the data to the monitoring center at the same time, and provides an alarm function.

Preferably, in the step (2), when the output voltage reaches 93% of the preset value, an effective PGOOD signal is output to the microcontroller, and the supercapacitor is charged at the same time; when the output voltage of the thermoelectric generator is lower than 20mV , the supercapacitor starts to discharge, and powers the microcontroller, the first wireless transceiver and the semiconductor temperature sensor through the energy harvesting management chip.

Preferably, in the step (3), each wireless sensor node in the cable channel has a unique serial number and location information.

Preferably, in the step (4), the user can set the configuration parameter data of the wireless sensor node through the LCD screen. - Node No. 1, and finally, Node No. 2 transmits it to Node No. 1; the configuration parameters include transmit power, data collection and sending interval, working mode, time and date.

Compared with prior art, the beneficial effect that the present invention reaches is:

1. In the on-line monitoring system for the temperature of the buried cable intermediate joint provided by the present invention, its wireless sensor nodes are powered by thermoelectric generators TEG and energy harvesters, which avoids the huge workload of laying special power supply cables or regularly replacing batteries, and eliminates the Due to the potential safety hazards and unreliability brought about by the use of electromagnetic induction power-taking devices for power supply, it has the advantages of maintenance-free, convenient installation, and low cost;

2. The wireless sensor node and the wireless temperature measurement concentrator in the present invention transmit data in a wireless manner, eliminating the need for additional communication cables, and the system has a strong ability to resist electromagnetic interference;

3. The wireless sensor node in the present invention works with a very low duty cycle, and its data upload adopts a point-by-point collection method, thereby reducing system power consumption;

4. The present invention utilizes energy harvesting technology to convert waste heat into electrical energy required for the work of wireless sensor nodes, thereby playing the role of energy saving and environmental protection.

Description of drawings

Fig. 1 is the structural diagram of the buried cable intermediate joint temperature online monitoring system provided by the present invention;

Fig. 2 is a schematic diagram of the wireless sensor node structure provided by the present invention.

detailed description

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Aiming at the problems of the existing on-line monitoring system for cable intermediate joints such as high cost, difficult power supply, difficult installation and maintenance, etc., the present invention uses a thermoelectric generator and an energy collector to convert temperature difference into electric energy to supply power for wireless sensors, and at the same time collect monitoring data wirelessly ; The wireless sensor works in a low-power mode, thereby reducing the power consumption of the entire monitoring system.

The structural diagram of the on-line temperature monitoring system for buried cable intermediate joints provided by the present invention is shown in Figure 1. The on-line temperature monitoring system includes at least one wireless sensor node, a thermoelectric generator (TEG), and It consists of a wireless temperature measurement concentrator and a background monitoring center (master station). Among them, the buried cable intermediate joint is located under the cable well, and the distance between adjacent joints is 100-400 meters; each wireless sensor node and thermoelectric generator are installed side by side on the outer surface of the cable intermediate joint; the wireless temperature measurement concentrator is installed on the In the switching station, ring network cabinet or cable branch box at the cable terminal or branch joint, its antenna is extended to the cable channel to collect the monitoring data of wireless sensor nodes, and send it to the background monitoring center through GPRS or optical fiber.

a) Thermoelectric Generator TEG:

The thermoelectric generator TEG applies the Seebeck effect (Seebeck Effect) to convert the temperature difference on both sides into a voltage, and the amplitude and polarity of the output voltage depend on the amplitude and polarity of the temperature difference. The high temperature side of the thermoelectric generator is pasted on the outer skin of the cable intermediate joint, and the low temperature side diffuses the heat flow into the air through the radiator to ensure the temperature difference between the two sides of the thermoelectric generator.

2) Wireless sensor node: It consists of an energy harvester, a microcontroller, a first wireless transceiver and a semiconductor temperature sensor. Connector connection, the schematic diagram of its structure is shown in Figure 2.

<1> The energy harvester mainly includes the energy harvesting management chip LTC3108, microtransformer T1 (model: LPR6235-752SMLB), supercapacitor and other capacitors. The energy harvester can convert the voltage (20mV ~ 500mV) output by the TEG to the working voltage (2.2V, 3.3V) of the microcontroller, the first wireless transceiver and the semiconductor temperature sensor. When the output voltage VOUT reaches the preset value At 93%, a valid PGOOD signal is output to the microcontroller, and the supercapacitor is charged to 5.25V at the same time. When the voltage output by the TEG is lower than 20mV, the supercapacitor starts to discharge and supplies power to the microcontroller, the first wireless transceiver and the semiconductor temperature sensor through the LTC3108.

<2>The semiconductor temperature sensor TMP36 converts the temperature signal into an analog voltage signal and outputs it to the microcontroller. When it works in normal mode, the working current is less than 50μA; when it is in off mode, the working current is less than 0.5μA.

<3> The microcontroller is the control center of the entire wireless sensor node, which integrates on-chip peripherals such as ADC, timer, general-purpose I/O, and interrupt controller. The microcontroller is connected to the first wireless transceiver SI4463 through the SPI interface, and uses the general I/O to output the SDN signal to control the power-on reset and working power of the first wireless transceiver. The microcontroller starts the ADC regularly to convert the temperature analog signal into a digital signal, and sends the monitoring data through the first wireless transceiver. When the A/D conversion is not performed, the microcontroller will set the #SHDN signal output to the temperature sensor low to reduce the power consumption of the temperature sensor, and at the same time disable the sending function of the first wireless transceiver. For data reception, a listening mode is used to reduce the average current consumed by the wireless transceiver. Sleep mode is entered when the microcontroller is not in use, reducing its operating current to 1µA and allowing a timer interrupt to wake up the device. Because the microcontroller and the first wireless transceiver work at a relatively low duty cycle, their average power consumption is very low, about a few milliwatts.

3) Wireless temperature measurement concentrator: powered by mains power, PT power supply or battery in the switching station/ring network cabinet/cable branch box, including microprocessor, second wireless transceiver, GPRS module/optical fiber Ethernet interface, LCD displays, radio frequency (RF) circuits, antennas, etc. Wherein, the wireless transceiver, GPRS module/optical fiber Ethernet interface and LCD display are respectively connected with the microprocessor, and the antenna is connected with the second wireless transceiver through a radio frequency (RF) circuit.

The functions of the wireless temperature measurement concentrator include: collecting temperature data uploaded by wireless sensor nodes in the cable channel, local display and alarm of temperature data, configuring parameters of wireless sensor nodes, receiving and executing commands from the monitoring center, uploading monitoring data, etc.

In the monitoring system provided by the present invention, the wireless communication frequency band between the wireless sensor node and the wireless temperature measurement collector is 433MHz, the communication protocol is IEEE802.15.4g, and authentication is performed through a key.

The present invention also provides a monitoring method for on-line monitoring of the temperature of the intermediate joint of buried cables, comprising the following steps:

(1) The thermoelectric generator TEG converts the temperature difference between its two sides into a voltage signal and outputs it to the energy harvester. The energy harvester converts the weak voltage (20-500mV) into a working voltage for the microcontroller and the first wireless transceiver, and the average output power P _OUT is about 1.5-2.5mW when the temperature difference between the two sides of the TEG is 5°C ( The specific value depends on the parameters of the TEG). Since P _OUT cannot maintain the wireless sensor node to work in normal mode in most cases, the node can only work with a certain duty cycle. The capacitor C _OUT at the output end of the energy harvester can ensure that V _OUT will not drop below normal operation after the wireless sensor node works at maximum power for a period of time. The value of C _OUT can be determined by the following formula:

C _OUT = I _PULSE *t _PULSE /ΔV _OUT ;

Among them: I _PULSE and t _PULSE are the maximum working current of the wireless sensor node and its corresponding working time, and ΔV _OUT is the maximum voltage drop allowed by the V _OUT output terminal.

If the power consumption of the wireless sensor node is P _N when it works normally, its working duty cycle should be smaller than P _OUT /P _N .

If the average power consumption of the wireless sensor node is P _Q when it works with a fixed duty cycle, then when the output voltage of the thermoelectric generator TEG is less than 20mV, the energy stored in the supercapacitor can maintain the working time of the node as:

t _S ＝C _STORE *(5.25V-3.3V)/P _Q ;

Among them: C _STORE is the capacitance value of the supercapacitor.

(2) Wireless sensor nodes upload monitoring data to the wireless temperature measurement concentrator in a point-by-point manner: each wireless sensor node in the cable channel has a unique number and location information. The data upload adopts a point-by-point collection method: suppose the node number farthest from the temperature measurement concentrator is 1, followed by 2, and the number closest to the temperature measurement concentrator is N; when uploading temperature data, the first node is No. 1 Send the data to node 2, then node 2 sends node 1 and its own data to node 3, and finally node N sends the data of all nodes to the wireless temperature measurement concentrator. All nodes only send data once in a data upload cycle, thus reducing their average power consumption.

(3) After the wireless temperature measurement concentrator receives the data sent by the sensor nodes, it will display it locally, and upload the data to the monitoring center as needed, and provide an alarm function. The user can set the configuration parameters of the wireless sensor node through the LCD screen (such as transmission power, data collection and transmission interval, working mode, time and date, etc.). When the data is sent, the wireless temperature measurement concentrator first transmits the data to the N node , and then passed from node N to node N-1, and finally from node 2 to node 1.

The on-line monitoring system and monitoring method for the temperature of the buried cable intermediate joint provided by the present invention takes energy collection and wireless sensing technology as the core, and converts the temperature difference between the surface of the cable intermediate joint and the environment into electrical energy through a thermoelectric generator and an energy collector. The wireless sensor is powered, thus eliminating the battery in the sensor, making it maintenance-free, safe and reliable, and easy to install.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (6)

1. a underground cable Joint Temperature on-line monitoring system, described system comprise be arranged at cable work downhole N number of wireless sensing node, thermoelectric generator, wireless temperature measurement manifold and Surveillance center, it is characterized in that, cable intermediate joint is arranged at cable work downhole, and single wireless sensing node and thermoelectric generator are installed on the outside surface of cable intermediate joint successively side by side; Described wireless temperature measurement manifold is installed in cable termination, the switching station of take-off connection, ring main unit or cable branch box, its Antenna extender collects the Monitoring Data of wireless sensor node to conduit line, and described wireless temperature measurement manifold carries out data interaction by GPRS or optical fiber and Surveillance center;

Described single wireless sensor node comprises and connects energy harvester, microcontroller and the first wireless transceiver successively, and semiconductor temperature sensor is connected with microcontroller; Semiconductor temperature sensor and the first wireless transceiver all obtain power supply by the VOUT pin of microcontroller;

Described energy harvester comprises collection of energy managing chip, miniature transformer, super capacitor and capacitor; Described miniature transformer, super capacitor and capacitor are all connected on collection of energy managing chip;

The voltage transitions that thermoelectric generator exports by energy harvester is the operating voltage of microcontroller, the first wireless transceiver and semiconductor temperature sensor, export effective PGOOD signal when output voltage reaches 93% of preset value to microcontroller, super capacitor is charged simultaneously; When the voltage that thermoelectric generator exports is lower than 20mV, super capacitor starts electric discharge, and by collection of energy managing chip be microcontroller, the first wireless transceiver and semiconductor temperature sensor power;

Described semiconductor temperature sensor adopts the sensor of TMP36 model, and when it is operated in normal mode, working current is less than 50 μ A; When it is in " shut " mode", working current is less than 0.5 μ A;

Described microcontroller integrated analog digit converter, timer, general purpose I/O, interruptable controller On-Chip peripheral;

Microcontroller is connected with the first wireless transceiver by serial peripheral SPI interface, and utilizes general purpose I/O output closedown or off signal SDN to control electrification reset and the working power of the first wireless transceiver;

Temperature analog signal is converted to digital signal by microcontroller start by set date analog to digital converter, and sends Monitoring Data by the first wireless transceiver; When not carrying out analog to digital conversion, the shutdown signal #SHDN exporting to temperature sensor sets low by microcontroller, forbids the first wireless transceiver sending function simultaneously;

Microcontroller adopts listen mode to carry out the reception of data;

Enter park mode when microcontroller leaves unused, its working current is down to 1 μ A, and allows timer interruption to wake device up;

Thermoelectric generator and energy harvester is utilized to convert the temperature difference of cable intermediate joint and environment to electric energy, for described wireless sensor node is powered.

2. temperature online monitoring system as claimed in claim 1, it is characterized in that, the side that described thermoelectric generator temperature is high is pasted onto on cable intermediate joint exocuticle, and hot-fluid is diffused in air by heating radiator by the side that temperature is low; The spacing of adjacent cable intermediate head is 100 ~ 400 meters.

3. temperature online monitoring system as claimed in claim 1, it is characterized in that, described wireless temperature measurement manifold, by the civil power in switching station, ring main unit or cable branch box, PT power supply or storage battery power supply, comprises microprocessor, the second wireless transceiver, GPRS module/fiber optic Ethernet interface, LCD display, radio circuit and antenna; Described second wireless transceiver, GPRS module/fiber optic Ethernet interface is connected with microprocessor respectively with LCD display, and described antenna is connected with the second wireless transceiver by radio circuit.

4. temperature online monitoring system as claimed in claim 3, it is characterized in that, described wireless temperature measurement manifold for collect wireless sensor node in conduit line and upload temperature data, this locality display of temperature data and alarm parameter, configuration wireless sensor node parameter; Receive and perform the order of Surveillance center and upload Monitoring Data.

5. temperature online monitoring system as claimed in claim 1, it is characterized in that, the frequency range of described wireless sensor node and wireless temperature measurement manifold radio communication is 433MHz, and communication protocol is IEEE802.15.4g, and carries out certification by key.

6. a underground cable Joint Temperature on-line monitoring method, is characterized in that, described method comprises the steps:

(1) temperature difference of its both sides is converted to voltage signal by thermoelectric generator, and exports the energy harvester of wireless sensor node to;

(2) voltage transitions that thermoelectric generator exports by energy harvester is the operating voltage of microcontroller, the first wireless transceiver and semiconductor temperature sensor, and wireless sensor node enters mode of operation;

(3) mode that described wireless sensor node adopts pointwise to collect uploads Monitoring Data to wireless temperature measurement manifold;

(4), after wireless temperature measurement manifold receives the data of wireless sensor node transmission, carry out this locality display, upload the data to Surveillance center simultaneously, and warning function is provided;

In described step (2), export effective PGOOD signal when output voltage reaches 93% of preset value to microcontroller, super capacitor is charged simultaneously; When the voltage that thermoelectric generator exports is lower than 20mV, super capacitor starts electric discharge, and by collection of energy managing chip be microcontroller, the first wireless transceiver and semiconductor temperature sensor power;

State in step (3), in conduit line, in each wireless sensor node, have unique numbering and positional information;

In described step (4), when user issues by the configuration parameter data that LCD screen arranges wireless sensor node, first data are passed to N node by wireless temperature measurement manifold, then pass to N-1 node by N node, finally pass to No. 1 node by No. 2 nodes; Described configuration parameter comprises emissive power, data acquisition and transmission interval, mode of operation and time and date.