CN101464488A - On-line monitoring system for high voltage cable - Google Patents

Abstract

The invention relates to an on-line monitoring system for high-voltage cables, which includes a sensor, a data acquisition unit, a power-taking device, and a network server, wherein the sensor is arranged at the joint of the high-voltage cable, and is used for collecting the sheath circulating current and the core current of the high-voltage cable joint , cable surface temperature, ambient temperature and humidity and other data, and send the collected data to the data acquisition unit. The data acquisition unit is set near the high-voltage cable joint to collect sensor data and send it to the network server through the wireless network. Power is taken from the high-voltage cable and supplies power to the data acquisition unit. The network server is installed in the control room to receive data from the data acquisition unit and determine whether the cable is in a safe operating state through specific data analysis, so that maintenance personnel can keep track of the cable. operation to avoid electrical accidents. If the cable fails, it can also report to the police in time and locate the fault point to provide help for cable maintenance.

Description

A high-voltage cable on-line monitoring system

【Technical field】

The invention relates to a monitoring system, in particular to a system for on-line monitoring of high-voltage cables.

【Background technique】

Modern urban construction puts forward higher requirements for power transmission. With the continuous development of electric power industry, the power transmission of urban overhead lines is being replaced by underground high-voltage cables, so the number of high-voltage cables is rising sharply. As a part of the transmission network, these cable lines are very important, and it is extremely important to ensure the safe operation of the cable lines.

Unlike overhead lines, the complex environment of underground cables brings difficulties to operation and maintenance. Because there are defects and hidden dangers in the cable, and it takes a lot of manpower and material resources to maintain the cable. For high-voltage cable lines, the following operation, maintenance and overhaul tests are required:

1. Regular or irregular inspections to discover abnormalities and hidden dangers of cables and their ancillary facilities and deal with defects or hidden dangers in a timely manner;

2. Carry out an infrared thermal imaging test on cable terminals, intermediate joints and auxiliary facilities every quarter;

3. Measure the circulating current of the cable sheath every quarter;

4. Conduct a preventive test one year after the new cable is put into operation, and then conduct a preventive test every 6 years. The main items are to test the main insulation resistance, sheath insulation resistance and main insulation for AC withstand voltage test.

In actual work, due to the increasing number of cable lines, it is impossible to strictly follow the regulations for operation, maintenance and inspection. There are a large number of direct grounding boxes or cross-connection grounding boxes at the cable connection. These boxes are either on the tower or in the joint well. It takes a lot of money to measure the circulating current of their sheath and the temperature of the cable joints and ancillary facilities. Human and material resources.

Power cables with a voltage level of 35KV and above are mainly single-core cables. The insulation of the sheath is often damaged during operation, and electrical accidents occur due to two or more ground faults. In our country, the insulation of the cable sheath is mechanically damaged during the laying process, chemically corroded during operation, bitten by mice and termites, etc., which have frequently occurred as the main cause of cable accidents. As an important indicator of safe cable operation, the cable operation and maintenance department needs to regularly measure the sheath circulating current and insulation resistance to ensure safe cable operation, but the traditional measurement methods for these two indicators have certain deficiencies.

At present, the circulating current and insulation resistance of the cable sheath are mainly measured manually, which requires operation and maintenance personnel to regularly go to the site to measure and record, and then manually analyze the data. When measuring the insulation resistance, the cable must be stopped, so these two methods are not only time-consuming, It is laborious, and it is impossible to find the insulation defect of the cable sheath in time.

In addition, it is very important to ensure that each metal sheath of the high-voltage cable line has at least one good grounding point. Whether it is a single-ended grounding system or a cross-connected grounding system, because the metal sheath of the single-core cable is hinged with the magnetic field lines generated by the alternating current in the core wire, a high induced voltage appears at both ends, so appropriate grounding measures must be taken , so that the induced voltage is within the safe voltage range.

Usually, the metal sheath of a short-circuit single-core cable is directly grounded at one end and the other end is grounded through a gap or a protective resistor; the metal sheath of a long-circuit single-core cable is grounded at both ends of a three-phase segmental cross-connection. If the direct grounding point is not effectively grounded due to various reasons, the potential of the cable metal sheath will rise sharply to several thousand volts or even 10,000 volts, and it is easy to break down the outer sheath of the cable and continue to discharge at the breakdown point , causing the temperature of the cable outer sheath to rise or even catch fire. There have been many such accident cases at home and abroad.

Therefore, how to design a cable automatic monitoring system that can accurately measure the indicators of cable metal sheath circulating current, cable core current, and cable surface temperature in real time, and use scientific analysis methods to judge the insulation status of the sheath to ensure that the cable It is an urgent problem to be solved that the operation is in a safe state, that there is no one on site, and that the cost of cable operation and maintenance is reduced.

【Content of invention】

The technical problem to be solved by the invention is to automatically monitor the running state of the high-voltage cable in real time and accurately.

In order to solve the problems of the technologies described above, the present invention proposes the following technical solutions:

The invention relates to an on-line monitoring system for high-voltage cables, which includes a sensor, a data acquisition unit, a power-taking device, and a network server. The data is sent to the data acquisition unit. The data acquisition unit is set near the high-voltage cable joint to collect the sensor data and send it to the network server through the wireless network. The power-taking device takes power from the high-voltage cable and supplies power to the data acquisition unit. The network The server is installed in the control room and is used to receive the data sent by the data acquisition unit and analyze and judge the data. It can browse the running status information of the high-voltage cable online and give an alarm to the cable fault.

Further, the data acquisition unit includes a sensor signal receiving circuit, a high voltage protection circuit, an A/D conversion circuit, a CPU and a GPRS data sending unit DTU.

Further, the data collected by the sensor includes the circulating current value of the sheath and the current value of the wire core, and the sensor transmits these data to the data acquisition unit.

Further, the data acquisition unit transmits the circulating current value of the sheath and the core current value to the network server, and the network server judges these data to determine the insulation condition of the high-voltage cable sheath.

Further, when the ratio of the circulating current value of the sheath to the current value of the core is greater than or equal to 8%, and the ratio of the change rate of the circulating current of the sheath to the change rate of the core current within the same period is greater than or equal to 1, it is determined to be a high-voltage cable. Layer insulation is abnormal and an alarm is given.

The monitoring system can automatically realize real-time monitoring of the sheath circulating current, core current, cable surface temperature and ambient temperature and humidity of the cable in operation on site, and judge whether the cable is in a safe operating state through specific analysis, so as to facilitate operation The maintenance personnel can keep abreast of the operation status of the cable at any time, so as to avoid the beneficial effects of electric accidents.

【Description of drawings】

Figure 1 is the architecture diagram of the high-voltage cable online monitoring system.

Figure 2 is a structural diagram of the data acquisition unit.

【Detailed ways】

As shown in Fig. 1, an online monitoring system for high-voltage cables according to the present invention includes a sensor (1), a data acquisition unit (2), a power-taking device (3) and a network server (4). The sensor (1) is arranged at the joint of the high-voltage cable, and is used for collecting data of each monitoring point at the joint of the high-voltage cable and sending the collected data to the data acquisition unit (2). The data acquisition unit (2) is arranged near the high-voltage cable joint, and is used for collecting the data of the on-site sensor (1) and sending it to the network server (4) through the wireless network. The power-taking device (3) is installed beside the data acquisition unit (2) and supplies power to it. The network server (4) is installed in the control room, and is used to receive the data sent by the data acquisition unit and analyze and judge the data. It can browse the running status information of the high-voltage cable online and give an alarm to the cable failure.

Sensor(1):

The on-site sensor detection information includes cable surface temperature, cable sheath circulation current, cable core current, ambient temperature and humidity, water level, smog, and harmful gas, and sends these detection quantities to the data acquisition unit (2).

Data Acquisition Unit (2):

The data acquisition unit includes a sensor signal receiving circuit, a high-voltage protection circuit, an A/D conversion circuit, a CPU and a GPRS data sending unit DTU, and is responsible for collecting data from field sensors (1) and sending them to a network server (4) through a wireless network.

Power-taking device (3):

The power-taking device obtains electric energy through the current mutual induction coil set on the bus bar of the high-voltage cable, and then obtains safe and sufficient direct current through the high-voltage protection circuit and the rectification and voltage stabilization circuit to provide power for the data acquisition unit (2).

webserver(4):

The network server is mainly responsible for receiving the data sent by the data acquisition unit (2) and analyzing and processing the data, and can browse the running status information of the high-voltage cable online. When the ratio of the circulating current value of the sheath to the current value of the core is greater than or equal to 8%, and the ratio of the rate of change of the circulating current of the sheath to the rate of change of the core current within the same period is greater than or equal to 1, it is determined that the sheath insulation of the high-voltage cable has occurred Abnormal conditions and alarm.

Through the above system, the operation and maintenance personnel can monitor the real-time data of the sheath circulating current, core current, cable surface temperature and ambient temperature and humidity of the operating cables on site, and can judge whether the cable is in a safe operating state to avoid electrical accidents.

Claims (5)

1. on-line monitoring system for high voltage cable, it is characterized in that: comprise sensor (1), data acquisition unit (2), electricity getting device (3), and the webserver (4), wherein sensor (1) is arranged on the high-voltage cable joint place, be used to gather the data of each monitoring point, high-voltage cable joint place and the data of gathering are sent to data acquisition unit (2), data acquisition unit (2) is arranged near the high-voltage cable joint, be used for the data of pick-up transducers (1) and send to the webserver (4) by wireless network, electricity getting device (3) is powered from the high-tension cable power taking and to data acquisition unit, the webserver (4) is installed in the pulpit, be used to receive the data that data acquisition unit (2) sends and data carried out analysis and judgement handle, but its online browse high-tension cable running state information and cable fault reported to the police.

2. a kind of on-line monitoring system for high voltage cable as claimed in claim 1 is characterized in that: described data acquisition unit (2) comprises sensor signal receiving circuit, high tension protection circuit, A/D change-over circuit, CPU and GPRS data transmission unit DTU.

3. a kind of on-line monitoring system for high voltage cable as claimed in claim 1 is characterized in that: comprise sheath circulating current value and core current value in the data that sensor (1) is gathered, sensor (1) is given data acquisition unit with these data transmission.

4. a kind of on-line monitoring system for high voltage cable as claimed in claim 3, it is characterized in that: data acquisition unit (2) is transferred to the webserver (4) with sheath circulating current value and core current value, the webserver (4) is judged these data, in order to determine the insulation situation of high-tension cable sheath.

5. a kind of on-line monitoring system for high voltage cable as claimed in claim 4, it is characterized in that: when the ratio of sheath circulating current value and core current value more than or equal to 8% the time, and the ratio of identical period sheath circulating current rate of change and core current changing rate is more than or equal to 1 o'clock, and the insulating sheath that is defined as high-tension cable unusual condition occurs and reports to the police.

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