As a physical channel for power transmission, transmission lines have wide geographical distribution and complicated operation conditions, are easily affected by the natural environment and destroyed by external forces, and require large inspection and maintenance work. It is more and more important and urgent to adopt advanced state-of-the-art monitoring techniques to get timely information on the operating status and environmental information of transmission lines.

First, the status quo

With the development of technologies such as sensors, data transmission, data processing and power supply of monitoring devices, transmission line condition monitoring technology has been developed rapidly in China. Currently, a great deal of information on breeze vibration, conductor temperature, wind deflection, ice coating, dancing, tower tilt, insulator contamination, micrometeorology, images (video ) And other on-line monitoring devices, has been the initial realization of the regional power grid and provincial-level power grid level monitoring; established a large span condition monitoring system for North China, Anhui, Fujian, Hubei, Hunan, Henan and other parts of the power grid lines and large span Ground breeze vibration and other real-time centralized monitoring; some municipal power company has built a centralized monitoring, manned state monitoring system.

Thunder and lightning monitoring system has been completed in the country's 28 provincial power grids, and to achieve national networking. A new generation of lightning monitoring system successfully developed by State Grid Electric Power Research Institute has also been linked to the network. The major technical indicators such as detection range and positioning accuracy have been greatly improved and improved.

Second, the key technologies

(A) data acquisition technology

The selection of monitoring device should have pertinence, it is necessary to combine with the actual situation of the project, reasonably choose the monitoring device which is safe, reliable, advanced and applicable, and easy to maintain for condition monitoring. The following is a brief introduction of the monitoring devices such as the temperature and sag of the conductor, the thickness of the equivalent ice, the vibration of the breeze, the dancing of the conductor, the inclination of the tower, the insulator contamination and the micro-meteorology which are closely related to the safe operation of the line.

1, wire temperature, sag monitoring device

In order to prevent running wire and fittings overheating, the use of platinum resistance or thermistor and other sensors to monitor the temperature of the wire and fittings, and to provide dynamic information transmission capacity expansion function of the circuit. In order to prevent the operation of the line to the ground or under the line of the lack of safety distance, the use of laser sensors, etc., to monitor the arc sag, for the state monitoring system to provide early warning information.

Wire temperature monitoring device is mainly installed in: â‘  need to improve the line transmission capacity of the important lines; â‘¡ across the main railway, highway, bridge, river, sea and other areas of the important span.

Wire temperature and sag monitoring devices are mainly installed in: â‘  need to verify the sag characteristics of the new line section of the wire; â‘¡ due to insufficient safety distance caused by failure (such as tree-line discharge) frequent line section.

2, equivalent ice thickness monitoring device

By means of weighing method or dip method, the mathematic model is established by real-time monitoring of the conductor inclination of the insulator string suspension or the wire outlet at the wire clip and the windage angle of the insulator string, and the equivalent thickness of ice coating is calculated, And characteristics, in order to take effective anti-icing, melting ice and deicing measures to provide technical basis.

Line equivalent icing thickness monitoring devices are mainly installed in: ① heavy ice zone section of the line; ② windward slopes, Pass, air duct, near the surface of the water and other easy to ice icing special geographical environment; ③ and the dominant direction of wind angle More than 45 ° line easy icing dancing area.

3, breeze vibration monitoring device

In order to determine the vibration level of the breeze and the fatigue life of the wire, the IEEE standard measurement method is used to monitor the dynamic bending strain of the guide / ground wire and OPGW to provide basic information for the condition monitoring system and to grasp the ground lead of the large span or ordinary wire. The OPGW breeze Vibration characteristics and the reasons for breaking shares, proposed control measures.

Breeze vibration monitoring device is mainly installed in: â‘  across the navigable rivers, lakes, straits and other large span; â‘¡ observed a larger vibration or occurred due to vibration fragmentation of ordinary span.

4, wire dance monitoring device

In order to prevent the wires from galloping, the tower, connecting hardware and the wires themselves are greatly damaged. The galloping and early warning can be found through the galloping monitoring device in time to facilitate the understanding of the characteristics and laws of the galloping in the easy-dancing area and propose the measures for prevention and control of galloping.

Dancing monitoring device consists of a plurality of wire galloping monitoring sensors, the number of sensors based on the file distance and line specific circumstances. Generally, at least eight dance sensors are installed in a lead wire. Mathematical models are established to analyze and calculate the dancing amplitude, the dancing frequency and the half-wave number of the wires, draw the dancing tracks, and send alarm messages in time to evaluate whether the dancing lines are damaged or not.

Wire galloping monitoring devices are mainly installed in: ① easy dancing zone; ② transmission line spacing larger or dominant wind direction with the winter angle greater than 45 °; ③ prone to galloping micro-topography, micro-meteorological areas.

5, tower tilt monitoring device

The tower inclination monitoring device uses dual-axis inclination sensor, which is mainly used for monitoring the on-line inclination, lateral inclination and comprehensive inclination, providing basic information for the condition monitoring system, facilitating to grasp the characteristics and regularity of the inclination of the tower, analyzing the reasons, Measures to avoid excessive tilt tower affect the operation of the line.

Tower tilt monitoring device is mainly installed in: â‘  goaf, subsidence area; â‘¡ bad geological sections, such as soft soil area, silt area, easy landslide area, weathered rock mountain or hills.

6, insulator contamination monitoring device

Insulator contamination monitoring devices usually include insulator contamination (salt / ash) monitoring devices. Optical fiber salt density sensor was used to monitor the contamination in the air near the insulator. The mathematical model was established to calculate the equivalent salt concentration, which provided the basic information for the pollution early warning, line cleaning and drawing of the pollution area.

7, micro-meteorological monitoring device

The main meteorological parameters such as wind speed, wind direction, rainfall, ambient temperature and humidity can effectively monitor the complex operating conditions of the line by causing accidents such as down-tower or trip when severe weather such as wind, typhoon and heavy rain occur along the line , Accumulate the line running weather data for the line

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