Ultrasonic Anemometers For Transmission Lines
Ultrasonic Anemometer Application Guide – Transmission Lines | Overhead Lines
Ultrasonic Anemometer Application Guide – Transmission Lines | Overhead Lines
Many years’operation experience of power grid shows that, transmission and transformation equipment such as overhead transmission lines are exposed to atmospheric environment for a long time, and are vulnerable to meteorological disasters such as thunderstorms, ice disasters, wind disasters, geological disasters and so on.
The safe and reliable operation of power grid is closely related to the external meteorological environment.
Let’s learn about it!
Meteorological disasters generally include weather, climate disasters, secondary and derivative meteorological disasters.
Weather and climate disasters refer to typhoons (storms), rainstorms, thunder and lightning, gales, hail, dust, tornadoes, and strong winds, mist, high temperature, low temperature, continuous rain, freezing rain, frost, ice accumulation, cold wave, drought, hot and dry wind, heat wave, flood, waterlogging and other factors directly caused disasters.
Meteorological secondary and derivative disasters refer to such disasters as mountain torrents, landslides, debris flows, mountain fires and haze caused by meteorological factors.
Lightning hazards to power grid can be classified into direct strikes (including shielding and counterattack), induction and intrusion.
Lightning overvoltage caused by lightning stroke has the characteristics of high steepness and large amplitude. It poses the greatest harm to the weak insulation equipment such as transformers in the power grid. It also endangers the insulating porcelain bottles of outdoor overhead transmission lines and equipment such as circuit breakers, disconnectors and transformers in substations.
Lightning intrusion wave also endangers the electrical equipment inside the house. In addition to the direct losses caused by damage to equipment, the indirect losses caused by power supply interruption or even large-scale blackouts due to line tripping may be greater.
Conductor icing is the main meteorological disaster that causes transmission line failure, especially for high mountain areas.
Icing on transmission lines will increase the load on lines and towers, increase the wind-affected area of conductors, and easily induce unstable galloping, which often leads to jumping, twisting, galloping, ice flashing tripping, even line breaking, tower inversion and other malignant accidents. Large-scale power blackouts caused by ice disasters occur in various countries to varying degrees.
At the same time, transmission lines are prone to ice galloping under the action of ice storms.
Wind disaster is one of the meteorological disasters that do great harm to the safety of transmission lines. Power transmission lines in many parts of the world are facing the threat of strong wind disasters.
According to the statistical data of power grids, the impacts of wind disasters on the safe operation of transmission lines are as follows:
First, the damage of transmission poles and towers caused by strong wind, such as blowing off conductors, blowing off crossbars, even blowing down poles and towers;
Second, the impact of strong wind on conductors, such as conductor vibration, wind yaw discharge, etc.
Under the action of strong wind or squall line wind, insulators are inclined toward towers, which reduces the air gap between conductors and towers. When the air gap distance can not meet the insulation strength requirements, wind bias discharges will occur, resulting in line tripping.
Another form of wind disaster is typhoon. For the power grid, the lighter typhoon causes the wiring to swing sharply and discharges the poles and towers, while the heavier one seriously damages the power facilities, which greatly delays the recovery time of power supply.
In recent years, with the continuous development of hydropower resources in mountainous areas, most of the hydropower outgoing channels Cross Mountains and forest-covered areas. The unique topographic conditions and climatic factors in these areas can easily cause forest fires, leading to overhead transmission line failure tripping.
Line faults caused by forest fires have a great impact on the safe operation of power grids, which are mainly manifested in:
1) Because of the mountainous terrain, two or more routes of the same transmission channel are usually erected with towers, and once a mountain fire occurs, it is possible that the towers will be erected with two or more routes of the same transmission channel.
As a result, the multi-circuit lines of the same transmission channel trip at the same time, resulting in a large number of hydropower can not be delivered, affecting the security and stability of the power grid;
2) Due to the low success rate of flashover tripping reclosure caused by mountain fire smoke, it is necessary to wait until the fire is controlled and the smoke disperses before forced transmission, so the forced outage time of the line is longer.
The types of geological hazards can be divided into landslides, debris flows, collapses, subsidence and earthquakes.
Ultra-high voltage and ultra-high voltage transmission lines in long-distance transmission channels often cross steep mountains and rivers. The characteristics of geomorphology, geological structure, hydrogeology and climate characteristics determine the particularity of risk analysis and assessment of engineering geological hazards in power lines.
In addition, earthquakes often cause serious damage to regional power grids.
Damage will also lead to tripping of several transmission lines in the earthquake area, or even permanent damage to transmission facilities, which may lead to the disintegration of large power grids in serious cases.
The damage forms of transmission lines caused by earthquakes include insulator string dropping, line breaking, tower collapse and so on. Earthquakes are also prone to cause regional power supply interruption, plant and station equipment damage and even cause plant and station shutdown, communication failure and even communication paralysis.
Other bad weather that may affect power grid production include hail, high temperature, frost and so on.
Hail often occurs together with thunderstorms and strong winds. Hail may damage outdoor electrical equipment. The combination of hail and strong winds may knock down trees or disconnect lines.
The impact of high temperature on power grid is that the power load increases sharply, which makes the capacity of power grid unable to meet the peak load demand. Secondly, high temperature is not conducive to line heat dissipation, coupled with the increase of current, which increases the line heat, and then leads to the increase of wire sag, which will accelerate the aging of the line and affect the line life, and may even cause line tripping due to too large sag.
Frost mainly causes icing of transmission lines and insulator strings.
By analyzing the amplitude and frequency of vibration and bending of the conductor and the meteorological environment parameters such as temperature, humidity, wind direction and wind speed around the conductor.
The system uses professional software to analyze and judge the breeze vibration and fatigue life of the conductor on-line, traces the failure of the fatigue damaged conductor and ground wire, analyses the causes of fatigue damage, and formulates the corresponding improvement measures to prevent the occurrence of the fatigue damage.
Greater damage, while assisting the relevant transportation and inspection departments to establish a reasonable condition-based maintenance plan.
The wire sag temperature monitor is installed at the lowest point of the wire monitoring, which monitors the temperature of the wire in real time. The data are sent to the monitoring center by the communication module in the base station.
Through the research and analysis of the system software, the system model of the wire sag and the temperature change of the wire is obtained, and the dynamic carrying capacity of the wire is calculated (combined with the meteorological environment observation device).
Then, according to the level of steady-state transmission capacity quota, the transmission capacity of the line can be improved, so as to fully tap the transmission capacity of the line, further solve the practical problem of insufficient transmission capacity of the line, and provide real-time and reliable data support for the line operation management department.
The system integrates wind yaw, elevation sensor and meteorological environment sensor.
Through the analysis and comparison of elevation and yaw, or wind speed, jumper wind yaw, wind direction, minimum electrical clearance and other parameters, the relationship between the relevant parameters is found, and reasonable early warning information is deduced.
The on-line monitoring system collects parameters such as inclination angle and sag of conductors, analyses relevant state equation of transmission lines, relevant line parameters and micro-meteorological environment parameters, and calculates specific load, weight and average thickness of icing conductors after icing. The dangerous grade of icing is judged and the deicing information is given in time. And accumulate the basic data of line icing observation, analyze the occurrence and growth law of icing, service line design and icing treatment.
The system monitors galloping by installing several galloping monitors on the transmission line. The monitors can collect wind speed and acceleration information from two directions at the same time.
By collecting and analyzing these accelerations, and using relevant professional system software, the frequency and amplitude of conductor galloping can be analyzed.
By calculating and analyzing the multi-point acceleration scattered in different positions in this gear, the galloping half-wave number of the line and the related parameters of the trajectory of the trajectory can be calculated, whether galloping endangers the operation of the line can be analyzed, and alarm information can be sent in time to avoid the occurrence of inter-phase short circuit or even tower inversion accidents.
Through on-line monitoring of tower lateral inclination, along-line inclination, micro-meteorological conditions and other data, combined with line design parameters, the early warning information of tower inclination is given, which provides practical basis for line operation and design departments.
Through early warning, the operators can timely grasp the safe operation of the line, reduce the probability of serious tower collapse accidents caused by tower tilt, assist the operation Department to find fault points, and analyze and judge the fault.
Because the mechanical three-cup anemometer is the most common and the cost is low, it is mainly used on transmission lines at present, but with the deepening of the application, more and more drawbacks are reflected.
The following will be shown by comparing the tables one by one.
|3-Cup Anemometer||Ultrasonic Anemometer|
|Volume & Weight||Normall||Small size and light weight|
|Maintainability||Regular maintenance and replacement of components||Free-Maintaince|
|Accuracy||Instable||High accuracy and sensitivity|
|Starting Velocity||At least 0.5m/s||Start-up wind speed is small, 0.1m/s|
|Heating Function||No||Yes. Outdoor use in winter|
|Life||1 Year||No moving parts, long life 5 Years|
|Price||High cost performance||More expensive than mechanical ones.|
|Notes||Operating at high altitude(Up to 60 meters), maintenance service fee is at least $1000||No additional cost|
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