With the rapid growth of the national economy, the power industry has developed rapidly, driving the rapid development of the transmission tower industry. During the 13th Five Year Plan period, China invested about 2.7 trillion yuan in the power grid. With the continuous increase of power grid investment, the demand for transmission line towers will also continue to increase, and the development prospects of the transmission line tower industry are broad. Transmission towers play a crucial role in the process of power transmission, but due to their high flexibility, lightweight, and low damping characteristics, as well as various factors such as crustal movement, harsh weather, aging and oxidation, and potential human theft and damage, these structures often suffer from damage, and even tilt and collapse of transmission towers. In 2015 alone, 18 500 kV transmission towers collapsed and 60 110 kV and above transmission towers collapsed in China. Causing extremely serious impacts on the economy, society, and people's lives.
At present, research on the safety of transmission towers only considers the effects of factors such as earthquakes, strong winds, and icing during the design phase. There are no corresponding standards and regulations for the safety testing and health evaluation of completed transmission towers, nor are there reliable testing methods and health assessment methods. The traditional method for detecting transmission towers is through inspection, mainly including manual visual inspection and helicopter aerial survey. This method has problems such as high cost, high risk, and blind spots, so the power supply department particularly needs a new monitoring method to replace traditional inspection methods.
Shenzhen Senther Technology Development Co., Ltd. adopts an independently developed and produced structural health monitoring system, including stable acquisition instruments, reliable sensors, and a powerful structural cloud platform, to meet the needs of transmission tower structural health monitoring. It has been put into use in multiple projects. The data is stable, the results are reliable, and it fully meets various usage requirements.
Monitoring purpose
Due to its high flexibility, lightweight, and low damping characteristics, the transmission tower is highly susceptible to damage from natural disasters and human destruction, including uneven settlement, tilting, and collapse. These deformations are not sudden, but rather have a developmental process. Measures can be taken during this process to reduce losses. This project achieves the following objectives through real-time monitoring of transmission towers:
(1) By real-time monitoring of the settlement, tilt, vibration, and environment of transmission towers, a large amount of effective data is accumulated to provide data support for understanding the deformation and development status of transmission towers.
(2) By real-time monitoring of transmission towers, replacing some manual inspection work, maintenance costs can be reduced, and an objective understanding of the safety status of transmission towers can be obtained. When deformation exceeds the set threshold, timely warnings can be issued.
(3) To provide a basis for determining the stability and safety of transmission towers, as well as reliable data support for future maintenance of transmission towers.
Overall design of monitoring plan
Transmission towers belong to high-rise structures, and their common forms of damage include tilting, collapse, foundation settlement, and so on. Considering the characteristics of transmission towers and the actual situation of the project, the main monitoring indicators include deformation, environmental, and structural indicators of transmission towers. Deformation indicators include uneven settlement of the foundation, tower inclination indicators, and vibration indicators. Environmental indicators include temperature and humidity, rainfall, and wind speed and direction. Structural indicators include stress indicators of key parts. In the case of unclear deformation patterns of transmission towers, through long-term uninterrupted monitoring by monitoring systems, real-time observation of transmission tower monitoring data is carried out to understand the health status of transmission towers. When the monitoring indicators exceed the set threshold, an alarm can be triggered in a timely manner to detect problems, eliminate hidden dangers, and avoid possible major safety accidents.
The entire monitoring system must meet the following requirements:
(1) The reliability of the system. The transmission tower monitoring system provides 24-hour real-time monitoring, so it is necessary to ensure system reliability and continuous and uninterrupted data collection.
(2) Progressiveness of the system. The selection of equipment and the functions of the monitoring system should be progressiveness, and should be compatible with the relevant theories of structural safety monitoring and the development level of monitoring technology.
(3) Reasonability of cost. One principle of the monitoring system is to use the optimal deployment method to arrange the most suitable sensors at the most needed locations, achieving both cost savings and reduced maintenance investment in the later stage, and maximizing the actual monitoring effect.
Data collection and transmission mode
There are many types and large quantities of sensors in the monitoring system of this project, and the real-time requirements for signal transmission and storage are high. At the same time, the tower structure is complex, and the construction itself is difficult. The signal acquisition and transmission system needs to minimize interference to the construction as much as possible, which puts high demands on the software and hardware of the data acquisition system. There are two types of data transmission modes: wireless transmission and wired transmission. The former uses GPRS network to achieve data transmission, and as long as the mobile phone signal is reachable, it can be transmitted with a wide transmission range; Wired transmission is suitable for locations without a network, without borrowing any other resources. Communication reliability depends on the quality of the device itself, with few uncontrollable factors and strong real-time performance. These two types have their own characteristics and need to be determined comprehensively based on the location, environment, and other factors of the project.
(1) Settlement monitoring. Install settlement sensors at the four corners of the transmission tower bottom plate, and install one settlement sensor as a reference point in a relatively stable area at a certain distance from the transmission tower to monitor the settlement of the transmission tower in real time.
(2) The tower body tilts. The inclination of a transmission tower is a direct reflection of the overall mechanical behavior characteristics of the tower body, including overall inclination and local fracture. For these two forms of damage, one biaxial inclination sensor is installed on the tower cage and one on the vertical pole of the tower body.
(3) Structural strain. Structural strain is a direct response to the overall and local stress safety status of a structure, and is an important aspect of monitoring. Considering the structural stress characteristics and relevant experience of common damage prone areas, a total of ten strain sensors are installed at the tower body, tower cage, and tower arm according to the principle of zoning and centralized arrangement.
(4) Tower vibration. The wind-induced vibration of the transmission tower structure is significant, and one vibration sensor is installed at each tower arm and cage position to monitor the real-time vibration of the transmission tower.
(5) Environmental factor monitoring. Wind speed, direction, temperature and humidity, as well as rainfall, also have a certain impact on structural deformation. Therefore, wind speed and direction sensors, as well as temperature and humidity sensors, should be installed on transmission towers. The rain gauge is installed in a stable area at a certain distance from the transmission tower. To monitor real-time changes in wind speed, direction, temperature, humidity, and rainfall.
Fixed inclinometer
Measurement range: ± 10 °± 30 °± 60 °± 90 °
Measurement axis: single axis/dual axis resolution: 0.001 °
Absolute accuracy: 0.005 °
Temperature range: -40 to+85 ℃
Waterproof rating: IP67
IEPE piezoelectric accelerometer sensor
Standard range: 5g
Sensitivity: 1000MV/g
Frequency range: 0.04-1500 Hz (± 10%)
Resolution: 0.00002g
This project plans to use monitoring equipment, including data acquisition devices and sensors, all produced by SenseTime Technology. The specific parameters are as follows:
(1) The data acquisition instrument proposed for this project includes two types: a universal 8-channel wireless data acquisition instrument and an 8-channel vibrating wire acquisition instrument specifically designed for vibrating wire sensors
The 8-channel wireless data acquisition device supports simultaneous transmission of WIFI and GPRS, and can directly connect to multiple sensors. It has good stability, simple operation, and maximizes the satisfaction of user needs.
8-channel vibrating wire acquisition instrument, designed specifically for vibrating wire sensors, using high-performance ARM controller, with stable performance and reliable operation. Supports RS485 and RS232 interfaces, and can be applied to most types of vibrating wire sensors in China. It has good stability, simple operation, and can meet user needs to the greatest extent possible.
