Tilt SensorSafety Monitoring of Tilt in Power Towers and Communication Towers

　　In recent years, due to reasons such as coal mining, engineering construction, and external damage, incidents of tilt in transmission line iron towers have occurred frequently, posing a significant threat to the safe operation of the power grid. Given the large number of transmission line iron towers and the various factors contributing to their tilt, it is challenging to detect tilt faults in a timely and accurate manner relying solely on the daily inspections by transmission line patrol personnel. Therefore, developing a system that is economical, practical, and capable of timely and accurate monitoring of the operational status of power line towers is of great significance. The intelligent monitoring system for tilt in transmission line iron towers is based on general wireless communication and technologies such as tower displacement monitoring, playing an important role in enabling line operation personnel to grasp the operational status of the towers in a timely manner and ensuring the safe operation of the power grid.

　　1. System Design Concept

　　The intelligent monitoring system for tilt in transmission line iron towers consists of a front-end monitoring device and a back-end monitoring center. The front-end monitoring device is designed using high-precision dual-axis tilt sensors and microelectronic control technology.Dual-axis Tilt SensorIt can measure the tilt angles of the tower in both the along-line and cross-line directions in real-time. The microprocessor sets its working mode and transmission method through program instructions, including zero-point setting, transmission baud rate setting, and data encoding methods. The tilt angle data monitored by the dual-axis tilt sensor is transmitted transparently via RS232 serial port communication with the microprocessor, and the measured data is sent to the non-volatile data storage area of the microprocessor. The microprocessor analyzes and calculates the measured values through software, then compares them with the set threshold. If the limit is exceeded, the microprocessor will initiate a re-measurement and confirmation process for the dual-axis tilt sensor to prevent false actions. Once it is confirmed that the measurement result indeed exceeds the limit, the microprocessor will send information such as the line tower number, tower tilt angle and direction, and device power supply voltage to the monitoring center and relevant staff's mobile phones in the form of Chinese text messages via the GSM short message module, reminding staff to pay timely attention to and check the operational status of the tower. In daily operations, the back-end monitoring center can set the parameters of the monitoring device via SMS commands as needed, such as setting the monitoring time interval for the dual-axis tilt sensor, zero-point adjustment, limit threshold, and reporting time.

　　2. System Hardware and Software Features and Functions

　　2.1 ATmega128 Microprocessor

　　The ATmega128 microprocessor is used, with the following functional characteristics.

　　1) It adopts a 232 bus structure, separating the internal data bus and instruction bus of the chip, and uses different widths to accelerate the execution speed of instructions.

　　2) It uses a reduced instruction set to improve code compression.

　　3) It has very strong anti-interference capability, suitable for stable operation in complex electromagnetic environments and under independent power supply conditions.

　　2.2 Solar Photovoltaic Power Supply System

　　The power supply system consists of monocrystalline silicon solar panels, solar controllers, and lithium battery packs. It is based on the floating charge of monocrystalline silicon solar panels and the power supply from lithium batteries. The main parameters of the solar panels are an open-circuit voltage of 7.5V and a short-circuit current of 240mA, which are used to control the operational status of the entire system and provide overcharge and over-discharge protection for the lithium batteries. The device uses a lithium battery pack, making the entire power supply system compact while ensuring reliable operation of the device in the absence of sunlight.

　　2.3 Front-end Monitoring Device Hardware Circuit Composition

　　The front-end monitoring device mainly consists of dual-axis tilt sensors, AVR microprocessors, GSM communication modules, and solar photovoltaic power supply systems. The principle of the device is shown in the figure below.

2.4 Dual-axis Tilt Sensor

　　High-precision dual-axis tilt sensors are small, waterproof, and dustproof, making them easy to install. They also have low operating voltage, small temperature drift, and a wide measurement range.

　　WL926MB Tilt Sensor

　　2.5 Main Functions of the Monitoring Center System Software

　　1) Parameter Setting of Monitoring Devices. Set the monitoring time interval for the dual-axis tilt sensor, zero-point adjustment for the tilt sensor, and limit threshold parameters via SMS.

　　2) Display. It can display data categorized by pre-set lines and by tower number, and can also show historical value curves.

　　3) Storage Content. Real-time data, historical data, operational records, current status.

　　4) Historical Data Organization. Organize historical data files, delete selected historical data files, and remove previous historical data.

　　3. Major Technical Challenges Addressed

　　3.1 Power Saving Mode Design

　　The power supply for the monitoring device is based on the floating charge of monocrystalline silicon solar panels and the power supply from lithium batteries. To ensure the long-term stable and reliable operation of the device,

　　low power consumption designs have been implemented in terms of power supply and device operation.

　　1) The GSM short message module operates in alarm mode for a long time, only activating during scheduled reporting or limit alarms, with constant current consumption during normal operation.

　　2) The ATmega128 uses timed sleep and timed wake-up modes, with static working current less than 0.1mA.

　　3) The tilt sensor is designed to operate in a timed (every n minutes or adjustable) measurement mode, shutting down immediately after measurement to reduce current consumption.

　　Through the above measures, the monitoring device maintains a constant current consumption during static operation, and the working current during tilt measurement is also constant, resulting in a very low average working current for the entire device.

　　The intelligent monitoring system for transmission line towers has high measurement accuracy, low power consumption, strong anti-interference capability, simple installation, and is maintenance-free. The design fully considers the operating environment and the need for reliable and stable operation. At the same time, it adopts a multi-point model with a monitoring center and monitoring terminal points, facilitating centralized management. Through on-site operation on 220 kV line towers, it has been found to be stable and reliable in operation, and it can also be widely used.

　　It is suitable for monitoring the horizontal state of communication towers, buildings, bridges, and other equipment, with good application prospects.