Optical sensor power transmission and transformation equipment salt density online monitoring system

The equivalent salt density method widely used by the power sector is a method of calibrating the pollution level based on annual cleaning. Although this method is simple to operate, it still requires the professionalization of personnel, the reliability of instruments, and the institutionalization of testing work. It also requires power outages or pole (tower) work, which requires huge human and material resources and has great limitations. This method does not fully consider the impact of pollution accumulation speed, cannot accurately guide the reasonable configuration of the external insulation creepage ratio, and the measurement results are highly dispersed, making it difficult to reasonably determine the measurement cycle. In addition, the National High Voltage Working Network Anti-pollution Flash Working Group has now clearly proposed to revise the pollution area distribution map based on saturated salt density, but the saturated salt density of the equipment cannot be obtained using traditional methods.

The use of optical sensors to conduct real-time online monitoring of salt density on insulators of power transmission and transformation equipment has solved a problem that has long plagued the power system, opened a door for the power system in this field, and is a major change in thinking!

The optical sensor power transmission and transformation equipment salt density online monitoring system is a real-time, online, scientific and accurate salt density monitoring method. It consists of two parts: the data monitoring terminal and the data monitoring center. It is an intelligent large-scale remote distributed salt density real-time monitoring system. The system networking is very convenient, and it can provide multi-level management functions for the monitoring center, realize the monitoring of monitoring points at different locations at the same time, and draw a pollution area distribution map to simulate the actual transmission network, and provide services for the three-level transmission business management of provincial bureaus, municipal bureaus and county bureaus.

In view of this, since 1992, Wuhan High Voltage Research Institute and Wuhan Compu Evergreen Software Technology Co., Ltd. have carried out research on the use of optical sensors to measure salt density, in order to obtain a new method for real-time and accurate salt density measurement. The field monitoring results of Xinxiang, Henan and Guangzhou Power Supply Company show that the optical sensor transmission and transformation equipment salt density online monitoring system is suitable for insulator pollution monitoring, and realizes the online continuous measurement of the equivalent salt density of the operating insulator. It is a scientific, simple, accurate and real-time monitoring measurement method. The monitored saturated salt density can provide a reliable basis for the drawing and revision of the pollution area distribution map of the power system operating equipment; the monitored real-time salt density value can enable the power department to understand the pollution accumulation of the operating equipment at the monitoring point at any time and conveniently, thereby guiding the power department to clean the power transmission and transformation equipment, and realize the status maintenance of the anti-pollution work of the power transmission and transformation equipment, which is of great significance to prevent the occurrence of pollution flash accidents. The project has been appraised by the Chinese Society of Electrical Engineering and has reached the international leading level.

The external insulation performance of power transmission and transformation equipment has a significant impact on the safe operation of the power grid. The surface contamination and moisture of insulators used in large quantities in the power system will seriously affect the electrical characteristics of the insulators and endanger the safe operation of the power grid. With the occurrence of large-scale pollution flashover accidents in regional power grids across the country, huge economic losses and social impacts have been caused to the power sector. Major power grids have carried out large-scale pollution flashover prevention renovations on the external insulation performance of power transmission and transformation equipment, so that the insulation level of the operating lines has been improved. However, with the increase in power grid capacity and transmission voltage levels, especially the further deterioration of the air environment, the situation of power grid pollution flashover prevention is still very severe.

Normally, in order to eliminate potential accidents in a timely manner, the operating department needs to monitor the insulators regularly. The relevant national standards clearly stipulate that the classification of the pollution level of the external insulation of transmission and transformation equipment should be determined by comprehensively considering the pollution and wet characteristics, operating experience and the salt density of the surface pollution. Among the above three factors, salt density is the only parameter that can be quantified. At present, the principle of external insulation configuration of transmission and transformation equipment is to implement it according to the ministry-issued GB/T16434, and to adjust it in time according to the approved pollution area distribution map. When approving the pollution area distribution map, the important basis for drawing and revising is to sort out and analyze the salt density measurement data of previous years. At the same time, according to the salt density measured at the monitoring point, the cleaning cycle of the transmission line is guided. It can be seen that the measurement of salt density is of great significance to the production and safety of the power sector.

//System Introduction//

The optical sensor power transmission and transformation equipment salt density online monitoring system mainly consists of two parts: the data monitoring terminal and the data monitoring center. It is an intelligent large-scale remote distributed salt density real-time monitoring system. The system networking is very convenient and can provide multi-level management functions for the monitoring center to achieve simultaneous monitoring of monitoring points at different locations. The data acquisition terminal is installed near the transmission line pole (tower) or the substation insulator to complete the real-time monitoring of on-site dirt (salt density), temperature, and humidity. The monitoring data is sent to the monitoring center via SMS. The data monitoring center completes the conversion and processing of the monitoring data.

//Salt density monitoring principle//

The optical sensor measures salt density based on the theory of light field distribution and light energy loss mechanism in dielectric optical waveguides. The low-loss quartz rod placed in the atmosphere is a multimode dielectric optical waveguide with the rod as the core and the atmosphere as the cladding. When there is no pollution on the quartz rod, the fundamental mode and higher-order modes in the optical waveguide transmit the energy of light together, most of which is transmitted in the core of the optical waveguide, but a small part of the light energy will be transmitted along the cladding at the core-cladding interface, and the light loss during the light wave transmission process is very small. When there is pollution on the quartz glass rod, the transmission conditions of the higher-order mode and the fundamental mode are changed due to the pollutants; at the same time, the absorption and scattering of light energy by the polluting particles will cause light energy loss; the amount of salt on the sensor surface can be calculated by detecting the light energy parameters. Since the sensor and the insulator string are in the same environment, the salt density value on the insulator surface can be obtained by calculation.

//System functions and features//

The system can provide real-time salt density electronic map, maximum (saturated) salt density electronic map, temperature, humidity, and reference curves of salt density data and time, etc.

◎Real-time salt density electronic map

The monitoring center provides real-time salt density electronic maps. The drawing of electronic maps follows the "Regulations on the Distribution Map of Polluted Areas in Power Systems" in the notice of the State Power Corporation Guodian Anyun [1998] No. 223 on the revision of the "Distribution Map of Polluted Areas in Power Systems". At the same time, the classification of polluted areas refers to the "Standards for Classification of Polluted Areas and External Insulation Selection for High-voltage Overhead Lines and Power Plants and Substations". Standard number: GB/T 16434-1996. The division and coloring of high-voltage lines of different voltage levels and polluted areas of different levels in the salt density electronic pollution area distribution map all follow this standard. The real-time salt density electronic map is used to reflect the salt density and other related data collected by the monitoring terminal in real time on the workstation of the monitoring center, and the information can be dynamically refreshed in real time. The operation department can use it to monitor the real-time salt density of the dynamic changes of the transmission and transformation equipment, and provide a basis for the cleaning of the transmission and transformation equipment, the value of the external insulation pollution resistance, and the timely adjustment.

◎Maximum (saturated) salt density electronic map

The monitoring center provides the maximum (saturated) salt density electronic map. The drawing principle is the same as above. The maximum (saturated) salt density electronic map is used to reflect the maximum salt density value in the area where the data monitoring terminal is installed on the monitoring center workstation, providing a reference for the power company in the drawing of pollution area distribution map and insulation configuration.

◎Draw a reference curve

The monitoring center provides a curve chart showing the temperature, humidity, and salt density data of the monitoring point of the data monitoring terminal and the curve of time. It allows the power department to understand the historical salt density changes of the power transmission and transformation equipment at the monitoring point at any time, conveniently and intuitively, and can analyze the pollution accumulation law and self-cleaning rate of the power transmission and transformation equipment at the monitoring point by combining the information of the relationship between temperature, humidity and time, and make corresponding countermeasures.