Application of optical sensor in measuring salt density of insulator

The equivalent salt density method widely used by departments at present 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 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, and the saturated salt density of the equipment cannot be obtained using traditional methods.

The use of optical sensors to conduct real-time online detection of salt density on insulators of power transmission and transformation equipment has solved a problem that has long plagued the power system 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.

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 power transmission and transformation equipment should be determined by comprehensively considering the pollution 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 power transmission and transformation equipment is to implement it according to the GB/T16434 issued by the ministry, 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.

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 mode 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 of 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 Environmental 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.

Electronic map of maximum (saturated) salt density

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.