Industry Overview

Coal is an important energy resource in China, and due to the special environment of coal mining, accidents are prone to occur. The coal mining industry is also known as a high-risk industry. Some early video surveillance systems used in coal mines were analog monitoring, with low scalability and stability, and inconvenient management. With the development of network technology and computer technology, the application of IP networks based on TCP/IP protocol has been widely popularized, and the advantages of wireless monitoring systems can be better reflected here. At present, underground operations in coal mines often occur due to their distance from the ground, complex terrain, and harsh environment, such as gas explosions and underground water seepage accidents. By using a remote video surveillance system, ground monitoring duty personnel can directly monitor the real-time situation of the underground working face. Not only can they intuitively monitor and record the safety production situation of the underground work site, but they can also quickly deal with potential hazards, avoid accidents, and provide relevant first-hand image data for post accident analysis. Therefore, wireless remote video monitoring system is an important component of modern mine safety production monitoring system.

Characteristics of Coal Mine Safety Production Monitoring and Information Management System

The wireless network system for coal mine safety production monitoring and information management includes: underground image acquisition system, wireless transmission system, and ground monitoring management command system. 

1. Many coal mine system projects are installed in harsh outdoor environments, with a large and scattered number of sub mining points. Therefore, it is necessary to choose wireless devices that are fully outdoor, easy to install, convenient to maintain, and have good network management functions to reduce construction and maintenance costs and meet real-time information transmission between sub mining and mining bureaus. 
2. Coal mines generally have multi-point branches, so it is necessary to choose wireless products that support point-to-point networking to save system costs. 
3. Coal mines attach great importance to monitoring and controlling underground safety production, so they have high requirements for the link of video, data, and voice feedback from the underground network to the command center, which cannot be interrupted or transmitted incorrectly. This requires the transmission link to have high stability and reliability, and wireless transmission equipment must ensure long-term stable operation. 
4. Underground image acquisition systems often use optical cables for video transmission in coal mine tunnels due to environmental factors. The use of optical signal transmission eliminates the electrical signals generated by traditional video cable transmission, reduces hidden dangers, and the optical fiber transmission distance is very long, up to 30km. The underground environment of coal mines is harsh, so high requirements are placed on video capture equipment: firstly, there is no light in the tunnels of coal mines, and infrared spotlights cannot be used, requiring the use of low light cameras; Secondly, there are only two voltages of 660V and 127V in the tunnel, and power conversion needs to be considered; Thirdly, the underground air contains high levels of gas and dust, which can easily lead to explosions. Therefore, it is necessary to use explosion-proof protective covers that have been certified by coal safety. 
5. The underground system not only needs to install cameras to monitor images, but also needs to place various sensors at different locations to monitor local water level, gas content, temperature, oxygen content and other data. The sensors are all RS-232 or RS-485 ports, while the bridge only provides RJ45 ports. Therefore, a port converter is needed to convert the RS-232/RS485 ports to RJ-45 ports, which converts analog signals into digital signals for transmission on the bridge. During on-site installation and debugging, various sensors, alarm linkage devices, and video encoders should be correctly connected to the 485 line, and the control protocol of the cloud mirror encoder, keyboard, or software should be kept the same. The baud rate settings of the front-end and back-end should be consistent, as well as the 485 address code settings. 
6. The images and sensor signals collected underground are transmitted back to the ground monitoring and management command center through wireless bridges installed at the well monitoring substation. At the same time, the monitoring substation can use a hard disk recorder to store images locally; The monitoring center can use matrix switching for video monitoring, or input it into the image splitter to use a large screen plasma TV for monitoring.
 
In addition to video surveillance services, scenic spots also require one-way voice transmission to facilitate the broadcasting of various information from the monitoring center to the monitoring points in the scenic area. Therefore, video codecs that support voice should be adopted.