Research on remote vision system of the hottest su

With the rapid development of power industry, China is carrying out the reform of "separation of power plants and bidding", in order to open the power market, introduce competition mechanism, reduce power generation costs, make rational use of resources, and ultimately make users profit. After the continuous improvement of the power market, users will be allowed to participate in the competition in the power market, production scheduling and market transactions will be integrated, and the role and status of scheduling will be further improved. This requires the substation to achieve unattended/few people, layoffs and efficiency

according to our understanding, at present, only some substations in developed provinces such as Guangdong and Jiangsu have realized "four remotes" (telemetry, remote signaling, remote control and remote regulation) and unattended (actually unattended and attended mode). The dispatcher on duty may monitor various electrical parameters of the substation and control the circuit breaker and electric knife switch in the remote control center. Unfortunately, siyao does not involve the monitoring content of substation environment (such as anti-theft, fire prevention, explosion-proof, anti stain, waterproof steam leakage, etc.), and people have doubts about this "unattended"

with the continuous maturity of multimedia technology and computer communication technology, the improvement of digital video technology, and the development of modern data transmission technology, the data transmission rate and bandwidth continue to make breakthroughs, providing a necessary foundation for the development of video monitoring technology. Therefore, remote image control and information management, that is, the research topic of remote viewing system, has been included in the agenda

2 graphene is designed to have ultra-thin, ultra-high strength, super conductivity, room temperature heat conduction and light transmittance. The substation remote viewing system mainly collects and processes the monitoring image, sound, alarm signal and data of various equipment at the substation site, and adopts advanced image encoding and decoding compression technology and transmission technology, integrating equipment monitoring, image acquisition, closed-circuit monitoring It is an integrated automation system with the functions of image monitoring and prediction linkage and video image. When developing the system, we should fully consider the specific requirements of users and local conditions, build on the technology of a high starting point, and design according to the unattended scheme

first of all, the system should meet the requirements of unattended substations, with a high degree of reliability and continuity of work, and can continuously monitor dozens of substations for 24 hours

secondly, the system should have multiple picture windows, and 1 ~ 16 pictures can be divided arbitrarily; The image is clear and smooth, and mosaic, image edge sawtooth and dragging phenomenon are completely eliminated; While ensuring high-quality pictures, it reduces the transmission code stream and realizes real mass storage

moreover, the system should provide transparent channels to meet a variety of high and low-speed communication channels

3 system composition

the remote viewing system is composed of multiple remote sites and a monitoring center, and there is a PCM 2m communication line connection between the remote site and the monitoring center. There are several cameras in each site. The lens and PTZ of the camera are controllable, and several sensors, alarm lights, alarm signals and other peripheral equipment can be added. In the monitoring center, you can monitor each site at will and collect the alarm information of each site. The monitoring center is composed of the multimedia monitoring host inside the central machine room and the network sub control computer outside the machine room

the system can conveniently and instantly retrieve and recover the stored images at any time, such as by time, place (lens) or image file. The playback image is stable and clear, and can be read and written repeatedly. There is no signal attenuation and wear of the video tape in the traditional monitoring system

the wind direction is parallel to the surface of the test piece 3.1 system configuration

3.1.1 the station end

includes camera unit, control decoder, video matrix, alarm control equipment, microphone and speaker, codec, etc. multimedia control computer can be set at the attended remote site, and control keyboard can also be set. These control equipment can control the camera switching, lens Under general conditions of pan tilt action, it is necessary to drain the settled oil in the oil tank from the oil drain at least once a week, and the alarm information can be processed. For unattended sites, computers can not be placed, and it is recommended to place control keyboards. The function of the station in the system is to collect all kinds of video, audio, data and other information on the site, process them through the codec, digitize and compress the analog signal, so as to facilitate transmission on the available digital communication line. At the same time, the station also has controllable devices such as lens and PTZ after decoding the control command transmitted from the main station

3.1.2 communication layer

optical fiber, microwave, DDN, ISDN, communication satellite, wired baseband modem, wireless spread spectrum modem, etc. can be used. The line interface can be G.703, V.35, rs449, etc

3.1.3 the master station terminal

includes codec, video matrix, audio matrix, microphone, speaker, multimedia computer, monitor, network video server and monitoring software. The function of the master station is to decode the digital signals collected by the communication line and convert the analog signals into multimedia computers, monitors and network video servers through the video matrix. It is used to monitor each site, collect the alarm information on site, and transmit graphics and other signals to the network layer at the same time

3.1.4 network layer

that is, the computer network (local or interconnected) is composed of network sub control computers at all levels, such as director sub control computers, substation sub control computers, etc. Its function is to transmit the remote field signal on the network video server on the local area or Internet, so as to share resources with the network sub control computers at all levels, such as the director sub control computer

3.2 three major areas of system

3.2.1 video technology

in the scheme design of many remote video monitoring systems, the problem often encountered is how to transmit the analog video signal of the monitoring site at a long distance. Using coaxial cable to transmit analog video signal will be limited in distance, and amplification and relay will be required if it exceeds hundreds of meters. Therefore, conventional video monitoring system is only suitable for use in a building or a certain area. In addition, conventional systems can only transmit a single video signal on one coaxial cable, and cables need to be laid separately to transmit control signals and voice. The feasible method of long-distance video transmission is to digitize the analog video signal, compress and encode it, and transmit it on the available digital communication line. Video data compression and decompression, video image information is huge. For example, one 640 × 480 medium resolution color image (24bit/pixel), with a data volume of 0.92mb. If it is played at the speed of 30 frames per second, the digital rate of the video signal is as high as 27.6mbps. Obviously, digitalization of video compression technology is the key of compression technology. At present, the image compression standards suitable for remote video surveillance include H.261 and MPEG-1. H. 261 standard abbreviation p × 64, formulated by an expert group of CCITT in December 1990, MPEG-1 became the standard in 1992. The core technologies of both are discrete cosine transform and motion compensation algorithm. Its main idea is to reduce the amount of data by reducing the temporal and spatial redundancy and correlation information between each frame of images. H. 261 is suitable for transmitting real-time video images at a low bandwidth of 64 ~ 384kbps, but the image quality is not ideal; MPEG-1 can achieve better image effect at the transmission rate of 800kbps ~ 2Mbps. Users can choose different compression standards according to different occasions and needs. Due to the huge video data stream, the compression method and format used will have a significant impact on the performance of the video server. When choosing the hardware platform, we should also carefully consider: system bandwidth, throughput capacity, number of channels, storage capacity, codec and code rate, connection capacity, etc

3.2.2 network technology

digital video can transmit image data on the computer network (local or wide area), which is basically not limited by distance, and the signal is not easy to be disturbed, which can greatly improve the image quality and stability; Moreover, digital video can be transmitted by computer network, and the network bandwidth can be reused without repeated wiring; In addition, digital storage is possible. Compressed video data can be stored in disk array or optical disc, which is very simple and fast

3.2.3 communication technology

the data communication of digital video remote monitoring system has the following characteristics:

1 real time video data belongs to real-time data and must be processed in real time, such as real-time compression, decompression, transmission and synchronization

2 the distributed on-site image acquisition and transmission host and the image receiving and display host are located in different places and are connected by local or wide area computers

3 synchronization Although video information is distributed, it must be synchronized when displayed on the user terminal. In addition, sound and video must also be synchronized

at present, tcp/ip network communication protocol is an industry standard that has become a reality. In order to run in various network structures, the video remote monitoring system must also adopt tcp/ip protocol. However, tcp/ip protocol is used for reliable transmission. As a result, if you send a packet to another computer on the Internet, you can be sure that it will arrive at the destination accurately, but you can never get the guarantee that the data will arrive within a specific time. In fact, the delay of data packets for hours or days before reaching the destination is tenable in theory. As a special case of video transmission, it is very sensitive to time, so we must ensure the real-time and synchronization of data. The International Telecommunication Union (ITU) and the international interconnection engineering task force (iete) have designed a Real-time Transmission Protocol RTP to solve the problem of transmitting real-time data. RTP generally runs on the unreliable protocol layer, such as UDP (in fact, the reliability of UDP packets is more than 99% according to Mathematical Statistics). Each data packet transmitted through RTP has time information and a related serial number, which makes it relatively easy for applications to mix audio and video information. Since the application can easily determine the correct packet number to jump to when the video frame needs to be skipped, the time information related to each packet can smooth the synchronization process

in the field of monitoring, digitalization and networking is a trend, which can be widely used in telecommunications, power, transportation, banking, water conservancy, intelligent buildings and other fields. In places such as unattended computer rooms of telecommunications bureaus, unattended power substations, hydrological stations, bank offices, etc., they usually have the following characteristics: they have great economic value, high security requirements, and are widely distributed or remote in geographical location. Using digital video remote monitoring technology, a monitoring and dispatching center can be established in this system to monitor the image, sound and other sensitive data of the remote site in real time, so as to quickly respond to sensitive events. The specific implementation method is to use various data communication networks such as DDN, ISDN, E1 and xDSL to transmit the digitally compressed and encoded video, audio and alarm sensing data to the monitoring center. The computer in the center decompresses and decodes various data, plays back video and audio at the same time, and processes alarm events

4 system communication scheme

the communication transmission part is the key component of the whole remote vision system. Its function is the same as that of human spinal cord, which is responsible for the uploading and issuing of various signals and instructions

remote viewing system can use digital optical fiber, digital microwave, satellite