Liu Jingxi, Liu Delin
I. Introduction
In recent years, the State Grid Corporation of China has successively issued a series of policies and measures on accelerating the construction of a smart grid. China's power grid construction is facing enormous challenges and opportunities. On the one hand, the power grid needs to deal with increasingly severe resources and environmental pressures, achieve optimal allocation of resources on a large scale, improve all-weather operation capabilities, and meet the needs of energy structure adjustment; on the other hand, transmission and distribution, power generation, information, and digital technologies The progress has also provided solid technical support for solving this series of problems. The International Conference on UHV Transmission Technologies in 2009 clearly stated that by 2020, China will build a unified and strong smart grid. Obviously, the smart grid is becoming the direction of the development of the modern power industry.
The power communication system is an important part of the smart grid. The data transmission method in the power system is realized by mobile communication technologies (such as GPRS, GSM, etc.). It has the characteristics of no need to establish a dedicated channel, small project investment, wide coverage, easy maintenance, and flexible installation. It has already been used for remote meter reading and load control. With the scheduling and other fields have achieved good results. The use of LTE technology will inject new vitality into the power system informationization. Compared with GPRS, GSM, and 3G that have already been applied, LET has a higher transmission rate, more secure and reliable performance, and can provide a full range of communication services for the construction of smart grids.
This article first introduced the relevant knowledge of smart grid and LTE, analyzed the application status of modern mobile communication technologies in power grids, pointed out the requirements of smart grids for power communication systems, and concluded that LTE applications have outstanding advantages in smart grids, and from The application of LTE technology in smart grid is introduced in several aspects such as grid video surveillance, smart inspection, intelligent load dispatch management, and emergency rescue command.
II Smart Grid
(A) Smart Grid Overview
1. The concept and characteristics of smart grid
A smart grid is a fully automated power supply network in which each user and node is monitored in real time and ensures the two-way flow of current and information at every point from the power plant to the customer premises equipment. Through the extensive application of distributed intelligence, broadband communications, and the integration of automatic control systems, the smart grid guarantees real-time market transactions and seamless connectivity and real-time interaction among members of the grid.
From a technical point of view, the smart grid has three levels of meaning: First, the use of sensors for real-time monitoring of the operation of key equipment such as power generation, transmission, distribution, and power supply; and then the acquired data is collected and integrated through the network system. Finally, by analyzing and excavating the data, the optimal management of the entire power system operation is achieved.
The smart grid has the following features:
1) Self-healing. Through real-time control of power grid operating status, timely detection, rapid diagnosis and elimination of hidden dangers; with minimal human intervention, quickly isolate faults, self-recovery, to avoid large-scale power outages.
2) Safe and reliable. It can deal with natural disasters, external damage and computer attacks, ensure the safety of people, equipment, and power grids, and automatically restore the operation of the power grid.
3) Cost-effective. It can optimize the allocation of resources, increase the transmission capacity and utilization of the equipment; timely dispatch between different regions to balance the power supply gap; support the competition in the power market, implement a dynamic floating electricity price system, and realize the optimal operation of the entire power system.
4) Compatible. It can be openly compatible with various types of equipment, including centralized power, distributed generation, and renewable energy, to meet the requirements for the harmonious development of electricity and the natural environment and social economy.
5) Friendly interaction with users. Realize intelligent interaction with customers, meet customer requirements with best power quality and power supply reliability; realize seamless operation of system operation and wholesale and retail power markets, and at the same time, better stimulate market participants to participate in power grid security management through market transactions. This will increase the level of safe operation of the power system.
2. Smart grid technology system
The construction and function realization of smart grid depend on the development, promotion and application of a number of basic technologies. The smart grid technology system is divided into basic technologies and advanced applications. Basic technologies include power equipment, measurement and communication equipment, information management systems, decision-making and control theory, advanced applications include intelligent control centers, smart substations, smart lines, intelligent protection systems, and intelligent demand side management. Through the organic combination of basic technologies and advanced applications, a smart grid is finally formed.
The status of application of three power communication systems
The power communication system is an integral part of ensuring the operation of the power system. The normal operation of the power system requires the effective communication means to accurately transmit the command of the control center to the remote terminal and collect the data information reflecting the operation of the remote device to the control center. Currently used communication methods include field bus, telephone line, fiber optic communication, power line digital carrier, and wireless spread spectrum. The common problem of these communication methods is to build a dedicated channel, and the investment in the project is large and the maintenance work is arduous. With the continuous development of wireless communication technology, the use of mobile communication technology provided by mobile operators to achieve data transmission in the power system will be an important development direction of the power system automation.
At the same time, GPRS (General Packet Radio Service) is also a widely used communication method. It is a 2.5G wireless packet switching technology based on the second generation mobile communication system GSM. It has a wide coverage, always online, and then Speed ​​of entry, support for high-speed data transmission, low input costs, and fee-based charges. At present, GPRS technology has been widely applied to all aspects of the power industry, such as distribution automation, power load management, wireless meter reading, dispatch automation, power quality monitoring, remote signal transmission of voltage level substations, power repair scheduling, transmission lines Contamination online monitoring and other fields. However, in practice, the GPRS transmission rate is only 57.6 kbit/s, and the confidentiality and security of the communication are not high enough, and it is no longer possible to meet the requirements of the development of the smart grid in the future. In contrast, LTE technology not only has the advantages of GPRS technology, but also makes up for the deficiencies of GPRS technology in terms of transmission speed, confidentiality, security, etc. Therefore, it can better adapt to the development direction and technical requirements of future smart grid construction.
Fourth LTE technology and its application in smart grid
1.LTE technology
The Long Term Evolution (LTE) project is the evolution of 3G. It began with the 2004 3GPP Toronto Conference. LTE is not a 4G technology that is commonly misunderstood, but a transition between 3G and 4G technologies. It is a global standard for 3.9G. It improves and enhances 3G air access technology, adopting OFDM and MIMO as its sole standard for the evolution of wireless networks. The peak bandwidth of 326 Mbit/s and 86 Mbit/s can be provided at a spectrum bandwidth of 20 MHz, which improves the performance of cell-edge users, improves cell capacity, and reduces system delay.
LTE technology features are mainly reflected in the following aspects:
1) The communication rate is high, the downlink peak rate is 100Mbps, and the upper behavior is 50Mbps.
2) With packet domain services as the main objective, the system will be based on packet switching in the overall architecture.
3) QoS guarantee, through the system design and strict QoS mechanism, to ensure the service quality of real-time services (such as VoIP).
4) The system is flexible in deployment and can support multiple system bandwidths from 1.25MHz to 20MHz. It also supports "paired" and "unpaired" spectrum allocation, which guarantees future system deployment flexibility.
5) Reduce the delay of wireless network: The subframe length is 0.5ms and 0.675ms, which solves the problem of backward compatibility and reduces the network delay. The delay can reach U-plan <5ms and C-plan <100ms.
6) Increase the cell boundary bit rate and increase the cell boundary bit rate while keeping the current base station position unchanged.
7) Emphasize backward compatibility and support the cooperative operation of existing 3G systems and non-3GPP specification systems.
Compared with 3G and other mobile communication methods, LTE has more technical advantages, such as: high data rate, packet transmission, delay reduction, wide area coverage, and backward compatibility.
2. LTE application in smart grid
The application advantages of LTE in smart grids are mainly manifested in: high-speed data transmission speed meets the requirements of large-scale information data transmission in power systems; high-speed and reliable data interaction provides a reliable communication mechanism for smart grids to be compatible with various types of equipment openly; LTE's video capabilities will increase the ability of the power grid to meet the demand side, generators, and the environment in a harmonious manner, providing them with information processing platforms and physical carriers to complete the transaction; LTE's security and reliability are to meet smart grid defense information attacks and improve information Security, improve the self-healing ability of the important guarantee for intelligent control, load scheduling, power repair, intelligent demand side management provides accurate, reliable, real-time data information.
The specific functions of the LTE technology in the smart grid are as follows:
1) Web video surveillance
In the distribution network, there are a large number of detection terminals and transformer monitoring equipment used to transmit various information to the dispatch center, such as telemetry, remote signaling, and remote control of major equipment status and alarm information. With the development of video surveillance technologies, more and more substations and computer rooms use unattended methods. Therefore, in order to improve security and reliability, the system puts forward higher requirements for the accessibility and bandwidth of the transmission channels. Using a combination of fixed broadband and mobile LTE communication technologies, clear dynamic video information can be transmitted in real time to meet the requirements of power networks for real-time monitoring using video.
The advantages of combining LTE mobile video services with existing video surveillance systems in the power system are: On the one hand, mobile video monitoring devices are installed at monitoring points where cable broadband cannot be reached to implement video surveillance; on the other hand, surveillance and maintenance personnel can use them. Mobile PC or mobile phone, real-time understanding of operating conditions. Due to the higher bandwidth requirements of mobile video surveillance, only LTE mobile communication networks can achieve better service quality.
2) Line inspection
High-voltage overhead transmission lines are an important part of the power system. Their transmission distance is long, and their geographical environment is complex. At present, the main method of manual fault detection is used to maintain the line. The patrolling personnel under this method has a high work intensity and it is difficult to detect faults. With the rapid development of electronic chips and robotics technology, Japan and the United States have successfully developed robots as vehicles and video cameras as the image acquisition equipment. They also use mobile communication technologies (handheld computers and bar code scanning technologies). , RFID radio frequency identification technology, etc.), inspection personnel can use handheld computers, mobile phones, PCs to send the scene conditions to the inspection center in real time in text, pictures, video, to ensure the accuracy and completeness of the field data. This method improves work efficiency, standardizes inspection and maintenance, and improves maintenance and management levels.
3) Load Management
Load management is an important part of power demand side management (DSM), and it is an important measure to ease the contradiction between power supply and demand, improve the efficiency of power use, and ensure the safe operation of power systems. Load management in DSM mainly includes step-down and load-reduction, periodic control of user-controllable load, and direct removal of user-controllable load in three ways. By adopting the wireless communication mode of the LTE mobile communication network, video can be used for comprehensive monitoring of the power grid, and at the same time, information is highly shared, multi-sector linkage is performed, coordination ability is enhanced, information flow is accelerated, remote monitoring and operation are realized, and load management is performed accurately and timely. And personnel scheduling, reduce labor costs and improve response speed.
4) Emergency rescue command
The autonomy and self-healing ability of the smart grid refers to the ability of the grid to maintain its stable operation, assess weaknesses and respond to emergencies. Due to the sudden occurrence of power network failure or power system damage caused by some unexpected situations, it is necessary to urgently improve the emergency rescue command capability and quickly restore the normal operation of the power grid. Install LTE mobile communication terminals in power emergency repair vehicles, transmit remote field information through audio and video, and interconnect the system with the conditions of power station repairs, equipment operation system information, service center repair system, and accident repair decision-making plan. In order to ensure the rapid circulation and interaction of various parts of information, the remote commanders can understand the on-site conditions of the power grid in real time, make correct judgments and commands, improve on-site command and dispatch capabilities, shorten rescue time, improve emergency response capabilities, and reduce the impact of disasters.
3. LTE technology application suggestions
Based on the above analysis of the characteristics of LTE and communication technologies in the power industry, the following recommendations are made for the practical application of LTE technology in smart grids:
1) Combining GPRS and LTE technologies to build a smart grid communication system
At present, GPRS has a wide range of applications in power systems, and it has formed supporting hardware and software facilities. However, 3G terminal equipment and communication costs are still relatively high. Therefore, in the current power grid, large data volumes, real-time performance, and high stability are required. In the technical field, LTE technology is properly applied, such as line fault inquiries, substation automation management, and electric power maintenance and repair commands, which not only meet the requirements of economic construction, but also satisfy the system performance requirements.
2) Establish an open, standard and integrated communication system
The smart grid needs to continuously integrate and integrate enterprise asset management and power grid production operation management platforms to provide a full range of information services for power grid planning, construction, and operation management. Therefore, broadband communications networks, including cables, optical fibers, power line carriers, and wireless communications, will all play an important role in the smart grid. The establishment of an open, standard, and integrated communication system is conducive to the sharing and interaction of information.
3) Improve the security of power communication systems
With the continuous expansion of the interconnected power grid, any weak parts of the power system and its associated control and communication systems will be subject to human or natural attacks, resulting in catastrophic accidents in the power system. The security, anti-interference, and robustness of the communications network should be improved, and the defense capabilities of the smart grid should be enhanced.
Five conclusions
The development of mobile communications to the LTE phase has resulted in a continuous increase in the data transmission rate. The services provided have evolved into multimedia IP such as mobile Internet, mobile TV, and video calls. Not only are there more types of services and higher service quality. The development of mobile communications, especially the completion of the LTE network in the future, will certainly promote the development of the power industry. The future smart grid will be a high-bandwidth, IP-based, multi-level QoS guarantee, providing a comprehensive platform for multiple services.
references
[1] Chen Jingsi. The smart grid rises to the national strategy, and the management pricing mechanism faces great changes [N]. Oriental Morning Post, 2009, 06.
[2] Liu Qilin. The practical significance of smart grid [J]. Internet Weekly, 2008, 4.
[3] Ding Minxuan, Wang Jing, Zhu Yezhong. The Ascendant Smart Grid [R]. National Grid, 2008, 5.
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