Application of GPRS technology in power distribution monitoring system [reprinted]

Keywords: Access Point name (APN) Global Mobile Communication System (GSM) Universal grouping wireless service (GPRS) Short Message Service (SMS)

1. Question proposal

With the rapid development of urban power grids, there are naturally two problems. One is the automation level of the distribution network, which involves fault detection, fault isolation, and power transfer. Second, the management level of power consumption involves the billing of power consumption. Communication problems are involved in both aspects. Communication is often the bottleneck of such systems, and there is always a conflict between reliability and economics. With the development of GSM and GPRS, the communication problem in the distribution network has taken a new opportunity. This paper proposes to use the mobile Internet for real-time data transmission, this paper introduces the communication technology of GPRS and the smart distribution Communication Equipment Based on GPRS technology and their applications in fault locating, configuration change monitoring and meter reading systems.

2 GPRS technology Overview

2.1 Definition of GPRS

The General Packet Radio Service (GPRS) is a universal group wireless Service. It is a set of wireless transmission methods developed by the concept of Packet-Switched. The so-called Packet Exchange is to encapsulate the Date into many independent packets, and then send these packets one by one. The form is similar to sending packages, the advantage of Packet Exchange is that bandwidth is occupied only when data needs to be transferred and can be priced based on the amount of data transmitted. This is a reasonable billing method for users, because most of the time bandwidths for data transmission such as the Internet are idle. In addition, in the GSM phase 2 + standard, GPRS can provide four different encoding methods, which also provide different Error Protection capabilities.

GPRS is a new type of GSM data service. It provides a connection between mobile users and data networks, providing high-speed wireless IP addresses and X.25 grouping data access services for mobile users. GPRS uses the group exchange technology, which allows multiple users to share some fixed channel resources. If the eight time slots in the TDMA frame on the air interface are used to transmit data, the data rate can reach up to 164 kbps. The channel resources of the GSM air interface can be used by both voice and GPRS data services. Of course, some channels can be defined as GPRS Dedicated channels when there are sufficient channels.

2.2 advantages of GPRS

Compared with the original GSM dialing method, GPRS is a group switching technology. Because of the use of the "Group" technology, users can access the Internet without interruption (the situation is probably similar to the use of the download software Net Ants ). In addition, the method of using GPRS to access the Internet is different from that of WAP. Using WAP to access the Internet is like accessing the internet at home. "dial-up connection" is performed first, and then the telephone line cannot be used at the same time, however, GPRS is superior, and data downloading and communication can be performed at the same time. Technically, the voice transmission (CALL) continues to use GSM, and the data transmission can use GPRS, the application of mobile phones is upgraded to a higher level. The development of GPRS technology is also very "economic", because it only needs to follow the existing GSM network to develop. GPRS is widely used, including sending and receiving emails through mobile phones and browsing the Internet.

The biggest advantage of GPRS is that its data transmission speed is not comparable to that of WAP. Currently, the transmission speed of the GSM mobile communication network is KB per second. At the beginning of this year, the GPRS mobile phone has reached the transmission speed of 56 kbps, up to 115 kbps (this speed is twice the ideal rate of commonly used 56kmodem ). In addition to the speed advantages, GPRS also features "always online", that is, users can keep in touch with the network at any time.

2.3 GPRS network implementation

The GPRS network is implemented based on the existing GSM network. Add some nodes in the existing GSM network, such as GGSN (Gateway GPRS Supporting Node, GPRS Gateway Support Node) and SGSN (Serving GSN, GPRS Service Support Node ). GSN is the most important network node in the GPRS network. GSN has the mobile Routing Management function. It can connect to various types of data networks and connect to GPRS registers. GSN can complete data transmission and format conversion between mobile terminals and various data networks. GSN can be an independent device similar to a router or integrated with MSC in GSM.

2.4 Working Principle of GPRS

During GPRS work, it uses route management to address and establish data connections. The GPRS route management is manifested in the following three aspects: the establishment of a route for the mobile terminal to send data; set up a route for the mobile terminal to receive data, and set up a data route when the mobile terminal is roaming. In the first case, when a mobile terminal generates a PDU (group data unit), the PDU is processed by the SNDC layer and is called an SNDC data unit. Then, the LLC layer processes the SGSN sent to the mobile terminal in the GSM network through the air interface. In the second case, when a public data network user transfers data to a mobile terminal, the routing between the data network and the GGSN is first established through the standard protocol of the data network. The data unit sent by the data network user (such as the PDU in PSPDN) sends the data unit pdu to the ggsn through the established route. The GGSN then sends the pdu to the sgsn where the mobile terminal is located. The SGSN encapsulates the PDU into an SNDC data unit, processes it as an LLC frame unit through the LLC layer, and finally sends it to the mobile terminal through an air interface. The third case is that a data network user transfers data to a roaming mobile user. In this case, data transmission must go through the GGSN of the primary location and then be sent to mobile user.

2.5 GPRS applications

GPRS is a new type of grouped data transmission service activated on the existing GSM network. Based on the standard network protocol supported by GPRS services, GPRS can provide a series of interactive services: point-to-point connection-oriented data service-this service is a multi-group service sent between two or more users. This service requires working programs such as establishing connections, data transmission, and releasing connections.

Single-point to multi-point business-the business can send a single message to multiple users according to the requirements of a service requestor. This service can also be divided into point-to-point multi-channel broadcast service, point-to-point group calling service, and IP multi-point transmission service. Point-to-Point connectionless network business-each data group in this business is independent of each other. Information Transmission between users does not require end-to-end call establishment programs, and there is no logical connection for group transmission, the delivery of the group is not guaranteed and is supported by the IP protocol.

2.6 GPRS and WAP

As a standard for wireless Internet, WAP is developed by a number of major vendors. It defines a layered and scalable architecture and provides a comprehensive solution for wireless Internet. One of the principles of WAP protocol development is to be independent from air interfaces. The so-called independent air interfaces mean that WAP applications can run on various wireless bearer networks, such as TDMA, CDMA, GSM, GPRS, and SMS.

GPRS corresponds to the 9.6kbps data service in GSM. In contrast, GPRS implements high-speed data transmission through group exchange. In other words, GPRS improves the GSM data service, it is a means to achieve high-speed data transmission in GSM.

It can be seen that WAP is a high-level application, while GPRS is the underlying transmission. The relationship between WAP and GPRS can be illustrated by reference to the famous mail example: If WAP is a plain letter, greeting card or postcard, then GPRS and gsm csd (9.6kbps circuit-switched data service) it is the means of transportation that ships letters, but the latter is a car, and the former is a plane.

3 GPRS application in fault locating, configuration change monitoring and meter reading systems

3.1 Fault Locating

A large number of fault indicators are used in the distribution network to detect the fault location and locate the fault point. It is simple and reliable. When a fault is detected, the fault is indicated by a flop or an output node. The GPRS communication device is equipped with a three-way switch quantity input, which can collect the switch quantity output status of the Fault Indicator of this line. When a line fails, the fault indicator is triggered. the GPRS communication device transmits the fault information to the control center over the INTERNET. After receiving the action information, the monitoring center performs network topology computing and analysis, combined with the geographic information system, you can directly display the geographic location information of the fault point.

3.2 configuration change monitoring

The transformer on the distribution network is equipped with a transformer Monitor-TTU. Its main functions include data collection for transformer working conditions and Automatic Reactive Power Compensation for the line. TTU's reactive power compensation function can be implemented in the local environment without the support of network communication. However, in the past, the distributed operation data was generally transmitted through communication methods such as RS485, with poor reliability and short distance, it is greatly affected by the geographical environment.

3.3 Energy Metering

Electric energy metering is an important part of modern power marketing systems. The traditional electricity settlement relies on manual copying of data to the site on a regular basis, which has many shortcomings in real-time, accuracy and applicability. By combining modern communication technology with computer technology and electric energy measurement technology, the power usage (sales) can be reflected in a timely, accurate, and comprehensive manner ). The GPRS wireless LAN private network provides real-time and stable data and event records for electricity management, enabling simultaneous freezing of meter reading for multiple tables. The system has the remote read-back function of device parameters. For example, the system compares the read-back parameters with the set parameters saved in the background system and reports an exception alarm. This system can detect illegal behavior of stealing parameter modification of the Power Meter. It has the following features: Pressure Loss, disconnection, error wiring alarm, display, recording, and active upload, so that management personnel can detect user exceptions in the company's headquarters, it provides an advanced and effective high-tech detection method for anti-theft of electricity. Based on the data of the 10 kV Line Summary table and table shards in real time, the power balance of the line is automatically analyzed to provide an accurate basis for Line Loss Assessment, so as to reduce the line loss in a large area. When the voltage and load measured by the user's Electric Energy Meter exceed a certain range, the electric meter sends an alarm to the system and can monitor and control the user load through the system software of the Intelligent Analysis Function.