1．1 System components
The whole monitoring system is mainly composed of three parts , namely, the front-end monitoring sensors , ZigBee transmission equipment, central monitoring system.
1.1.1 Front-end monitoring data acquisition devices
The normal operation of the entire system requires real-time monitoring of the health of a number of parameters , the sensor is used to implement each monitoring node data acquisition , and data collection was sent to the ZigBee through the serial port or via analog transmission equipment .
1.1.2 ZigBee Transmission equipment
ZigBee transmission equipment used throughout the system to achieve the establishment of the transmission channel , when the ZigBee device monitoring data received from the sensor is sent to the monitoring center through wireless network transmission from the formation , while the monitoring center can also be monitored by the respective ZigBee network two-way communication node sends control commands , enabling data to achieve the purpose telemetry, remote control .
This scenario ZigBee transmission equipments which we used , there are has two kinds , one is the only ZigBee we named it F8914, the other is ZigBee + GPRS named F8114 RS422 ZigBee Modem, the difference between both of these is that F8914 is completely transmitted by ZigBee wireless network , which can be first through the ZigBee wireless data transmission to the central node ( served by the F8114), and then transmitted to a remote monitoring center through GPRS wireless network.
1.1.3 Central monitoring system
Central monitoring system consists of a server unit and platform software main composition , when the central monitoring system receives the monitoring data , will perform a variety of data analysis and the results of the analysis carried out according to various control operations, such as an alarm message to the terminal monitoring equipment issue control instructions , and so on .
1.2 Network Architecture
According to the monitoring center and from the wind power plant , we present two network implementation framework , the monitoring center when it laid in wind power stations , wireless data transfer using ZigBee direct access to short-distance transport , the entire ZigBee wireless network be set up using the F8914 ZigBee Terminal.
Wind wireless network monitoring data collected by acquisition and control systems , ZigBee wireless transmitter module and data collection and transmission of data files generated by the data transfer software for data on GPRS wireless terminal will compress and encrypt data transmitted to the serial port , and then ZigBee wireless network or through the GPRS network to send data to a central server to achieve the specified remote transmission through wireless carriers .
As shown below:
When the center of the wind power plant monitoring and farther away , the terminal data transmission through ZigBee wireless network to a central node and the central node and then transmitted through the GPRS network to a central control room, the central node using the device with GPRS- F8114.
When the central node transmits the data through the GPRS network to the monitoring center, which has a variety of network access network :
1）Center uses APN line, all terminals are used within the network a fixed IP, Customer Center Mobile GPRS network access through a dedicated APN establish GRE tunnel between the GGSN and Mobile Internet router. For customers assigned a dedicated APN, other users can not apply for the APN. Only within the private network SIM card to enter the APN, to prevent other unauthorized users from entering. Users can establish internal RADIUS server , to ensure that users of internal security . Users to create a DHCP server ( or router in the APN enable DHCP function ) Internally, the internal address is assigned by the user authenticated users .
Such solution , whether real-time, security, and stability has greatly improved over the previous one , suitable for high security requirements , data points are more time-critical applications. Best networking permitted under the funding situation .
2）Internet control centers and other public network using ADSL connection , using the public network dynamic IP + DNS resolution service . Customers first contact with DNS dynamic domain name service provider opened , IP MODEM first connection using the domain name addressing DNS server, and then find the center of public DNS server dynamic IP, establish a connection. Such methods can greatly reduce the cost of public fixed IP , but the stability of the DNS server is subject to stable , so to find a reliable DNS service provider. Such programs suitable for small -scale applications.
3）Internet control centers and other public network using ADSL connection , using the public network fixed IP services. This solution mast to apply for ADSL and other broadband services from operators first, the center has a public fixed IP . IP MODEM initiates a connection directly to the center. Stable and reliable operation , it is recommended that such solution .
二、The solution features
ZigBee its flexible , reliable, easy layout and other features in many fields has been widely used. The advantages of applied substation monitoring system are:
1、Wireless, reduce the complexity of the wind power plant connection
2、 Low cost , ZigBee protocol is simple and free of royalties. Intelligent, each ZigBee nodes automatically search establish a connection
3、 Support a variety of network topologies star, tree , mesh -type network , the largest network connectivity , and can support 65,000 nodes.
4、 Transmission module using industrial-grade design, metal case, an external power supply DC 12V/500mA; Communications Current : <250mA (12V); Working temperature -25 ~ +65 º C; Storage temperature -40 ~ +85 º C; 95% relative humidity ( non-condensing ) ; multiple hardware and software watchdog design, suitable for oil field work .
5、good environment for ZigBee wireless communication distance can up to 2000 meters .
6、ZigBee communication does not require any fees, save a lot of expenses for the entire project
7、Device configuration is simple , understandable, high degree of integration , the technology is mature , easy installation.
With further growth in demand for sophisticated and technology , Zigbee have broader applications in a variety of remote monitoring applications.
ZigBee wireless data collection and transmission system acquires stable, reliable , convenient and practical. Low installation cost , easy maintenance, no excellent upgrade , do not need to rent a public network , and without the huge operating costs. This is the modern remote data acquisition system optimal solution.