GPS timing server applications in video surveillance system of power plant
application of GPS timing server video surveillance system of power plant
Preface
In recent years, with increasing levels of automation substation in comprehensive automatic converting station computer monitoring system, computer protection device, fault recording devices and a variety of data management machines have been widely used, but with the work of these automatic devices We need to have a precise uniform time. Cause When the power system failure, the system can achieve the station of each post accident monitoring and failure analysis operation at uniform time reference, may also be analyzed through the accident protection action, switching division and the order of the exact time and process. With the increasing complexity of the grid, expand capacity and improve power grid, provides a standard time clock reference is an urgent need for power plants, substations and the whole power system, unified clock system is to ensure the safe operation of power, to improve the level of running a significant measures, is one of the most basic requirements of integrated automation substation automation system.
A, GPS timing server advantages
Substations different manufacturers of computer monitoring system, automation and computer circuit protection devices, fault recorder, electric energy billing systems, SCADA system, in the form of time synchronization substation are the following:
(1) The equipment provider that separate clock, and the respective clock quality of the product due to the difference in the deviation of the time has a certain accuracy, so that the whole plant each of the system data can not be analyzed on the basis of a unified time reference and compared to the post-failure analysis to determine the correct great risk.
(2) When manner, command control center master clock synchronization within each plant system for the issued through a communication channel, this approach requires a dedicated communication channel when the master station, since the arrival of each substation from the dispatch center distance is not the same, the communication delay are not the same, so only the system clock to ensure that the level of error in 100 milliseconds.
(3) a small GPS receiver, a plurality of RS232 ports, serial cable connected individually to the respective computer, time synchronization. But in fact there are also disadvantages such synchronous manner, use can not be too long cable lengths; delayed reaction speed server, the client have a direct impact on the accuracy of the time. Further stations often have different needs to receive clock synchronization signal means, different interfaces, such as RS-232/422/485 serial port, pulse, IRIG-B code, DCF77 format interface; nor the number of devices and the like, resulting in insufficient number of certain types of interfaces GPS device or a lack of a certain type of interface, you need to increase or even a GPS receiver, which tend to be underfunded or not installed location restrictions.
When the server is a good solution to a unified time reference substation GPS timing problems, or even accurate to the station between stations, it has become an inevitable trend in the best time of the program, but also the development of technology. According to "Guangdong Power Grid 110 ~ 220kV substation automation systems technical specifications" requirement, our new establishment in recent years or comprehensive self-transformation stations are used when time synchronization system for substation equipment be calibrated. In September 2005 the Guangdong Power Grid Corporation issued a "Guangdong power grid substation GPS time synchronization system technical specifications," and the subsequent management of new sites or retrofit stations GPS time synchronization system, design, installation, testing and operation are by the technical specifications implementation.
Introduction to GPS time server and works
Server using the GPS timing signals transmitted from the GPS satellite received RS232 interface, protocol conversion and then by the main CPU of the central processing unit, converted to local time meet the various requirements of the standard interfaces (RS232 / RS422 / RS485, etc.) and the time code output (IRIG_B code, ASCII code, etc.). GPS satellite clock synchronization system consists of a GPS satellite signal reception section, the CPU part, or extension output, power supply section, the man-machine interaction module parts.
GPS timing synchronization server main pulse output, and a serial output time information IRIG-B time code output three kinds of ways. Synchronous output pulse, i.e., a certain time interval synchronized clock output an accurate sync pulse intervals. When the device is subjected to timing to after receiving the sync pulse, to eliminate the internal timekeeping errors clock means. Pulse drawback is unable to provide direct synchronization time information, when the device is granted if the time on the wrong source, will always go wrong. Serial synchronous output mode, the time information is output to the serial data stream. Various devices are granted when the received time information every second serial obtain time synchronization, is not received within the period of seasonal intervals, means clock error exists a problem itself to the way broadcast manner when the serial pulse ratio complex manner, also in the receiving process, the information processing will affect the time it takes when the precision, it is mainly used to timestamp an event, if you want to increase the accuracy, then field application also needed to give sec Pulse signal. The rising edge 1PPS (pulse per second) signal, an external clock to achieve synchronization with the GPS clock errors and inhibit the synchronization in the system to meet the accuracy requirements range.
