Technology and its application in power system when the Compass satellite grant
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I. Introduction
, But also one of the most critical national infrastructure for a large country into the modern information society, navigation, positioning and timing system is the most important. Precision Time is scientific research, the basic physical parameters of scientific experiments and technical aspects of engineering. It provides essential timing and coordinates all the system dynamics and quantitative measurement of the timing process. In order to communicate, power, control and defense industries have extensive and important applications when precise timing. Modern weapons real (test) test, it needs to protect the war, the establishment of intelligent transportation systems and digital support it needs to Earth. Modern communication network and power grid construction has become increasingly enhanced reliance on precision time and frequency. From the establishment of a modern state of the overall consideration of large-scale systems engineering, navigation and timing systems it should be said that the foundation base. It supports community as a whole is almost round, when satellite-based navigation and timing is an inevitable trend in the future.
Current satellite timing synchronization technologies include the US global satellite navigation system GPS, Russia's Global Navigation Satellite System GLONASS, China's Compass navigation system and the EU's Galileo global navigation system Galileo, based on security considerations when granted, at this stage domestic power enterprises mainly rely on global positioning system GPS time synchronization technology, but restrictions by the US GPS and GPS is free to use, and therefore low reliability, autonomy poor. In order to meet the terms of electricity production and business management business time requirements and security needs, it is necessary to Beidou granted when time synchronization technology research and application. In this article apply only Beidou timing and technology in the power system.
(UTC) time synchronization is referred to herein means a network synchronization clock, and each of the respective nodes connected by a network application interface clock time and the UTC time interval.
two. Compass timing principle and features
1. When Compass award principles
A receiver to obtain timing clock means and the local time difference between the standard time Compass in some way, and then adjust the local clock so that the time difference is controlled within a certain range of accuracy.
Satellite navigation system typically consists of three parts: navigation timing satellite, terrestrial detection correction and maintenance system user receiver. For local Compass satellite system, ground testing center to help users locate granted complete synchronization together. 1 illustrates a timing Beidou system.
1 a schematic view of the working Compass system timing
In the Compass navigation system, according to the timing the user positioning information satellite broadcast or the approved continuous clock clock error can be very high precision clock; timing features through the multicast or navigation data by a counter, synchronized with high accuracy can be obtained 1pps second pulse signal for synchronous operation with / remote multichannel data acquisition and control.
"Compass" user machine to provide two timing ways: one-way and two-way time service award. Timing accuracy is unidirectional 100ns, bidirectional timing accuracy of 20ns. In the unidirectional mode timing, it does not require the user machine and the ground central station exchanges information just received a broadcast message Compass signal obtained independent local clock time and the standard time difference Compass, time synchronization; granted under the bidirectional mode, the user machine exchanging information with the central station, the signal application timing transmitting to the central station, the central station is calculated from the time difference between the user machine, and then forwarded to the user through the outbound signal via satellite, the user Click to adjust the local clock time and the standard time-aligned signals.
1.1-way grant
Compass time is precisely maintained centralized control standards Compass time, user clock time of the clock face of the clock time of the user, if they are not synchronized clock error exists, then the clock time and user time Compass While it appears the same reading timing is different .
Ground hub station broadcasts the outbound signal in each superframe timing is unidirectional Compass user machine by receiving information through broadcast message, an autonomic computing machine by a user clock error and the local time correction, so that the local time and the time synchronization Compass. A first frame position information in the transmission period data segment Compass Standard Time (days, hours, minutes and time correction data signal) and the satellite, while the time stamp information in a special way in the outbound modulation signal, passing through the center station to delay transmission of the satellite, the satellite delay to the user machines and other various machines delayed delivery to the user (e.g., troposphere, ionosphere, Sagnac effect, etc.), the user that is in the local machine clock face time of the observed satellites the time delay between the received signal and the local timing signal obtained by the measurement unit by the user, after the position information based on the satellite navigation message, the delay corrected self-position information and a receiver information acquired beforehand calculated.
In general, it is known to the user precision fixed coordinates, a observation satellites, precise measurement or time synchronization can be achieved. If two or more satellites satellite observations, provides more observables, increases the robustness of the timing.
Figure 2 Compass Block diagram of the timing of the one-way award
1.2 Bidirectional Timing
All two-way information processing timing performed in the central control station, the user machine simply timing signal received can be returned. For convenience of explanation, a simplified model: the center station transmits the system timing signal ST0 time T0, the timing signal after a delay of arrival of satellite, a satellite transponder after forwarding the user machine timing signal, received by the user machine reaches processing may also be considered as signal repeaters, through the spatial propagation delay reaches the satellite, the satellite signals are relayed through the spatial propagation delay transmission back to the central station system. That represents a time T0 timing signal ST0, the final time T0 + + + + system back to the central station. The central station system time signal and the reception timing difference between the time of transmission, to give a two-way propagation delay + + +, by 2-way propagation delay from the central station to the user machine. The central station sends a one-way propagation delay to the user machine, the timing of when the user receives the beacon signal and the one-way propagation delay of the local clock correction is calculated difference with the local clock time of the central control system, so that the central control time synchronization system.
3 Compass block diagram of the timing of two-way grant
Timing when comparing the timing bidirectional and unidirectional 1.3
Principle timing service from the bidirectional timing and way (1): Introduction can be seen, the bidirectional timing and unidirectional main difference timing service that from the central system to a user machine propagation Obtaining delay: unidirectional timing with the system broadcast satellite position information according to a certain calculation model autonomic computing machine by a user-way propagation delay, satellite position error, modeling error (troposphere model, ionosphere models, etc.) will affect the accuracy of the delay estimation, timing accuracy influence the final ; need to know the position of the bidirectional timing user machine and the satellite position, two-way round-trip propagation time divided by 2 mode acquisition, a more accurate reflection of the various delay information, so that higher precision estimation. Precision timing Beidou system unidirectional system design is 100ns, is 20ns, the actual timing of the user machine performance indicator generally superior to the bidirectional timing.
(2) calculate the position of the check requires prior user machine timing, if the position is unknown, you first need to send a location request to obtain location information. The user need not know the location of the bidirectional timing when the machine, all the processing by the central station to complete the system.
(3) Since the one-way timing passive manner, without occupying the system capacity (need to obtain position location information). And the bidirectional timing is performed by the timing way to interact with the central station, and therefore consume system capacity, subject to certain restrictions.
2. Compass feature when the grant
(1) Beidou timing accuracy of better than 20 ~ 100ns, a high degree of precision;
(2) timing systems and equipment is stable and reliable, small interfering;
(3) Multiple output;
(4) low-power portable
(5) Applications: aviation and maritime, land transport, scientific investigation, polar explorer, inspection equipment, system monitoring.
Third, the application in the power system timing Beidou
Currently internal power system to send each end, by the end of the wide distribution and dispersion, automated device comes with an internal real-time clock, which is inherently difficult to avoid errors, with the increase in running time, the accumulated error will be larger and will lose the right time metering role. How to achieve real-time clock can be synchronized, the time to reach a unified whole network, the power system has been a goal. If mounted at each end of a bucket Taipei grant timing, the timing Beidou timing precision can be guaranteed throughout the time signal UTC relative error does not exceed 20 ~ 100ns. This time precision within the satellite coverage synchronized with high utility value in the detection and measurement of the electric power system.
In practice, using the timing signal from the satellite precise places or with precise synchronization purposes multi-channel data acquisition and control, mainly using the second pulse signals from the satellite signal receiving end to obtain pps or using another thereby resulting signal PPM, PPH a pulse signal, the data synchronous start multichannel analog to digital converter ADC, digitally controlled analog to digital converter, the synchronous opening or closing the respective channel switch; also used to measure the determining, making precise time tag, fault location, such as a variety of power system Wait. In the timing device, a receiving end and second pulses sent per second 1PPS positioned outwardly clock information. PPS PPS signal and data information rumor strict time relationships, in use, it is also possible to achieve the conversion time.
Figure 4 block diagram Application Timing Compass in Power System
Power system time synchronization requirements in Table 1
| business system |
signal type |
Signal accuracy |
Signal Interface |
| Traveling wave so Barrier distance measuring device |
Second pulse and time the message |
1us |
Static air contacts |
| LLS |
Second pulse and time the message |
1us |
RS-232 |
| Power angle measurement system |
Second pulse and time the message |
40us |
RS-232 |
| Fault recorder |
IRIG-B or sub-pulse and time message |
1ms |
RS-422 |
| The sequence of events recording device |
IRIG-B or sub-pulse and time message |
1ms |
RS-422 |
| Microcomputer Protection |
IRIG-B or sub-pulse and time message |
１０ms |
RS-232 |
| RTU |
IRIG-B or sub-pulse and time message |
1ms |
RS-422 |
| SCADA system at all levels |
IRIG-B or sub-pulse and time message |
1ms |
RS-232 |
| Substation monitoring system |
IRIG-B or sub-pulse and time message |
1ms |
RS-422 |
| Automatic recording instruments |
IRIG-B or sub-pulse and time message |
10ms |
RS-232 |
| Load Monitoring System |
Time of packets |
≤0.5s |
RS-422 |
In recent years, with the improvement of the technological level of grid operation, most of the substation integrated automation solutions, remote centralized control, operation, both to improve labor productivity, and reduce the possibility of misuse of thought. Therefore, real-time clock synchronization requirements of the automation system is the most basic requirements of substation automation system. In order to ensure safe and economic operation of the grid, with a variety of computer and communication technology-based automation devices are widely used, these devices work and role play, the same can not do without a unified network-wide time base.
Epilogue
Technology has gradually matured Beidou satellite time, daily production depth, all areas and aspects of life. Stable and reliable, portable and low consumption, low cost Beidou satellite timing device, accurate clock timing and synchronizing data acquisition and control, has broad application prospect in industrial their time synchronization. Use of satellite navigation object positioning, and synchronous data acquisition clock feedback control, it can achieve accuracy of traditional measurement and control instruments that fall, marine aviation, land transport, scientific investigation, polar exploration, geophysical measurements, weather forecasting, equipment inspection in aspects, system monitoring and other widely used.
