Application of ultra short baseline positioning system in submarine cable detection of 500kV trans-sea transmission system
Qiongzhou strait 500 kv high-voltage cable transmission system is our country the first super high pressure, long distance, large capacity across the network engineering is also the world's second after Canada similar engineering project Starting point is the substation of 500 kv harbour city in the zhanjiang, guangdong province ꎬ end point to Chengmai hainan fushan substation of 500 kv the system engineering to solve the problem of small net hainan power grid big machine, improve power supply quality of hainan province obviously ꎬ ended the history issue of the power island of hainan province engineering 3 single long about 32 km submarine cable (another second phase 4 Submarine cable under construction) is the core equipment of the system. The safety of submarine cable is the priority among priorities for the stable operation of the transmission system. Regular detection of submarine cable is a key part of the operation and maintenance of submarine cable.
1. Acoustic positioning system
Acoustic positioning systems were first developed in the 1860s to support underwater research and since then they have played an important role in locating underwater targets such as towed ROVs to provide very high repeatable accuracy of position in limited areas even far from shore in the 1950s and 1960s In the international era, with the continuous development of light, sound, magnetic and other technologies, underwater detection technology has been greatly developed in the process of vigorously developing Marine natural resources and Marine engineering. A series of advanced and efficient underwater detection equipment has been developed successively In various underwater detection of light, sound, magnetic technology, because underwater light wave attenuation is fast, even the longest wavelength, the farthest propagation of infrared light wave in the water after a few meters of attenuation, sound wave and electromagnetic wave in the water have good propagation, so sonar, magnetic exploration and ultra-short baseline become the effective methods of underwater detection.
There are three main techniques in acoustic positioning system [1] : long baseline positioning (LBL), short baseline positioning (SBL) and ultra-short baseline positioning (SSBL /) Some modern positioning systems can use a combination of the above technologies. Among the three different acoustic positioning systems, long baseline positioning (LBL) has the highest positioning accuracy. However, it is difficult and expensive to locate known points with high precision by laying on water bottom Engineering Short baseline positioning (SBL) requires hull modification to place transducers arrays. The requirements on ships limit the application of short baselines. The advantages of the ultra short baseline acoustic positioning system (USBL) are obvious.
2 Project Case
Sonardyne British company is the world's most famous production under water acoustic positioning equipment suppliers ꎬ acoustic positioning system equipment of the company include: locate the host (+ receiving array transducer), transponder, interface power supply unit, data acquisition and processing unit (including software), coding procedures, RFID test unit Equipment used in this project is the ultra short baseline (USBL) : ultra-short baseline positioning of the ship can changer ꎬ has at least three receiving array unit ꎬ transponder is installed on the need for positioning of the target of the transducer to measure the transponder horizontal and vertical Angle and slope distance as shown in figure 1.
Figure 1. Transducer and transponder distribution diagram of the ultra short baseline positioning system
This project specific implementation process of the installation of underwater robot at the same time the ultra-short baseline positioning system of receiving and transmitting transducer array installed in both the mother ship ꎬ transponder fixed ꎬ on underwater robot and the mother ship of the existing GPS signal into two road concrete as shown in figure 2
FIG. 2 Schematic diagram of ultra short baseline positioning system
In order to achieve more accurate positioning accuracy, it is necessary to correct and set the ultra-short base line system. The positioning accuracy of the ultra-short baseline positioning system is affected by many factors, specifically as follows:
(1) Sound waves in different waters are affected by density and salinity and travel at different speeds
(2) The influence of the transducer installation mode and location
(3) The influence of tilting and rocking of the mother ship itself
(4) The actual position and direction of the GPS satellite receiving device on the mother ship
(5) The position and direction of the transponder on the underwater vehicle when it actually enters the water vertically
For example, a small attitude error of the ultra-short baseline system will result in the final position (cable coordinate) deviation of the underwater vehicle that needs to be located, as shown in Figure 3
FIG. 3 Schematic diagram of the influence of attitude deviation of ultra-short baseline system on final positioning data
Transducer 1 ° posture error caused in 2 km distance from 35 m position deviation error rate is 1. 75% in the deepest qiongzhou strait 100 m depth estimation can cause the ultimate goal of location error is 1. 75 MB in actual construction engineering ship rocking causes can changer The posture error of 1 ° if ultra short baseline system after installation does not make correction for the ultimate goal position coordinates (cable) the positioning of the influence is quite big.
After complete the installation, calibration and setting the ultra short baseline system of data acquisition and processing unit through receiving GPS signals to get the actual location data ꎬ mother ship by receiving transponder signal for underwater machine people relative position data by the signal processing unit of professional software to calculate the underwater robot in the actual location data with professional software The relative distance between the mother ship and the underwater vehicle, the head direction of the mother ship and the underwater vehicle, and the speed of the other sensors carried by the underwater vehicle will also be displayed simultaneously.
3 Conclusion
In this paper, based on an engineering example by introducing the ultra-short baseline positioning system system structure, characteristic, principle, installation and calibration reference factors ꎬ robot underwater acoustic positioning system is discussed in the qiongzhou strait sea 500 kV high-voltage cable transmission system, the application of the submarine cable testing project.
References:
[1] Wu Yongting ꎬ xing-hua zhou Yang Long. Underwater acoustic positioning system and its application [J]. Ocean Surveying and Mapping, 2003, 23(4): 18-21
