GPS/Beidou fusion positioning technology for transmission line grounding line

The grounding wire plays a role in buffering high-voltage electricity in power transmission lines. However, during operation, it is difficult for personnel to obtain real-time information about the location of the grounding wire. The existing positioning technology for grounding wires in power transmission lines can prevent accidents caused by missing grounding wires or transmitting electricity through grounding wires. However, due to the vast scale of power transmission lines, there are often limited visible satellites and poor satellite signal quality, resulting in insufficient accuracy of satellite positioning and navigation. This paper first discusses the necessity of online monitoring of grounding wires in power transmission lines. Then, based on this, it introduces the positioning methods of GPS and Beidou positioning systems. Finally, it focuses on the GPS/Beidou fusion positioning technology. Through experimental verification, the GPS/Beidou fusion positioning technology is shown to greatly enhance the reliability of positioning by coordinating and complementing various navigation systems.


Introduction
In the power system, the grounding wire is an important safety device during power maintenance, providing protection for the personal safety of workers [1].The process of installing and removing transmission grounding wires mainly includes outbound delivery, transportation, on-site installation, removal completion, loading and return, and inventory management.The correct use of grounding wires is crucial for ensuring the safety of field operators' lives.Installing and removing grounding wires is a high-risk operation in electrical work.Any operational error in the process can lead to irreparable consequences for the safe operation of the entire power system [2].During maintenance operations, it is common to use several to dozens of grounding wires [3].However, there is a high risk of serious mistakes such as not installing grounding wires, improperly connecting them, or neglecting to remove them during high-intensity work, which can result in severe personal injuries and equipment damage accidents.With the rapid development of productivity in China, it is of great significance to combine advanced technology, improve existing work methods, and transform the existing grounding wire equipment to achieve online supervision of grounding wires.In the twenty-first century, Zhang Zhanlong proposed the application of Global Positioning System (GPS) satellite positioning technology to the grounding wire status monitoring and warning system to achieve the grounding wire geographic location status information management.This technology allows for real-time monitoring and early warning of grounding wires.However, with the successful establishment of China's Beidou Navigation Satellite System (BDS), integrating navigation and positioning has become an important development trend in the field of positioning [4].This article discusses the characteristics of the standalone positioning system that cannot meet the requirements of grounding wires.It first introduces the positioning principles of GPS satellite positioning technology and Beidou Navigation Satellite System.Then, it proposes the integration of GPS/Beidou positioning and further optimised by the Hekmert variance component estimation method.Finally, it demonstrates the superiority of the fusion algorithm through accuracy testing.

Analysis of satellite navigation and positioning technology
The principle of Global Navigation Satellite System (GNSS) is to utilize satellites orbiting the Earth to measure time and distance for navigation and positioning.Currently, there are four major positioning systems worldwide: GPS (United States), BDS (China), GLONASS (Russia), and Galileo (European Union).In China, the Beidou system and GPS system are widely used.

GPS satellite positioning technology
The GPS positioning system consists of a total of 24 satellites in medium Earth orbit, including 3 inactive backup satellites.These satellites are evenly distributed in 6 orbital planes with an angular separation of 60 degrees.The design ensures that at any time and any location, theoretically at least 4 satellites can be observed, guaranteeing the excellent positioning capability of GPS.Satellite navigation systems have three components: the space satellite constellation, ground control system, and ground user equipment [5]. he establishment of specific three-dimensional spatial positions in GPS is indeed achieved through time delays.It utilizes the navigation information generated by atomic clocks on GPS satellites, which continuously transmit signals.By obtaining the time difference between the satellite and the receiver, the method of intersection from the back using spatial distances is employed to determine the threedimensional spatial coordinates of the point to be calculated.This is illustrated in Figure 1.Assuming t represents the reception time at the mobile terminal, Δ t is the difference between the transmission time of the satellite signal and its arrival at the receiver.Since three-dimensional spatial coordinates need to be calculated, signals from at least four satellites are required.The corresponding equations can be example as: In the equations mentioned above, x, y, and z represent the three-dimensional spatial coordinates of the mobile terminal, i represents the satellite index, and xᵢ, yᵢ, and zᵢ represent the three-dimensional spatial coordinates of the navigation satellite.c represents the speed of light, V t i represents the clock bias for each satellite, and V t 0 represents the clock bias for the mobile terminal.By solving these equations simultaneously, the three-dimensional coordinates of the terminal can be obtained.

Beidou Navigation Satellite System
The structure of the Beidou system is similar to that of the GPS system, consisting of three main components: space segment, user segment, and ground control segment.The space segment consists of more than 50 satellites, including geostationary orbit satellites, medium Earth orbit satellites, and inclined geosynchronous orbit satellites.The positioning capability of the system relies on the collaboration between the space segment and the ground control segment [6].
Ground user equipment achieves positioning by receiving radio signals.The receiver is composed of an antenna module and a reception module.The antenna module captures satellite signals and feeds them into the reception module.The reception module receives and amplifies the signals, decodes the Beidou signals, and calculates positioning information such as latitude and longitude.One distinguishing feature of the Beidou positioning system compared to the GPS system is its ability to enable two-way communication between user terminals and satellites.This feature expands the application prospects of the Beidou system in specific scenarios.The utilization of triple-frequency signals in the BeiDou system enables more effective mitigation of higher-order ionospheric delays, resulting in enhanced positioning reliability, improved data preprocessing capabilities, and significantly increased efficiency in ambiguity resolution.In situations where one frequency signal faces challenges, conventional methods can still leverage the other two frequencies for positioning, thereby bolstering the system's resilience to interference and ensuring dependable positioning.Remarkably, BeiDou stands as the world's pioneer satellite navigation system to offer triple-frequency signal services.One of the advantages of active positioning is that it can still achieve positioning even when the quality and quantity of observed satellites are poor.While theoretically GPS provides comparable global positioning accuracy, the Beidou system has been specifically enhanced for China and its surrounding regions, where the geometric conditions of domestically deployed satellites are comparatively favorable [7].

GPS/Beidou fusion positioning
In the positioning of grounding wires in power transmission lines, there are significant accuracy issues associated with the application of both the Global Positioning System (GPS) and the Beidou Navigation Satellite System.However, a combination of multiple systems can greatly increase the real-time utilization of satellites, thereby enhancing the redundancy of observations during the positioning process.This, in turn, improves the accuracy of the positioning and accelerates the development of the navigation industry, all while maintaining relatively low costs.
Satellite positioning technology has now advanced to the stage of dual-system utilization.When compared to a single system, the combined use of GPS and Beidou systems notably improves the positioning effectiveness for grounding wires, particularly in challenging observation conditions or unfavorable satellite positions.This method involves simultaneous processing and computation of the observation data from both GPS and Beidou systems, followed by a series of data fusion techniques such as format conversion, time and coordinate transformation, and carrier phase combination.A unified solution and variance component estimation are then performed.The robustness and accuracy of positioning can be significantly improved by integrating and processing observations from GPS and Beidou systems.2, satellites transmit three-dimensional position information to the GPS/Beidou module.Through frequency conversion and signal demodulation, the position information is decoded and stored in the memory, retaining the current position information.This enables a hybrid positioning approach with a combination of some Beidou data and some GPS data.This fusion-based positioning system greatly improves the accuracy of localization and allows the two positioning systems to complement each other.In the process of GPS/Beidou positioning, the pseudorange observation equation can be expressed as follows: where P is the observation pseudorange data; superscripts G and B denote the GPS and Beidou systems, respectively; I is the geometric distance from the receiver to the satellite; c is the speed of light; d t 0 and d t i denote the receiver clock difference and the satellite clock difference, respectively; and I e , T e , and O e represent the current-layer modeling error, the tropospheric modeling error, and the other errors, respectively.Due to differences in receiver errors between the GPS and Beidou systems, there exist quality variations in the pseudorange signals between these two systems.In order to improve the accuracy and establish a scientific stochastic model, this paper adopts the Hekmert variance component estimation method to construct a combined positioning stochastic model for the dual-system.
The following steps are taken to establish the stochastic model based on the Hekmert variance component estimation process during the GPS and Beidou combined positioning solution:  The GPS and Beidou pseudorange data are a priori weighted P G and P B in a 1:1 ratio for initial positioning;  Calculate the 3D position coordinates and receiver clock difference parameters based on the least squares squared difference principle, and at the same time calculate the V i T P i V i (i = G, B) results of the two systems GPS and Beidou respectively;  The V i T P i V i results of the two systems obtained after the previous leveling are estimated the variance components according to the following equation.
The fusion of GPS and BeiDou positioning can increase the number of positioning satellites, improve the coverage and strengthen the anti-interference ability of the positioning system.In addition, through Helmert conversion, the weights of different systems can be adjusted according to the error situation, effectively identifying and eliminating the error components in each system, thus improving the accuracy and reliability of positioning and realizing higher precision position calculation.

Experimental results and analyses
In order to further validate the positioning accuracy of the GPS/BeiDou fusion positioning technology and to comprehensively assess its performance, this study conducted a series of comparison experiments on a self-built positioning platform.These experiments aim to explore the accuracy differences between different positioning methods and to determine whether the fusion positioning technology can significantly improve the positioning accuracy.During the experiments, 40 GPS positioning, BeiDou positioning and GPS/BeiDou fusion positioning were conducted respectively.And the following data were obtained:    From the figure, it can be seen that the accuracy under GPS/BeiDou fusion positioning is between 0.5 and 1.5cm.The analysis shows that GPS/BeiDou fusion positioning technology has performance advantages in several aspects.First, it can effectively utilize the advantages of GPS and BeiDou to eliminate their respective positioning errors.GPS requires high signal strength and receiver performance, while BeiDou has less impact on the receiver but lower accuracy.By fusing the two, GPS can provide highly accurate data to correct for BeiDou, ensuring signal stability and reliability.This can maximize the advantages and achieve higher positioning accuracy.Second, fusion positioning technology enables more comprehensive processing and analysis of the signal.Compared with the use of GPS or BeiDou alone, it uses complex mathematical algorithms and a complete data model for accurate position estimation and error correction.It takes full advantage of the data variability of GPS and BeiDou, resulting in improved accuracy and reliability.In conclusion, GPS/BeiDou fusion positioning technology excels in accuracy, reliability, fault tolerance and robustness.

Conclude
In this paper, starting from the problem that a single positioning system cannot meet the needs of grounding line positioning, we propose the GPS/BeiDou fusion positioning method, and by using Hekmert variance component estimation method to solve the problem of quality difference between the pseudo-ranging signals of the GPS positioning method and BeiDou positioning method, which significantly improves the positioning accuracy and precision of the grounding line.The application of this method will have a positive impact on the condition monitoring of grounding line and the safe operation of the power system, improve the work efficiency and protect the safety of the staff.In future research and applications, the fusion positioning algorithm can be further optimised and improved to achieve a higher level of positioning accuracy and to explore its potential for application in other fields.

Figure 2 .
Figure 2. GPS/Beidou Fusion Positioning Principle.As shown in Figure2, satellites transmit three-dimensional position information to the GPS/Beidou module.Through frequency conversion and signal demodulation, the position information is decoded and stored in the memory, retaining the current position information.This enables a hybrid positioning approach with a combination of some Beidou data and some GPS data.This fusion-based positioning system greatly improves the accuracy of localization and allows the two positioning systems to complement each other.In the process of GPS/Beidou positioning, the pseudorange observation equation can be expressed as follows:

Figure 3 .
Figure 3. GPS Positioning.The horizontal coordinate of the line graph is the number of times, and the vertical coordinate is the positioning accuracy in m.From the experiment, it can be seen that the accuracy under GPS positioning is between 1~2cm.

Figure 4 .
Figure 4. Beidou Positioning.Figure4represents the coordinate accuracy under BeiDou single-mode positioning, from which it can be seen that the accuracy under BeiDou single-mode positioning is in the range of 3 to 6 cm.

Figure 4
Figure 4. Beidou Positioning.Figure4represents the coordinate accuracy under BeiDou single-mode positioning, from which it can be seen that the accuracy under BeiDou single-mode positioning is in the range of 3 to 6 cm.

Figure 5 .
Figure 5. GPS/Beidou fusion positioning.From the figure, it can be seen that the accuracy under GPS/BeiDou fusion positioning is between 0.5 and 1.5cm.The analysis shows that GPS/BeiDou fusion positioning technology has performance advantages in several aspects.First, it can effectively utilize the advantages of GPS and BeiDou to eliminate their respective positioning errors.GPS requires high signal strength and receiver performance, while BeiDou has less impact on the receiver but lower accuracy.By fusing the two, GPS can provide highly accurate data to correct for BeiDou, ensuring signal stability and reliability.This can maximize the advantages and achieve higher positioning accuracy.Second, fusion positioning technology enables more comprehensive processing and analysis of the signal.Compared with the use of GPS or BeiDou alone, it uses complex mathematical algorithms and a complete data model for accurate position estimation and error correction.It takes full advantage of the data variability of GPS and BeiDou, resulting in improved accuracy and reliability.In conclusion, GPS/BeiDou fusion positioning technology excels in accuracy, reliability, fault tolerance and robustness.

Table 1 .
Comparison of Beidou Positioning System and GPS Positioning System.