Research and application on intelligent monitoring and early warning system for Inner-Suspended gin poles

The pressure of the inner suspension pole body is one of the key control indicators that need to be focused on in the design and use of the pole. A real-time intelligent monitoring and early warning system for the working status of the internal suspension pole tower is developed to address safety issues such as excessive inclination, excessive force on the stay wire or support rope during the construction process, including pole body pressure monitoring. The system monitors the axial pressure and inclination angle of the pole body using an integrated sensor for the axial pressure and inclination angle of the pole body. The tension sensor monitors the tension of the lifting, pulling, and supporting ropes, and the anemometer monitors the environmental wind speed. The monitoring data is fed back to the monitoring system through a wireless transmission module, and the safety of the pole state is determined in real-time through an embedded algorithm. When the preset threshold is exceeded, an audible and visual warning is issued. A comparison was made between the actual lifting test and theoretical calculation values, and engineering applications were completed.


Introduction
The gin pole stands as one of the important tower erection equipment in power grid construction.Common types of gin poles include inner-suspended gin poles, double-rocker gin poles, and doubleboom gin poles.The choice among these type hinges on factors such as terrain, road conditions, and load requirements.Among these options, the inner-suspended gin pole finds extensive application for its simple structure, lightweight design, low operating costs, and convenient transportability.These advantages are particularly notable in tower erection construction in mountainous areas [1,2].However, the inner-suspended gin pole involves numerous guy-wires and bearing ropes.Throughout the construction process, the pole body must be inclined at a specific angle towards the lifting side to fulfill its hoisting function.The existence of multiple force-bearing ropes and ambiguous force conditions can introduce disparities between actual and theoretical force computations.Furthermore, the absence of efficient angle monitoring during inclined lifting may readily result in the inclination angle surpassing the design value.These circumstances could cause the gin pole to buckle or topple, giving rise to severe safety incidents [3,4].To ensure the safety of tower erection utilizing innersuspended gin poles, the development of an intelligent monitoring and early warning system (hereinafter referred to as "monitoring and early warning system") becomes imperative.This system enables real-time monitoring and early warning concerning key condition parameters of the gin pole.It furnishes condition parameters such as pole body's inclination angle and guy-wire tension to offer guidance to construction personnel as they carry out their operational tasks.

Figure 1. Layout of Inner-Suspended Gin Pole with External Guy-Wires in Tower Erection
During tower erection, one end of the lifted component is connected to the power system (motorized winch) through the lifting rope, lifting pulley block, and corner block, while the other end is connected to the control rope.In order to facilitate the lifting and positioning of the lifted component, the gin pole body necessitates an appropriate inclination towards the lifted component side.At this point, the guy-wires of the gin pole situated on the opposing side are experiencing tension to prevent the gin pole from toppling.With the gradual elevation in the erected tower's height, the suspended support position of the gin pole ascends accordingly.This cyclic process continues until the entire tower is erected.
It is evident that the external guy-wires of the gin pole maintain the equilibrium and stability of the gin pole.The gin pole body bears the compression load arising from the lifted component and the guywires, while the bearing ropes support both the weight of the gin pole and the load transmitted from the lifted component through the pole body.

Computation of Principal Component Forces
The decomposed force distribution during the tower erection of an inner-suspended gin pole with external guy-wires is depicted in Figure 2. Assuming a linear configuration for all wireropes, disregarding the impacts of deflection of wireropes such as guy-wires, the computational formulas for each individual component are deduced as follows.
(1) Lifting rope forces The computational formula for the resultant force of the lifting rope (lifting pulley block and lifting point rope) is as follows: In which, T -Resultant force of the lifting rope (lifting pulley block and lifting point rope), in kN.
In which, T0 -Static tension on the tow rope, in kN; n -Number of working ropes among the lifting pulley block wireropes, i.e., the ratio; η-Block efficiency, η=0.96.
(3) Static tension on gin pole guy-wires Typically, the gin pole's inclination angle ranges from 5º to 10º.When subjected to the gravity of the lifted component, only the tension on the two primary guy-wires is taken into account.To account for layout errors, a balancing factor of 1.3 is introduced for the two guy-wires.The resultant force of the two primary guy-wires is calculated as follows: sin( ) cos( ) Through the substitution of Equation (1) into Equation (3), the resulting equation is: In which, Ph -Resultant force of primary guy-wires, in kN; γ -Angle between the resultant force line of the gin pole guy-wires and the ground, in º; δ -Angle between the gin pole axis and the vertical line (i.e., gin pole's inclination angle), in º.
The static tension on each individual primary guy-wire can be expressed as:

2 cos
In which, P -Static tension on the primary force-bearing guy-wire, in kN; θ -Angle between the guy-wires on the force-bearing side and the resultant force line, in º.
(4) Computation of gin pole body forces In which, N0 -Axial compression on the gin pole exerted by the lifting rope and the gin pole guywires, in kN.
Through the substitution of Equation ( 1) into Equation ( 6), the resulting equation is: The calculated composite compression on the gin pole shall include the compression exerted by the tow rope on the gin pole, thus: In which, N -Calculated composite axial compression on the gin pole, in kN.
(5) Bearing ropes The bearing ropes bear not only the external load on the gin pole but also the gravity of the gin pole and its accessories such as guy-wires.
1) When the gin pole is in a vertical state: In which, S1 -Resultant force of two bearing ropes, in kN; N -Calculated composite axial compression on the gin pole, in kN; G0 -Gravity of the gin pole and its accessories like guy-wires, in kN;  -Angle between the resultant force line of the two bearing ropes and the axis of the gin pole, in º.
2) When the gin pole is inclined in the force-bearing direction, the resultant force of the bearing ropes on the force-bearing side exceeds that on the opposite side, with its value as follows: In which, S2 -Resultant force of the bearing ropes on the force-bearing side when the gin pole is inclined in the force-bearing direction, in kN.
φ-Angle between the resultant force line of the bearing ropes on the force-bearing side and the axis of the gin pole, in º.

Determination of Monitored Parameters
(1) Pole body compression.During the tower erection process utilizing inner-suspended gin poles with external guy-wires, the gin pole body is subjected to compression.Its design and operation are under the control of stability.Excessive axial compression on the gin pole body can lead to consequential secondary deformations and the generation of additional bending moments within the gin pole.Under such circumstances, the applicability of the force computational formulas in Section 2 becomes inapplicable [5,6].Consequently, the electric power industry standard DL/T 319-2018 General Technical Conditions and Test Methods for Holding Pole of Overhead Transmission Line Construction specifies the permissible axial compression for the body of the inner-suspended gin pole.Data for some models are presented in Table 1 (2) Pole body's inclination angle.When the pole body's inclination angle exceeds 10°, both the axial compression on the pole body and the load on the guy-wires will experience a rapid escalation, which can lead to stresses on various components approaching their safety limits swiftly.
(3) Lifting weight.Surpassing the rated lifting capacity will lead to an inadequate safety margin for the gin pole.The electric power industry standard DL 5009.2-2013Code of Safety Operation in Power Engineering Construction and relevant company safety regulations rigorously mandate that the lifting weight must remain within the rated lifting capacity.
(4) Loads on guy-wires and bearing ropes.Guy-wires and bearing ropes exceeding their load limits could result in abrupt alterations in the gin pole condition, potentially pushing it into an unstable state.The electric power industry standard DL/T 319-2018 General Technical Conditions and Test Methods for Holding Pole of Overhead Transmission Line Construction mandates that members and flexible accessories must maintain a safety factor of no less than 3.
Based on the preceding analysis, it is imperative to monitor compression on the inner-suspended gin pole body, pole body's inclination angle, lifting weight, and the loads on guy-wires and bearing ropes.Furthermore, the influence of wind speed on construction shall be taken into account.

Development of Monitoring and Early Warning System
Existing monitoring and early warning systems for inner-suspended gin poles primarily concentrate on monitoring the tension on guy-wires and bearing ropes, while disregarding the axial compression on the pole body [7,8].This paper presents an intelligent monitoring and early warning system for innersuspended gin poles, which utilizes cutting-edge sensor technology to facilitate real-time monitoring and analysis of factors such as axial compression, spatial inclination angle of the inner-suspended gin pole body, tension on guy-wires and bearing ropes, lifting weight, and environmental conditions.The system further incorporates an intelligent early warning device based on preset threshold values.Built with a modular design, the monitoring and early warning system displays real-time force value, temperature, humidity, wind speed, inclination angle, and other pertinent information at its terminal.It presents several benefits, including manual-free operation, real-time computation of early warning thresholds based on current conditions, data accuracy, and reliable warning.This system finds applicability across inner-suspended gin poles of varying cross-sectional sizes, playing a pivotal role in supporting their construction and bolstering operational safety [9].

Composition of Monitoring and Early Warning System
The monitoring and early warning system utilizes a minimal sensor configuration model, comprising an axial compression-inclination angle integrated monitoring module for the pole body (incorporating temperature and humidity sensors), force sensors (for measuring lifting weight, as well as tension on guy-wires and bearing ropes), wind speed sensor, gateway, display terminal, and warner (see Figure 3).(2) Guy-wire force sensors and bearing rope force sensors provide real-time monitoring of the tension on guy-wires and bearing ropes.Real-time analysis of axial compression on the gin pole body is conducted through edge computing.This result is then subjected to contrastive analysis with the data from the axial compression monitoring module for the pole body, ensuring closed-loop monitoring information.
(3) The wind speed sensor monitors the wind speed at the construction site in real time, contributing to the analysis of the gin pole forces.It also warns on-site operators, ensuring that construction adheres to the safety regulations regarding wind speed.
The monitoring and early warning system exhibits exceptional responsiveness and a rapid data acquisition rate.It leverages wireless transmission to ensure a long transmission range and employs multi-frequency signal transmission alongside forward error correction to guarantee both safety and reliability.The edge nodes function in a low-power mode, affording prolonged standby periods.Moreover, the system is outfitted with a high-decibel warner to ensure favorable warning effects.

Parameters of Monitoring and Early Warning System Model
Based on the cross-sectional width of the inner-suspended gin pole body, the current array of models offered for the monitoring and early warning system is tailored for gin poles featuring crosssectional widths of 500, 600 and 800 (see Table 2).Moreover, the option of customization is readily accessible to cater to precise gin pole specifications.he installation of the pole body compression sensor for the monitoring and early warning system is shown in Figure 4.The experiment encompassed the lifting of the curved arm of a specific wine glass-shaped tower, bearing a load of 620kg (equivalent to 6,076N).
The inclination angle of the gin pole body, measured by the axial compression-inclination angle sensor on the pole, was recorded as (1.28°, 2.52°).The monitoring curves for the lifting weight, pole body compression, and tension on one of the bearing ropes are shown in Figure 5. Their values stand at 6,274N, 39,524N and 10,094N, respectively.The monitored lifting weight value measures 6,274kN, with an error of 3.4%, well within the specified engineering accuracy requirements.Employing the computational formulas presented in Section 2, the derived pole body compression totals 33,687N, while the tension on one of the bearing ropes stands at 8,598N.Given that all sensors within the monitoring and early warning system underwent calibration prior to utilization, their readings can be deemed true values.The primary source of error arises from the inherent inaccuracy of the theoretical computational model, which is influenced by the presence of sag in the guy-wires.(Transmission tower heights typically span from 60m to 120m, and taller structures exhibit greater wirerope sag, thereby resulting in more pronounced disparities between theoretical models and real-world conditions.)Moreover, variations in the lengths of different guy-wires and bearing ropes, errors in angle measurements of lifting and control ropes, and other contributing factors collectively contribute to the observed error.

Engineering Application
In Section Yu-1 of the ±800kV Baihetan-Zhejiang UHVDC Transmission Project, the intelligent monitoring and early warning system for inner-suspended gin poles was applied to the erection construction of several foundation towers, including SN2064, SN2092 and SN2152 (see Figure 6).The system undertook comprehensive monitoring and early warnings concerning the operational conditions of inner-suspended gin poles, including axial compression and inclination angle of the pole body, tension on guy-wires, bearing ropes, and lifting wireropes, along with wind speed, temperature, and humidity.This system effectively tackled the challenges associated with uncertain on-site operational conditions and the complexity of safety supervision, which ensured the quality and safety of tower erection construction of the transmission line.

Conclusion
In response to the issues arising from relying solely on visual observation and experiential judgment to determine the construction status of tower erection using inner-suspended gin poles, coupled with poor safety, this paper proposes a safety early warning system for the real-time monitoring of operational conditions of inner-suspended gin poles.The system ensures that while erecting the tower, a range of monitored parameters -including the axial compression on the inner-suspended gin pole's body, inclination angle, tension on guy-wires and bearing ropes, and lifting weight -are all maintained within their safety threshold ranges.It significantly boosts the safety of tower erection utilizing innersuspended gin poles and facilitates construction personnel in obtaining real-time conditions such as the gin pole's inclination angle.This system has been utilized in the erection of several foundation towers in Section Yu-1 of the ±800kV Baihetan-Zhejiang UHVDC Transmission Project.The outcomes underscore its stability and reliability, suggesting a promising outlook for its future applications.

Figure 2 .
Figure 2. Force Diagram of Inner-Suspended Gin Pole with External Guy-Wires during Tower Erection (2) Static tension on tow ropes

1 -Figure 3 .
Figure 3. Composition of Monitoring and Early Warning System(1) The axial compression-inclination angle integrated monitoring module for the pole body is outfitted with four high-precision force sensors, enabling real-time monitoring of the force-bearing conditions across the four primary limbs on the gin pole body.A 3D inclination angle sensor monitors the spatial inclination angle of the gin pole body in real time, offering insights into its inclination state.Based on the lifting weight value gauged by the lifting force sensor, the built-in algorithm performs real-time computing to ascertain the gin pole's safety and stability under the current load conditions.(2)Guy-wire force sensors and bearing rope force sensors provide real-time monitoring of the tension on guy-wires and bearing ropes.Real-time analysis of axial compression on the gin pole body is conducted through edge computing.This result is then subjected to contrastive analysis with the data from the axial compression monitoring module for the pole body, ensuring closed-loop monitoring information.(3)The wind speed sensor monitors the wind speed at the construction site in real time, contributing to the analysis of the gin pole forces.It also warns on-site operators, ensuring that construction adheres to the safety regulations regarding wind speed.The monitoring and early warning system exhibits exceptional responsiveness and a rapid data acquisition rate.It leverages wireless transmission to ensure a long transmission range and employs multi-frequency signal transmission alongside forward error correction to guarantee both safety and reliability.The edge nodes function in a low-power mode, affording prolonged standby periods.Moreover, the system is outfitted with a high-decibel warner to ensure favorable warning effects.

Figure 4 .
Figure 4. Installation of Pole Body Compression Sensors

Figure 6 .
Figure 6.Engineering Application of Intelligent Monitoring and Early Warning System for Inner-Suspended Gin Poles

Table 2 .
Key Technical Parameters of Monitoring and Early Warning System In order to validate the reliability and stability of the monitoring and early warning system for innersuspended gin poles, experiments were conducted at the Emergency Rescue Training Base of Heilongjiang Provincial Transmission and Transformation Engineering Co., Ltd.These tests were specifically directed towards the monitoring and early warning system for gin poles with a crosssectional width of 500.The key technical parameters of the gin pole employed are outlined in Table3.

Table 3 .
Key Technical Parameters of Tested Gin Pole