Research on Energy Efficiency of Typical Construction Equipment for Transmission Lines in Tibet

The construction of transmission line in Tibet high altitude area has the characteristics of low pressure, low oxygen and low temperature. In the special environmental condition, the transmission line construction equipment with engine as the power source is highly effective, which affects the efficiency and safety of construction[1].The experimental study on engineering mechanical industry plateau transmission line is still in the blank stage,thus relying on the Tibet networking project selects 5 different high altitude test points to plateau 500kV transmission line construction commonly used types of pullers, tensioners and powered winch as an object of study to carry out the typical construction equipment energy efficiency test of field measurements effective output power equipment in different altitude environment from the perspective of practical application and analysis of law and effect mechanism of falling equipment.


Introduction
The Tibet area has a special environment with high altitude, high cold, anoxia and so on. The bad construction conditions cause the engineering construction personnel and the machinery to reduce the efficiency seriously. With the increase of EHV power transmission project construction projects in Tibet area, 500kV transmission line voltage will gradually become the backbone network in Tibet power grid, the special construction environment, increase construction quantity and construction workers in the Tibet area that will be more dependent on machinery [2]. Therefore, in the Tibet area to carry out research on typical construction equipment adaptability, analysis of its height decreases and regularity of effect mechanism in different altitude, and puts forward some concrete measures for typical construction equipment and reduce efficiency reduction principle, equipment capacity, construction personnel can reduce the labor intensity and improve the construction efficiency for future power grid construction in high altitude area to give full play to.

Test object and method
The energy efficiency test of the typical construction equipment is aimed at the environmental characteristics of the high altitude environment in Tibet, and carries out the research on the pullers, tensioners and powered winch application with the engine as the power source in the transmission line construction equipment.The experimental research samples are commonly used in the 500kV transmission line projects in Tibet area, such as pullers, tensioners and powered winch as the research sample [3], the details are shown in Table 1. The typical construction equipment efficiency test method is to use the test sample equipment as the traction terminal, the auxiliary equipment as the braking terminal to pull through the wire rope, the test layout is shown in Figure 1 to 3, and the test condition is shown in Table 2.The test is carried out by using the sample machine to drive the auxiliary machinery at the maximum speed at the same load and engine speed. At the same time, the dynamic wireless sensor and the wire rope speed measuring device are used to record the tension and speed data during the whole test.

Test implementation
Select 5 different high altitudes test points as the data acquisition point in the area of Tibet [4]; select 1 plain test points as a reference point in Zhengzhou. The typical construction equipment efficiency test were carried out a total of 6 test points, the scene is shown in Figure 4, the specific implementation place as shown in table 3.

Data processing method
The data collected by the dynamic wireless tension sensor and the wire rope speed measuring device used during the test are all the database with frequency of 5Hz.The tension time curve and the speed time curve are drawn into two databases, and the two curves are compared by the time zero point reclosed.From the whole process of the test selection of tension relatively stable and relatively stable period of time speed as the effective time period, as shown in Figure 5.
The data in the effective time segment is calculated according to the power point formula, and the average value of all data points in the effective time period is taken as the last effective output power [5], as shown in Figure 6.

Data results
A summary of the effective output power collation of 6 test points is summarized as shown in Table 4.  From table 4, it can be seen that the effective output power of the typical construction equipment is gradually reduced with the elevation of the altitude test points.

Result analysis
The test results of high altitude test are compared with the results of the benchmark datum in the plain. The average reduction range of different load cases is used to reflect the descending effect of the typical construction equipment at the altitude test point. It is summarized and summarized as shown in Table 5, and is drawn up and made into a chart as shown in Figure 7. In typical construction equipment samples, the engine of traction and tension machine is a diesel engine with turbocharger, and the motor form of engine is a turbocharger diesel engine.

Conclusion
The adaptability of typical construction equipment is studied based on the Tibet Internet project. The eff effective output power of the typical equipment is taken as the research object, and the effective output power of the equipment is measured: (1) The typical construction equipment energy efficiency test results representation in the special environment of Tibet low, hypoxia and low temperature, choose to adapt to the harsh construction environment to maintain a certain amount of reserve power construction equipment can be better with a turbocharged engine and use conditions.
(2) Under the restriction of construction hardware conditions, we can also take the efficiency reduction test curve of typical construction equipment in Figure 7 as reference for selection, and consider the factors such as old equipment, engine calibration power and other factors.
(3) In the research and design of special plateau type construction equipment, it is recommended to consider comprehensively from two aspects of engine power margin and practical measures, and enhance the applicability of equipment through overall design accounting.