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Parameter Measurements of Pantographs and Contact Line Systems
CHAPTER 9
Parameter Measurements of Pantographs and Contact Line Systems 329
9.1 OVERVIEW With the development of theoretic research on interactions between pantographs and contact lines, measuring techniques and measuring devices for technical evaluation and diagnosis of pantographs and overhead contact line systems are born at the right moment. Measuring techniques and devices developed under the requirement of technical evaluations and diagnosis can be used in the following three aspects: j
j
j
Evaluating only pantographs. Taking a pantograph as an independent component, use the vibration test table to apply excitation at corresponding amplitude and frequency to the pantograph and measure dynamic response parameters of pantographs at the same time to evaluate dynamic performance of pantographs based on measured results. Evaluating only contact lines. Measure the initial position of the contact wire and contact wire lift under a special uplift force, and calculate elasticity of the contact line based on the measured result; inspect accessories of the contact line at regular intervals, especially the position of the steady arm and registration arm and clearance between the live part and support device and tunnel wall; and measure residual thickness of the contact wire within certain operation cycles and forecast its service life. Evaluating dynamic interaction between pantographs and contact lines. In addition to dynamic contact force, contact wire lifts, running traces of heads, number of arcs and arcing time have been deemed as parameters for evaluating pantographs and overhead contact line dynamic performance.
For parameters of evaluating pantographs and overhead contact line dynamic performance and measurement requirement, see Table 9.1. Besides arc rate, the parameters in Table 9.1 also have the following characteristics: j
evaluating continuous and progressive change of contact quality, not only providing the comment of “Yes/No”;
Pantograph and Contact Line System. http://dx.doi.org/10.1016/B978-0-12-812886-2.00009-4 Copyright © 2018 Elsevier Inc. All rights reserved.
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Pantograph and Contact Line System Table 9.1 Parameters of Evaluating Pantograph and Overhead
Contact Line Dynamic Performance and Measurement Requirement
Purposes
Parameter Types
Parameters
Evaluate pantographs
Dynamic characteristics of pantograph
Amplitude and frequency of pantograph
Evaluate contact lines
Characteristics of contact line
Transverse and vertical parameters of contact wire Abrasion of contact wire Elasticity of contact line Slope of steady arm
Evaluate pantograph and overhead contact line dynamic interaction
Pantograph and overhead contact line dynamic performance
Pantograph and overhead contact line contact force (or arc rate) Running trace of head Uplift of contact wire at registration point
Electric contact performance Temperature of pantograph of pantograph and contact and overhead contact line line contact point (or of contact wire)
j
j
j
allowing actual measurement and simulation calculation for the convenient comparison of the measured result and forecasted result; in the same condition, repeated measurements have the identical result and are not influenced by random factors; and evaluation parameters of pantographs and overhead contact line dynamic interactions are measurable on dynamic pantographs.
Early references also take the number and duration of arcs as the physical quantity of evaluating pantographs and overhead contact line contact quality. However, if there is no, or very rare, arc, such characteristics will be useless to the comparison of pantographs and overhead contact line systems. Arcs cannot be simulated. Measurements show that the result of repeated tests cannot be reproduced even on the same line and in the same condition. Arcs are also associated with currents through pantographs and overhead contact line contact points. If there are no currents through such points, even pantographs and overhead contact line contact quality are bad, no apparent arcs will appear in pantographs and overhead contact line systems. Obviously, evaluating pantographs and overhead contact line contact quality with arc rate has some limitations. For the sake of effective quality evaluation and technical diagnosis on contact lines and pantographs and overhead contact line systems, each railway
Parameter Measurements of Pantographs CHAPTER 9 department has developed a measurement technology and method based upon its own need to obtain measured value of quality evaluation parameters. These technologies and methods can be applied to the parameter measurement of pantographs, as well as parameter measurements of contact lines and pantographs and overhead contact line interactions, but they should conform to applicable measurement requirements.
9.2 MEASUREMENT OF DYNAMIC CHARACTERISTIC PARAMETERS OF PANTOGRAPHS Fig. 9.1 shows the pantograph vibration test table of Deutsche Bahn. This test table utilizes a vertical lifting support to simulate progressive changes of contact wire heights, such as drops or lift of contact wires; another horizontal support that can slide is mounted in the vertical support and can simulate reciprocating movement of contact wires on strips. The exciter is mounted on the horizontal sliding support to generate a vertical vibration acting on the head. Excitation signal acting on the exciter, horizontal,
FIGURE 9.1 Vibration test table of pantograph.
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Pantograph and Contact Line System and vertical supports can be derived from operation test records of actual lines or simulated by computers based on models of contact lines. Vibration test tables can be used to analyze and evaluate the dynamic properties of pantographs. To reach such a purpose, pantographs are connected to exciters through strips and subject to vibrations. The measurement systems calculate associated parameters, such as various forces, acceleration, and shifts, and evaluate them.
9.2.1 Measurement Frequency Response To analyze vibration performance of pantographs within various freedom ranges and verify that it has no excessive reaction, the exciter and pantograph strips are connected as loosely as possible and dynamic excitation at 0.1–70 Hz is applied to the heads through exciters during frequency response analysis. Depending on the pantograph, excitation force systems with measurement devices and frequency response analyzers can obtain the following characteristics of pantographs: j j j j
dynamic apparent mass function; mechanical impedance; disturbance transfer function; and transfer function of contact force measurement system.
These parameters show a relation between frequency and amplitude and phase, the two measured quantities, and can be expressed with response functions. Dynamic performance and the operation quality of pantographs can be inferred from the form of response functions. Dynamic apparent mass actually expresses the relation between the excitation force (contact force) and strip vibration, and can be used as a reference for evaluating the dynamic performance of the pantograph. If the pantograph has an ideal operation performance, there should be only several forms of weak natural vibrations on its apparent mass graphic, even when the apparent mass is small. A similar conclusion can be inferred from disturbance transfer functions of pantographs. A disturbance transfer function is the ratio of contact force to amplitude excited by coupling pantographs to contact line models (mass-spring buffer systems). The frequency response analysis method can be used to study dynamic performance of pantographs on test tables, and identify improvement measures of the dynamic performance of pantographs based on study results, to save costs for line operation tests. Important data required by building simulation models and evaluations can be obtained through measurement and analysis methods of frequency responses. A simulation model is the mathematic form describing dynamic performance of pantographs. Linking simulation models of pantographs to that of overhead
Parameter Measurements of Pantographs CHAPTER 9 contact lines will be useful for quantitative research on dynamic interaction between pantographs and contact lines.
9.2.2 Structure Analysis Simple optical structure analysis can be conducted on vibration test tables using stroboscopes. Short-time intermittent exposure of a part of the pantograph can be used to monitor the vibration state of such a part. Wave nodes and wave loops (in extreme conditions) of vibrations may produce fatigue failure. Conclusion of material stress during operations can be obtained depending on the structure of wave nodes and loops.
9.2.3 Line Operation Simulation When analyzing frequency responses, periodic or random excitation signals can be transferred to pantographs. In actual operations, only limited measurement and evaluation on movement parameters and mechanical stress can be conducted. Simulated line operation on test tables can generate parameters of dynamic interaction between pantographs and special contact lines. Through simplified contact line models, changes of contact wire heights, impacts of lateral positions of contact wires, and strong impacts on dynamic movements of excitation on pantographs can be considered. Operation performance of pantographs in different design structures of contact lines can be precisely evaluated through the calculation of associated parameters, such as internal force and contact force.
9.3 MEASUREMENT OF SPATIAL POSITION PARAMETERS OF CONTACT WIRES As shown by measured results of pantographs and overhead contact line contact forces, discontinuity of the spatial position of contact wires may usually lead to large transient changes of pantographs and overhead contact line contact forces. Such discontinuity is reflected in height directions of contact wires, and also in shift directions of contact wires from the centerline of heads. From the view of conforming to dynamic performance and operational safety of pantographs and contact lines, designing correct spatial positions of contact wires for corresponding lines is very important. Moreover, prior to dynamic evaluation on completed contact lines, noncontact measurement equipment will be used to inspect the spatial position of contact wires to ensure conformity of it to design requirements. The spatial positions of contact wires are measured in static and dynamic conditions. Without external disturbances (in static condition), the spatial positions of contact wires obtained are static parameter; with dynamic interaction with pantographs (in dynamic condition), the spatial positions of contact wires obtained are dynamic parameters. Usually, noncontact measurement equipment is used to acquire the static spatial position the parameter of contact wires.
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Pantograph and Contact Line System Portable measuring devices, measuring devices mounted on ladder trolleys, and measuring devices mounted on inspection cars can be utilized to measure the spatial position contact wire parameters.
9.3.1 Portable Optical Measuring Device Laser measuring device is a kind of portable optical measuring device imaging contact wire through lens system with crossline and sighting device to identify position of contact wire, as shown in Fig. 9.2. Once contact wires can be seen at the crosslines, contact wire heights can be identified depending on shifts of optical systems from millimeter scales. A change of 1 mm on the scale is equivalent to a 10-mm height difference of contact wire. To acquire accurate measured data using laser measuring devices, a lot of practices and verification are conducted. Portable measuring devices for spatial positions of contact wires are often used to measure and verify lateral and vertical parameters of some specific points on contact lines.
9.3.2 Onboard Measurement Device 9.3.2.1 MEASUREMENT DEVICE MOUNTED ON LADDER TROLLEY Mounting noncontact optical sensors onto the mobile ladder trolleys can realize continuous measurement of spatial position of contact wires. Fig. 9.3 shows the measurement devices mounted on ladder trolleys.
FIGURE 9.2 Manual measurement of spatial position of contact wire using laser measuring device.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.3 Spatial position–measuring device mounted on ladder trolley.
Fig. 9.4 shows the measurement principle of the optical sensor. The illuminator will light up the lower surface of the measured contact wire. Bright spots are imaged in a CCD camera. According to the spot imaging position in CCD cameras, the lateral and vertical distance of contact wires to CCD cameras can be identified. Then, spatial positions of contact wires relative to rail levels can be acquired through some calculations. Prior to measuring, using a ladder trolley measuring device, use a portable optical measuring device to calibrate and verify it.
FIGURE 9.4 Principle of optical measurement.
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FIGURE 9.5 Relation curve of spatial position and shift of contact wire.
When the ladder trolley moves on the rail level, it will have no shaking and side shift from rail levels. The spatial position information of contact wire acquired by the device is the static spatial position parameter of the contact wire desired. When the measuring device is mounted on other rail cars, shaking and side shifts of cars from rail levels during movement will influence measured results of spatial positions of contact wires. Necessary measures are taken to eliminate such influence. Therefore, shaking and side shift of vehicles from rail levels are measured at the same time, and measured results of optical measuring devices are corrected to acquire spatial positions of contact wires relative to rail levels. Combining spatial positions of contact wires with shifts of vehicles running along lines can generate the relation curve of spatial positions and shifts of contact wires, as shown in Fig. 9.5.
9.3.2.2 MEASUREMENT DEVICE MOUNTED ON INSPECTION CAR Fig. 9.6 shows the measurement principle of a type of spatial position–measuring device that is mounted on an inspection car and developed by Deutsche Bahn. Such a device consists of three spotlights with high condensation, four high resolution cameras, and a data processor, which can measure spatial position and abrasion face width of contact wires and calculate area loss of contact wires depending on abrasion face width. Spotlights and cameras mounted on the roof are shown in Fig. 9.7. Intervals of data samplings on measuring devices depend on travel speeds and design speeds, and is approx. 80 mm at 300 km/h. Its precision of detecting contact wire heights and lateral shifts is up to 5 mm. In operations of vehicles, the car body will shake, shift laterally, and vibrate, which cannot be entirely recorded or detected, so the precision of detection is impaired. Considering that, the total deviation of detection is modified to 10 mm (vertical parameter of contact wire) and 20 mm (lateral parameter of contact wire). This device can also measure static spatial positions of contact wires effectively and quickly at travel speeds more than 330 km/h to identify directions and
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.6 Principle of a type of spatial position–measuring device.
FIGURE 9.7 Spotlights and cameras mounted on roof.
targets for repairs of contact lines. When detecting static spatial positions of contact wires, the inspection car is towed by a diesel rail car to avoid changes of spatial positions of contact wires due under the uplift force of pantographs. This device can also be used to observe and record pantographs and overhead contact line interactions. In such a case, the inspection car is towed by a locomotive. The vertical parameters of contact wires acquired are the spatial position parameters under uplift forces of pantographs. Measurements can be conducted in any weather condition, except for heavy snow. Notwithstanding, when in cold or damp weather, or the inspection car is
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Pantograph and Contact Line System stopped outdoors overnight, the lens of the camera may be foggy and the shooting quality may be reduced. In such a case, the viewing window is connected to warm wind for 1 h to remove fog on the lens. If this doesn’t work, open the lens cover of the camera and wipe the glass surface of the lens using a soft cloth. Prior to starting measurements, identify the precision of the measuring device. This device can be used to measure the contact line of a short test section containing linear and curves. Then, measure such a test section manually by using a portable laser measuring device and comparing two groups of data. Through this method, a sensor can be correctly calibrated to ensure that the measuring device is in good condition. When the measurement is completed, measured results of spatial position parameters of contact wires can be outputted with a printer in an offline state. Analytic programs can display spatial positions and residual thickness of contact wires, and also calculate dynamic uplifts depending on nondisturbance position data of contact wires and position data after uplifts of pantographs, and calculate the elasticity of contact lines based on the contact force data stored. Nondisturbance position parameter measurements for contact wires are often deemed as the measurement steps of acceptance procedures after completing adjustments of new or existing contact lines. Deviation of actual positions of contact wires from design values can be acquired from simulation records of measured data, as shown in Fig. 9.8. In addition to contact wire height and lateral parameter, other useful data can be displayed, such as kilometer post, mast position, dropper position, and contact wire slope. Dropper and mast positions are identified automatically by analytic programs.
FIGURE 9.8 Deviation of actual positions of contact wires from design values can be acquired from simulation records of measured data.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.9 Cross-section of contact wire after abrasion.
Besides manual inspection of measured data by operators, analytic programs also support automatic diagnosis, automatic analysis of measured data, and records of any defect of contact lines (critical record). Critical records include the following data: j j
j
overmaximum permissible lateral position; height difference between adjacent droppers is more than maximum permissible value; and overallowable counter slope at dropper.
The measuring device can measure the spatial position of the contact wire, and also measure the abrasion face width of the contact wire at the same time, and can identify the contact wire abrasion in a critical position. A cross-section of contact wire after abrasion is shown in Fig. 9.9. After measuring the abrasion face width W of contact wire directly, the area loss Av of the contact wire can be calculated indirectly using Eq. (9.1). A = v
π ⋅ r 2 ⋅ arcsin 180°
W 2 2 2r − W 4 r − W 4
(9.1)
9.4 MEASUREMENTS OF ELASTICITY OF CONTACT LINES Contact wire uplifts under unit uplift forces are called elasticity of contact lines. To measure elasticity of contact lines, two issues are solved: first, identify the initial height of the contact wire; and second, measure the contact wire height under a certain uplift force. Uplift of contact wires is equal to the difference of contact wire height before and after action of the uplift force. Thus, the height of contact wire in one section is measured twice to calculate elasticity of the contact line and uplift of contact wire depending on the results of the two measurements. First, measure the initial height of the contact wire. Adjust uplift force of simulated pantograph to 5–8 N to keep contact with the contact wire. However, a
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Pantograph and Contact Line System change of the initial position of the contact wire is minimized. Measure and record heights of contact wires at low speed. Noncontact measuring devices can also be used to acquire the height of contact wires. Second, measure the height of the contact wire under uplift force. Adjust uplift force of simulated pantographs to a specified value to keep them in contact wire with the contact wire. Measure and record height of the contact wire under uplift force. The uplift force is selected depending on average uplift force of pantographs selected in the contact line design. Usually, for the contact line with a target speed of 200 km/h, the uplift force of simulated pantographs can be 100 N; for contact lines with target speeds more than 250 km/h, uplift forces of simulated pantographs can be 120 N. To verify conformity of static performance of catenary suspensions in point ranges to requirements, simulated uplift forces of pantographs can be 250 N. In the end, the difference between the two measured results is the uplift of contact wires under a certain uplift force, and the ratio of such an uplift to uplift force is the elasticity of contact line. Combine elasticity of each point with kilometer posts of lines to acquire elasticity curves of contact lines corresponding to kilometer posts. Fig. 9.10 shows the simulated pantograph mounted temporarily on a catenary work car for measuring elasticity of the contact line. Data acquisition and data processing equipment is mounted in the car. Fig. 9.11 shows the measured elasticity curve. Here, stitched catenary suspension with a span of approx. 48 m is used for the contact line; the cross-section of
FIGURE 9.10 Simulated pantograph used in elasticity measurement.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.11 Measured elasticity curve of contact line.
messenger wire is 120 mm2 and tension of messenger wire is 23 kN; the crosssection and tension of the contact wire are, respectively, 150 mm2 and 28.5 kN; length and tension of the stitch wire are, respectively, 18 m and 3.5 kN; and structural height is 1.6 m.
9.5 MEASUREMENT OF PANTOGRAPHS AND OVERHEAD CONTACT LINE CONTACT FORCES 9.5.1 Basic Principle Pantographs and overhead contact line contact points are used to ensure the uninterrupted and faultless transmission of electric energy from contact lines to running electric trains through pantographs. To ensure reliable transmission of electric energy and minimize abrasion of strip and contact wires, pantographs and overhead contact line contact forces remain in a certain range: excessive contact force will cause increased abrasion and contact wire uplift while insufficient contact force will lead to frequent arcing and increase abrasion. Measured data of pantographs and overhead contact line contact forces can be used for evaluation and fault diagnosis of pantographs and overhead contact line dynamic performances. Measurement of pantographs and overhead contact line contact forces conform to the requirements in Section 4.5. According to Section 2.3, pantographs and overhead contact line contact forces are the vertical forces applied by strips onto contact wires, and the results of superposition of static contact forces F0, friction forces FR, aerodynamic forces FAER, and inertial forces FDYN. Measuring forces upon pantographs and overhead contact line contact points directly in dynamic conditions is impossible because contact points will move back and forth continuously on strips. Force sensors can be mounted directly at the joint between strip bases and the strips to measure contact forces, as shown in Fig. 9.12. In total, four force sensors are mounted under two strip rows of each pantograph. The sum of signals of left and right sensors of a strip row can reflect the contact force of a strip row, and that of four sensors can reflect the entire pantograph and overhead contact line contact force. The approximate position of contact wires on strips can be calculated using the sums of signals of sensors, right signals, and left signals on the basis of level principles.
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FIGURE 9.12 Pantograph with force sensors.
However, in this measurement, force sensors cannot record the mass inertia force acting on strips and aerodynamic forces related to operation speeds, and correction values are added to correct inertia forces and aerodynamic force of strips.
9.5.2 Technical Description of Measuring Device Measuring devices of pantographs and overhead contact line contact forces can measure vertical forces acting on contact lines, vibration acceleration of heads, positions of contact wires on strips (indirect calculation using signal of force sensor), head heights, and acceleration of pantograph bases. Acceleration of bases can reflect the impact of vehicle vibrations on pantographs and overhead contact line contact forces. Fig. 9.13 shows the structural diagram of the contact force–measuring device. All measuring sensors work in a high-voltage (HV) environment equipotential to pantographs. Signals of sensors, after being converted to digital signals on HV sides, will be transmitted to inspection cars at ground potential in optical forms and displayed and analyzed on data processors. Fig. 9.14 shows the pantograph with a measuring sensor. The measurement of the contact force is completed by four force sensors and four acceleration sensors mounted at a strip-fixing point. A force sensor is integrated with an acceleration sensor and they are mounted between the strip and support, as shown in Fig. 9.15. This connection manner requires a special sensor, and can measure vertical force precisely provided that the mechanical stability and head mass are not changed significantly. These force and acceleration sensors are provided with temperature compensation,
FIGURE 9.13 Structure of contact force–measuring device. HV, High voltage.
FIGURE 9.14 Layout of sensors (DSA380D pantograph). 1, Vertical force and acceleration sensor; 2, inductive sensor; 3, angular displacement sensor; 4, base acceleration sensor; 5, data acquisition unit; 6, optical data transmitter; 7, supply transformer.
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FIGURE 9.15 (A) Force sensor module with acceleration sensor and (B) mounted between strip and frame.
and connected to a data acquisition unit in the car through a special cable and connector. A force sensor should be as close as possible to the contact point. If force and acceleration sensors are mounted far from the strip, some flexible connections may appear between the sensor and contact point. This will reduce the range and accuracy of dynamic measurement. If force and acceleration sensors are mounted on two springs of the head, they will be incapable of measuring distribution of contact force on the two strips or analyzing measured values generated by the two strips. Distribution of force can provide necessary information for the correct working of pantographs and measured results. An acceleration sensor is mounted on the base of the pantograph. A sensor signal is used to identify the impact of track regularity and impact of base vibrations on contact forces. The output signal of the force and acceleration sensor is transmitted to a data acquisition unit for processing, and is often converted to a frequency-modulated pulse signal by an electronic module through an overvoltage/frequency (V/f) converter. The pulse signal can be converted to an optical signal and transmitted via an optical fiber. Electronic element equipotential to the contact line is mounted in a data acquisition unit as shown in Fig. 9.16. A data acquisition unit is fixed to the base of a pantograph through a special connection device to collect all sensor signals on the pantograph and convert them to optical signals. A special transformer can transmit electric energy from the control cabinet at ground potential to the pantograph component on the HV side. This transformer is provided with insulation strength withstanding against the voltage level of the contact line. To shorten an optical fiber, lead the optical fiber through an optical data transmitter, as shown in Fig. 9.17.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.16 Data acquisition unit mounted on pantograph base.
FIGURE 9.17 Power supply transformer (left) and optical data transmitter (right).
Measurement of pantographs and overhead contact line contact forces is often combined with measurement of other parameters of pantographs and overhead contact line systems, such as spatial positions of contact wires to acquire overall information of pantographs and overhead contact line system states. Fig. 9.18 shows an example of a graphic of measured result, where the shift of contact wire from the strip centerline is acquired through indirect calculation using the output of the force sensor.
9.5.3 Correction of Inertia Force of Strip Measuring gravity on vibrating objects may cause the so-called acceleration error. There is no exception for measurements of pantographs and overhead
FIGURE 9.18 Diagram of measured result.
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Pantograph and Contact Line System contact line contact forces. To identify actual forces acting on pantographs and overhead contact line contact points, an additional vector should be created to eliminate “intermediate” mass. Corrected mass of pantographs (one strip row) is equal to twice the sum of strip mass and mass of half force sensors (one strip row). To correct such an error, vibration acceleration of the strip is measured and the inertia force generated by strip is corrected.
9.5.4 Correction of Aerodynamic Force Force sensors measuring pantographs and overhead contact line contact forces are mounted below the strips, so the sensors cannot measure effects of aerodynamic forces on strips. To avoid missing an aerodynamic force component generated with running speed, a correction factor related to speed is added when calculating contact force. Aerodynamic force components are identified through measuring uplift forces under International Union of Railway (UIC) rules. Fig. 9.19 shows the method of measuring aerodynamic force. Fix the pantograph with a contact force– measuring device using two ropes so that each strip will not contact with the contact wire during operation. The clearance between the strip and contact wire is approx. 100 mm. Mount forces measure cells, respectively, to the lower parts of two ropes to record the forces transmitted by ropes to strips. Meanwhile, pantographs and overhead contact line contact force–measuring devices will also record the internal force under the strip. Vertical aerodynamic force (Faero = Faero_I + Faero_II) is equal to the difference between the force (Fseil = Fseil_I + Fseil_II) recorded by force measuring cells at the bottoms of the two ropes and the internal force (FS = FS_I + FS_II) recorded by the contact force–measuring device.
FIGURE 9.19 Correction of aerodynamic force.
Parameter Measurements of Pantographs CHAPTER 9 This measurement method can be used to identify the function relation between functions, such as aerodynamic force and operation speed acting on the strip, operation direction (pantograph joint pointing at operation direction/ reverse operation direction), and layout of the pantograph on the vehicle. Such a function relation can be written into system software for immediate correction of measured results of pantographs and overhead contact line contact forces.
9.6 MEASURING UPLIFT OF CONTACT WIRES AT REGISTRATION POINTS The fixed measuring device mounted on contact line supports can be used to correctly measure the uplift of contact wires at the registration point. This is necessary in the following cases: j
j j
in dynamic evaluation, verify conformity of design scheme of pantograph and overhead contact line system to standard; identify maximum allowable speed of new vehicle or pantograph; and fixed monitoring of pantograph in commercial operations.
In Fig. 9.20, regular monitoring of the uplift at the registration point is available at the support device through connecting the steady arm and rotary encoder with pretensioned rope. The insulated section is provided on a rope to realize potential isolation. The output of the encoder can be received directly by the computer to calculate uplift at the registration point. Fig. 9.21 shows the steady arm vibration–measuring device used by Shinkansen. Such a device can analyze contact wire uplift at the registration point, and also vibration of the steady arm and strain of the contact wire. The measuring device is divided into two parts. One part is mounted on the support device of the contact line, and equipotential to the contact line. The
FIGURE 9.20 Registration point uplift–measuring device with pretensioned rope.
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FIGURE 9.21 Steady arm vibration–measuring device used by Shinkansen. (A) Measuring device mounted on support device and (B) information-receiving device mounted in vehicle.
angular displacement sensor measuring steady arm vibration is connected to the end of the steady arm through fine wire. This part is fed by the battery and transmits information collected by it in a wireless form. The other part is an information-receiving and -processing device and is temporarily placed in the mobile vehicle. The vibration acceleration of the contact wire mainly represents the vertical vibration strength upon the conductor when the pantograph passes. Through measuring the bending strain of the conductor, bending strength upon the conductor can be identified and the antibending life of the conductor can be forecasted. Fig. 9.22 shows the noncontact displacement-measuring device mounted on the contact line mast of the Beijing–Shanghai high-speed railway line. It is used to measure contact wire vibrations at registration points. The measured result is shown in Fig. 9.23.
FIGURE 9.22 Noncontact contact wire vibration displacement–measuring device mounted on mast.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.23 Vibration at registration point for double-pantograph collection. Contact line wire combination: JTMH120 + CTMH150; tension combination: 20 + 40 kN; distance between pantographs: 197 m, pantograph model: DSA380; maximum uplift of front pantograph is 81 mm and that of rear pantograph is 99 mm at the speed of 373 km/h; anchor mast; push-off mode.
9.7 MEASUREMENT OF CONTACT LINE TEMPERATURES If contact line equipment on main circuit lines have defects, such as relaxed connection bolt, failed crimping connection, serious corrosion of terminal board connection, reduced cross-sectional area of contact wire due to abrasion or corrosion, and defective switch contact point, temperature of and near these equipment may rise. Any object in nature, as long as its temperature is over absolute zero (−273.15°C), radiates out energy in the form of electromagnetic waves of different lengths. However, wavelength is mainly within the infrared region of 0.8–15.0 µm. Infrared radiation energy of the object is distributed by the wavelength and closely related to the surface temperature of the object. Surface temperature of the object can be correctly sensed through measuring infrared energy radiated by the object. Thermal infrared imagers can acquire temperatures of equipment quickly in long distance and real time, without contact, and can be used to measure temperatures of contact lines. Thermal infrared images mainly consist of optical systems, scanning mechanisms, infrared detectors, preamplifiers, video signal preprocessing circuits, display and recording systems, and ancillary peripherals. Infrared detectors are the core component of thermal infrared imagers and can be classified into unit detectors, multiunit detectors, and detectors without internal processing. The working process of thermal imagers is imaging surface temperature distribution of detected objects on infrared detectors through optical systems and scanning mechanisms in the form of infrared radiation signals, and converting it into video signals using infrared detectors. Such a weak video signal is further amplified by a preamplifier, the terminal display will display a thermal image of surface temperature distribution of the detected object.
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FIGURE 9.24 Thermal infrared imager mounted on the roof of inspection car.
Contact line temperature–measuring devices mainly consist of thermal infrared imagers, pan-tilt and protection equipment, and infrared data processing computers. The thermal infrared imager mounted on the roof of an inspection car is shown in Fig. 9.24. For a thorough inspection on contact line temperature, a thermal infrared imager should have the following features: j
j
j
A wide field of view. To shoot all live equipment of contact line during measurement, including messenger wire, contact wire, electric connection wire, dropper, various clamps, and supports. High resolution. To identify profile of contact line equipment, such as clamp and steady arm on temperature image. High sampling frequency. To collect clear infrared image of contact line equipment during train operations at high speed.
After receiving the temperature image data of thermal infrared imagers, infrared data processing computers will process each frame of temperature image, identify exceptional points of contact line temperatures, store exceptional temperature and current positions, and save images of exceptional temperatures on hard disks of computers. Analytical program can conduct statistical analysis on the exceptional temperature of contact lines and print reports so that contact line service departments can take proper countermeasures. Contact line maintenance personnel can diagnose the heating of contact line equipment depending on absolute or relative temperatures. 1. Diagnosis by absolute temperature. Judge whether maximum temperature in thermal image exceeds the limit depending on maximum allowable working temperature of various equipment (contact wire, messenger wire, dropper, and various clamps) of contact lines. This method is simple, but has the following shortcomings: a. Heating of contact line equipment is associated with many factors. It is unavailable to judge equipment operation is normal just because
Parameter Measurements of Pantographs CHAPTER 9 absolute temperature of contact line equipment does not reach the limit. However, the part where temperature is up to the limit is definitely subject to poor contact. b. Emissivity of electromagnetic wave of contact line equipment may vary depending on its material, and is related to oxidation degree of equipment. However, thermal infrared imagers can set only one emissivity, thus absolute temperature of each pixel in infrared image may have measurement deviations. c. Temperature of contact line equipment is also linked to atmospheric environment. Solar radiation, rain, snow, wind, and different atmospheric temperatures will all influence absolute of contact lines. 2. Diagnosis by relative temperature. Calculate the average temperature of each contact line temperature image acquired by thermal infrared imager, and take the average temperature of currently n continuous infrared images free of overheating as current reference temperature. Then, compare maximum temperature of currently acquired image with reference temperature to judge overheating point. In the infrared image of contact line as shown in Fig. 9.25, the reference temperature is 27.5°C, the maximum temperature at electric connection wire clamp of catenary is 55.6°C, and the difference between them is 28.1°C. As known from analysis on infrared image, such a clamp may have poor contact and to be inspected and processed by maintenance personnel. Fig. 9.26 shows the infrared image when the pantograph passes through section insulators. The reference of the contact line is 27.4°C. A maximum temperature of 73.9°C appears in contacting positions of pantographs and section insulators. The difference between maximum and reference temperature is 46.5°C. As known from analysis on infrared images, arcs appear when pantographs pass through section insulators.
FIGURE 9.25 Infrared image of contact line at electric connection clamp.
FIGURE 9.26 Infrared image when pantograph passes through section insulator.
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Pantograph and Contact Line System BRIEF SUMMARY 1. This chapter mainly introduces measurement methods and measurement equipment of pantographs and overhead contact line system parameters. Measurement technology and devices developed depending on technical evaluation and diagnosis requirement can be used only to evaluate pantographs, contact lines, or dynamic interactions between pantographs and contact lines. 2. Inspection parameters of pantograph and overhead contact line system have the following features: a. evaluating continuous and progressive change of contact quality, not only providing comment of “Yes/No”; b. allowing actual measurement and simulation calculation for convenient comparison of measured result and forecasted result; c. in the same condition, repeated measurements have identical results and are not influenced by random factors; and d. evaluation parameters of pantographs and overhead contact line dynamic interactions are measurable on dynamic pantographs. 3. Sufficient manners and methods are provided to check and verify output of pantographs and overhead contact line system parameter measurement equipment.
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9.1 OVERVIEW With the development of theoretic research on interactions between pantographs and contact lines, measuring techniques and measuring devices for technical evaluation and diagnosis of pantographs and overhead contact line systems are born at the right moment. Measuring techniques and devices developed under the requirement of technical evaluations and diagnosis can be used in the following three aspects: j
j
j
Evaluating only pantographs. Taking a pantograph as an independent component, use the vibration test table to apply excitation at corresponding amplitude and frequency to the pantograph and measure dynamic response parameters of pantographs at the same time to evaluate dynamic performance of pantographs based on measured results. Evaluating only contact lines. Measure the initial position of the contact wire and contact wire lift under a special uplift force, and calculate elasticity of the contact line based on the measured result; inspect accessories of the contact line at regular intervals, especially the position of the steady arm and registration arm and clearance between the live part and support device and tunnel wall; and measure residual thickness of the contact wire within certain operation cycles and forecast its service life. Evaluating dynamic interaction between pantographs and contact lines. In addition to dynamic contact force, contact wire lifts, running traces of heads, number of arcs and arcing time have been deemed as parameters for evaluating pantographs and overhead contact line dynamic performance.
For parameters of evaluating pantographs and overhead contact line dynamic performance and measurement requirement, see Table 9.1. Besides arc rate, the parameters in Table 9.1 also have the following characteristics: j
evaluating continuous and progressive change of contact quality, not only providing the comment of “Yes/No”;
Pantograph and Contact Line System. http://dx.doi.org/10.1016/B978-0-12-812886-2.00009-4 Copyright © 2018 Elsevier Inc. All rights reserved.
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Pantograph and Contact Line System Table 9.1 Parameters of Evaluating Pantograph and Overhead
Contact Line Dynamic Performance and Measurement Requirement
Purposes
Parameter Types
Parameters
Evaluate pantographs
Dynamic characteristics of pantograph
Amplitude and frequency of pantograph
Evaluate contact lines
Characteristics of contact line
Transverse and vertical parameters of contact wire Abrasion of contact wire Elasticity of contact line Slope of steady arm
Evaluate pantograph and overhead contact line dynamic interaction
Pantograph and overhead contact line dynamic performance
Pantograph and overhead contact line contact force (or arc rate) Running trace of head Uplift of contact wire at registration point
Electric contact performance Temperature of pantograph of pantograph and contact and overhead contact line line contact point (or of contact wire)
j
j
j
allowing actual measurement and simulation calculation for the convenient comparison of the measured result and forecasted result; in the same condition, repeated measurements have the identical result and are not influenced by random factors; and evaluation parameters of pantographs and overhead contact line dynamic interactions are measurable on dynamic pantographs.
Early references also take the number and duration of arcs as the physical quantity of evaluating pantographs and overhead contact line contact quality. However, if there is no, or very rare, arc, such characteristics will be useless to the comparison of pantographs and overhead contact line systems. Arcs cannot be simulated. Measurements show that the result of repeated tests cannot be reproduced even on the same line and in the same condition. Arcs are also associated with currents through pantographs and overhead contact line contact points. If there are no currents through such points, even pantographs and overhead contact line contact quality are bad, no apparent arcs will appear in pantographs and overhead contact line systems. Obviously, evaluating pantographs and overhead contact line contact quality with arc rate has some limitations. For the sake of effective quality evaluation and technical diagnosis on contact lines and pantographs and overhead contact line systems, each railway
Parameter Measurements of Pantographs CHAPTER 9 department has developed a measurement technology and method based upon its own need to obtain measured value of quality evaluation parameters. These technologies and methods can be applied to the parameter measurement of pantographs, as well as parameter measurements of contact lines and pantographs and overhead contact line interactions, but they should conform to applicable measurement requirements.
9.2 MEASUREMENT OF DYNAMIC CHARACTERISTIC PARAMETERS OF PANTOGRAPHS Fig. 9.1 shows the pantograph vibration test table of Deutsche Bahn. This test table utilizes a vertical lifting support to simulate progressive changes of contact wire heights, such as drops or lift of contact wires; another horizontal support that can slide is mounted in the vertical support and can simulate reciprocating movement of contact wires on strips. The exciter is mounted on the horizontal sliding support to generate a vertical vibration acting on the head. Excitation signal acting on the exciter, horizontal,
FIGURE 9.1 Vibration test table of pantograph.
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Pantograph and Contact Line System and vertical supports can be derived from operation test records of actual lines or simulated by computers based on models of contact lines. Vibration test tables can be used to analyze and evaluate the dynamic properties of pantographs. To reach such a purpose, pantographs are connected to exciters through strips and subject to vibrations. The measurement systems calculate associated parameters, such as various forces, acceleration, and shifts, and evaluate them.
9.2.1 Measurement Frequency Response To analyze vibration performance of pantographs within various freedom ranges and verify that it has no excessive reaction, the exciter and pantograph strips are connected as loosely as possible and dynamic excitation at 0.1–70 Hz is applied to the heads through exciters during frequency response analysis. Depending on the pantograph, excitation force systems with measurement devices and frequency response analyzers can obtain the following characteristics of pantographs: j j j j
dynamic apparent mass function; mechanical impedance; disturbance transfer function; and transfer function of contact force measurement system.
These parameters show a relation between frequency and amplitude and phase, the two measured quantities, and can be expressed with response functions. Dynamic performance and the operation quality of pantographs can be inferred from the form of response functions. Dynamic apparent mass actually expresses the relation between the excitation force (contact force) and strip vibration, and can be used as a reference for evaluating the dynamic performance of the pantograph. If the pantograph has an ideal operation performance, there should be only several forms of weak natural vibrations on its apparent mass graphic, even when the apparent mass is small. A similar conclusion can be inferred from disturbance transfer functions of pantographs. A disturbance transfer function is the ratio of contact force to amplitude excited by coupling pantographs to contact line models (mass-spring buffer systems). The frequency response analysis method can be used to study dynamic performance of pantographs on test tables, and identify improvement measures of the dynamic performance of pantographs based on study results, to save costs for line operation tests. Important data required by building simulation models and evaluations can be obtained through measurement and analysis methods of frequency responses. A simulation model is the mathematic form describing dynamic performance of pantographs. Linking simulation models of pantographs to that of overhead
Parameter Measurements of Pantographs CHAPTER 9 contact lines will be useful for quantitative research on dynamic interaction between pantographs and contact lines.
9.2.2 Structure Analysis Simple optical structure analysis can be conducted on vibration test tables using stroboscopes. Short-time intermittent exposure of a part of the pantograph can be used to monitor the vibration state of such a part. Wave nodes and wave loops (in extreme conditions) of vibrations may produce fatigue failure. Conclusion of material stress during operations can be obtained depending on the structure of wave nodes and loops.
9.2.3 Line Operation Simulation When analyzing frequency responses, periodic or random excitation signals can be transferred to pantographs. In actual operations, only limited measurement and evaluation on movement parameters and mechanical stress can be conducted. Simulated line operation on test tables can generate parameters of dynamic interaction between pantographs and special contact lines. Through simplified contact line models, changes of contact wire heights, impacts of lateral positions of contact wires, and strong impacts on dynamic movements of excitation on pantographs can be considered. Operation performance of pantographs in different design structures of contact lines can be precisely evaluated through the calculation of associated parameters, such as internal force and contact force.
9.3 MEASUREMENT OF SPATIAL POSITION PARAMETERS OF CONTACT WIRES As shown by measured results of pantographs and overhead contact line contact forces, discontinuity of the spatial position of contact wires may usually lead to large transient changes of pantographs and overhead contact line contact forces. Such discontinuity is reflected in height directions of contact wires, and also in shift directions of contact wires from the centerline of heads. From the view of conforming to dynamic performance and operational safety of pantographs and contact lines, designing correct spatial positions of contact wires for corresponding lines is very important. Moreover, prior to dynamic evaluation on completed contact lines, noncontact measurement equipment will be used to inspect the spatial position of contact wires to ensure conformity of it to design requirements. The spatial positions of contact wires are measured in static and dynamic conditions. Without external disturbances (in static condition), the spatial positions of contact wires obtained are static parameter; with dynamic interaction with pantographs (in dynamic condition), the spatial positions of contact wires obtained are dynamic parameters. Usually, noncontact measurement equipment is used to acquire the static spatial position the parameter of contact wires.
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9.3.1 Portable Optical Measuring Device Laser measuring device is a kind of portable optical measuring device imaging contact wire through lens system with crossline and sighting device to identify position of contact wire, as shown in Fig. 9.2. Once contact wires can be seen at the crosslines, contact wire heights can be identified depending on shifts of optical systems from millimeter scales. A change of 1 mm on the scale is equivalent to a 10-mm height difference of contact wire. To acquire accurate measured data using laser measuring devices, a lot of practices and verification are conducted. Portable measuring devices for spatial positions of contact wires are often used to measure and verify lateral and vertical parameters of some specific points on contact lines.
9.3.2 Onboard Measurement Device 9.3.2.1 MEASUREMENT DEVICE MOUNTED ON LADDER TROLLEY Mounting noncontact optical sensors onto the mobile ladder trolleys can realize continuous measurement of spatial position of contact wires. Fig. 9.3 shows the measurement devices mounted on ladder trolleys.
FIGURE 9.2 Manual measurement of spatial position of contact wire using laser measuring device.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.3 Spatial position–measuring device mounted on ladder trolley.
Fig. 9.4 shows the measurement principle of the optical sensor. The illuminator will light up the lower surface of the measured contact wire. Bright spots are imaged in a CCD camera. According to the spot imaging position in CCD cameras, the lateral and vertical distance of contact wires to CCD cameras can be identified. Then, spatial positions of contact wires relative to rail levels can be acquired through some calculations. Prior to measuring, using a ladder trolley measuring device, use a portable optical measuring device to calibrate and verify it.
FIGURE 9.4 Principle of optical measurement.
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FIGURE 9.5 Relation curve of spatial position and shift of contact wire.
When the ladder trolley moves on the rail level, it will have no shaking and side shift from rail levels. The spatial position information of contact wire acquired by the device is the static spatial position parameter of the contact wire desired. When the measuring device is mounted on other rail cars, shaking and side shifts of cars from rail levels during movement will influence measured results of spatial positions of contact wires. Necessary measures are taken to eliminate such influence. Therefore, shaking and side shift of vehicles from rail levels are measured at the same time, and measured results of optical measuring devices are corrected to acquire spatial positions of contact wires relative to rail levels. Combining spatial positions of contact wires with shifts of vehicles running along lines can generate the relation curve of spatial positions and shifts of contact wires, as shown in Fig. 9.5.
9.3.2.2 MEASUREMENT DEVICE MOUNTED ON INSPECTION CAR Fig. 9.6 shows the measurement principle of a type of spatial position–measuring device that is mounted on an inspection car and developed by Deutsche Bahn. Such a device consists of three spotlights with high condensation, four high resolution cameras, and a data processor, which can measure spatial position and abrasion face width of contact wires and calculate area loss of contact wires depending on abrasion face width. Spotlights and cameras mounted on the roof are shown in Fig. 9.7. Intervals of data samplings on measuring devices depend on travel speeds and design speeds, and is approx. 80 mm at 300 km/h. Its precision of detecting contact wire heights and lateral shifts is up to 5 mm. In operations of vehicles, the car body will shake, shift laterally, and vibrate, which cannot be entirely recorded or detected, so the precision of detection is impaired. Considering that, the total deviation of detection is modified to 10 mm (vertical parameter of contact wire) and 20 mm (lateral parameter of contact wire). This device can also measure static spatial positions of contact wires effectively and quickly at travel speeds more than 330 km/h to identify directions and
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.6 Principle of a type of spatial position–measuring device.
FIGURE 9.7 Spotlights and cameras mounted on roof.
targets for repairs of contact lines. When detecting static spatial positions of contact wires, the inspection car is towed by a diesel rail car to avoid changes of spatial positions of contact wires due under the uplift force of pantographs. This device can also be used to observe and record pantographs and overhead contact line interactions. In such a case, the inspection car is towed by a locomotive. The vertical parameters of contact wires acquired are the spatial position parameters under uplift forces of pantographs. Measurements can be conducted in any weather condition, except for heavy snow. Notwithstanding, when in cold or damp weather, or the inspection car is
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Pantograph and Contact Line System stopped outdoors overnight, the lens of the camera may be foggy and the shooting quality may be reduced. In such a case, the viewing window is connected to warm wind for 1 h to remove fog on the lens. If this doesn’t work, open the lens cover of the camera and wipe the glass surface of the lens using a soft cloth. Prior to starting measurements, identify the precision of the measuring device. This device can be used to measure the contact line of a short test section containing linear and curves. Then, measure such a test section manually by using a portable laser measuring device and comparing two groups of data. Through this method, a sensor can be correctly calibrated to ensure that the measuring device is in good condition. When the measurement is completed, measured results of spatial position parameters of contact wires can be outputted with a printer in an offline state. Analytic programs can display spatial positions and residual thickness of contact wires, and also calculate dynamic uplifts depending on nondisturbance position data of contact wires and position data after uplifts of pantographs, and calculate the elasticity of contact lines based on the contact force data stored. Nondisturbance position parameter measurements for contact wires are often deemed as the measurement steps of acceptance procedures after completing adjustments of new or existing contact lines. Deviation of actual positions of contact wires from design values can be acquired from simulation records of measured data, as shown in Fig. 9.8. In addition to contact wire height and lateral parameter, other useful data can be displayed, such as kilometer post, mast position, dropper position, and contact wire slope. Dropper and mast positions are identified automatically by analytic programs.
FIGURE 9.8 Deviation of actual positions of contact wires from design values can be acquired from simulation records of measured data.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.9 Cross-section of contact wire after abrasion.
Besides manual inspection of measured data by operators, analytic programs also support automatic diagnosis, automatic analysis of measured data, and records of any defect of contact lines (critical record). Critical records include the following data: j j
j
overmaximum permissible lateral position; height difference between adjacent droppers is more than maximum permissible value; and overallowable counter slope at dropper.
The measuring device can measure the spatial position of the contact wire, and also measure the abrasion face width of the contact wire at the same time, and can identify the contact wire abrasion in a critical position. A cross-section of contact wire after abrasion is shown in Fig. 9.9. After measuring the abrasion face width W of contact wire directly, the area loss Av of the contact wire can be calculated indirectly using Eq. (9.1). A = v
π ⋅ r 2 ⋅ arcsin 180°
W 2 2 2r − W 4 r − W 4
(9.1)
9.4 MEASUREMENTS OF ELASTICITY OF CONTACT LINES Contact wire uplifts under unit uplift forces are called elasticity of contact lines. To measure elasticity of contact lines, two issues are solved: first, identify the initial height of the contact wire; and second, measure the contact wire height under a certain uplift force. Uplift of contact wires is equal to the difference of contact wire height before and after action of the uplift force. Thus, the height of contact wire in one section is measured twice to calculate elasticity of the contact line and uplift of contact wire depending on the results of the two measurements. First, measure the initial height of the contact wire. Adjust uplift force of simulated pantograph to 5–8 N to keep contact with the contact wire. However, a
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Pantograph and Contact Line System change of the initial position of the contact wire is minimized. Measure and record heights of contact wires at low speed. Noncontact measuring devices can also be used to acquire the height of contact wires. Second, measure the height of the contact wire under uplift force. Adjust uplift force of simulated pantographs to a specified value to keep them in contact wire with the contact wire. Measure and record height of the contact wire under uplift force. The uplift force is selected depending on average uplift force of pantographs selected in the contact line design. Usually, for the contact line with a target speed of 200 km/h, the uplift force of simulated pantographs can be 100 N; for contact lines with target speeds more than 250 km/h, uplift forces of simulated pantographs can be 120 N. To verify conformity of static performance of catenary suspensions in point ranges to requirements, simulated uplift forces of pantographs can be 250 N. In the end, the difference between the two measured results is the uplift of contact wires under a certain uplift force, and the ratio of such an uplift to uplift force is the elasticity of contact line. Combine elasticity of each point with kilometer posts of lines to acquire elasticity curves of contact lines corresponding to kilometer posts. Fig. 9.10 shows the simulated pantograph mounted temporarily on a catenary work car for measuring elasticity of the contact line. Data acquisition and data processing equipment is mounted in the car. Fig. 9.11 shows the measured elasticity curve. Here, stitched catenary suspension with a span of approx. 48 m is used for the contact line; the cross-section of
FIGURE 9.10 Simulated pantograph used in elasticity measurement.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.11 Measured elasticity curve of contact line.
messenger wire is 120 mm2 and tension of messenger wire is 23 kN; the crosssection and tension of the contact wire are, respectively, 150 mm2 and 28.5 kN; length and tension of the stitch wire are, respectively, 18 m and 3.5 kN; and structural height is 1.6 m.
9.5 MEASUREMENT OF PANTOGRAPHS AND OVERHEAD CONTACT LINE CONTACT FORCES 9.5.1 Basic Principle Pantographs and overhead contact line contact points are used to ensure the uninterrupted and faultless transmission of electric energy from contact lines to running electric trains through pantographs. To ensure reliable transmission of electric energy and minimize abrasion of strip and contact wires, pantographs and overhead contact line contact forces remain in a certain range: excessive contact force will cause increased abrasion and contact wire uplift while insufficient contact force will lead to frequent arcing and increase abrasion. Measured data of pantographs and overhead contact line contact forces can be used for evaluation and fault diagnosis of pantographs and overhead contact line dynamic performances. Measurement of pantographs and overhead contact line contact forces conform to the requirements in Section 4.5. According to Section 2.3, pantographs and overhead contact line contact forces are the vertical forces applied by strips onto contact wires, and the results of superposition of static contact forces F0, friction forces FR, aerodynamic forces FAER, and inertial forces FDYN. Measuring forces upon pantographs and overhead contact line contact points directly in dynamic conditions is impossible because contact points will move back and forth continuously on strips. Force sensors can be mounted directly at the joint between strip bases and the strips to measure contact forces, as shown in Fig. 9.12. In total, four force sensors are mounted under two strip rows of each pantograph. The sum of signals of left and right sensors of a strip row can reflect the contact force of a strip row, and that of four sensors can reflect the entire pantograph and overhead contact line contact force. The approximate position of contact wires on strips can be calculated using the sums of signals of sensors, right signals, and left signals on the basis of level principles.
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FIGURE 9.12 Pantograph with force sensors.
However, in this measurement, force sensors cannot record the mass inertia force acting on strips and aerodynamic forces related to operation speeds, and correction values are added to correct inertia forces and aerodynamic force of strips.
9.5.2 Technical Description of Measuring Device Measuring devices of pantographs and overhead contact line contact forces can measure vertical forces acting on contact lines, vibration acceleration of heads, positions of contact wires on strips (indirect calculation using signal of force sensor), head heights, and acceleration of pantograph bases. Acceleration of bases can reflect the impact of vehicle vibrations on pantographs and overhead contact line contact forces. Fig. 9.13 shows the structural diagram of the contact force–measuring device. All measuring sensors work in a high-voltage (HV) environment equipotential to pantographs. Signals of sensors, after being converted to digital signals on HV sides, will be transmitted to inspection cars at ground potential in optical forms and displayed and analyzed on data processors. Fig. 9.14 shows the pantograph with a measuring sensor. The measurement of the contact force is completed by four force sensors and four acceleration sensors mounted at a strip-fixing point. A force sensor is integrated with an acceleration sensor and they are mounted between the strip and support, as shown in Fig. 9.15. This connection manner requires a special sensor, and can measure vertical force precisely provided that the mechanical stability and head mass are not changed significantly. These force and acceleration sensors are provided with temperature compensation,
FIGURE 9.13 Structure of contact force–measuring device. HV, High voltage.
FIGURE 9.14 Layout of sensors (DSA380D pantograph). 1, Vertical force and acceleration sensor; 2, inductive sensor; 3, angular displacement sensor; 4, base acceleration sensor; 5, data acquisition unit; 6, optical data transmitter; 7, supply transformer.
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FIGURE 9.15 (A) Force sensor module with acceleration sensor and (B) mounted between strip and frame.
and connected to a data acquisition unit in the car through a special cable and connector. A force sensor should be as close as possible to the contact point. If force and acceleration sensors are mounted far from the strip, some flexible connections may appear between the sensor and contact point. This will reduce the range and accuracy of dynamic measurement. If force and acceleration sensors are mounted on two springs of the head, they will be incapable of measuring distribution of contact force on the two strips or analyzing measured values generated by the two strips. Distribution of force can provide necessary information for the correct working of pantographs and measured results. An acceleration sensor is mounted on the base of the pantograph. A sensor signal is used to identify the impact of track regularity and impact of base vibrations on contact forces. The output signal of the force and acceleration sensor is transmitted to a data acquisition unit for processing, and is often converted to a frequency-modulated pulse signal by an electronic module through an overvoltage/frequency (V/f) converter. The pulse signal can be converted to an optical signal and transmitted via an optical fiber. Electronic element equipotential to the contact line is mounted in a data acquisition unit as shown in Fig. 9.16. A data acquisition unit is fixed to the base of a pantograph through a special connection device to collect all sensor signals on the pantograph and convert them to optical signals. A special transformer can transmit electric energy from the control cabinet at ground potential to the pantograph component on the HV side. This transformer is provided with insulation strength withstanding against the voltage level of the contact line. To shorten an optical fiber, lead the optical fiber through an optical data transmitter, as shown in Fig. 9.17.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.16 Data acquisition unit mounted on pantograph base.
FIGURE 9.17 Power supply transformer (left) and optical data transmitter (right).
Measurement of pantographs and overhead contact line contact forces is often combined with measurement of other parameters of pantographs and overhead contact line systems, such as spatial positions of contact wires to acquire overall information of pantographs and overhead contact line system states. Fig. 9.18 shows an example of a graphic of measured result, where the shift of contact wire from the strip centerline is acquired through indirect calculation using the output of the force sensor.
9.5.3 Correction of Inertia Force of Strip Measuring gravity on vibrating objects may cause the so-called acceleration error. There is no exception for measurements of pantographs and overhead
FIGURE 9.18 Diagram of measured result.
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9.5.4 Correction of Aerodynamic Force Force sensors measuring pantographs and overhead contact line contact forces are mounted below the strips, so the sensors cannot measure effects of aerodynamic forces on strips. To avoid missing an aerodynamic force component generated with running speed, a correction factor related to speed is added when calculating contact force. Aerodynamic force components are identified through measuring uplift forces under International Union of Railway (UIC) rules. Fig. 9.19 shows the method of measuring aerodynamic force. Fix the pantograph with a contact force– measuring device using two ropes so that each strip will not contact with the contact wire during operation. The clearance between the strip and contact wire is approx. 100 mm. Mount forces measure cells, respectively, to the lower parts of two ropes to record the forces transmitted by ropes to strips. Meanwhile, pantographs and overhead contact line contact force–measuring devices will also record the internal force under the strip. Vertical aerodynamic force (Faero = Faero_I + Faero_II) is equal to the difference between the force (Fseil = Fseil_I + Fseil_II) recorded by force measuring cells at the bottoms of the two ropes and the internal force (FS = FS_I + FS_II) recorded by the contact force–measuring device.
FIGURE 9.19 Correction of aerodynamic force.
Parameter Measurements of Pantographs CHAPTER 9 This measurement method can be used to identify the function relation between functions, such as aerodynamic force and operation speed acting on the strip, operation direction (pantograph joint pointing at operation direction/ reverse operation direction), and layout of the pantograph on the vehicle. Such a function relation can be written into system software for immediate correction of measured results of pantographs and overhead contact line contact forces.
9.6 MEASURING UPLIFT OF CONTACT WIRES AT REGISTRATION POINTS The fixed measuring device mounted on contact line supports can be used to correctly measure the uplift of contact wires at the registration point. This is necessary in the following cases: j
j j
in dynamic evaluation, verify conformity of design scheme of pantograph and overhead contact line system to standard; identify maximum allowable speed of new vehicle or pantograph; and fixed monitoring of pantograph in commercial operations.
In Fig. 9.20, regular monitoring of the uplift at the registration point is available at the support device through connecting the steady arm and rotary encoder with pretensioned rope. The insulated section is provided on a rope to realize potential isolation. The output of the encoder can be received directly by the computer to calculate uplift at the registration point. Fig. 9.21 shows the steady arm vibration–measuring device used by Shinkansen. Such a device can analyze contact wire uplift at the registration point, and also vibration of the steady arm and strain of the contact wire. The measuring device is divided into two parts. One part is mounted on the support device of the contact line, and equipotential to the contact line. The
FIGURE 9.20 Registration point uplift–measuring device with pretensioned rope.
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FIGURE 9.21 Steady arm vibration–measuring device used by Shinkansen. (A) Measuring device mounted on support device and (B) information-receiving device mounted in vehicle.
angular displacement sensor measuring steady arm vibration is connected to the end of the steady arm through fine wire. This part is fed by the battery and transmits information collected by it in a wireless form. The other part is an information-receiving and -processing device and is temporarily placed in the mobile vehicle. The vibration acceleration of the contact wire mainly represents the vertical vibration strength upon the conductor when the pantograph passes. Through measuring the bending strain of the conductor, bending strength upon the conductor can be identified and the antibending life of the conductor can be forecasted. Fig. 9.22 shows the noncontact displacement-measuring device mounted on the contact line mast of the Beijing–Shanghai high-speed railway line. It is used to measure contact wire vibrations at registration points. The measured result is shown in Fig. 9.23.
FIGURE 9.22 Noncontact contact wire vibration displacement–measuring device mounted on mast.
Parameter Measurements of Pantographs CHAPTER 9
FIGURE 9.23 Vibration at registration point for double-pantograph collection. Contact line wire combination: JTMH120 + CTMH150; tension combination: 20 + 40 kN; distance between pantographs: 197 m, pantograph model: DSA380; maximum uplift of front pantograph is 81 mm and that of rear pantograph is 99 mm at the speed of 373 km/h; anchor mast; push-off mode.
9.7 MEASUREMENT OF CONTACT LINE TEMPERATURES If contact line equipment on main circuit lines have defects, such as relaxed connection bolt, failed crimping connection, serious corrosion of terminal board connection, reduced cross-sectional area of contact wire due to abrasion or corrosion, and defective switch contact point, temperature of and near these equipment may rise. Any object in nature, as long as its temperature is over absolute zero (−273.15°C), radiates out energy in the form of electromagnetic waves of different lengths. However, wavelength is mainly within the infrared region of 0.8–15.0 µm. Infrared radiation energy of the object is distributed by the wavelength and closely related to the surface temperature of the object. Surface temperature of the object can be correctly sensed through measuring infrared energy radiated by the object. Thermal infrared imagers can acquire temperatures of equipment quickly in long distance and real time, without contact, and can be used to measure temperatures of contact lines. Thermal infrared images mainly consist of optical systems, scanning mechanisms, infrared detectors, preamplifiers, video signal preprocessing circuits, display and recording systems, and ancillary peripherals. Infrared detectors are the core component of thermal infrared imagers and can be classified into unit detectors, multiunit detectors, and detectors without internal processing. The working process of thermal imagers is imaging surface temperature distribution of detected objects on infrared detectors through optical systems and scanning mechanisms in the form of infrared radiation signals, and converting it into video signals using infrared detectors. Such a weak video signal is further amplified by a preamplifier, the terminal display will display a thermal image of surface temperature distribution of the detected object.
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FIGURE 9.24 Thermal infrared imager mounted on the roof of inspection car.
Contact line temperature–measuring devices mainly consist of thermal infrared imagers, pan-tilt and protection equipment, and infrared data processing computers. The thermal infrared imager mounted on the roof of an inspection car is shown in Fig. 9.24. For a thorough inspection on contact line temperature, a thermal infrared imager should have the following features: j
j
j
A wide field of view. To shoot all live equipment of contact line during measurement, including messenger wire, contact wire, electric connection wire, dropper, various clamps, and supports. High resolution. To identify profile of contact line equipment, such as clamp and steady arm on temperature image. High sampling frequency. To collect clear infrared image of contact line equipment during train operations at high speed.
After receiving the temperature image data of thermal infrared imagers, infrared data processing computers will process each frame of temperature image, identify exceptional points of contact line temperatures, store exceptional temperature and current positions, and save images of exceptional temperatures on hard disks of computers. Analytical program can conduct statistical analysis on the exceptional temperature of contact lines and print reports so that contact line service departments can take proper countermeasures. Contact line maintenance personnel can diagnose the heating of contact line equipment depending on absolute or relative temperatures. 1. Diagnosis by absolute temperature. Judge whether maximum temperature in thermal image exceeds the limit depending on maximum allowable working temperature of various equipment (contact wire, messenger wire, dropper, and various clamps) of contact lines. This method is simple, but has the following shortcomings: a. Heating of contact line equipment is associated with many factors. It is unavailable to judge equipment operation is normal just because
Parameter Measurements of Pantographs CHAPTER 9 absolute temperature of contact line equipment does not reach the limit. However, the part where temperature is up to the limit is definitely subject to poor contact. b. Emissivity of electromagnetic wave of contact line equipment may vary depending on its material, and is related to oxidation degree of equipment. However, thermal infrared imagers can set only one emissivity, thus absolute temperature of each pixel in infrared image may have measurement deviations. c. Temperature of contact line equipment is also linked to atmospheric environment. Solar radiation, rain, snow, wind, and different atmospheric temperatures will all influence absolute of contact lines. 2. Diagnosis by relative temperature. Calculate the average temperature of each contact line temperature image acquired by thermal infrared imager, and take the average temperature of currently n continuous infrared images free of overheating as current reference temperature. Then, compare maximum temperature of currently acquired image with reference temperature to judge overheating point. In the infrared image of contact line as shown in Fig. 9.25, the reference temperature is 27.5°C, the maximum temperature at electric connection wire clamp of catenary is 55.6°C, and the difference between them is 28.1°C. As known from analysis on infrared image, such a clamp may have poor contact and to be inspected and processed by maintenance personnel. Fig. 9.26 shows the infrared image when the pantograph passes through section insulators. The reference of the contact line is 27.4°C. A maximum temperature of 73.9°C appears in contacting positions of pantographs and section insulators. The difference between maximum and reference temperature is 46.5°C. As known from analysis on infrared images, arcs appear when pantographs pass through section insulators.
FIGURE 9.25 Infrared image of contact line at electric connection clamp.
FIGURE 9.26 Infrared image when pantograph passes through section insulator.
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Pantograph and Contact Line System BRIEF SUMMARY 1. This chapter mainly introduces measurement methods and measurement equipment of pantographs and overhead contact line system parameters. Measurement technology and devices developed depending on technical evaluation and diagnosis requirement can be used only to evaluate pantographs, contact lines, or dynamic interactions between pantographs and contact lines. 2. Inspection parameters of pantograph and overhead contact line system have the following features: a. evaluating continuous and progressive change of contact quality, not only providing comment of “Yes/No”; b. allowing actual measurement and simulation calculation for convenient comparison of measured result and forecasted result; c. in the same condition, repeated measurements have identical results and are not influenced by random factors; and d. evaluation parameters of pantographs and overhead contact line dynamic interactions are measurable on dynamic pantographs. 3. Sufficient manners and methods are provided to check and verify output of pantographs and overhead contact line system parameter measurement equipment.