Composite Cross-arm Research Articles

Experimental Research of Mechanical Behaviour of GFRP Cross Arm of 500kV Transmission Tower

Glass fibre reinforced polymer (GFRP) material is used in the field of transmission tower structure because of its excellent electrical and structural performance. In this paper, a full scale GFRP composite cross arm of 500kV transmission tower is designed and a triaxial load-unload experiment is conducted to study the mechanical properties of it. Three kinds of the most unfavourable load cases of GFRP cross arm are loaded, and the strain changes of the upper, middle and lower parts of the cross arm are obtained. It is verified that the bearing capacity of GFRP cross arm meet the design requirements and GFRP cross arm can be used safely in the transmission tower engineering.

Research on Construction Method, Risk Identification and Evaluation Technology of UHV AC Composite Cross Arm Pole and Tower

The research on construction method of UHV AC composite cross arm pole and tower mainly combines the material and structural characteristics of composite cross arm insulator, analyzes the danger sources which may cause damage to construction links such as packaging, transportation, storage, construction hauling, lifting and installation, and then this paper conducts evaluation, and proposes corresponding construction measures, thus forming the construction technical scheme of UHV AC composite cross arm pole and tower. This paper conducts analysis and assessment to the risk (danger source) of damage to composite cross arm insulator during the construction by utilizing the risk evaluation method, and then proposes corresponding construction full-protection measures and counter measures targeting the assessment results.

FUNDAMENTALS OF CREEP, TESTING METHODS AND DEVELOPMENT OF TEST RIG FOR THE FULL-SCALE CROSSARM: A REVIEW

Most of transmission line (TL) towers are designed and fabricated in the form of lattice using galvanized steel. The crossarm of the TL is made of Neobalanocarpus or Chengal wood. Recently, it has been reported by an electrical corporation situated in Malaysia that mechanical performance of the wooden crossarm declined below their service life of 40 years due to the extreme tropical weather in Malaysia. At present, composite crossarm made of glass fibre reinforced polymer composite were introduced as substitute in the 132 kV TL tower. However, the research findings lack of information on creep life estimation for the full-scale crossarm. Hence, a new test rig has to be developed to cater the testing operation using the uniaxial tension creep test. The primary objective of this review is to provide an overview of the creep theory and the existing creep testing methodology.

Numerical Simulation on the Statics Deformation Study of Composite Cross Arms of Different Materials and Configurations

This study focuses on the deformation of cross arms made from composite material under static loading. Two materials properties of fiberglass with are assigned to the cross arms model and it is subjected to a load at the one end of the cross arms. A bracing support is then installed, and the deformation and stress experienced by the cross arms are observed and compared with the case where no bracing support is used. The results obtained show that material B has lower deformation value, but experienced greater stress compared to material A. The bracing managed to reduce the total deformation by about 12% and 20% for material A and B respectively. The reduction of stresses experienced by the cross arms ranges from 4% to 30%.

Effect of Laminate Properties on the Failure of Cross Arm Structure under Multi-Axial Load

This study investigated the influence of laminate properties toward the collapse of composite cross arm structure under multi-axial quasi-static loading. A three-dimensional finite-element model of a cross arm was developed and integrated with Hashin’s failure subroutine to predict the inter-laminar damages of the composite upon its application. The mechanical deformation and failure of the composite structure were evaluated over three laminate properties. This investigation revealed that variation in laminates properties yielded different structural deflection and laminate damages. The cross arm with a greater young modulus and ultimate stresses (laminate B) experienced a single failure mode of fiber buckling in compression at deflection of 0.082 m. For the given multi-axial load, the laminate configuration and properties considered in this study failed to prevent the failure of the cross arm.

Numerical Study of Composite Fiberglass Cross Arms under Statics Loading and Improvement with Sleeve Installation

In this paper, the structural deformation of fiberglass composite cross arms under statics loading were numerically simulated using the ANSYS software. The alternate variant of cross arms with one-meter sleeve span installed on both arms was considered as an improvement study. By comparing both cross arms systems, it is found that the total deformation was reduced from 127.49 mm to 95.367 mm by introducing the sleeve. Besides, the stress level appears to be lowered in the cross arms with sleeve installed. The sleeve is regards as a viable solution to reduce both deformation and stress level of cross arms, thus lengthen its life span and saving maintenance costs.

An Improved Polyurethane using as Glass Fiber Reinforced Polymer Transmission Poles and Crossarms

By the design of molecular structure, improved polyurethane was synthesized and the material exhibited excellent mechanic properties, electrical insulation, resistance to chemical corrosion and UV aging. Its tensile and flexural strength were 58.4 MPa and 101.2 MPa; surface and volume resistivity were 9.68 × 1015 Ω and 2.60 × 1016 Ω.cm, respectively; and their loss modulus was less than 13% exposed under serious chemical substance and UV irradiation. Moreover, the properties of the polyurethane were superior to traditional epoxy and unsaturated polyester resin. Herin, resulted composite material poles and cross arms were operation under demonstration line, and accumulated relevant operating parameters.

Experimental Study on High-Cycle Fatigue Behavior of GFRP-Steel Sleeve Composite Cross Arms

To overcome the fatigue safety problem of transmission tower cross arms caused by the wind-induced vibrations, an experimental study on the high-cycle fatigue performance of a new type of GFRP-steel sleeve composite cross arms was carried out. A total of six specimens were subjected to 500 thousand cyclic loadings based on the practical engineering background. The stress state was monitored, and a variety of load-displacement-time curves, the energy dissipation capacity, and the dynamic strain were analyzed to examine the effects of fatigue loading. After the fatigue test, the specimens without significant fatigue failure were evaluated to derive the residual bearing capacity. Based on the residual strength theory, the cumulative damage was examined, and the fatigue life was predicted under various loading conditions to ensure the reliability of composite cross arms. It is shown that the new type full-scale GFRP-steel sleeve composite cross arms can demonstrate a high level of safety redundancy on antifatigue performance and can be expected for wide application in power transmission towers.

Investigation on tracking wheel test of large-diameter composite insulators under AC voltage

The tracking wheel test specified in IEC/TR 62730:2012 provides a method that can be used to evaluate the resistance of composite insulators to tracking and erosion for rejecting inadequate materials or designs. Currently, most of the tests have been conducted on composite line insulators and some other insulator types with relatively small diameters. As the usage of large-diameter composite insulators, such as composite station insulators and composite cross-arms, increases rapidly, it is urgent to investigate if the tracking wheel test method is also suitable for their evaluation. In this study, a tracking wheel device for composite insulators with different diameters, designed and constructed in accordance with the IEC standard, is presented. The relationships between the leakage current and NaCl content as well as the average diameter of the specimen are investigated. It is shown that the test parameters specified in the IEC standard are not suitable for specimens of relatively large diameters. Accordingly, a relevant modification of test parameters has been introduced and verified, showing similar phenomena during the verified test as those observed during previous studies on composite line insulators. It is thus claimed that the modified test procedure is feasible for being applied on large-diameter insulators.

Electric stress computations for designing a novel unibody composite cross-arm using finite element method

This paper deal with the electrical performance of a newly proposed fully composite pylon in Denmark, which has a unibody composite cross-arm at 420 kV highest system voltage level. Electric field consideration along the insulations of the novel unibody cross-arm is one of the most important requirements in the design process of a non-traditional pylon. In this paper, ANSYS finite element software is used to calculate the electric field and potential distribution around and inside the fully composite pylon. Electric field criteria related to the design of composite cross-arms are reviewed and applied for interpreting the electrical performance of the unibody cross-arm at power frequency stresses. Three different designs of non-conductive conductor clamp are assumed for the attachment points between phase conductors and the unibody cross-arm. The side effects of conductor clamp are included in 2D modeling in order to determine the minimum required height for phase conductors at the top of the unibody cross-arm. Considering the side effects of phase conductors at both sides of conductor clamp, the application of steel enclosures with an appropriate diameter is introduced to be used around the phase conductors in order to reduce the electric field magnitudes in the region of the conductor clamp. Finally, the feasibility of utilizing steel enclosures for modifying electric stresses inside the conductor clamp and unibody cross-arm is investigated by a 3D finite element analysis.

A Comparative Study of Distribution Structure Cross Arms

Background: The structural performance of cross arms used on distribution poles is studied in this paper. Tangent and Dead End configurations involving conventional (wood) and composite (fiber glass) cross arms are analyzed. Strength-to-Stiffness and Weight-to-Stiffness ratios associated with study cases are determined and evaluated. Results and Conclusion: It is observed that although initial costs are higher, composite cross arms offer long-term advantages in terms of strength, stiffness, performance and durability.

Electric Field and Potential Distribution in a 420 kV Novel Unibody Composite Cross-Arm

The use of uni-body composite cross-arm in a fully composite-based pylon is a new concept for the next generation of overhead transmission lines. The crossarm is stressed by phase-to-phase voltages except in two regions, which are stressed by phase-to-ground voltages caused by installation of shield wires. Due to a major difference between the novel cross-arm structure and traditional composite cross-arms, the electric field distribution in the uni-body composite cross-arm is of considerable interest. This paper presents and analyses the electric field distribution around and inside the hollow core uni-body cross-arm through which ground cable passes to connect the shield wires. Two different shed profiles are considered on the cross-arm and evaluated based on the guidelines of IEC 60815-3. The 2D geometry of pylon is modeled in ANSYS Finite Element Analysis package. The electric field and potential distribution along the pylon is graphically depicted and the effectiveness of assigned shed profiles in controlling the power frequency stresses are investigated in the areas with high field intensities.

Pollution Characteristics of AC 500 kV Composite Cross-arm in High Altitude Area

Pollution Characteristics of AC 500 kV Composite Cross-arm in High Altitude Area

Transient electric field computation for composite cross-arm in 750 kV AC transmission line under lightning impulse voltage

The transient electric field distribution under lightning impulse voltage (LIV) is vital to the reliability of 750 kV composite cross-arm. However, the transient electric field of electrical equipment under impulse voltage has usually been substituted by the equivalent sinusoidal voltage, without considering the variation of permittivity with frequency. Using the frequency decomposition computation method (FDCM) based on finite element method (FEM), this paper presents the study of transient electric field under LIV for a 750 kV composite cross-arm. The LIV waveform has been decomposed via Fourier transformation. The complex dielectric functions of the insulation materials used in composite cross-arm have been investigated, and the computation parameters for the dc and each harmonic component of LIV have been obtained. Then, the transient electric field distribution can be computed through the superposition of responses from dc and each harmonic component. Moreover, the computation results have been compared with that using traditional method. The comparison indicates that the potential distribution of composite cross-arm is similar. The maximum percentages of electric field strength difference on fittings and silicone rubber sheath are 2.9 %, 14 %, respectively.

Composite cross-arms for power transmission lines

Composite cross-arms for power transmission lines

Potential distribution computation and structure optimization for composite cross-arms in 750 kV AC transmission line

As composite cross-arm will be used in domestic 750 kV AC transmission line for the first time, careful and meticulous preparatory work is highly needed. Using a three-dimension (3-D) finite-element method (FEM) software, this paper presents computation results of the potential and electric field distribution for composite crossarms in the process of structure optimization. Several optimization programs for composite cross-arm have been studied and the final design is made to omit the suspension insulator string, to increase the length of post insulators and to configure suitable grading and shielding rings based on preliminary design. A set of grading and shielding rings configuration program has been proposed. The comparison between optimized composite cross-arms and 750 kV line composite insulators indicates that composite cross-arms have better potential distribution. The electric tests demonstrate that optimized composite cross-arms have good electrical performance and can meet operation requirements.

RPC Pole Composite Cross Arm Design and Wind-Induced Dynamic Analysis

The author puts forward a new insulation cross arm, uses the insulation and high strength composite materials (FRP), to replace the steel applied to the RPC pole cross arm, this not only has a full bar maintenance-free features, and can shorten transmission corridor again, for the construction of resource intensive transmission lines has important practical significance. In addition, this paper uses finite element analysis software ANSYS, considering the influence of fluctuating wind, in the modal analysis and dynamic response illustrates the actuality of cross arm application of composite materials.

Analysis and experimental testing of a built-up composite cross arm in a transmission line tower for mechanical performance

This paper discusses the development of a composite cross arm for a power transmission line tower using FRP pultruded profiles. The mechanical performance of the composite cross arm has been evaluated using experimental testing and an analytical solution as well as a finite element simulation. By using the composite cross arm in place of a steel cross arm with ceramic insulators, considerable reduction of transmission corridor is achieved.