UHV Transmission Lines Research Articles

Analysis of passive interference on radio station from AC UHV power

The problems of Electromagnetic Interference in Airborne Intelligence Radar Stations near the AC UHV Transmission Lines is researched in this paper, which is mainly passive interference. And then analyzed the passive interference of AC UHV lines. It mainly studied the influence of the tower and line on the distance detection performance of the air-to-air intelligence radar of the UHV transmission lines. and integrated the influence of the surface reflection surface, the shadowing effect and the secondary radiation echo interference, Proposed a passive interference protection distance for UHV transmission lines and airborne intelligence radar stations

Application of Copper Cladding Aluminum Composites in UHV Portable Earthing and Short-circuiting Wires

Aiming at the heavy weight and inconvenience when carrying and installing copper earthing wires on the UHV transmission lines, in this paper, we present the use of copper clad aluminum(CCA) composite materials as a lightweight method for UHV earthing wire conductor. Theoretical calculations and tests of the fusing current in a short time for copper and CCA material are conducted. The results show that the theoretical value of the earthing wire conductor's fusing current corresponds with the test value on condition of the conductor cross section greater than 4mm2 as well as fusing time less than 1.5s. The CCA-10 earthing wires get 36.2% weight reduction compared with copper wires.

A Study on the Transient of Secondary Arc Current of UHV Transmission Lines

Secondary arcs are a type of alternating-current electric arc burning in open space, the arcing times of which are closely related to the transient of their currents. To elucidate the formation mechanism of the transient, the secondary current was first decomposed into the natural component and the forced component. Then, the corresponding circuit models were established and the formulas calculating these two components were derived. By means of the electromagnetic transients program simulation, the typical secondary arc current waveform is gotten, and its evolution is divided into three stages based on its characteristics. The influences of key factors (e.g., secondary arc resistance, shunt compensation degree, and neutral reactor) on the transient were investigated, and the most critical factor was obtained. It indicates that the transient of secondary arc current is mainly characterized by its natural component. Furthermore, using the Laplace transform method, and along with the simplification of the system circuit, the characteristic equation for the UHV transmission line was developed, and the damping factors and resonant frequencies of the natural component were solved. Compared with the previous steady-state analysis, the relationship between the decaying and oscillating processes with the system parameters is quantitatively explained. Rather than the line length, the neutral reactor, the decay of secondary arc current is directly proportional to the arc resistance, but inversely proportional to shunt reactor. The proposed methodology can be also applied to recovery voltage study. The results are essential for the transient analysis, the choice of neutral reactor, as well as the implementation of single-phase auto-reclosing strategy.

Study of Non-contact Voltage Detector of 1000kV UHV AC Based on MEMS Electric Field Sensor

This paper expounds the working principle of non-contact voltage detector and the electric field sensor which made by the technology of microelectromechanical systems (MEMS), determined the requirements of the detecting area and the threshold of the detector through simulation, and correct the threshold by carrying out experiments, which shows that by setting the threshold of the detector at 25kV/m, when the detector is 10-15m away from the conductors, or 2m away from the tower toward the conductor at the tower body whereas the same high as the conductor or on the crossarm, the detector can effectively identify whether the conductor is power on or off. The MEMS no-contact voltage detector and the method put forward by this paper can solve the problem of voltage detecting on UHV transmission lines, which has wide popularization and application value.

Single-ended method to accurately calculate UHV AC transmission line frequency parameters

The power frequency parameter of transmission line is the basic parameter of line over-voltage calculation. It is necessary to get the parameters of 1000kV AC double-circuit line on the same tower in order to guide the operation of the project. In this paper, a method of accurately calculating UHV transmission line parameters is proposed. The length of the line is known, the voltage and current at the head of the line are measured, and the zero sequence, positive sequence total impedance and total capacitive reactance are obtained. Based on the distribution parameters Calculation formula, the line unit capacitance, resistance and inductance parameters can be obtained. The method of this paper is compared with the simulation of transmission line parameters in ATP simulation. And Through the actual measurement of the frequency parameters of Yu-heng 1000kV transmission line, it is verified that this method is suitable for the calculation of distribution parameters of UHV transmission lines.

Analysis of active interference on radio station from AC UHV power

The problems of Electromagnetic Interference in Airborne Intelligence Radar Stations near the AC UHV Transmission Lines are researched in this paper, which is mainly active interference. The calculation method for the interferences is analysed, and then the proper protection distances of the AC UHV transmission line to the radar station are given. The paper analyzed the active interference of AC UHV transmission lines, and focuses on the active interference caused by the line corona on the active radar of nearby airborne intelligence when the transmission line is under normal operation. In the end, this paper proposes the recommended values of active interference protection distance for 1000kV AC UHV transmission lines and airborne intelligence radar stations.

FCAW vertical welding of “V” butt plate in AC UHV transmission line construction

In twenty-first Century, China vigorously promoted the research and construction of AC and DC transmission technology in order to ensure the optimal allocation of energy resources in a large scale[1]. In the construction of AC UHV transmission line, the welding quality of tower and stiffening plate as the load bearing tower and the tension of the welded structure plays an important role in the overall quality of the steel structure. In the past, the welding process of semi automatic carbon dioxide solid core welding wire often has the characteristics of weld spatter not easy to clean up and low efficiency of welding. The semi-automatic CO2 flux cored arc welding, has the characteristics of current and voltage to adapt to a wide range, melting speed, has important significance for improving the process, this paper describes the technology in practical engineering applications, and developed the basic strategy of training for grid steel structure welding technicians. This paper also lists both V groove plate butt FCAW welding typical welding project, hope this welding process will continue to spread.

Fast Algorithm for Passive Interference of UHV Transmission Lines

Passive interference analysis of transmission lines to radio stations is almost entirely based on the method of moments (MOM) or the rapid multipole method and multi-layer fast multipole method (FMM) developed by the method of moments. Based on the above algorithm, this paper proposes to use a diffraction model (UTD) and an optical diffraction method (PO) to model different transmission lines with different radii. The calculation results show that the difference of field strength generated by transmission lines with different radii varies with the distance of the observation point on the transmission line, and the accuracy of the UTO method is much smaller than that of the PO method. It can make good results that provides technical foundation for future modeling.

Ultrahigh Insulator Detection Robot System Design

With the problem of charged insulator zero detection in UHV transmission line has become increasingly prominent, In this paper, We take the UHV transmission line as the background to design and develop a kind of insulator detection robot based on STM32, which can realize the automatic detection of insulator chain, this paper mainly introduces the electrical system design and mechanical design of insulator detection robot. The insulator detection robot greatly improves the efficiency of insulator detection and automation of power operation and maintenance, reduces the cost of manpower operation and creates higher economic and social benefits.

Research for the Working Method of Live Replacing the L-type Insulator String on ±800kV DC Transmission Lines

It would be hard to be repaired in the case of a power outage if the ±800kV ultra high voltage DC (UHVDC) transmission line was put into operation, so live working is the guarantee for its security and stability. Insulator strings of duplex L-type are widely used in UHVDC small angle towers. In the meantime, the tower structure and the insulator strings’ arrangement type is different than the V-type. In order to ensure the security and stability of the transmission line, this paper presents a method of live replacing the duplex L-type insulators based on the actual parameter of the UHVDC L tower type and develops apparatus as a complementary supporting by mechanics analysis. In order to ensure the safety of working staff, the safe distance and combined gap of the hanging basket method are checked. Safety precautions are also proposed in the paper by the calculation of body surface field strength of the persons doing live working in the finite element method. It is shown by the field application that the live working task of replacing the L-type insulator strings can be accomplished successfully by the method put forward in this paper, which provides reference for the following live working on the UHV transmission line.

Research on the shape coefficient of disc insulator strings for UHV transmission lines

Following continuous lengthening of the ultra-high voltage disc shaped insulator strings, wind load plays a more important role in controlling of the disc insulator string. It is necessary to carry out deep study about the shape coefficient of disc insulator strings, learn the concrete wind pressure distribution, and wake flow condition of the insulator string in detail. To this end, we used the SST turbulence model to operate value simulation for the three-dimensional flow field of disc insulator strings. Results showed that value simulation could clearly simulate surface pressure of the insulator and distribution of tail flow; the fitness of calculation results for nonstructural grid and structural grid was very high; the structural grid could control every part of the grid well, but classification was complicated; the structure adaptability of the nonstructural grid was stronger compared with structural grid.

Improved Electrogeometric Model Suitable for EHV and UHV Transmission Lines Developed through Breakdown Testing for Long Air Gaps

As a type of engineering model used for solving lightning-shielding problems, the electrogeometric model has been widely used for assessing lightning-shielding failure in high-voltage and extra-high-voltage transmission lines. However, with the increase of voltage levels in ultra-high-voltage lines and the growth of the air gap, the results previously yielded by the electrogeometric model are no longer consistent with those observed. Therefore, this study corrected the equation for the relationship between lightning current and striking distance, by using data on a negative polarity 50% discharge voltage from the rod-rod gap −20/2500 μs switching impulse test wherein an air gap of up to 10 m was first tested. Subsequently, the return stroke velocity distribution observed by Idone was newly applied. In addition, the correction factor for the ground was corrected in this study. Thus, an improved electrogeometric model for application in EHV and UHV transmission lines is proposed in this paper. By employing the improved electrogeometric model to calculate the frequency of lightning strikes of 500 and 1000 kV transmission lines in Japan and a 1000 kV transmission line in China, we found that the results calculated using the improved electrogeometric model were closer to the actual observations in Japan than was the original electrogeometric model. The improved electrogeometric model provides a more reliable foundation for lightning-shielding design of extra-high-voltage and ultra-high-voltage transmission lines.

Characteristics of streamer propagation along the insulation surface: Influence of air pressure and humidity

Most of the UHV transmission lines passed the high altitude and high humidity area. It was necessary to study the influence of air pressure and humidity on characteristics of flashover along the insulation surfaces. In the three-electrode arrangement, the characteristics of streamer propagation in air alone and along the silicone rubber surface were measured at Shenzhen, Kunming, and Yangbajing, respectively. The data of the streamer ‘stability’ propagation field and velocity were measured at the different air pressure and humidity. Empirical equations were presented expressing the effects of the air pressure and humidity on the streamer ‘stability’ propagation field and velocity. Furthermore, the variation of the streamer ‘stability’ propagation field and velocity with air pressure and humidity was analysed. The test results showed that the streamer stability propagation field was in proportion to air pressure or humidity. Under the same electric field, the streamer propagation velocity was in inverse proportion to air pressure or humidity. Therefore, it was easier for streamer propagation in the lower air pressure or humidity. Furthermore, the effect of the humidity and air pressure on stability fields of streamer propagation along silicone rubber surface was larger than that in air alone.

Experimental investigation on pollution flashover performance of multiple parallel suspension insulators

In order to meet the requirement of mechanical properties, multiple parallel suspension insulators will be used in UHV lines. In this paper, pollution flashover performance of multiple parallel insulators has been investigated based on artificial contamination tests under both AC and DC voltage. Four types of multiple parallel suspension mode are used in the tests, which has 2 strings, 3 strings, 4 strings and 6 strings, respectively. Experimental results indicated that multiple parallel insulators’ pollution flashover voltage was lower than that of single string. Study showed that the result is not only affected by the multiple string leads to reduced pollution flashover probability, but also affected by the ionization of air. When the parallel number was less than 4, pollution flashover voltage of multiple parallel porcelain insulators was about 4% lower than that of a single string. If the parallel number was greater than or equal to 4, the value of flashover voltage was reduced by more than 10%. For composite insulators, the voltage drop of the multiple parallel insulators is not as obvious as that of porcelain insulators. In actual project application of the multiple parallel strings, the number of porcelain insulators and the insulation length of composite insulator was proposed to increase. The conclusion of this work can provide technical reference for the external insulation design and construction of UHV transmission lines.

Statistical characteristics of breakdowns in long air gaps at negative switching impulses

Discharge characteristics in long air gaps follow certain statistical regularities. Statistical methods and finite element simulation were both employed to deeply study discharge characteristics. The statistical results indicate that the height of grounding rod has a slight influence on the 50% breakdown voltage of rod-rod air gaps and that the breakdown time is longer than the wave front time when 20/2,500 μs switching impulse is applied and shorter than the wave front time when 80/2,500 μs switching impulse is applied. Furthermore it can be shown that the distribution of the breakdown voltages in 10 m rod-plane gap follow the normal distribution and that the V-t characteristics of rod-rod gaps is lower than that of rod-plane gaps. Calculation results indicate that the non-uniform coefficient of the electric field increases with increasing gap distance and that the ratio of gap distance to the non-uniform coefficient also increases with the gap distance. The work described in this paper can be used for the insulation coordination of UHV transmission lines.

Experimental research on lightning shielding performance of large scaled UHV transmission line

In actual operation, the shielding failure rate of UHV transmission line is much higher than that in simulation, so it is crucial to study the lightning shielding performance by experimental research. The testing UHV transmission line model is scaled down in the ratio of 12.5 which is relatively large comparing to other testing models. Two kinds of negative switching impulse waveform were applied to HV rod to simulate the lightning descending leader. The probability of transmission line being stroked was calculated statistically by recording more than two thousand discharges and the factors that affecting the discharge probability were studied through contrast tests. The results show that the grounding condition, DC bias, the protection angle, the switching impulse voltages have an influence on the discharge probability, breakdown voltage and breakdown time. The spatial boundary of shielding failure area was determined in the middle of the span. The upper and lower spatial boundary and the distance between them increased with the increasing of the lateral distance between HV rod tip and transmission line model simultaneously.

A Frequency-Domain Approach to Compute Surge Propagation on a Single-Phase Transmission Line Under Corona

The corona phenomenon occurs whenever the electrical field at the conductor surface exceeds a certain critical level. It is a very important aspect to be considered for an adequate design and performance evaluation of EHV and UHV transmission lines. Corona produces losses, noise and electromagnetic interference. It also affects surge propagation and can contribute to a decrease in the insulation levels of transmission lines. For an adequate assessment of the phenomena involved, an accurate representation of both frequency-dependent and nonlinear phenomena is needed. The latter is best described in the time domain, while the former is more easily studied in the frequency domain. In this work, we propose an alternative scheme implemented on a frequency-domain approach based on piecewise linear approximation of the corona (charge vs. voltage) characteristics. Numerical Laplace transform is applied to obtain the actual time responses.

Effect of profiles on ac contamination flashover performance of large-tonnage suspension disc insulators

From field experience and laboratory experiments, it was indicated that the flashover performance of contaminated insulators was significantly influenced by the insulator geometry. In the paper, insulators with three different profiles including seven types of deep under-ribs disc insulator, three types of two-shed disc insulator and three types of three-shed disc insulator were tested in an artificial climate chamber to investigate the influences of insulator profile parameters on the flashover performance of large tonnage disc insulators. The artificial contamination test results indicated that 50% flashover voltage stress (E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> ) decreased with the increasing insulator diameter and creepage distance. The influence of salt deposit density (SDD) was also investigated, and it was found that E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> of alternating-shed insulator decreased more rapidly than that of deep under-ribs insulator with the increase of SDD. An empirical expression was proposed, by employing the least-square method, to describe the relationships between E <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50%</sub> and insulator configuration parameters as well as SDD. Through analyzing the generalized fitting coefficients (r) of the equation and the standard error of estimate (s), it can be concluded that the calculated results are in good agreement with the experimental data. Moreover, special attentions were also paid to the influence of the under-ribs and the ratio of shed overhang distance to the shed spacing on flashover performance respectively. This work can enrich the investigation of insulators parameters and may provide useful reference for performance evaluation and selection of insulators in EHV and UHV transmission lines.

Discussion on Active Television Interference Characteristic of UHV AC Transmission Line

High-voltage transmission line corona and sparking will bring television interference (TVI). Study has been seldom executed about active TVI from HV transmission line, and much less research on UHV AC lines. Based on present literatures, this paper brings forward test method of TVI from HV transmission line. Near straight span and tension tower of Chinese UHV AC Pilot Demonstration Project, several tests about TV picture, TVI field strength, the television signal field strength before and after lines energized, has been carried out in good weather. According to observation, interference characteristics to TV picture has been analyzed. Results indicate that, with increasing distance from the outer phase, UHV single circuit TVI field strength in fine weather attenuates negative exponentially. This paper illustrates it is questionable to use CISPR quasi-peak value for assessment of interference on TV picture caused by UHV transmission line corona and sparking noise.

Application of Large Size and High Strength Angle in UHV Transmission Line Tower

Considering width and thickness of large width angle steel, the section area of large width angle steel is larger than that of normal angle steel. Application of large width angle can increase bearing capacity of the member. Therefore it is feasible that large width angle steel replaces double combined angle steels. Taking the tower for ±800 kV DC transmission line from Jin ping to south Jiangsu Province, under the same design conditions, large width angle steel and double combined angle steels are used respectively in the main members of the tower to modeling finite element analysis.The results indicate that the stiffness variation is more uniform, causing rod end bending bar additional stress is about the axial stress of about 2%~3%.