Haijun Niu

Statistical analysis and research on galloping characteristics and damage for iced conductors of transmission lines in China

Galloping is a major impact on the design of overhead transmission lines and has caused various kinds of structural damage. With rapid development of construction content and scale for China grid and with frequent appearance for worse severe weather in recent years, galloping accidents of iced conductors are becoming more frequent in China, which has caused severe economic losses and social impacts. The statistic data is collected based on historical records about galloping accidents in nearly 20 years in China. And the statistic results are presented by probability statistic methods, which includes statistical characteristics of structural parameters for transmission lines,different ices coated on the conductors, different meteorological conditions (wind, rain, snow, temperature and humidity etc.) and different damages caused by galloping when galloping accidents take place. Using dimensional analysis, the major parameters to influence galloping accidents occurrence are proposed and the statistic relations between relevant parameters and galloping occurrence are derived. And based on the new characteristics, changes for galloping accidents occurrence in time domain and areal distribution are proposed to obtain the new trend for transmission lines galloping in China. The results and conclusions in this paper can provide a research direction and data support for galloping theoretical analyses and anti-galloping design.

Effect of Heat Treatment on the Low-temperature Resistance of 42CrMo Steel in Electric Power Fittings

The mechanical properties and low-temperature resistance of the 42CrMo steels utilized in electric power fittings after different heat treatments were comparatively investigated. Results indicated that a tempered sorbite with refined structure was obtained in the steels and the mechanical properties and low-temperature resistance were consequently improved after quenching + quenching + tempering and cyclic quenching and tempering, especially after the latter. The product of strength and elongation reached up to 25725 MPa% and the impact energy at -50 °C increased to 48 J after cyclic quenching and tempering as compared to 16562 MPa% and 19 J after conventional quenching and tempering. The 42CrMo steel after cyclic quenching and tempering can be considered as a suitable candidate for connection fittings in electric power transmission line.

JL1X1/LHA1-1040/550 development of aluminum alloy core forming aluminum twisted line pair splicing sleeve

UHVDC project will be prepared by JL1X/LHA1-1040/550 aluminum alloy core forming aluminum twisted line to reduce the load on the tower, improves the safety performance of the circuit, and has the function of upgrading line capacity. For such a wire, the domestic currently has no relevant research experience of line pair splicing sleeve, in order to meet the needs of practical engineering, this paper completed the pair splicing sleeve material and a compression ratio development according to the structural characteristics of this guide line; through a splicing sleeve manufacturing and testing, the development of aluminum JL1X/LHA1-1040/550 aluminum alloy core aluminum twisted wire pair splicing sleeve grip strength meets 95%RTS.

Economic Analysis on Application of Large Section Conductor in Ultra-High Voltage DC Engineering

At present, large section conductors applied in domestic ±800kV ultra-high DC power transmission line consist of 6×720mm2, 6×900mm2 and 6×1000mm2 conductors. This paper analyzes initial engineering investment and mechanical performance of 6×JL1/G2A-720/50, 6×JL1/G3A-900/40, 6×JL1/G3A-1000/45, 6×JL1/G2A-1250/70 and 6×JL1/G2A-1520/125 conductor plans, carry out economic comparison of the whole life period of these 5 conductor plans, demonstrate economic of 6×JL1/G2A-1250/70, and 6×JL1/G2A-1520/125 conductor plans in ±800kV ultra-high DC power transmission line is more advantageous when annual loss hours is too high, and the 6×JL1/G2A-1250/70 plan can save initial investment of engineering compared to the 6×JL1/G2A-1520/125 plan.

Vacuum Zincification Technical Study of Fitting Material in Power Transmission Line

Fittings of the power transmission line are requested to have good anti-corrosion performance when they are use at atmosphere environment. The fittings of the power line have certain mutual movement during application process, which mutually produce friction. In particular to the fittings of the power line which are applied in the area and environment with strong wind sand such as western area, wind sand will produce corrosion wear of the fittings in the line. Therefore the fittings of the power line are requested to have good anti-abrasion and corrosion resistant comprehensive performance. In combination with application environment of the power fittings and characteristics of vacuum zincification technology, carry out analysis on possibility of application of vacuum zincification in the fittings in the power line from performance requirements, fitting materials, geometrical features of the fittings, economy of vacuum zincification etc several aspects.

Research on Combination Anti-Galloping Method between Interphase Spacer and Rotary Clamp Spacer for Transmission Lines

The efficacy of single anti-galloping equipments is limited due to shortage of relevant galloping mechanisms or more complex wind and ice conditions. In this paper, a combination anti-galloping method between interphase spacers and rotary clamp spacers is proposed to avoid or reduce the “whole galloping” and “subspan” galloping phenomenon which occur notwithstanding installing interphase spacers. The combination method is designed using multi-mechanisms anti-galloping design, controlling phase-to phase clearance, affecting structural whole properties, and changing iced shape. The galloping critical conditions of wind and ice to excite “whole galloping” and “subspan” galloping are increased by using rotary clamp spacers than by using only interphase spacers. The anti-galloping effect can be improved greatly by using the combination method.