Study On Corona Characteristics Of 1000kV UHV AC Transmission Lines At High Altitude

The corona's onset and corona loss of the conductors are important technical indexes for the erection of ultra high voltage(UHV)AC transmission lines.In high altitude areas,the conductors are more likely to get corona discharge because of the thin air and the strong ultraviolet light.Therefore,the study of corona characteristics of UHV AC transmission lines at high altitude has certain theoretical significance and important engineering value.Based on the UHV corona cage of Xining Ping'an UHV experimental base,the corona characteristics of LGJ-630 and LGJ-720 conductors with different bundle numbers were systematically studied by using the corona measurement system and Ultraviolet(UV)imager developed independently.The research results can be used as the important data reference for the type selection of UHV AC wire in China.The hardware of the measurement system is redesigned,and a set of integrated photoelectric corona loss measurement system is developed.The improved system is composed of the remote optical communication acquisition module and the local merging unit module,which improves the integration degree of the existing fiber digital measurement system.The optical pulse triggering ensures the synchronous acquisition of each remote optical communication data acquisition module,and successfully solves the time delay problem in the corona current and voltage acquisition process.The error test shows that the phase difference and the ratio displacement of the measurement system are better than the existing measuring system.The corona characteristic curves of 8 x LGJ630 and 4,6,8 and 10×LGJ-720 conductors at 2200 m altitude were obtained for the first time,and the corona's onset characteristics of the split conductors were analyzed.First,the corona's onset voltage and field strength of the conductors are obtained by the tangent method.The data of the 8×LGJ-630 conductor at 2200 m are compared with the data obtained from Wuhan(altitude 19m).The influence rule of altitude on 8×LGJ-630 conductor is analyzed,and altitude correction is got.Then the influence of the rainfall rate on the corona's onset voltage is analyzed,and the regularity of the saturation characteristic of the corona voltage with the increase of the rainfall rate is obtained.Finally,based on the calculation model of the onset voltage,the roughness coefficient of the bundle conductors under different weather conditions is calculated.The corona loss characteristics of bundle conductors are studied.Taking the typical tower type of 1000 kV UHV AC double circuit transmission tower as an example,the surface electric field strength of actual line conductor is simulated by finite element calculation software.The corona loss of the wire at high altitude is calculated,and the corona loss data of the double circuit transmission lines at the same tower are obtained at an altitude of 2200 m.The results show that if 8×LGJ630 bundle conductors are still used at the altitude of 2200 m,the corona loss will be large.It provides a data reference for our country to build UHV AC double-circuit transmission line on the same tower in high altitude area.