Overvoltage Suppression for UHV Transmission Lines

The overvoltage phenomena of ultra high voltage (UHV) transmission lines are analyzed and verified by EMTDC/PSCAD simulation. Referring to the theoretical analyses and operating experiences of extra high voltage (EHV) transmission lines in China and UHV transmission lines in Russia and Japan, the methods to suppress the internal overvoltage in UHV transmission lines by protection and control strategies are discussed. Through the cooperation among the recloser, shunt reactor, tripping and closing resistance, and metal oxide varistor(MOV), the overvoltage can be restrained within an acceptable level.

Effects of Un-transposed UHV Transmission Line on Fault Analysis of Power Systems

The conventional fault analysis method based on symmetrical components supposes that the three-phase parameters of un-transposed transmission line are symmetrical in case of fault. The errors caused by the method with the symmetrical distributed parameter circuit model as the equivalent circuit of the un-transposed ultra high voltage(UHV) transmission line were studied under both normal operation and fault,and the corresponding problems arising were pointed out. By contrast with electromagnetic transient and power electronics(EMTPE) simulation results with the asymmetrical distributed parameter circuit model of un-transposed line, it is shown that the conventional method cannot show the existence of negative and zero sequences before fault happening and there are many errors on voltage and current after fault happening which are different with fault types. The error ranges of voltage and current are 2.13%-81.13% and -7.82%- -86.15%, respectively.

The first UHV experimental line section constructed

The first UHV experimental line section of 1000 kV class in China, situated at the outdoor test yard of Wuhan High Voltage Research Institute under the Ministry of Electric Power has been built just before July 1st, 1996. This experimental line section is 200 m long with 3 phase, 8

Statistical Analysis of Radio Interference of 1000 kV UHV AC Double-circuit Transmission Lines in Foul Weather

Analyzing the impact of radio interference(RI)variation during foul weather conditions is an area that has received limited study.This paper provides a statistical analysis of RI measurements obtained from a long-term observation station close to the world’s first commercially operating 1000 kV UHV AC double-circuit transmission line in China.During six months of observations,the impact of RI was studied on the line during fog,drizzle,and light snow and rain.It was found that RI increases linearly with the natural logarithm of the precipitation intensity.The Levenberg-Marquardt algorithm(LMA)is employed to fit the RI value with the precipitation intensity.The reasonable distribution of RI in different foul weather is verified by one-sample K-S test.This test is seen as beneficial for further RI prediction based on statistical weather mode.

Corona Onset Voltage Gradient of Bundle Conductors for EHV/UHV AC Power Lines in Corona Cages Considering Altitude Correction

The corona onset voltage gradient(COG)of conductors is a key parameter in the design of overhead transmission lines.The commonly used semi-empirical calculation formula proposed by Peek(1910s)at present can roughly estimate the COG of single conductors and is not applicable to large cross-section bundle conductors.In this paper,experiments are conducted to investigate the corona characteristics of a whole series of bundle conductors at different altitudes,and a prediction formula is proposed for the COG of large cross-section bundle conductors on AC transmission lines considering the altitude correction.The calculated values using the proposed prediction formula are compared with the experimental values of the COG in two cases:UHV eight-bundle conductors at an altitude of 19 m;500 kV UHV four-bundle conductors in Wuhan,Xining,Geermu,and Nachitai at four different altitudes.The results show that the use of the formula can predict the COG of bundle conductors with the radius of 1.34 cm to 1.995 cm and the number of subconductors of 4 to 12 at altitudes of 19 m to 4000 m above the mean sea level.The research findings can provide a reference for the design of EHV and UHV overhead transmission lines and even those in higher voltage levels.

Digital simulation studies on long transmission line protection based on balance of energy

The protection based balance of energy is a new technique specially proposed for long transmission lines. This technique depends upon the calculation of net energy into the transmission line by two independent methods and comparing them to indicate healthy and faulty conditions. In order to study the performance and feasibility of the protection based on balance of energy, the new protection has been extensively tested by using EMTP on a long transmission line with various configurations and operating conditions (including single pole line, double circuit lines and two phase operation). The results calculated by EMTP show that under any condition of a power system, the proposed technique has excellent performance,the viability even for high resistance ground faults and a short operation time.

Analysis of the harmful effects to buried oil pipeline from power line short-circuit fault

Based on the transmission line theory of the buried metallic structures, the concerned harmful effects to the buried oil and natural gas pipelines caused by the power line short-circuit fault are further discussed. A closed-form expression of the induced voltage caused by the short-circuit fault of the ultra-high voltage power （UHVAC） transmission line is given. The transmission line model of the buried pipeline is set up and a set of formulas for calculating induced voltage on the pipeline and the parameters of the buried pipeline in actual environment condition are given. At last, the characteristic of the harm^hl effects on the buried pipeline from the power line short-circuit fault are discussed.