Shengqiang Zhu

Study on Traveling Wave Propagation Characteristics of ±800 UHVDC Transmission Lines

Traveling wave produced by a short-circuit fault or lightning will propagate along transmission lines with deformation and attenuation, which are due to energy loss and frequency-dependent line parameters. By the phase-modal transform method, the multi-conductor transmission lines could be decoupled into independent modal. Each modal is a single uniform line described as two-port networks. In this paper, the frequency-dependent parameters of uniform transmission lines are calculated in complex frequency domain. Based on the telegraph equation in complex frequency domain, the transfer functions between traveling wave signal source and observation point (relay location) are derived. The time domain waveforms of traveling wave at the observation point are calculated by Hosono numerical Laplace inverse transform method. Compared with PSCAD/EMTDC simulation results, the proposed method in this paper is proved effective.

Modeling and Simulation of Lightning Electromagnetic Transient and Identification of Shielding Failure and Back Striking in ±800kV UHVDC Transmission Lines - Part II: Identification of Shielding Failu

The identification of shielding failure and back striking in transmission lines has always been a difficult subject. This paper analyzed the process of back striking and shielding failure in ±800kV UHVDC transmission lines. Because the mechanisms of produced transient zero module voltage and its propagation paths is different between back striking and shielding failure, their wavelet energy of different frequency bands of transient voltages is different. Thereby, from the perspective of protective relaying, this paper proposed an identification method to shielding failure and back striking in ±800kV UHVDC transmission lines based on wavelet energy. The data can be acquired from high speed protection device. The EMTDC simulation shows that the proposed method can effectively identify shielding failure and back striking in the whole UHVDC transmission lines, and is not affected by various wave shapes of lightning current.

Modeling and Simulation of Lightning Electromagnetic Transient and Identification of Shielding Failure and Back Striking in ±800kV UHVDC Transmission Lines - Part I: Modeling and Simulation of Lightni

Lightning stroke to transmission lines was introduced in this paper. Modeling and implementation method of tower, corona and insulator for lightning electromagnetic transient research was discussed. Comprehensive model for study of UHVDC lightning electromagnetic transient was built, and lightning caused fault and lightning disturbance were simulated in PSCAD/EMTDC based on the model, which offered a research platform for identification of shielding failure and back striking in plusmn800 kV UHVDC transmission lines.

Analysis on Cascading Outages of Yunnan-Guangdong Ultra-High Voltage Transmission System

Many severe cases of black outs have taken place recently among different countries, which has been the significant factor on power systems safe and stable operation. Taking 2010 Yunnan-Guangdong ultra-high voltage transmission system as example, power flow diversion is analyzed when faults occur on the sending Yunnan power system. Action of resistance three segment protection is obtained by comparing calculating resistance and protection setting, which provides the suggestion that how to prevent the cascading outage of Yunnan power grid. The research is constructive, and the conclusion has been applied on the manufacture of Yunnan power grid.

Analysis on cascading outages of Yunnan-Guangdong Ultra-high voltage transmission system

Many severe cases of black outs have taken place recently among different countries, which has been the significant factor on power systempsilas safe and stable operation. Taking 2010 Yunnan-Guangdong ultra-high voltage transmission system as example, power flow diversion is analyzed when faults occur on the sending Yunnan power system. Action of resistance three segment protection is obtained by comparing calculating resistance and protection setting, which provides the suggestion that how to prevent the cascading outage of Yunnan power grid. The research is constructive, and the conclusion has been applied on the manufacture of Yunnan power grid.