China Southern Power Grid Technology Research Center

Guangzhou, China

China Southern Power Grid Technology Research Center

Guangzhou, China

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Wang Z.,Northeast Dianli University | Wang L.,Northeast Dianli University | Xie X.,Tsinghua University | Yang Y.,China Southern Power Grid Technology Research Center | Wang Y.,Northeast Dianli University
Dianwang Jishu/Power System Technology | Year: 2011

In allusion to subsynchronous resonance (SSR) risk of power transmission system with series compensator, a quantitative evaluation method in which the frequency scanning and complex torque coefficient are integrated is proposed. Firstly, in the proposed method the impedance-frequency scanning is utilized to obtain the simplified equivalent model of power transmission system with series compensator and its parameters; then based on complex torque coefficient the explicit expressions of damping under various torsional vibration modes, in which the mechanical damping and electrical damping of shafting are taken into account, are derived. Case study results show that the results from the proposed method conform to those by eigenroot analysis, however the proposed method is succinct and intuitional and its calculation burden is less, besides, the expressions of the proposed method are the explicit function of parameters of generators and power network, so the proposed method can offer direct, accurate and quantitative damping results for multi-mode SSR. The proposed method can be applied to power grid with multi-series compensators and multi-voltage grades to perform SSR risk evaluation.


Xie K.,Chongqing University | Wu T.,Chongqing University | Huang Y.,China Southern Power Grid Technology Research Center | Jian H.,Southern Company | And 3 more authors.
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2010

Reliability optimal distribution (ROD) for high voltage direct current (HVDC) transmission systems can be used to choose reliability parameters of components to meet the requirement of a pre-specified system reliability performance. It is becoming an important means of decision-making for HVDC transmission project of bidding, planning and designing processes. Based on the property of the system reliability increasing with the reliability performance of components, this paper proposes a non-linear programming model for the ROD, which considers a wide range of constraints including the pre-specified system reliability. This model can be solved using the bisection method. Therefore, the optimal reliability parameters of components can be obtained. Case study of a HVDC transmission system of single 12-pulse was used to illustrate the performance of the proposed algorithm. A wide range of system reliability indices including the forced energy unavailability (FEA) and monopole forced outage times (MUOT) are the pre-specified indices. Results from the case study show that the method is feasible and effective.


Chen S.,Tsinghua University | Zhang G.,Tsinghua University | Xu S.,Tsinghua University | Luo B.,China Southern Power Grid Technology Research Center | Zhao Y.,China Southern Power Grid Technology Research Center
Qinghua Daxue Xuebao/Journal of Tsinghua University | Year: 2011

Laser de-icing is a new non-contact method for electrical system component deicing. A finite element model of laser de-icing was used to analyze the effect of laser de-icing and ascertain the theoretical basis for choosing the best laser de-icing parameters. The model simulates the temperature and stress fields in the ice during the laser de-icing process. The temperature and stress fields and the penetration rates are given for different initial temperatures, laser powers and beam widths. Specific requirements are given for choosing reasonable parameters to improve laser de-icing.


Hu B.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Xie K.-G.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Li X.-L.,China Southern Power Grid Technology Research Center | Cao K.,State Key Laboratory of Power Transmission Equipment and System Security and New Technology | Liu Y.-S.,China Southern Power Grid Co.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

Generally, HVDC transmission system has a quite complex structure with a large number of components. As is well known, each component has a different impact on the system reliability. The technique of determining the contribution of each component to the system unreliability can be used to identify the system weak parts and provide a useful tool for the decision-making on HVDC system operation and planning processes. This paper proposes an unreliability-tracing principle based on the proportional sharing principle (PSP), and an unreliability-tracing model for HVDC transmission systems. The PSP was used in this model twice based on the sub-system division scheme. In the unreliability-tracing process of the sub-system, the contribution of each component to a sub-system unreliability index can be calculated using the PSP. In the unreliability-tracing process of the whole system, the contribution of each sub-system to the system unreliability can also be calculated using the PSP. The contribution of each component to the system unreliability can be obtained by combining the two contribution results. The case study indicated that the proposed technique can distribute the HVDC transmission system reliability index to components or sub-systems impartially and reasonably, and it can also be used to identify the system weak parts. © 2010 Chin.Soc.for Elec.Eng.


Huang X.-B.,South China University of Technology | Huang X.-B.,Polytechnic University of Mozambique | Luo B.,China Southern Power Grid Technology Research Center | Wang Y.,Polytechnic University of Mozambique | Li X.-L.,China Southern Power Grid Technology Research Center
Gaodianya Jishu/High Voltage Engineering | Year: 2010

It is very difficult to online diagnose the insulation of MOA due to the lack of effective theory and methods of online monitoring of MOA. Firstly, an online monitoring system of MOA was produced, the voltage sampling circuit, current sampling circuit, lightning counting circuit, wireless communication unit and A/D correcting circuit of which were designed. The grey relational analysis was introduced into quantifying the similarity between online monitoring data of MOA and environmental factors. The resistant current I, relative humidity Hr, temperature θ were analyzed and the climatic factors with maximum relation degree was determined. The running results show that the maximum relational degree with low current of NO.125 tower is 0.9238, the degree with high current is 0.9225, and the row with maximum relation degree is relative humidity. Then the current of MOA is influenced by above climatic factors and greatly by relative humidity.


Fothergill J.C.,University of Leicester | Dodd S.J.,University of Leicester | Dissado L.A.,University of Leicester | Liu T.,China Southern Power Grid Technology Research Center | Nilsson U.H.,Borealis
IEEE Transactions on Dielectrics and Electrical Insulation | Year: 2011

The dielectric response of crosslinked polyethylene (XLPE) insulated, miniature power cables, extruded with inner and outer semicons, was measured over the frequency range 10-4 to 104 Hz at temperatures from 20 to 100 °C. A dielectric spectrometer was used for the frequency range 10-4 to 10-2 Hz. A bespoke noise-free power supply was constructed and used to measure the dc conductivity and, using a Fourier transform technique, it was also used to measure the very low dielectric tanδ losses encountered at frequencies of 1 to 100 Hz. Tanδ measurements of <10-5 were found in this frequency range and attributed to a ?-mode dielectric relaxation lying above 100 Hz due to motion of chain segments in the amorphous region and an α-mode relaxation lying below 1 Hz window due to twists of chains in the crystal lamellae. The dc conductivity measurements were consistent with those of the dielectric spectrometer and indicate lower dc conductivities in vacuum degassed cables than have been previously reported for XLPE (less than 10-17 S.m -1). The conduction process is thermally activated with an activation energy of approximately 1.1 eV. Higher conductivities were found for nondegassed cables. A transformer ratio bridge was used for measurements in the range 1 to 10 kHz; loss in this region was shown to be due to the series resistance of the semicon layers. Thermal ageing of the cables at 135 °C for 60 days caused significant increases in the conductivity and tanδ and it is considered that such measurements may be a sensitive way of measuring electrical degradation due to thermal aging. © 2011 IEEE.


Xie K.-G.,Chongqing University | Wang L.-B.,Chongqing University | Liu Y.-S.,China Southern Power Grid Co. | Hu B.,Chongqing University | And 2 more authors.
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

How to determine the optimum type of components to obtain the maximum benefit considering the cost and operational reliability is becoming an important issue in the HVDC system planning and design processes. Based on the cost-benefit principle, the model and algorithm of determining the optimum type of components in HVDC systems is proposed. Considering the investment, maintenance and outage costs, this problem was formulated as a nonlinear and discrete optimization model. An improved genetic algorithm with an integer coding technique and adaptive probabilities of crossover and mutation was used to solve this problem. The computation effectiveness of the proposed method was also improved using the technique of saving the reliability of subsystems according to the inherent characteristics of HVDC systems. A single 12-pulse HVDC system was used to illustrate the proposed technique. Case studies indicated that the model and algorithm were feasible. Results also showed that the proposed method is an appropriate tool to determine the optimum type of components in HVDC planning and design processes. © 2010 Chin. Soc. for Elec. Eng.


Sun H.-F.,North China Electrical Power University | Cui X.,North China Electrical Power University | Qi L.,North China Electrical Power University | Wang Q.,China Southern Power Grid Technology Research Center | Li X.-L.,China Southern Power Grid Technology Research Center
Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering | Year: 2010

Converter valves are the kernel components in HVDC transmission system, which are exposed to various overvoltages from both internal and external system during operation. A wideband equivalent circuit for the whole valve tower was built upon the stray capacitances and inductance of the valves extracted with different methods. Based on this circuit model, the voltage gradient of valve layers and voltage distribution among valve components were calculated under different kinds of overvoltages including switching, lightening and fast front overvoltage, and the influence factors were also discussed. Some regularity was obtained, e.g. the stray capacitances of the valves have an effect on the overvoltage distribution among valve components, while the parameters of the valve components can influence the voltage drop on thyristors. Lastly, some improved measures are proposed. © 2010 Chin. Soc. for Elec. Eng.


Liu J.,North China Electrical Power University | Zhao C.,North China Electrical Power University | Li G.,China Southern Power Grid Technology Research Center
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

The nonlinear relationships between their on-state voltage drop or switching loss and the current are represented by the quadratic polynomial for IGBT and diode at specified temperature, which is simple and accurate. Based on the mechanism analysis of diode-clamped three-level converter, the conduction rules and conduction duty cycle are determined according to the relationship between voltage and current. The characteristic curve of IGBT is fitted with polynomial to establish its loss model, based on which its loss calculation method is proposed. With the proposed method, the power loss of each switching device is calculated for the diode-clamped three-level converter. It is concluded that, the loss distribution of each switching device is unbalanced, varying with the power factor and the modulation index. The loss distribution graphs are given for four special operating conditions.


Jiao C.,North China Electrical Power University | Qi L.,North China Electrical Power University | Cui X.,North China Electrical Power University | Wang Q.,China Southern Power Grid Technology Research Center
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2010

Based on transmission theory, the theoretic model of power line de-icing with medium frequency excitation is established. How to select the optimal excitation frequency is presented. For different loss tangent of ice layer, the corresponding optimal frequency, heat power distribution and its uniformity, and the power factor of de-icing power source are calculated. Numerical results show that, both heat power distributions with high uniformity and up to 100% power factor can be achieved by using the de-icing technology.

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