Advanced Materials Research Vols. 1070-1072

Abstract: Developing bilateral power trade with surrounding regions is not only in favor of improving economic benefit of units in Shanghai grid, but also contributing to the economic development and power distribution safety of Shanghai and surrounding regions. In this paper, considering the situation of indicator control of environmental capacity in key area on power generation enterprises, completion situation of pollution control in generation enterprises, bilateral trade model and evaluation method under the constraints of mandatory environmental indicators are analyzed. Furthermore, solution on achieving clean electricity generation of bilateral trade power in the city of Shanghai is proposed.

Abstract: The paper represents a research of transient stability accessing of power system and distributed generation sources. The methodology of modeling is presented. The analysis of transient stability of DG sources is presented and shows the impact of DG on transient system stability.

Abstract: Based on the UHVDC project from Hami to Zhengzhou, two typical faults for transient stress calculation of DC filter including ground fault on the DC line and incoming switching surge on the DC line are presented. The simulation steep-fronted models and factors including protective characteristics of arresters, parasitic inductances should be considered for these two faults are introduced. The protective level of arresters are obtained according to the calculated maximum according current of arresters, and the insulation levels of the filter equipment are defined according to the insulation margin. The research can provide technical supports for project construction.

Abstract: Since the strong coupling property between partial discharge and external interference, how to obtain an acceptable Resolution is a huge challenge during partial discharge measure. In terms of interference suppression, many methods associated with analog and digital technique are devised. Whatever the methods are, the way to eliminate pulse interference is the toughest task due to the closest feature in the respect of time and frequency field compared with partial discharge. In this paper, we propose a wavelet based interference separation method to separate partial discharge signal compounding with random pulse signal, mobile communication signal and white noise, providing valid data for the following partial discharge measurement. Both simulation and practical results verify the effectiveness of our proposed method.

Abstract: There are plenty of intrinsic cation states on the surface of nano-semiconductor crystals. When the crystals contact the transformer oil，surface states that can capture electrons easily are formed. In this paper, TiO2 nano-powders with different surface modifications have been used to improve the property of transformer oil (Karamay 25#). The modification effects of nano-power’s on insulating property of transformer oils have been investigated. And the modifying effects of TiO2 nano-powder with different concentrations on transformer oil have been studied. The breakdown property tests and fitting results show that TiO2 nano-powder can improve the breakdown properties of transformer oil and within some concentrations，the higher the concentration of TiO2 nano-powder，the better the power frequency insulating property of modifying transformer oil. Besides，The modifying agents play a key role in the dispensability of TiO2 nano-powder in the transformer oil. With the increasing of nonpolar segment in the modifying agent, the breakdown property of the modified oils gets more enhancements.

Abstract: Due to the large capacity of large power transformers, normally the power capacity of a load test is difficult to meet the test requirement, which makes the ancillary devices such as induction regulator, intermediate transformer etc. difficult to meet the test demands too. The transformer factories with limited power capacity can only perform load test under less than fifty-percent of the rated load current, which not obeys the standards and technical protocols. Thus, a field load test method for large power transformers is proposed in this paper. It carries out the reactive power compensation with compensation capacitors, which reduces the capacity of test power supply and makes the field load test possible. This method also gives a guarantee for the safe and stable operation of power transformers.

Abstract: High temperature superconducting (HTS) cable termination is an important component of the HTS cable system, which functions to connect the HTS cable and the conventional cable accessory. The stress cones of the HTS cable termination can improve the internal electric field distribution and the electrical insulation strength of the cable termination. In this paper, the mathematical model and equivalent circuit model of the stress cones are built and the genetic algorithm is adopted to the design of 110-kV HTS cable terminal stress cone. The capacitance, radial electric field, axial electric field, voltage, insulation thickness and other parameters of the stress cone were compared before and after the optimization of the stress cone. Finally, the simulations of the stress cone with the optimized structure were made using finite-element analysis software COMSOL to test the optimization result.

Abstract: ±UHV (Ultra-high voltage) DC (direct current) wall bushing is an important equipment of UHV DC transmission system. It plays a key role in the economic transfer, flexible allocation and safe usage of power. In this paper, the methods of improving the electric field distribution and insulation construction optimization are explored. The choice of insulation materials is discussed. Some calculations are made about how to optimize and design the capacitor core and how to optimize the parameters of grading rings. The research results would provide useful reference for further design and development of UHV DC wall bushings.

Abstract: Transformers health index calculation method based on cloud model and fuzzy evidential reasoning is proposed. According to the multi-level and multifactor of evaluation index information of power transformers, a layered evaluation index model is established. In order to deal with the ambiguity and uncertainty information of evaluation index, a normal cloud model is introduced, inferred the fuzzy degree of belief in the health state of evaluation index. Then use the fuzzy evidential reasoning method merge information of evaluation Index, inferred the degree of belief in the health state-level of transformer, calculated the health index of transformer. The results of an example analysis test its rationality and effectiveness.

Abstract: Jiangxi ultra high voltage (UHV) accessed program is introduced. Based on uniform transfer equation, UHV π-type equivalent circuit is derived by considering the distributed parameter characteristics of UHV transmission line without conductance. Based on advanced digital power system simulator, the relationship of shunt reactor and steady-state voltage, as well as the relationship of shunt reactor and transient voltage, is achieved by using electromechanical and electromagnetic hybrid simulation, where the UHV between Hubei and Jiangxi is considered. Influences of shunt reactors’ location and the degree of compensation on UHV’s steady-state voltage and transient power frequency overvoltage are analyzed. The Logical results provide a meaningful guidance for the introduction of UHV power grid into Jiangxi power grid.