Applied Mechanics and Materials Vols. 448-453

Abstract: Four typical defects in GIS for PD detection are proposed, and the pulse, amplitude, phases, number of PD has been used to form the three-dimensional PQN matrix. Based on the PQN matrix, three two-dimensional distributions of Hqmax~Phi, Hqmean~Phi and Hn~Phi can be achieved. Then the new GK clustering method is introduced to separate the four different defects according to separate the four different partial discharge defects in gas in GIS, according to the parameters of Skewness (Sk), Kurtosis (Ku), number of peaks (Pe), cross-correlation factor (CC) and the discharge factor Q.

Abstract: Partial discharge signal in GIS is a kind of typical non-stationary signal, using the time or frequency domain simply is not enough to describe the time-varying information of PD. Based on the reason above, this paper introduces a joint time-frequency analysis method according to the reassignment theory for analyzing the PD of GIS. After the processing of the PD signals simulated and on field, we conclude that this method provides a higher concentration in the time-frequency plane and reduces the most influence of the cross-interference terms.

Abstract: In order to classify and identify different types of defects in GISs, this paper introduces a novel adaptive affinity propagation clustering (adAP) algorithm, which is used for classification of UHF signals of four kinds of typical defects. The algorithm has overcome the conventional affinity propagation (AP) algorithms defects, namely inability to acquire cluster number accurately and inability to cease oscillations, by technologies of adaptively scanning preference space to search for the number of clusters to find the optimal clustering results, adaptively adjusting the damping factor to eliminate oscillation and adaptively escaping oscillations. Finally, validity verification is performed over classification results using a variety of validity indexes. It is discovered that adAP algorithm can accurately tell the number of classes and realize classification of different types of defects. It is also superior to conventional AP algorithm in regards of the processing time and the number of loops.

Abstract: It is well known that state detecting and evaluating of grounding grid in substation especially defect diagnosis is highly necessary for power system. To detect and evaluate the state efficiently, relevant parameters should be obtained exactly as existing standards all put great emphasis on different parameters should be well-considered. This paper proposed a grounding grid parameter measuring system composed of three devices, through which grounding grid resistance, step voltage, contact voltage under alternating current, connection resistance under direct current and surface potential under square current are available, square current is present in this paper for defect diagnosis . IPC is utilized as the superior computer in this system together with digital touch screen that directly lead to larger storage capacity, simple operation and more friendly convenience for communication between human and computer compared with traditional SCM system. Through experiments it is proved to be accurate ,reliable and repeatable, especially effective for square current devices in defect diagnosis. This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text.

Abstract: At present, the operational parallel compensating capacitors can only through the protection action for the information, so we cant location the fault capacitor. In order to obtain every parallel capacitor running status information and according to internal structure and the operation mode of film capacitor, this paper propose a method of locating a capacitor, and based on this method constructs a set of hardware monitoring system. This method can eliminate the affection caused by the environment and measurement error of sensor accuracy effectively and the hardware monitoring system can solve the insulation problem, which high-potential power supply and wireless collection and transmission technology bring.

Abstract: A numerical simulation for DC PD in void is put forward based on the PD physical process. The finite difference method is used to calculate the electric field distribution, and both of the stochastic property and the accumulation of the charge after PD on the void surfaces are considering in the model. The time of PD occurring, the amount of discharge and the voltage across the void are calculated. Meanwhile, the relationship between the DC voltage and the PD time interval or repetition rate is also simulation, the results show that with the increase of the DC voltage, the PD interval corresponding decreases exponentially and the repetition rate increases exponentially.

Abstract: Based on the synchronous machine in AC-DC-AC Frequency speed drag System, a new power supply method of phase shifting combination is proposed by a detailed study of the impact in the power grid harmonics. With regard to the main Motor drive system of hot-rolling finishing mills, a large number of varying parameters quantitative analysis is made respectively for power load, LC filter, pulse-width modulation circuit and transformer, in which the grid side harmonic rate and waveform distortion rate is focused on. The simulation results show that the power supply method with reasonable parameters design of the drag system can be drastically reduce the grid side harmonic interference that the total harmonic distortion is suppressed within 4.0%. Results of this study provides an effective method for the design of the factory drag system, reactive power compensation system as well as fault diagnosis of electric drag system.

Abstract: An on-line monitoring system of vacuum pressure for 35KV vacuum tube is designed in this paper. The operation principle, hardware structure and software plan are explained in details. The system can valuate the internal pressure of the vacuum tube by monitoring the static charge of the shields using electrical field sensors with rotating electrode. At the same time, the data-collecting machine and the controller are developed for long-range and on-line monitoring. The result shows that such system runs steadily and reliably. It can estimate the vacuum degree accurately laying 35cm from the vacuum tube. Besides, it is steady and anti-jamming with less-cost.

Abstract: Various harmonics exist in the electrical power system, and the harmonics include both integer harmonics and non-integer harmonics. It is hard to analyze all the harmonics accurately. In order to improve the precision of harmonic analysis and the minimum resolution, this paper presents a new algorithm named binary scale time windows FFT based on traditional algorithm.This algorithm considers the calculative time and precision well. The results of the test indicate that this algorithm can both guarantee the accuracy and raise the resolving power in the harmonic analysis without increasing the hardware level and the time of calculation obviously. It can restrain the increasingly serious harmonic pollution in power system effectively.

Abstract: A new partial discharge online detecting equipment based on TEV method is introduced in this paper. Its application to 3~35kV metal-enclosed switchgear partial discharge detection is clarified by an instance. Advice for improvement is also presented.