Papers by Keyword: Transformer

Abstract: Transformer vibration research is an effective diagnosis of DC bias fault. The vibration signal acquired is actually the mix signal of vibration from both the core and windings, and this makes it difficult to analyze the above two separately. Therefore the paper presents a new approach to separate vibration signal of core and windings by Fast-ICA algorithm. The simulated results of core and windings vibration are given and compared with experiment test. Comparative analysis verify that transformer vibration in no-load is core vibration and vibration in short circuit is windings vibration. Transformer vibration signals under different DC bias are tested by experiment. Vibration signals are separated by Fast-ICA algorithm. Core vibration signal and windings vibration signal are respectively obtained. The research lays the groundwork for further research of transformer DC bias vibration.

Abstract: Relaxation function can well reflect the microscopic polarization mechanism of dielectric. In order to analyze the influence of moisture and temperature on relaxation function of oil-paper insulation, building a physical model of the oil-paper insulation system containing moisture and obtaining the expression of relaxation function. Setting up a testing device for the oil paper insulation dielectric spectroscopy in the laboratory, the parameter values of relaxation function expression were obtained according to test result by Fourier inverse transformation. The results show that the relaxation function containing three relaxation factors are more suited for the relaxation of oil-paper insulation containing moisture content and microscopic polarization mechanism, moisture and temperature have a significant effect on relaxation function.

Abstract: According to the Evaluation and Expression of Uncertainty in Measurements, the author establishes the mathematical model for measuring the purity of hydrogen in transformer oil by means of Gas Chromatography. Meanwhile the author analyses resources of uncertainty and deduces formulas of uncertainty measurement. By calculating uncertainties of the components, the author obtains the synthesis uncertainty.

Abstract: Many successful applications for the online monitoring of the insulation condition for electric power transformers have been reported over last thirty years. However, false or unsolved alarms have been quite frequently generated by those condition monitoring systems. Failures and some occasionally catastrophic accidents involving transformers have still occurred. A highly reliable insulation condition online monitoring and real-time alarm system has been developed, to help resolve these problems. An electric power transformer has strongly linked mechanical, electrical, magnetic, chemical and thermal characteristics, and is also directly linked to circuit breakers and generators. Team Intelligence (TI) was employed to integrate all the monitoring modules of the various different aspects of the transformer into one unique system. This system could also be integrate with the condition monitoring systems of various linked facilities, such as the monitoring systems of the turbine and the generator in a Optimal Maintenance Information System for Hydropower Plant (HOMIS). Highly reliable monitoring and real-time alarms of transformer insulation condition could be achieved, due to highly coordinated and rapid response features. This system has been deployed in several hydropower plants. The industrial application examples are demonstrated.

Abstract: By analyzing the main transformer substation operation mode change various calculation methods of loss are conducted on how to determine the economic operation mode of the double main transformer substation. According to load changes, in order to achieve best value for economy it is neccessary to reduce variable transformer loss. In this paper, a practical method of substation transfomer determination is analyzed.

Abstract: This paper establishes a simulation model of a simplified power system with transformer differential protection based on an embedded Matlab function block. The differential protection consists of percentage restraint differential protection, second harmonic restraint, differential current instantaneous trip protection and over-excitation protection. The model is able to correctly simulate the transformer’s inrush current and internal and external faults. The results from the simulation show that the circuit breaker correctly operates for a transformer internal fault and provides a good braking effect for an external fault. In addition, the protection model is able to identify the inrush current of the transformer and avoid a protection mis-trip event.

Abstract: The paper work had improved some inference information report show functions of the expert system shell Pro/3 by using graph in combination with text . By analyzing some forward reasoning application mechanisms of the Pro/3, this work had also created a transformer fault diagnosis knowledge base rule model based on dissolved gas analysis in transformers such that using the rules of sentence in model had implemented an expert system of transformer fault diagnosis. The basic application shows the effectiveness of the system.The modeling approach created by the Pro/3 can be also applied to some diagnosis or analysis of other equipments. Exploring the Pro/3 has certain practical significance for establishing some expert systems or assistance decision support systems.

Abstract: According to the characteristics of fault types of the transformer ,RBF neural network is used to diagnose transformer fault. The paper regards six gases as inputs of the neural network and establishes RBF neural network model which can diagnose six transformer faults: low temperature overheat, medium temperature overheat, high temperature overheat, low energy discharge, high energy discharge and partial discharge . The Matlab simulation studies show that transformer fault diagnosis model based on RBF neural network diagnosis for failure beyond the traditional three-ratio method. The rate of the transformer fault diagnosis accuracy reaches 91.67% which is also much higher than the traditional three ratio method.

Abstract: EVT (electronic voltage transformer) is one of the key devices of the intelligent substation. This paper introduces the basic principles of EVT error tests. By analyzing the test environment of EVT with GIS structure, this paper establishes the high-voltage side equivalent circuit for the field EVT calibration methods and proposes to carry out field boost for the EVT with GIS structure, which could effectively improve the field calibration efficiency of EVT. Based on the research on the complex field environment of EVT, this paper puts forward the field test methods of EVT with AIS structure and the results show the effectiveness and correctness of this study.

Abstract: This work develops a 2KVA inverter with timing capability for load supply.The development of timing-capable inverter draws from a DC input which could be a solar/deep cycle battery source. Public power supply could be used to charge the battery. The inverter used the pulse width modulation (PWM) approach and used the SG3524N IC as the Pulse Width Modulator (PWM).Dual channel MOSFETs are supplied current of 10ms duration every 20ms and are used to alternately supply the primary windings of a step up transformer thereby producing an AC in the secondary of the transformer. A step-down transformer, bridge rectifier, and the pulse width modulator were used to provide voltage regulation of the output supply to the load. A keypad, a GDM1602A LCD screen and a PIC16F84A microcontroller were employed in the timing control of the voltage from the output of the inverter. Relays were employed in switching the voltage to the output based on the timing algorithm from the microcontroller. A prototype 2kVA inverter with timing was designed and implemented with a satisfactory output and suitable timing control.