Modeling and simulation of substation fault diagnosis based on Petri nets
In order to improve the efficiency of the substation fault diagnosis with multiple protections, the proposed method describes protection grades by varied weight of the transition vector in the Petri net models. According to relays and circuit breakers, special markings are produced in the diagnosis results that enhance the identifying capability of error information. The process of fault diagnosis is accomplished by algebra matrix calculation. A simulation on actual substation fault diagnosis process indicates that the improved method has fast calculation speed and high veracity
APPLICATION OF PETRI NETS IN TRANSFORMER FAULT DIAGNOSIS
The Petri nets theory which takes the net theory and algebra theory for mathematical basis can be used to describe the various relations and behaviors in the discrete event dynamic system by graphical means. Because the Petri nets is suited to describe the computer system model under the asynchronous concurrent phenomena and to make the behavior analysis on parallel and concurrent system, so it is more and more widely applied in artificial intelligence field. In this paper a fault diagnosis model for power transformer based on Petri nets is proposed in which by use of Petri nets the matrix operation algorithm for knowledge representation and inference is dissertated, the relation between the fault omen and the fault itself is described. The presented model is simple and clear, in which only simple matrix calculation based on Petri nets theory is used. Thus, the time for fault diagnosis can be obviously reduced and the diagnosis accuracy is improved. Testing the presented model by practical examples, the results show that this model is fast and accurate.
Effect of stress conditions on collapse deformation behavior of a rockfill material
A set of saturated and dry-saturated large-scale triaxial tests were conducted in order to explore the effects of stress conditions on the saturation-induced collapse deformation behavior of a rockfill material. Specimens were tested in different confining pressures and for dry-saturated tests the specimens were submerged in various shear stress levels. The results indicate that in all of the dry-saturated tests a sudden reduction in the volume of the specimens was observed during the submerging process. The ratio of the minimum axial strength of a submerged specimen (at the end of the saturation process) to the shear strength of the specimen before saturation is defined as the coefficient of stress recovery, Csr. Results of the dry-saturated tests showed that this ratio increases as the confining pressure increases and decreases by increasing the shear stress level. According to the results of dry-saturated tests the values of internal friction angle reduction caused by saturation (Δϕc), the ratio of the elasticity modulus of the material after saturation to its elasticity modulus in dry condition, i.e., Ewet/Edry, and also the saturation induced sudden volumetric strain (εvc) decrease as the confining pressure increases. However the shear stress level does not have any meaningful effect on the variation of Dfc, Ewet/Edry and (εvc).