H. Yaghobi, K. Ansari, H. Rajabi Mashhadi,
Volume 7, Issue 4 (12-2011)
Abstract
A reliable and accurate diagnosis of inter-turn short circuit faults is a challenging problem in the area of fault diagnosis of electrical machines. The purpose of this challenge is to be more efficient in fault detection and to provide a reliable method with low-cost sensors and simple numerical algorithms which not only detect the occurrence of the fault, but also locate its position in the winding. Hence, this paper presents a novel method for diagnosis of different kinds of inter-turn winding faults in a salient-pole synchronous generator using the change in the magnetic flux linkage. It describes the influence of inter-turn winding faults on the magnetic flux linkage distribution of the generator. The main feature of the proposed method is its capability to identify the faulty coils under two types of inter-turn winding faults. Also, simple algorithm, low cost sensor and sensitivity are the other feature in the proposed technique. In this method, generator air gap flux linkage is measured via search coils sensor installed under the stator wedges. Theoretical approach based on Finite Element Method (FEM) together with experimental results derived from a 4-pole, 380U, 1500 rpm, 50 Hz, 50 KVA, 3-phase salient-pole synchronous generator confirm the validity of the proposed method.
M. Samami, H. Yaghobi, M. Niaz Azari,
Volume 13, Issue 2 (6-2017)
Abstract
This investigation deals with a mathematical model for a distribution transformer including saturation effect. To this end, the equations related to a three phase transformer are specified and the effect of an inter-turn fault is included. Naturally by applying an inter-turn fault the inductance and resistance matrix will change. Thus, unknown quantities of inductances and resistances for completing the matrix are calculated and the inputs, outputs and state variables are specified. All the equations will be rewritten in terms of state variables, subsequently saturation effect is added to the model. Finally the block diagram of the specified model based on the obtained equations are designed and the ultimate model is simulated. The saturation effect, added to the mathematical model and also the variable fault parameters are known as two significant contributions which distinguish this study from other investigations. Various results obtained from the simulation of the final model confirm the changes in the behavior of faulty transformer such as: a large circulating current flowing in the shorted turns, lower impact on terminal voltages and currents, a sudden increase in current flowing in the primary winding, asymmetrical flux distribution and inverse proportion of the fault severity and the limiting resistor.
