Testing of Motor Protection for Internal Faults

Protection in electrical power system plays an important role in human and material safety during abnormal operating conditions. The heart of electrical protection system is the relay which senses abnormalities and commands the switches to break the circuit during a fault. Hence, optimization of protection parameters has gained paramount importance to ensure optimum system protection. Induction motors are employed in a majority of the industries. Failures in motors due to undetected stator inter-turn faults are a major concern in industrial applications. Such an event perturbs not only the electrical network but also the production process due to unplanned shutdowns. Although modern day numerical relays offer advanced protection to motors with a wide range of functionalities, turn-turn fault detection at incipient stage proves to be an uphill task. The imbalance due to turn-turn fault draws the attention of protection engineers to focus more on the negative sequence protection. In most motor protection failure cases where a possible turn-turn fault in stator has occurred, either the relay fails to detect the fault at an incipient stage or false trips, disrupting the process. This leads to a conclusion that the settings of protection relay parameters especially those of negative sequence are not accurate for stator turn-turn faults. This thesis concentrates on (i) Simulation of stator turn-turn faults in ATP-EMTP MODELS to generate COMTRADE files (ii) Dynamic testing of the relay for negative sequence protection at various inter-turn fault severities using Omicron secondary injection. Finally, an ideal setting for negative sequence protection, taking into account of current transformer saturation and errors, is suggested for the induction motor under consideration and the results are presented accordingly.Electrical Engineering, Mathematics and Computer ScienceElectrical Sustainable Energ