Distance relay plays a pivotal role in the detection of faults and subsequent isolation in transmission lines. However, severe distortion in the measured voltage and current waveforms (such as due to Current Transformer (CT) saturation), affects their performance. This paper focuses on a compensation method for signal reconstruction using Extended Kalman Filter (EKF) algorithm to improve relay functioning, enhancing the safety of transmission lines. The proposed fault detection scheme was tested extensively by running simulations using PSCAD and MATLAB for different types of faults at various distances and CT burden. The CT model in PSCAD was developed based on the Jiles-Atherton phenomenological theory in order to closely resemble a real-time CT with its saturation effects. The simulation results show that the proposed method is highly efficient in determining the exact fault point with improved zone approaching times even with measured signals having high noise and harmonic content. In cases where the conventional relay fails to detect the fault in the correct zone, the compensated data from the proposed method accurately detects the zone. Hardware experimental tests were carried out to further verify the effectiveness of the scheme in real-time, where the EKF based algorithm was implemented using a DSP-based microcontroller
The micro-grid should operate in a well controlled manner both during grid connected and islanded mode. Also, micro-grid equipped with conventional overcurrent relays has protection issues during faults due to the difference in fault currents when micro-grid operation changes from one mode to the other. This paper proposes suitable relaying scheme based on curve-fitting technique for micro-grids and performs well without using any extensive communication facility. A new algorithm is developed to create large number of fault data for fitting the curve. The fitness of curve is accessed by measuring the value of coefficient R-squared value (R
2). More number of polynomials is added to improve the value of R
2. Results show that the actual tripping time of the relay is very close to desired tripping time by introducing more number of polynomials. Efficiency of the proposed method is evaluated by comparing with conventional over current relay. The protection logic of the curve-fit relay has been implemented on a TMS32F28377S micro-controller based hardware. A laboratory based experimental setup has been established to test the operational performance of curve-fit relay for a five bus system.
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