Impedance reach of numerical distance relay is severely affected by Fault Resistance (RF), Fault Inception Angle (FIA), Fault Type (FT), Fault Location (FL), Power Flow Angle (PFA) and series compensation in transmission line. This paper presents a novel standalone adaptive distance protection algorithm for detection, classification and location of fault in presence of variable fault resistance. It is based on adaptive slope tracking method to detect and classify the fault in combination with modified Fourier filter algorithm for locating the fault. To realize the effectiveness of the proposed technique, simulations are performed in PSCAD using multiple run facility & validation is carried out in MATLAB® considering wide variation in power system disturbances. Due to adaptive setting of quadrilateral characteristics in accordance with variation in fault impedance, the proposed technique is 100 % accurate for detection & classification of faults with error in fault location estimation to be within 1 %. Moreover, the proposed technique provides significant improvement in response time and estimation of fault location as compared to existing distance relaying algorithms, which are the key attributes of multi-functional numerical relay.
Sudden changes in loading or configuration of an electrical network causes power swing which may result in an unwanted tripping of the distance relay. Hence, it becomes utmost necessary to rapidly and reliably discriminate between actual fault and power swing conditions in order to prevent instability in power network due to mal operation of distance relay. This paper proposes a novel method for the discrimination between fault and power swing based on rate of change of voltage and reactive power measured at relay location. The effectiveness of the proposed algorithm is evaluated by simulating series of power swing conditions in PSCAD/EMTDC® software for different disturbances such as change in mechanical power input to synchronous generator, tripping of parallel line due to fault and sudden application of heavy load. It is revealed that the distance relay gives successful tripping in case of different fault conditions and remains inoperative for power swing with the implementation of the proposed algorithm. Moreover, the proposed scheme has ability to distinguish the symmetrical and asymmetrical fault occurrence during power swing condition.
Medium and Low voltage busbar is important equipment in the electrical power system, and its protection demands simple, reliable, economic & sensitive relaying scheme. This paper presents design, implementation and testing of low voltage busbar relaying scheme in laboratory environment using TMS320LF2407A Digital Signal Processor (DSP). Current differential algorithm is designed based on the DSP platform which can reduce large amounts of calculation, expedite the protection's trip and reduces the hardware requirements. Authors have developed a laboratory prototype of the threephase busbar system containing 3-phase bus, current transformers, line components, fault switches and DSP trainer kit. Experimental results are provided to verify the effectiveness of the proposed scheme. The scheme provides stability against external faults, sensitivity towards high resistance internal faults and better reliability in discriminating in-zone and out of zone faults.
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