A Linear Programming Approach For Optimal Relay Coordination Of Numerical Overcurrent Relay

  Nikunj K. Chauhan

The transmission line fault results in a much larger postfault current than the prefault load current. So overcurrent relaying is widely used for transmission lines. The speed of relaying and selectivity can be sacrificed, to some extent, in LV or MV lines. The other line relays like distance protection relays are too expensive. The percentage cost of the protection, which can be justified is around 10% to 15% of the cost of the equipment or section to be protected. Hence directional overcurrent relays are commonly used as an economic alternative for the protection of interconnected sub transmission systems, distribution systems, or as a secondary protection of transmission systems. Nowadays, “Numerical Overcurrent relays” are widely used. So we have considered numerical relay in our case-study. The most important task when installing numerical overcurrent relay on the system is selecting their suitable settings such that their basic protection function is met under sensitivity, selectivity, reliability and speed. The settings should be designed for minimum relay time of operation. That is, the settings should be such that the overall time of operation is minimized while maintaining the selectivity and reliability. Thus, the numerical relay problem is an optimization problem, where the solution is the optimal settings of each relay. Various methods have been proposed to formulate and find the optimal solution for the numerical overcurrent relay problem. In, this paper the proposed techniques are discussed. In this paper the data taken for research is of the real field of The power system at TATA Motors Ltd, Pimpri . The problem is formulated as linear programming problem as a basic case study. The problem is solved using linprog function of the optimization toolbox of the MATLAB software.

Keywords- Linear Programming, Numerical Overcurrent Relay, Power System Protection, Relay Coordination.

Unique Identification Number - IJEDR1801085
Page Number(s) - 492-498
Pubished in - Volume 6 | Issue 1 | January 2018
DOI (Digital Object Identifier) -    http://doi.one/10.8/ijedr.17499
Publisher - IJEDR (ISSN - 2321-9939)

  Nikunj K. Chauhan,   "A Linear Programming Approach For Optimal Relay Coordination Of Numerical Overcurrent Relay", International Journal of Engineering Development and Research (IJEDR), ISSN:2321-9939, Volume.6, Issue 1, pp.492-498, January 2018, Available at :http://www.ijedr.org/papers/IJEDR1801085.pdf