Alternative Methodology to Calculate the Directional Characteristic Settings of Directional Overcurrent Relays in Transmission and Distribution Networks

Abstract

When addressing the problem of calculating the settings for directional overcurrent elements, the focus is usually the determination of the pickup, time dial and operating characteristic, in order to ensure proper selectivity with adjacent protection elements, thus limiting the problem related to the settings calculation of the direction determination characteristic to the application of typical settings and general guidelines, which cannot provide a reliable measure of the suitability of such settings. The present article describes in detail an alternative methodology for determining these settings, based on a characterization of the power system where the directional protection is to be applied, through the performance of a detailed short-circuit sensitivity analysis. From this, an optimization problem is formulated and solved to obtain the main settings shaping the direction determination characteristic, and then, a series of variables are used to measure the performance of the obtained settings, and even to improve it. The obtained results show the advantages of the application of the proposed methodology over the traditional methodology, based on typical settings and general guidelines, pointing out the risks of using the later.

Optimal Coordination of Overcurrent Relays in Microgrids Considering a Non-Standard Characteristic

“…Microgrids have changed the traditional paradigm of radial DNs into non-radial and flexible systems. Therefore, finding a protection scheme that ensures speed, selectivity and reliability has become one of the most challenging tasks in microgrids operation planning [8].…”

Optimal Coordination of Over-Current Relays in Microgrids Using Unsupervised Learning Techniques

“…According to [7,8], protection systems in microgrids must face two remarkable challenges: the first one corresponds to their inherent dynamic behavior, due to intermittent loads and generators, and the second one is related to their operating characteristics (grid connected or islanded). These two aspects tangle the problem of microgrid protection coordination; therefore, finding a protection scheme that guarantees speed, selectivity, and reliability has become one of the most challenging tasks in planning microgrid operation [9]. Directional over-current relays (DOCRs) are widely used in distribution networks (DNs) and they are recognized as the main protection device due to their simplicity and low implementation cost [10].…”

Adaptive protection coordination scheme in microgrids using directional over-current relays with non-standard characteristics

“…MGs are flexible systems that may have multiple operating modes which makes their protection coordination a challenging task [2] , [3] ; MGs also tend to grow in size and complexity and the fact of harboring DG introduces bidirectional power flows and variable short-circuit currents [4] . MG operation modes render inefficient the conventional design of protection coordination which considers fixed short circuit levels and unidirectional power flows; therefore, researchers around the world are in constant search of new models and methodologies regarding the protection coordination problem of MGs [5] . One of the new challenges in designing protection schemes for MGs, is to deal with their dynamic behavior resulting from the use of intermittent energy resources and the possibility of being connected and also disconnected to the main power network [6] , [7] .…”