An alternative method for obtaining the optimal directional characteristic angle of directional overcurrent relays in transmission networks

Abstract

Directional overcurrent elements, both phase and ground, are widely used as backup protection for transmission lines in interconnected power systems around the world. Traditionally, the specialized literature has focused on the determination of the time dial settings of such elements for improving selectivity, as well as the polarization method to be used, for improving security; leaving the directional characteristic settings, and more specifically, the determination of the directional characteristic angle, to the application of the so-called typical settings. This setting, most commonly known as Maximum Torque Angle (MTA) or Relay Characteristic Angle (RCA), is the basis for the direction determination algorithm. Therefore, it is of paramount importance to establish a methodology for its proper calculation. The main contribution of this paper is an alternative methodology to stablish the MTA/RCA settings of directional overcurrent relays, by using a detailed shortcircuit sensitivity analysis and a non-linear optimization technique. The application of this novel approach on real complex transmission systems increases the reliability of directional overcurrent protection elements, and has shown that the values required by the actual fault conditions of the transmission system could present a large deviation from the so-called typical settings.

Calculation of Distance Protection Settings in Mutually Coupled Transmission Lines: A Comparative Analysis

“…For every apparent impedance stored in subsets D1 and F1, a probability of occurrence is calculated, considering only the following categories, and corresponding distribution: 1) Fault type p(Tf), for which the following probability distribution is assumed [19]: single-phase to ground faults (80%), double-phase to ground faults (12%) and three-phase faults (8%). 2) Operative status of the mutually-coupled circuit p(Eo), assuming an empirical distribution:…”

“…(1) Fault type p(Tf), for which the following probability distribution is assumed [19]: single-phase to ground faults (80%), double-phase to ground faults (12%) and three-phase faults (8%). (2) Operative status of the mutually-coupled circuit p(Eo), assuming an empirical distribution: both circuits in service (90%), coupled circuit out of service and grounded at both ends (6%), coupled circuit out of service and isolated from ground (4%).…”

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

“…Reference [13], which was developed by the same authors of the present article, describes an alternative method for obtaining the directional characteristic angle (RCA) of directional overcurrent elements in transmission networks; by formulating the problem of obtaining such angle through the performance of a complete short-circuit sensitivity analysis and the solution of a simple optimization problem. However, the principles for the application of the method described in [13] to evaluate the performance of the direction determination algorithm, along with the verification of the settings obtained from the solution of the optimization problem, and the detailed development of the general methodology for using this approach to define other settings related to the direction determination algorithm are missing in [13].…”

“…Reference [13], which was developed by the same authors of the present article, describes an alternative method for obtaining the directional characteristic angle (RCA) of directional overcurrent elements in transmission networks; by formulating the problem of obtaining such angle through the performance of a complete short-circuit sensitivity analysis and the solution of a simple optimization problem. However, the principles for the application of the method described in [13] to evaluate the performance of the direction determination algorithm, along with the verification of the settings obtained from the solution of the optimization problem, and the detailed development of the general methodology for using this approach to define other settings related to the direction determination algorithm are missing in [13]. This article will describe the general guidelines for the application of the method described in [13] to calculate key settings of the direction determination characteristic of directional overcurrent relays, such as the relay characteristic angle, the selection of the polarizing quantities (negative sequence or zero sequence) for the directional ground overcurrent protection function, and the minimum thresholds for the activation of the voltage memory for the directional phase overcurrent element.…”

“…Since the work presented in [13] was focused on the formulation of the optimization problem to calculate the RCA and its advantages over the use of traditional setting criteria, the present article will describe in more detail the factors affecting the most commonly used polarization techniques, the factors to be considered when configuring the short-circuit sensitivity analysis block, the processing of the results obtained from it, the application of the method to define other important settings related to the directional characteristic different from the RCA, such as the polarization quantities for directional ground overcurrent elements, and the discussion of the results obtained from the application of this method to several study cases, based on a comparative analysis with the traditionally used typical settings, from which the advantages of the application of the proposed methodology are outlined. Additional variables to those introduced by [13] were defined in order to measure the performance of any given settings, typical or optimal, of the direction determination characteristic, so that selectivity issues related to the incorrect direction determination, or sensitivity issues, related to the starting settings, were easily identified, from the extensive fault conditions simulated in the short-circuit sensitivity analysis. Finally, based on the additional variables defined to address the performance of the settings related to the direction determination characteristic, a methodology for the controlled modification of the RCA setting, in order to improve the coverage of the Forward and Reverse regions is included, in order to enhance the advantages of using the methodology, based on the approach described in [13].…”