Optimal-Probabilistic Method to Compute the Reach Settings of Distance Relays

Abstract

This paper presents a novel method to optimize the settings of the resistive and reactive reaches of the zones of the distance relays. The method considers the probabilistic behavior of the variables that affect the apparent impedance seen by relays: prefault load flow, fault type, faulted line, distance up to the fault, fault resistance, and measurement errors. The optimization has been conceptually formulated as a multiobjective problem, with two objective functions: 1) minimize the probability of loss of sensitivity and 2) minimize the probability of loss of selectivity. To solve this problem, a preference function is defined, which is equal to the weighted sum of the two objective functions. A factor of weight represents the relative importance of selectivity regarding the sensitivity, and it is selected for each zone. This method was applied to a system with 7 busbars (3 of them with generation), where there are 18 distance relays with quadrilateral characteristic, and with an independent setting of the reactive and resistive reaches for the phase distance function and the ground distance function. The results obtained are compared with the results of other methods of adjustment.

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

“…The main contribution of this paper, when compared to previous works used as reference [2,[7][8][9][10][11][12], is the simplification of some of the premises of the optimization problem formulation, based on a comparative analysis with the techniques currently employed to determine the settings of the distance protection relays, according to its application to mutually-coupled transmission lines, which involve a series of additional problems and special considerations, not included in the reference works. On the other hand, the optimization techniques described in previous works [7][8][9][10][11][12] do not include details on the methodology to set its parameters according to the natural bounds and application limits of distance protection relays to transmission lines, which causes higher computing times and the addition of data that should not affect the actual performance of the distance protection relays. The solution method proposed in [10] uses the Monte Carlo method to estimate system model parameters, thus improving the accuracy of the calculations related to the impedance loops; however, its main disadvantage is related to the excessive number of fault conditions required to provide enough reliability to the proposed settings, with the high computation cost related.…”

“…The method presented in [12] is limited in both scope and application, since it only improves the sensitivity of Zone 1 reach, and it is formulated for series compensated transmission lines. Finally, the approaches proposed in [7][8][9], based on probability distribution functions related to the fault conditions simulated have the inconvenient that these functions are difficult to estimate; however, for this particular case, the proposed method will eliminate some of the probability distribution functions according to performance criteria expected from the distance relay under specific fault conditions, as otherwise, the protection system could perform undesirably for events with low probability of occurrence, included in the preference objective function.…”

“…The proposed method to solve the optimization problem related to the determination of the reach settings of the distance protection is thus based on the formulation outlined in [7], improving the technical basis for the formulation of the optimization problem, which will include a short-circuit sensitivity analysis for establishing the actual performance of the relay to be set under the multiple fault and system conditions affecting the measured impedance loops, and including the probability of occurrence of every single fault simulated in an specialized software tool, in order to determine the preference function related to the optimization problem to be solved. In addition, the solution method will be flexible enough to accommodate to special performance requirements of the distance protection elements, which will depend on the evaluation of the fault conditions obtained from the short-circuit sensitivity analysis.…”

“…The methodology and proposed optimization algorithm (genetic algorithm) are entirely based on the main factors that actually affect the performance of these protection schemes, therefore, the results obtained for the distance protection reach settings have a wider and stronger base for ensuring its proper performance in terms of reliability when compared to previous works [7][8][9][10][11][12]. The proposed optimization algorithm, successfully used in [13] in comparison with conventional calculation methods, will prove to be a compromise between the in-depth short-circuit sensitivity analysis, obtained through simulation, and the computing time required to obtain a good solution.…”

An Enhanced Adaptive Algorithm to Mitigate Mis-coordination Problem of the Third Zone of Distance Relays

“…In [9] a new method is presented to increase the secondzone coverage of distance relays without causing over-reaching problems. A novel method to optimize the settings of the resistive and reactive reaches of the zones of the distance relays is represented in [10]. The method considers the probabilistic behavior of the variables that affect the apparent impedance seen by relays: pre-fault load flow, fault type, faulted line, distance up to the fault, fault resistance, and measurement errors.…”