Abstract
This paper introduces a methodology for modelling a digital admittance-type distance relay using PSCAD/EMTDC. The proposed distance relay was tested in a simulation of the Brazilian power grid with predetermined fault scenarios. The goal of this paper is to make a detailed evaluation of the mho distance relay. The main aspects include the correct operation of the distance relay, fault resistance effects on the mho characteristics, and the fault detection time of this relay. A new approach to analyse the fault detection time is presented, considering several simulated fault scenarios. The results demonstrate that the fault resistance influences the fault detection time and severely affects the distance relay’s general performance. The fault detection time is not constant. It varies within a time interval, considering different fault types, fault locations, and fault resistances. The confidence interval calculation provides a detailed range of the fault detection time, considering its upper and lower limits.
Highlights
Power system protection is a wide area of study with many challenges regarding electrical equipment safety and power system reliability
It is possible to notice, in this reference, that the quadrilateral characteristic is suitable to cover faults with a high impedance, and varying the angle of power transfer affects the impedance calculation. Some of these steps adopted in [12] are applied to the mho distance relay model proposed in this paper (e. g., the anti-aliasing filter and the fast Fourier transform)
This paper presented a detailed methodology on how to model a digital distance relay using PSCAD/EMTDC
Summary
Power system protection is a wide area of study with many challenges regarding electrical equipment safety and power system reliability. The increasing insertion of digital distance relays in electrical power systems led to several works regarding their modelling The goals of these works are, in general, to make an accurate evaluation of their algorithms and to propose new ones to solve common problems of distance protection. It is possible to model a complete digital relay, beginning with voltage and current measurements and up to the command signals to trip circuit-breakers This reference considers two different operational characteristics for the distance relay. The paper aims to describe the process of modelling a digital admittance distance relay (mho) and to make a detailed evaluation of its behaviour during several simulated fault scenarios This evaluation focuses mainly on its correct operation, analyses the effects of fault impedances on distance protection, and the fault detection time of the proposed distance relay. The paper is structured as follows: section 2 presents related works regarding the modelling of distance relays, section 3 depicts the proposed distance relay, section 4 provides more details about the studied scenario and presents simulation results, section 5 presents the conclusions
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