This paper presents the concept of the impact of harmonic distortion on a digital protection relay. The aim is to verify and determine the reasons of a mal-trip or failure to trip the protection relays; the suggested solution of the harmonic distortion is explained by a mathematical model in the Matlab Simulink programming environment. The digital relays have been tested under harmonic distortions in order to verify the function of the relays algorithm under abnormal conditions. The comparison between the protection relay algorithm under abnormal conditions and a mathematical model in the Matlab Simulink programming environment based on injected harmonics of high values is provided. The test is separated into different levels; the first level is based on the harmonic effect of an individual harmonic and mixed harmonics. The test includes the effect of the harmonics in the location of the fault point into distance protection zones. This paper is a new proposal in the signal processing of power quality disturbances using Matlab Simulink and the power quality impact on the measurements of the power system quantities; the test simulates the function of protection in power systems in terms of calculating the current and voltage values of short circuits and their faults. The paper includes several tests: frequency variations and decomposition of voltage waveforms with Fourier transforms (model) and commercial relay, the effect of the power factor on the location of fault points, the relation between the tripping time and the total harmonic distortion (THD) levels in a commercial relay, and a comparison of the THD capture between the commercial relay and the model.

Process bus communication has an important role to digitalize substations. The IEC 61850-9-2 standard specifies the requirements to transmit digital data over Ethernet networks. The paper analyses the impact of IEC 61850-9-2LE on physical protections with (analog-digital) input data of voltage and current. With the increased interaction between physical devices and communication components, the test proposes a communication analysis for a substation with the conventional method (analog input) and digital method based on the IEC 61850 standard. The use of IEC 61850 as the basis for smart grids includes the use of merging units (MUs) and deployment of relays based on microprocessors. The paper analyses the merging unit’s functions for relays using IEC 61850-9-2LE. The proposed method defines the sampled measured values source and analysis of the traffic. By using neural net pattern recognition that solves the pattern recognition problem, a relation between the inputs (number of samples/ms—interval time between the packets) and the source of the data is found. The benefit of this approach is to reduce the time to test the merging unit by getting the feedback from the merging unit and using the neural network to get the data structure of the publisher IED. Tests examine the GOOSE message and performance using the IEC standard based on a network traffic perspective.

IEC 61850 is the standard for communication substation which determines new applications of protection based on peer-to-peer communications between multifunctional protection devices (IEDs). The GOOSE messages (Generic Object Oriented Substation Event) can be used to replace the hard wired control signals exchanged between IEDs for interlocking and protection purposes. The idea is that the implementation of high-speed peer-to-peer communications should be equal or better than what is achievable by existing technology. The paper focus on using IEC 61850 based protection relays and on possibility of modeling of this processes in Matlab.

This paper analyses the influence of current harmonics on protections devices connected to the power system which can cause serious problems. This paper outlines work that has been conducted to test of overcurrent relay and to identify the impacts of harmonics on distribution utility protection and control systems. The overcurrent relay REJ 525 is based on a microprocessor environment. A self-supervision system continuously monitors the operation of the relay.

The distance protection relay measures the line voltage and line current at the relay location and evaluates the ratio between these quantities. Distance relays are widely used on transmission, and even distribution systems. Current transformers (CT) are the very important part of the power system protection. The main purpose of a CT is to transform the primary current in a high voltage power system to single level that can be handled by delicate electronic device. This paper deals with the influence of CT saturation on distance digital relay. Saturation of the CT is evaluated for fault close to the relay location.

This paper explains the possibility of implement of a model of a quadrilateral characteristic type of distance relay with the zones by using MATLAB / SIMULINK package. Sim Power System was used to present modeling of distance relay. The quadrilateral R-jX plain was created to show the trajectory of measured impedance using the distance relay. The relay identifiers the fault locations as expected. The impedance path reflects to the power system model under fault conditions. The goal of this paper is to describe the building and designing distance relay by using Simulink model, inside the modeling, impedance calculation, zone coordination were designed.