Abstract
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.
Highlights
In electrical engineering, the protective relay is a relay device designed to trip a circuit breaker when a fault is detected, and has the ability to measure the power system quantities through the internal logic of a microprocessor
It is important to bear in mind that the impact of the power quality on the protection relays can cause incorrect trips and relay mal-operation, while an incorrect tripping time occurrence depends on the power frequency variations and harmonic distortion [7,16]
Fault points were used in the tests, and a single phase with ground (SLG) was chosen; the fault points were included in the harmonic components
Summary
The protective relay is a relay device designed to trip a circuit breaker when a fault is detected, and has the ability to measure the power system quantities through the internal logic of a microprocessor. Various power quality disturbances are investigated and possible methods of quantifying both the effect and cost are presented [13,14,15], it aims at analyzing and probing the influences of harmonics to differential relays. It analyzes and compares the mathematic models which are constructed by using. This paper explains the signal processing of power quality disturbances using Matlab 2016, MathWorks, Natick, MA, USA) Simulink, especially 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 model characteristics are calculated from the parameters of the component with the intention to protect the relay, such as the transmission line, the transformer, and the generator, etc
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