Analysis of the harmonic distortion impact on the operation of digital protection systems

It is well documented in the open literature that protection systems are affected by the presence of harmonic pollution on voltage and current waveforms, producing missoperation and therefore diverse problems such as economic losses, discontinuity of service, or even worse, the presence of a permanent fault due to a failure of the protection system operation. However, it will be shown in this contribution that while this is true for old electromechanical protection systems, solid state and even early digital systems, it is not for modern digital protection systems (MDPS). This paper details the results obtained from a set of tests carried-out in modern digital protection systems of the newer microprocessor-type family relays working under harmonic distortion conditions.