•The system is a continuous real time PQ monitoring based on the concept of Digitally Enabled Substation Architecture or Substation 4.0 (SB4.0).•It presents a scalable architecture that allows the analysis of data from multiple substations.•It presents a practical implementation of the SB4.0 concept by proposing a novel multi-functional Substation Edge Device called here as PQMC (Power Quality Monitoring Center).•The system was installed in two substations that are part of the electrical Brazilian transmission grid. From the knowledge of the authors the system is one of the first PQ monitoring system using the concept SB4.0.•The PQMC receives voltage and current samples from a Merging Unit (MU), using the IEC 61850 Sampled Values (SV) format, and calculates various power quality parameters.•The system also provides a Data Logger application triggered by instantaneous Total Harmonic Distortion (iTHD) and by short duration voltage disturbance.•The Power Quality Monitoring and the Data Logger systems are software applications running in an industrial computer.•The System is time synchronized by GPS, providing time synchronized power quality parameters as well as waveform signals.•Results obtained from the proposed system was compared with commercial IED.•Experimental validation of the system in the laboratory and in the field.•This work is the result of a Research and Development Project with a power transmission company located in northern Brazil.•Modular architecture of the PQMC based on asynchronous queues is also a contribution of this work. This approach grants to the proposed IED a great scalability owing to the use of the single-producer multiple-consumers design pattern.•In the PQMC architecture, the signal processing routines of different channels are completely independent and do not depend on each other.•The proposed architecture allows for the modification of the PQMC features just by reconfiguring the software and without hardware changes, which is quite adherent to the SB4.0 concept. The growth of penetration of large blocks of inverter based renewable energy in transmission power systems may lower the power quality of these systems, especially with rising of harmonic and interharmonic distortion and voltage fluctuation. Poor Power Quality (PQ) can negatively affect the protection system and may cause premature aging of electrical equipment connected to the power system. Thus, real-time and continuous PQ monitoring can be of great value for operation, maintenance and expansion of the system. This paper presents a recently implemented real-time PQ monitoring system based on the concept of Digitally Enabled Substation Architecture or Substation 4.0 (SB4.0). The proposed PQ monitoring system receives voltage and current signal samples from a Merging Unit (MU) and calculates the various power quality parameters. Since the system uses the SB4.0 concept the power quality monitoring is a software application implemented in an industrial computer. Also, the system provides a Data Recording application, running as additional software task that provide oscillography triggered by instantaneous Total Harmonic Distortion (iTHD). This paper presents the architecture of the developed and implemented system as well as the field results gathered from a transmission system in the north of Brazil.