Power quality monitoring for substation ancillary services

The assurance of the power quality supplied to consumers represents one of the most important issues that have to be fulfilled, related to substation ancillary services power supply sources. The aspects concerning the power quality are highlighted for the designed and planning of the substations belonging to the transmission network. Within the monitoring process several quantities are analyzed. The voltage is the main qualitative element, influencing the proper operation of the receptors. That is why its quality practically defines the power quality. The electric energy is a “product”, but a very particular one, affected by electromagnetic perturbations, considering the relation between the supplier and the consumer, the main aspect being the voltage quality. From the monitored quantities, the authors are focusing on voltage acquisition, processing and analyzing. The case study refers to a real substation within the Romanian transmission network. The ancillary services are supplied from the tertiary winding of the 200 / 200 / 60 MVA and 231 / 121 / 10.6 kV autotransformer. The tertiary winding autotransformer voltage variation is computed. For the electric quantities monitoring process the TOPAS 1000 equipment has been used. The flowchart of the entire monitoring process is presented within the paper. Specific definitions and parameters corresponding to the EN 50160 standard are presented, followed by the characteristics of the main perturbations, being largely presented.