This paper aims to provide an insight into the measured background changes of harmonics due to operational changes in a typical Dutch transmission grid. Multiple use cases on different locations throughout a meshed 150kV grid have been considered. The nodes that were studied had measured exceedances of planning levels or were indicated to be critical for the future in earlier studies. This study provides an insight into the measured response of harmonics with respect to different operational changes such as specific scheduled outages that occurred and the impact of capacitor banks. Per use-case, individual conclusions are reported. The analysis was conducted on data of power quality meters (PQM) and various other data sources provided by the Dutch TSO TenneT. Data-processing, visualization, and computations were performed using Python. These results are useful for model validation, planning purposes, and maintaining power quality.