The Nordic synchronous power system must continuously be in balance with respect to the electricity produced and consumed to function optimally. The system frequency is a good measure of the actual balance. The Swedish Transmission System Operator, Svenska kraftnät (Svk), is responsible for making sure such a balance is achieved. This study was conducted with the overall aim of investigating how Svk works in practice to balance the Nordic synchronous power system. This includes describing the main aspect of the power system structure, the existing methods regarding automatic and manual frequency control, the main operating systems as well as the tools and methods used by Svk. The study also examines how operational plans and forecasts available through the Nordic Operational Information System (NOIS) can be used to predict at what operational situations the risk of unwanted frequency deviations will be higher than normal. Furthermore, the study also investigates the possibility to conduct frequency regulation in a proactive manner based on these correlations. This was accomplished mainly through a literature review and interviews. The results shows that frequency deviations where the frequency is outside the interval 49.9–50.1 Hz often occur in correlation with the specific time at which the planned system balance quickly changes. Frequency simulations show that proactive regulation, which aims to reduce the planned imbalance, appears to also reduce frequency deviations. Further studies should however be conducted to study such frequency correlations in depth, and to investigate how proactive regulatory practices can be implemented in the most optimal manner.