An Estimation for Short-Circuit Power Changes in the Dutch Grid to Analyze the Impacts of Energy Transition on Voltage Dips

The Dutch grid code establishes regulations for both transmission and distribution network operators in terms of power quality. Recently, more detailed regulation of voltage dips has come into force [1] to retain the same voltage quality.

Depending on the severity (depth and duration), a maximum number of dips is established per connection. The limits are based on historical data characterizing the "as-is." The Dutch grid code defines limits for the number of voltage dips that each client in high voltage (HV), extra-high voltage (EHV), and medium voltage (MV) grids could experience.

The system strength, and particularly the short-circuit power supplied by the synchronous generation units (SGUs), has enabled the power system to maintain the voltage along the grid within specified limits even during extreme occurrences. A generation shift occurs as a consequence of the energy transition. Inverter-based renewable energy sources (IBRs) will provide a substantial portion of electrical energy in the future. Compared to SGUs, the short-circuit contribution from IBRs is lower [2], and their connection points are often located in areas with a weaker grid.

Reduced system strength may result in decreased residual voltages and a wider propagation area during short circuits [3]. This research aims to determine which nodes are most likely to change in terms of system strength and, therefore, the amount and depth of dips.

The results of this paper indicate both positive (+) and negative (-) impacts on short-circuit power as an indicator of system strength for the following changes in the grid:
1. Grid developments and changes in network configuration (+/-)
2. Generation shift from SGUs toward renewable energy sources (RES) generation (+/-)

As short-circuit power is considered a local phenomenon/parameter, a study is required to assess the changes in the short-circuit power between existing situation and foreseen future scenarios.

An analysis of causes of changes demonstrates the influence of future grid developments, and future dispatch patterns provide insight into the effects of these changes. The implications of short-circuit power are presented for some typical cases by regional heatmaps of the short-circuit levels. Some key findings of this paper are as follows:

• The mutual impact of all changes on the short-circuit power is time- and location-dependent.
• The generation shift and phase-out of synchronous generation would alter the short-circuit power locally; thus, clients connected within a vicinity of SGUs that will be phased out or dispatched less frequently are anticipated to experience lower residual voltages during voltage-dip events.
• The short-circuit contribution from the RES generation in the MV grids will help increase the short-circuit power in some areas where the grid is currently weak.
• Applying grid openings and converting meshed HV grids into multiple radial connections generally limit the propagation area of the voltage dips, which is considered a positive attribute. However, they may cause lower residual voltages for the clients connected to the boundaries of the load pockets.