It becomes easier and easier to meet the needs of the grid (because less energy is being taken out), so the turbines speed up. This increases the frequency of t

It becomes easier and easier to meet the needs of the grid (because less energy is being taken out), so the turbines speed up. This increases the frequency of the electrical oscillations on the grid. If the deviation is small this is mostly noticeable in clocks running too fast, but as the deviation increases large spinning structures start spinning too fast and break, often violently.